Tag Archives: space

Astronomy, Space Travel

Welcome to the 22nd Century!

(Excerpt from my upcoming ebook ‘The Next Billion Years’)

A not unlikely interplanetary spacecraft design using known technology. Image Credit.

Thinking ahead to the 22nd seems no more of a challenge than what we had in the 1960s when we considered the mythical 21st century. But one thing is for certain, we had no idea that the socially transformative impacts of computers, smartphones and the internet would be on the horizon. We also had no idea that Stanly Kubrick’s 2001: A Space Odyssey would be way too imaginative even after Neil Armstrong walked on the moon. In the 1950s, we thought we would be driving atomic-powered cars by the 1960s. And of course, we had no idea that global warming was going to be such a problem only 40 years after the first Earth Day. One thing we do know for sure is that on April 27, 2109 Rutgers University will be opening a Time Capsule! 

This essay covers some ideas in space exploration and travel. A future essay will cover climate change and other issues.

Space Travel

Historically before 2025 CE, NASA’s budget was locked at about 0.5% of the federal discretionary budget and human spaceflight was allotted from this $10 billion (0.17% of federal budget). At this sustained pace,  there should be an accumulated minimum of $770 billion invested in manned activities in space by 2100 CE – the lions share going to lunar and Martian bases.  You can buy a lot of infrastructure for that amount of money even with expensive billion-dollar launch vehicles!

A stable population of over 50  researchers and engineers would be a conservative estimate. This requires only an annual off-world population growth rate of 2% by 2100 CE. They would be operating inside habitats protected from radiation exposure, have sophisticated medical and surgical facilities, and the low gravity of the moon (0.2 g’s), would not be an issue impacting astronaut (Lunites?) health. The location of this base would be near the shadowed craters in the South Pole where water ice would be mined for fuel and atmosphere. The buildings would be robotically built using 3D printing techniques developed in the 2020s. They would also be covered by radiation-proof lunar regolith. Better yet, find a lava tube and seal off its ends, then erect a pair of pressurized bulkheads and build ordinary habitats at low cost. Using 3D printing, this process can be automated.

By the start of the 22nd century, if the first human expedition to Mars occurred in 2050 CE, then 50 years have now elapsed. While a lunar base at this time may have 50-100 people, the level of difficulty in transporting material and people to Mars may not allow a Martian base with more than a dozen ‘Martians’ on a  2-year rotation back to Earth. The Planetary Society thinks there could be over 1,000 people living in a sustained way on Mars by 2070, but the devil is in the details as they say. At an off-world sustained growth rate of 2% per year, we only get to about 200 people by then including the lunar base. Of course, the  rapid commercialization of space may well create its own demand for people to visit the moon and Mars, and so extra capacity will have to be built by private companies.

Aside from billionaires, it is not known how much a trip will cost and if ordinary people being chased by climate change issues, will have the spare cash. The truth of the matter is that on Mars, there is simply nothing for a non-scientist to do to occupy their time. You will always live inside a cramped ‘dome’ and only venture outside in a spacesuit. You could hike or drive to a new destination, but you would always see essentially the same rust-red landscape unless you visited the ice-covered poles, which would be hazardous.  Psychologists say that we have limited coping skills to deal with this kind of monotony,

However, if any traces of life are discovered either as fossils or as living systems, this will entirely change the game. It is not unlikely that with indigenous Martian life, Mars will be under extreme quarantine to prevent humans from contaminating the Martian biosphere with terrestrial DNA, or coming into contact with potentially lethal viruses. 

As for the rest of the solar system, we have had tremendous success deploying robotic explorers to the moon and Mars. This technology will continue to be used with even more advanced systems that have sophisticated artificial intelligence and can operate autonomously for long periods. By the end of the 22nd century, these systems will have been placed on the surfaces of Mercury, Venus, the large moons of Jupiter and Saturn, and even a few of the distant moons of Uranus, Neptune and some asteroids too. The Curiosity rover cost $2.5 billion and has lasted over 10 years, so this technology is extremely cost-effective for the science returned. Making them fully autonomous using AI will eliminate the need for long time delays to Earth to operate them telerobotically. These systems will return to Earth high-def video that will be immediately incorporated into fully immersive Virtual Reality experiences for the general public not just a few lucky scientists.

 Astronomy

Meanwhile, astronomers will continue to have no problems forecasting eclipses and unusual planetary alignments with enormous accuracy to the day, hour and minute across the centuries.  We are still going to have two or three solar eclipses every year, but the one on June 25, 2150 will be the longest one since 1973 at 7 minutes and 14 seconds. It will be followed on July 16, 2186 by the longest total solar eclipse in 10,000 years at 7 minutes and 29 seconds. Most eclipses last only 2-5 minutes so these will be truly exceptional. 

The first transit of Venus across the face of the sun since 2012 will occur on December 11, 2117. The previous one was a major media event observed by billons of people.  Its companion event will occur 8 years later on December 8, 2125. 

Then on September 14, 2123 from Earth, Venus transits across the disk of Jupiter. The last time this happened was on November 22, 2065 and it will no doubt still be a public spectacle of some interest. 

Venus transit of Jupiter

Mars gets into the act three years later as it ducks behind the planet Mercury on July 29, 2126. Then on November 15, 2163 Mars colonists will see Earth pass across the face of the sun. This Earth transit will be repeated on May 10, 2189. Some lucky ‘Martians’ may actually get to see both events.

From Neptune, there will also be a transit of Jupiter across the sun on August 8, 2188, so if you were clever you could see the Jupiter transit first and then travel to Mars to see the Earth transit a few years later.

And among the other astronomical events, the nerds among us will wait patiently for the astronomical ‘Julian Day’ calendar to roll over to 2500000 on August 18, 2132. We also get to  celebrate the return of Halley’s Comet on March 27, 2134. Forty years later in 2178, Pluto returns to the same place in its orbit where it was discovered in 1930. But one astronomical activity will continue its essential work. 

Killer Asteroids

Earth orbits the sun in a veritable shooting gallery of asteroids that share nearly the same orbit, and comets that arrive unexpectedly from the far reaches of the solar system. 

Chelyabinsk Meteor….20-meters….1,000 people injured. Image credit.

By 2023 CE, the orbits of 20,000 ‘Near Earth Objects’ had been calculated. Hundreds of these  NEOs have been placed on a Potentially Hazardous Object watch list  because they are larger than 100 meters and could be ‘City Killers’ or worse if they impacted a populated area. The highest risk of impact for a known asteroid is a 1 in 714 chance by an asteroid designated 2009 FD in 2185, meaning that the possibility that it could impact then is less than 0.2 percent. The Sentry Risk Table only lists 2017WT28,  about 8 meters in diameter, as an impact risk for the year 2104. Its odds are about one-in-100. A 2021 survey estimates that there are over 4 million NEOs larger than 10 meters yet to be found.  However, current surveys are estimated to be more than 95% complete for objects bigger than 200 meters. This means that there are no Dinosaur Killer events of the 6km-class anytime soon.

The DART spacecraft impact with the 5-million-ton asteroid Dimorphos was a success and demonstrated we can alter the orbits of asteroids to avoid collision with Earth. (Image credit: NASA)

By the end of the 22nd century, we will have had at least one if not two more events like Tunguska in 2009 and Chelyabinsk in 2013. If we are unlucky, a city or town may be obliterated, but chances are we will be able to divert its orbit to avoid impacts using the DART technology from 2021.

New Physics

Among physicists and astronomers, the search for the nature of dark matter and clues on how to go beyond the so-called Standard Model will inevitably be helped by new instruments. Current designs already have 100 TeV available by the end of the 21st Century, and likely 1,000 TeV by the 22nd century. Along the way, we may even discover new approaches to achieving these high energies, perhaps by harnessing free cosmic ray protons. These are known to have energies above 300,000,000 TeV, but they are unfortunately few and far between. You get one or two of these during the lifetime of a typical physicist.

Although no ‘new physics’ has been detected by 2023 CE, it is almost certain that the Standard Model will start to show its incompleteness somewhere above 20 TeV. Hopefully, the missing ingredients we discover will explain both the nature of dark matter and the origin of dark energy, which were discovered by astronomers in the 20th century.

Dark matter (blue) in the Bullet galaxy cluster. Still a mystery after 100 years?

The really good news is that even with these mysterious ‘dark’ ingredients to the universe, there are almost no examples in history where some new scientific observation did not have a complete explanation within a century of its discovery.  

Exoplanets and the Search for Life

Astronomers will also be very busy studying exoplanets and discovering ones with signs of a biosphere, leading to a surge of innovative techniques for trying to actually image the surfaces of these worlds and detect artificial illumination on their dark hemispheres or signs of industrial pollution. Beyond the ‘baked-in’ mysteries of our dark universe, the search for extraterrestrial life will have matured in some fascinating directions by now. In our solar system, we will have explored the deep oceans of Europa, Titan, probed the crust of Mars, and settled the question of whether in our solar system any other abode than Earth ever  experienced life. 

 Beyond our solar system, our catalog of over 500,000 exoplanets by then, and a thousand nearby habitable worlds discovered, will have been followed by an equally intense period of searching for biomarkers in their atmospheres, or illumination on their nighttime hemispheres. This isn’t to say that it is a certainty we will find extraterrestrial life by the 22nd century, but we will have certainly studied all the ‘low hanging fruit’ exoplanets for signs of it. Within 500 light years of the sun, we will know what planetary systems to avoid if we chose to visit them with AI-enabled spacecraft. If we don’t find any exoplanets with biosignatures in the solar neighborhood by this time, humans may never take the next step and conduct interstellar travel, at a cost of trillions of dollars per mission. What would be the point?

Meanwhile, another search-for-life pursuit will have started to mature so that it can inform us about an even bigger picture. 

Intelligent Life in the Universe

Since the late-20th century, a small cadre of intrepid and patient astronomers have been using radio telescopes to search for signs of intelligent life. On Earth, a biosphere in existence for 3.8 billion years led to beings with radio technology only in the last 100 years. The goal of these radio searches is to detect the ‘spillover’ radiation from other civilizations across the Milky Way, far outside the 1,000 light year limits we are searching for viable biospheres. Every year that goes by, and every negative result that turns up, only reinforces the statistical assessment that intelligent life capable of, or interested in, radio technology are dismally few and far between in our Milky Way.

Science fiction author Arthur C Clarke  once remarked, “Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.” I don’t find the prospects of extraterrestrial life ‘ terrifying’  and am more inclined to agree with what Ted Arroway said in the movie Contact, “I don’t know Sparks. But I guess I’d say if it was just us…seems like an awful waste of space”.

 Gravity Astronomy

The discovery of gravity waves in 2015 will lead to far more sensitive instruments by the 22nd century that will lay-bare the details of the Big Bang event itself along with actual hard data on the origin of time and space. Cosmology should largely become a closed textbook with all of the essential physical details worked out and covered by newer Big Bang theories. This, of course, depends on whether the issue of dark matter and dark energy are also resolved. Stay tuned!

 Science Fiction

Recognizing the futility of creating interesting science fiction stories that begin only a few decades out, some writers have moved their stories to 2050 and beyond. Only a few Old School stories written in the mid to late-20th century still find the first decades of the 21st century interesting, and with the right technology twists to make entertaining reading. None of them were very good at predicting what the end of the 20th century would look like, so we take any fictional prognostication with  grain (ton?) of salt. Still…

2100   The Ring of Charon. Earth accidentally destroyed by a Graduate Student(Allen)

2101   Babylon 5. First Martian base established (TV).

2115   Childhood’s End. Adult humans extinct. Killed by their own mutated children(Clark)                    

 2119   Orphans of the Sky. The first Centauri expedition (Heinlein)            

 2123   Starwings. Earth Holocaust;  Interstellar travel begins. (Proctor) 

2125   Methusela’s Children – Interstellar colonies (Heinlein)  

2125  Childhood’s End. The Earth is destroyed by its evolved children (Clark)

2130   Rama Revealed. Alien artifact found(Clark)   

2140   New York 2140. Major flooding (Robinson)  

2144   Aliens.  Movie events. Need I say more?

2149   The Seeds of Aril.  Interstellar Expeditions in 1-person pods(Robertson)

2150   Dr Who.  Earth overrun by the Daleks. (TV)

2150   The Expanse – Mars population 100 million (TV)

2156   Babylon 5 – The Centauri civilization contacts Earth.

2171   Moving Mars – Major Mars colony established (Bear)

2190   Seetee Ship – Story events (Williamson)

2195   Ender’s Game –  Interstellar war with aliens (Card)

Astronomy, NASA

Desciphering Webb Telescope Images

Astronomers can look at images of celestial objects like planets, nebulae and galaxies and immediately see their significance, but for the average person seeing them on the Evening News the pictures are, of course, beautiful but at the same time, generally mysterious. My recent book The Hidden Universe takes 68 images you might have encountered, shows you how they were created, and what interesting story lurks beneith their gorgeous countenences. This blog will describe one of these.

By now you have seen the spectacular images provided by the Webb Space Telescope (JWST), and boy are they breath-taking even for an astronomer! I have been waiting all my professional life for HD-quality images of objects in the mid-infrared spectrum (wavelength: 1 to 28 microns), and JWST has not dissappointed. NASA’s Spitzer Space Telescope also produced high-quality infrared images to be sure (wavelength: 3 to 160 microns), but JWST is a much-larger telescope (50-times larger than Spitzer) with decades-more-modern sensors!

For a full array of Webb’s first images and spectra, please visit: https://esawebb.org/initiatives/webbs-first-images/

Selecting Your Color Pallet

The first thing to remember when looking at JWST images at wavelengths between 0.6 and 28-microns is that they are not colorized the way your eye would see the light. Human eyes end their color sensitivity to visible light at around 0.6-microns, so the idea that something seen by JWST would ‘look green or red’ is completely incorrect. JWST, in fact many astronomical images used in research, are colorized to help the astronomer detect differences in how objects emit light at different wavelengths.

Our brain has evolved our color vision to be a sophisticated pattern-recognizer, so all you have to do is put your data into ‘RGB’ form, and BANG! you can use the image processing power of the wet-ware in your brain to quickly survey a new subject.

The particular color pallet an astronomer uses is all about their artistic sensibility and what they want to emphasize, so it is not unreasonable for a bright red color to be used to represent hot dust and bright blue colors for cooler dust, etc. Ironically, in the electromagnetic spectrum, red wavelengths are cooler objects and blue wavelengths are hotter objects, but humans feel that blue is a cooler color than red, so our interpretation of color is backwards! For astronomers, you can even colorize the speeds of gas clouds (ie Doppler shift) so that blue colors represent clouds moving towards you and red clouds are clouds moving away from you, irrespective of the wavelength being used.

Image Analysis 101.

To analyze JWST images, let’s start with an image that has become an astronomical and even world-wide ‘classic’: The Pillars of Creation.

Vital Statistics: The ‘Pillars’ are actually a small part of the Eagle Nebula, also called Messier 16. This is a beautiful star-forming region in the constellation  Serpens located 7,000 light years from Earth. With a size of about 60 light years, the region contains 8,000 stars  of which the brightest of these, HD-168076, is 80 times the mass of our sun and only a few million years old. Its intense ultraviolet light illuminates the nebular gas and causes the atoms to emit the colorful patina of light that we see in optical photographs. Here is what the entire nebula looks like with ‘true color’ RGB filters in the visible spectrum:

        This three-color composite optical image was obtained with the Wide-Field Imager camera on the MPG/ESO 2.2-meter telescope at the La Silla Observatory. At the center of the nebula you can see the Pillars silhouetted against the bright nebular gases, which makes these ‘dark nebulae’ really stand out. The cluster of bright stars to the upper right is called NGC 6611, which the Pillars are pointing at, and are the home to the massive and hot stars that illuminate the Pillars.

Ionizing Radiation: The intense ultraviolet radiation from the massive stars in the cluster at the upper-right is actively eating away at the dense interstellar cloud that gave birth to them at the lower-left. These are what astronomers classify as O and B-type stars or just ‘OB’ stars. Each is more than 5 times as massive as our sun, and with surface temperatures above 20,000o C they emit most of their light at ultraviolet wavelengths. Astronomers can detect this ionized gas at radio-wavelengths too. They are called ‘HII’ (H-two) regions because HI is the symbol for ordinary ‘neutral’ hydrogen and ‘II’ means that the neutral hydrogen atoms have lost one electron to make them ionized, hence ‘HII’. This ultraviolet radiation streaming through the hydrogen HI gas to ionize it into HII results in many unusual wind-swept shapes including what astronomers call ‘elephant trunks’ such as the Pillars. Their shapes act like ‘wind socks’ and point towards the main source of the ionizing gas flow, which is expanding outwards from the OB star cluster at speeds up to 10 km/s….. that’s about 22,000 mph. At this pace, the ionzation front can travel 4 light years in 100,000 years, which is enough to cross the space of most star-forming regions.

What you also notice is that the optical image shows the Pillars as dark and obscurring the background nebula which we call ‘dark nebulae’, while the JWST image shows the Pillars being very bright as ’emission nebulae’. The bright emission nebula produced by the stars is also missing in the JWST image, and instead you see thousands of stars in the background. The reason this happens is your first exposure to astrophysics!


Here is a side-by-side comparison of the Hubble (left) and Webb images (right).

Interstellar Dust: Interstellar gas clouds would be entirely invisible were it not for the fact that for about every trillion atoms of gas you have one dust grain. These dust grains are about 1-micron in diameter and were formed in the cool atmospheres of ancient red super giant stars like rain condensing out of a storm cloud on Earth. The dust grains do two things. First they scatter light at optical wavelengths, just like the dust in our atmosphere does, making the sky (or a nebula) appear blue. Secondly, they are very cold, but even so they emit their own ‘heat radiation’ in the infrared spectrum. If a cloud contains lots of dust grains, it will obscure the light from background stars, but at the same time emit infrared radiation making them appear bright at infrared wavelengths. This is what we see in the Pillars.

These linear Pillar clouds are about 2 to 4 light years in length and are rich in dust grains, so they block optical light in the famous Hubble images making them look dark, but emit their own radiation making them look bright at infrared wavelengths in the JWST images. For the first time, astronomers can study just how lumpy the surfaces of these interstellar clouds are by looking at the infrared light they are emitting directly. Taking a closer look at the Pillars gives even more information.

Close up of the Pillars dust cloud showing stars being born – red dots and color near center of image.

Star-forming regions: Zoom in a little more, until you see red dots springing into view. There are dozens of them. Each of those red dots covers an area larger than our solar system. The finger-like protrusions are also larger than our solar system, and are made visible by the shadows of evaporating gaseous globules (EGGs), which shield the gas behind them from intense UV flux. EGGs are themselves incubators of new stars. The stars then emerge from the EGGs, which then are evaporated.

So there you have it! One picture rendered into ‘a thousand words’. To be sure, this one image will easily form the basis for someone’s PhD thesis because it is so rich in detail missing from even the best Hubble images. When combined with spectroscopic data from JWST and data from radio astronomy, we will have a detailed understanding of just ONE star-forming region in our Milky Way. We are definitely living in exciting times for astronomical research!

If you want to see more astronomical images analyzed this way, have a look at my new book ‘The Hidden Universe’ available at Amazon.

Check back here for my next blog!

Astronomy, Brain Research, Physics

This is Not Your Father’s Universe!

When I was learning astronomy in the 60s and 70s, we were still debating whether Big Bang or Stady State were the most accurate models for our universe. We also wondered about how galaxies like our Milky Way formed, and whether black holes existed. The idea that planets beyond our solar system existed was pure science fiction and no astronomers spent any time trying to predict what they might look like. As someone who has reached the ripe old age of 70, I am amazed how much progress we have made, from the discovery of supermassive black holes and exoplanets, to dark matter and gravitational radiation. The pace of discovery continues to increase, and our theoretical ideas are now getting confirmed or thrown out at record pace. There are still some issues that remain deliciously mysterious. Here are my favorite Seven Mysteries of the Universe!

1-How to Build a Galaxy: In astronomy, we used to think that it would take the universe a long time to build galaxies like our Milky Way, Thanks to the new discoveries by the Webb Space Telescope, we now have a ring-side seat to how this happens, and boy is it a fast process!

The oldest galaxies discovered with the Hubble Space Telescope date back to between 400 and 500 million years after the Big Bang. A few weeks ago, Webb spotted a galaxy that seems to have formed only 300 million years after the Big Bang. Rather than the massive galaxies like the Milky Way, these young galaxies resemble the dwarf galaxies like the Large Magellanic Cloud, perhaps only 1/10 the mass of our galaxy and filled with enormus numbers of massive, luminous stars. The above image from Hubble is a nearby galaxy called M-33 that has a mass of about 50 billion suns. There were lots of these smaller galaxies being formed during the first 300 million years after the Big Bang.

It looks like the universe emerged from the Dark Ages and immediately started building galaxies. In time, these fragments collided and merged to become the more massive galaxies we see around us, so we are only just starting to see how galaxy-building happens. Our Milky Way was formed some 1 billion years after the Big Bang, so the galaxy fragments being spotted by Webb have another 700 million years to go to make bigger things. Back in 2012, Hubble had already discovered the earliest spiral galaxy seen by then; a galaxy called Q2343-BX442, camping out at 3 billion years after the Big Bang. In 2021, an even younger spiral galaxy was spotted, called BRI 1335-0417, seen as it was about 1.4 billon years after the Big Bang.

So we are now watching how galaxies are being formed almost right before our eyes! Previous ideas that I learned about as an undergraduate, in which galaxies are formed ‘top-down’ from large collections of matter that fragment into stars, now seem wrong or incomplete. The better idea is that smaller collections of matter form stars and then merge together to build larger systems – called the ‘bottom-up’ model. This process is very, very fast! Among the smallest of these ‘galaxies’ are things destined to become the globular clusters we see today.

2-Supermassive Black Holes: The most distant and youngest supermassive black hole was discovered in 2021. Called J0313-1806, its light left it to reach us when the universe was only 670 million years old. Its mass, however, is a gargantuan 1.6 BILLION times the mass of our sun. Even if the formation of this black hole started at the end of the Dark Ages ca 100 million years after the Big Bang, it would have to absorb matter at the rate of three suns every year on average. That explains its quasar energy, but still…it is unimaginable how these things can grow so fast! The only working idea is that they started from seed masses about 10,000 the mass of our sun and grew from there. But how were the seed masses formed? This remains a mystery today.

3-The Theory of everything: The next Big Thing that I have been following since the 1960s is the search for what some call the Theory of Everything. Exciting theoretical advancements were made in the 1940s and 1960s to create accurate mathematical models for the three nongravity forces, called the electromagnetic, weak and strong forces. Physicists call this the Standard Model, and every physicist learns its details as students in graduate school. By the early 1980s, string theory was able to add gravity to the mix and go beyond the Standard Model. It appeared that the pursuit of a unified theory had reached its apex. Fifty years later, this expectation has all but collapsed.

Experiments at the Large Hadron Collider continue to show how the universe does not like something called supersymmetry in our low-energy universe. Supersymmetry is a key ingredient to string theory because it lets you change one kind of particle (field) into another, which is a key ingredient to any unified theory. So the simplest versions of string theory rise or fall based on whether supersymmetry exists or not. For over a decade, physicists have tried to find places in the so-called Standard Model where supersymmetry should make its appearance, but it has been a complete no-show. Its not just that this failure is a problem for creating a more elegant theory of how forces works, but it also affects astronomy as well.

https://penntoday.upenn.edu/news/making-sense-string-theory

Personally, when string theory hit the stage in the 1980’s I, like many other astronomers and physicists, thought that we were on the verge of solving this challenge of unifying gravity with the other forces, but this has not been the reality. Even today, I see no promissing solutions to this vexing problem since apparently the data shows that simple string theory is apparently on a wrong theoretical track.

One cheerful note: For neutrinos, the path from theoretical prediction to experimental observation took 25 years. For the Higgs boson, it took 50 years. And for gravitational waves, it took a full 100 years. We may just have to be patient…for another 100 years!

4-Dark Matter: The biggest missing ingredient to the cosmos today is called dark matter. When astronomers ‘weigh’ the universe, they discover that 4.6% of its gravitating ‘stuff’ is in ordinary matter (atoms,. stars, gas, neutron stars etc), but a whopping 24% is in some other ‘stuff’ that only appears by its gravity. It is otherwise completely invisible. Putting this another way, it’s as though four out of every five stars that make up our Milky Way were completely invisible.

Dark matter in Abell 1679.

Because we deeply believe that dark matter must be tracable to a new kind of particle, and because the Standard Model gives us an accounting of all the kinds of elementary particles from which our universe is built, the dark matter particle has to be a part of the Standard Model…but it isn’t!!!! Only by extending the Standard Model to a bigger theory (like string theory) can we logically and mathematically add new kinds of particles to a New Standard Model- one of which would be the dark matter particle. String theory even gives us a perfect candidate called the neutralino! But the LHC experiments have told us for over a decade that there is nothing wrong with the Standard Model and no missing particles. Astronomers say that dark matter is real, but physicists can’t find it….anywhere. Well…maybe not ALL astronomers think it’s real. So the debate continues.

Personally, I had heard about ‘missing mass’ in the 1960s but we were all convinced we would find it in hot gas, dim red dwarf stars or even black holes. I NEVER thought that it would turn out to be something other than ordinary matter in an unusual form. Dark matter is so deeply confounding to me that I worry we will not discover its nature before I, myself, leave this world! Then again, there isnt a single generation of scientists that has had all its known puzzles neatly solved ‘just in time’. I’m just greedy!!!

5- Matter and Antimatter: During the Big Bang, there were equal amounts of matter and anti matter, but then for some reason all the antimatter dissappeared leaving us with only matter to form atoms, stars and galaxies. We don’t know why this happened, and the Standard Model is completely unhelpful in giving us any clues to explain this. But next to dark matter, this is one of the most outstanding mysteries of modern, 21st century cosmology. We have no clue how to account for this fact within the Standard Model, so again like Dark Matter, we see that at cosmological scales, the Standard Model is incomplete.

6- Origin of Time and Space: Understanding the nature of time and space, and trying to make peace with why they exist at all, is the bane of any physicists existence. I have written many blogs on this subject, and have tried to tackle it from many different angles, but in the end they are like jigsaw puzzels with too many missing pieces. Still, it is very exciting to explore where modern physics has taken us, and the many questions such thinking has opened up in surprising corners. My previous blog about ‘What is ‘Now’ is one such line of thinking. Many of the new ideas were not even imagined as little as 30 years ago, so that is a positive thing. We are still learning more about these two subjects and getting better at asking the right questions!

https://iopscience.iop.org/journal/0264-9381/page/Focus-issue-loop-quantum-gravity

7-Consciousness: OK…You know I would get to this eventually, and here it is! Neuroscientists know of lots of medical conditions that can rob us of consciousness including medical anesthesia, but why we have this sense about ourselves that we are a ‘person’ and have volition is a massively hard problem. In fact, consciousness is called the ‘Hard Problem’ in neuroscience..heck…in any science!

https://www.technologynetworks.com/neuroscience/articles/what-if-consciousness-is-not-what-drives-the-human-mind-307159

The ‘Soft Problem’ is how our senses give us a coherant internal model of the world that we can use to navigate the outside world. We know how to solve the Soft Problem, just follow the neurons. We are well on our way to understanding it thanks to high-tech brain imaging scanners and cleverly-designed experiments. The Hard Problem is ‘hard’ because our point-of-view is within the thing we are trying to undertand. Some think that our own ‘wet ware’ is not up to the task of even giving us the intelligence to answer this qustion. It will not be the first time someone has told us about limitations, but usually these are technological ones, and not ones related to limits to what our own brains can provide as a tool.

So there you have it.

My impression is that only Mysteries #1 and #2 will make huge progress. The Theory of Everything is in experimental disarray. For antimatter, there has been no progress, but many ideas. They all involve going outside the Standard Model. Dark matter might be replaced by a modification of gravity at galactic and cosmological scales.

Beyond these ‘superficial’ mysteries, we are left with three deep mysteries. The origin of space, time and consciousness remain our 21st century gift to children of the 22nd century!

Check back here in a few weeks for the next blog!

Physics

Quantum Gravity – Again!

In my previous blogs, I briefly described how the human brain perceives and models space (Oops one more thing), how Einstein and other physicists dismiss space as an illusion (Relativity and space ), how relativity deals with the concept of space (So what IS space?), what a theory of quantum gravity would have to look like (Quantum Gravity Oh my! ), and along the way why the idea of infinity is not physically real (Is infinity real?) and why space is not nothing (Thinking about Nothing).  I even discussed how it is important to ‘think visually’ when trying to model the universe such as the ‘strings’ and ‘loops’ used by physicists as an analog to space (Thinking Visually)

And still these blogs do not exhaust the scope of either the idea of space itself or the research in progress to get to the bottom of our experience of it.

This essay, based on a talk I gave at the Belmont Astronomical Society on October 5, 2017 will try to cover some of these other ideas and approaches that are loosely believed to be a part of a future theory of quantum gravity.

What is quantum gravity?

It is the basic idea that the two great theories of physics, Quantum Mechanics and General Relativity are incompatible with each other and do not actually deal with the same ingredients to the world: space(time) and matter. Quantum gravity is a hypothetical theory that unifies these two great ideas into a single language, revealing answers to some of the deepest questions we know how to ask about the physical world. It truly is the Holy Grail of physics.

Why do we need quantum gravity at all?

Quantum mechanics is a theory that describes matter and fields embedded in a pre-existing spacetime that has no physical effect on these fields other than to provide coordinates for describing where they are in time and space. It is said to be a background-dependent theory. General relativity is only a theory of space(time) and does not describe matter’s essence at all. It describes how matter affects the geometry of spacetime and how spacetime affects the motion of matter, but does so in purely ‘classical’ terms. Most importantly, general relativity says there is no pre-existing spacetime at all. It is called a background-independent theory. Quantum gravity is an overarching background-independent theory that accounts for the quantum nature of matter and also the quantum nature of spacetime at scales where these effects are important, called the Planck scale where the smallest unit of space is 10^-33 cm and the smallest unit of time is 10^-43 seconds.

We need quantum gravity because calculations in quantum mechanics are plagued by ‘infinities’ that come about because QM assumes space(time) is infinitely divisible into smaller units of length. When physical processes and field intensities are summed over smaller and smaller lengths to build up a prediction, the infinitesimally small units lead to infinitely large contributions which ‘blow up’ the calculations unless some mathematical method called ‘renormalization’ is used. But the gravitational field escribed by general relativity cannot be renormalized to eliminate its infinities. Only by placing a lower limit ‘cutoff’ to space(time) as quantum gravity does is this problem eliminated and all calculations become finite.

We need quantum gravity because black holes do not possess infinite entropy. The surface area of a black hole, called its event horizon, is related to its entropy, which is a measure of the amount of information that is contained inside the horizon. A single bit of information is encoded on the horizon as an area 2-Planck lengths squared. According to the holographic principle, the surface of a black hole, its 2-d surface area, encodes all the information found in the encompassed 3-d volume, so that means that the spacetime interior of a black hole has to be quantized and cannot be infinitely divisible otherwise the holographic principle would be invalid and the horizon of the black hole would have to encode an infinite amount of information and have an infinite entropy.

We also need quantum gravity because it is believed that any fundamental theory of our physical world has to be background-independent as general relativity shows that spacetime is. That means that quantum mechanics is currently an incomplete theory because it still requires the scaffolding of a pre-existing spacetime and does not ‘create’ this scaffolding from within itself the way that general relativity does.

So what is the big picture?

Historically, Newton gave us space and time as eternally absolute and fixed prerequisites to our world that were defined once and for all before we even started to describe forces and motion. The second great school of thought at that time was developed by Gottfrid Leibnitz. He said that time and space have no meaning in themselves but only as properties defined by the relationships between bodies. Einstein’s relativity and its experimental vindication has proven that Newton’s Absolute Space and Time are completely false, and replaced them by Leibnitz’s relativity principle. Einstein even said on numerous occasions that space is an imaginary construct that we take for granted in an almost mythical way. Space has no independent existence apart from its emergence out of the relationships between physical bodies. This relationship is so intimate that in general relativity, material bodies define the spacetime geometry itself as a dynamical solution to his famous relativistic equation for gravity.

How does the experience of space emerge?

In general relativity, the only thing that matters are the events along a particle’s worldline, also called its history. These events encode the relationships between bodies, and are created by the intersections of other worldlines from other particles. This network of fundamental worldlines contains all the information you need to describe the global geometry of this network of events and worldlines. It is only the geometry of these worldlines that matters to physical phenomena in the universe.

The wireframe head in this illustration is an analog to worldliness linking together to create a geometry. The black ‘void’ contains no geometric or dimensional information and any points in it do not interact with any worldline that makes up the network. That is why ‘space’ is a myth and the only thing that determine the structure of our 4-d spacetime are the worldliness.

General relativity describes how the geometry of these worldlines creates a 4-dimensional spacetime. These worldlines represent matter particles and general relativity describes how these matter particles create the curvature in the worldlines among the entire system of particles, and thereby creates space and time. The ‘empty’ mathematical points between the worldlines have no physical meaning because they are not connected to events among any of the physical worldlines, which is why Einstein said that the background space in which the worldlines seem to be embedded does not actually exist! When we look out into ‘space’ we are looking along the worldlines of light rays. We are not looking through a pre-existing space. This means we are not seeing ‘things in space’ we are seeing processes in time along a particle’s history!

There are two major quantum gravity theories being worked on today.

String theory says that particles are 1-dimensional loops of ‘something’ that are defined in a 10-dimensional spacetime of which 4 dimensions are the Big Ones we see around us. The others are compact and through their geometric symmetries define the properties of the particles themselves. It is an approach to quantum gravity that has several problems.

 

This figure is an imaginative rendering of a ‘string’.

First it assumes that spacetime already exists for the strings to move within. It is a background-dependent theory in the same spirit as Newton’s Absolute Space and Time. Secondly, string theory is only a theory of matter and its quantum properties at the Planck scales, but in fact the scale of a string depends on a single parameter called the string tension. If the tension is small, then these string ‘loops’ are thousands of times bigger than the Planck scale, and there is no constraint on what the actual value of the tension should be. It is an adjustable parameter.

This figure is an imaginative rendering of a ‘loop’

Loop Quantum Gravity is purely a theory of spacetime and does not treat the matter covered by quantum mechanics. It is a background-independent theory that is able to exactly calculate the answers to many problems in gravitation theory, unlike string theory which has to sneak up on the answers by summing an infinite number of alternate possibilities. LQG arrives at the answer ‘2.0’ in one step as an exact answer while for example string theory has to sum the sequence 1+1/2+1/4+1/8+1/16 +…. To get to 2.000.

LQG works with elementary spacetime ingredients called nodes and edges to create spin networks and spin foam. Like a magnetic field line that carries magnetic flux, these edges act like the field lines to space and carry quantized areas 1 Planck length squared. By summing over the number of nodes in a spin network region, each node carries a quantum unit of space volume. These nodes are related to each other in a network of intersecting lines called a spin network, which for very large networks begins to look like a snapshot of space seen at a specific instant. The change of one network into another is called a spin foam and it is the antecedent to 4-d spacetime. There is no physical meaning to the nodes and edges themselves just as there is no physical meaning to the 1-d loops than make up strings in string theory. . They are pure mathematical constructs.

So far, the best idea is that LQG forms the bedrock for string theory. String theory looks at spacetime and matter far above the Planck scale, and this is where the properties of matter particles make their appearance. LQG creates the background of spacetime that strings move through. However there is a major problem. LQG predicts that the cosmological constant must be negative and small, which is what is astronomically observed, while string theory says that the cosmological constant is large and positive. Also, although LQG can reconstruct the large 4-d spacetime that we live in, it does not seem to have have any room for the additional 6 dimensions required by string theory to create the properties of the particles we observe. One possibility is that these extra dimensions are not space-like at all but merely ‘bookkeeping’ tools that physicists have to use which will eventually be replaced in the future by a fully 4-d theory of strings.

Another approach still in its infancy is Causal Set Theory. Like LQG it is a background-independent theory of spacetime. It starts with a collection of points that are linked together by only one guiding principle, that pairs of points are ordered by cause-and-effect. This defines how these points are ordered in time, but this is the only organizing principle for points in the set. What investigators have found is that such sets create from within themselves the physical concepts of distance and time and lead to relativistic spacetimes. Causal Sets and the nodes in LQG spin networks may be related to each other.

Another exciting discovery that relates to how the elements of quantum spacetime create spacetime involves the Holographic Principle connected with quantum entanglement.

The Holographic Principle states that all the information and relationships found in a 3-d volume are ‘encoded’ on a 2-d surface screen that surrounds this volume. This means that relationships among the surface elements are reflected in the behavior of the interior physics. Recently it was discovered that if you use quantum entanglement to connect two points on the surface, the corresponding points in the interior become linked together as a physical unit. If you turn off the entanglement on the surface the interior points become unconnected and the interior space dissolves into unrelated points. The amount of entanglement can be directly related to how physically close the points are, and so this is how a unified geometry for spacetime inside the 3-d ‘bulk’ can arise from unconnected points linked together by quantum entanglement.

 

Additional Reading:

Exploring Quantum Space  [My book at Amazon.com]

Quantum Entanglement and quantum spacetime [Mark Raamsdonk]

Background-independence  [Lee Smolin]

Holographic Principle [ Jack Ng]

Causal Sets: The self-organizing universe [Scientific American]

 

Astronomy, Brain Research, Physics

Thinking Visually

Look at the two images  for a few minutes and let your mind wander.

What impressions do you get from the patterns of light and dark? If I were to tell you that the one at the top is a dark nebula in the constellation Orion, and the one on the bottom is a nebula in the Pleiades star cluster, would that completely define for you what you are experiencing…or is there something more going on?

Chances are that, in the top image you are seeing what looks like the silhouette of the head and shoulders of some human-like figure being lit from behind by a light. You can’t quite put your finger on it, but the image seems vaguely mysterious and perhaps even a bit frightening the more you stare at it.

The image on the bottom evokes something completely different. Perhaps you are connecting the translucence and delicacy with some image of a shroud or silken cloak floating in a breeze. The image seems almost ghost-like in some respects…spiritual

“But of course this is rather silly” you might say. “These are interstellar clouds, light-years across and all we are doing is letting our imaginations wander which is not a very scientific thing to do if you want to understand the universe.” This rational response then tempts you to reach for your mouse and click to some other page on the web.

What has happened in that split second is that a battle has been fought between one part of your brain and another. The right side of your brain enjoys looking at things and musing over the patterns that it finds there. Alas, it cannot speak because the language centers of the brain live in the left cerebral hemisphere, and it is here that rules of logic and other ‘scientific’ reasoning tools exist. The left side of your brain is vocal, and talking to you right now. It gets rather upset when it is presented with vague patterns because it can’t understand them and stamp them with a definite emotion the way the right hemisphere can. So it argues you into walking away from this challenge of understanding patterns.

If you can suspend this indignation for a moment or two, you will actually find yourself thinking about space in a way that more nearly resembles how a scientist does, though even some scientists don’t spend much time thinking about space. This indifference has begun to change during the last 20 years, and we are now in the midst of a quiet revolution.

There are three child-like qualities that make for a successful scientist:

Curiosity. This is something that many people seem to outgrow as they get older, or if they maintain it as adults, it is not at the same undiluted strength that it was when they were a child.

Imagination. This is something that also wanes with age but becomes an asset to those that can hang on to even a small vestige of it. It is what ‘Thinking out of the box’ is all about.

Novelty. As a child, everything is new. As an adult we become hopelessly jaded about irrelevant experiences like yet another sunset, yet another meteor shower, yet another eclipse. In some ways we develop an aversion for new experiences preferring the familiarity of the things we have already experienced.

If you wish to understand what space is all about, and explore the patterns hidden in the darker regions of nature, you will have to re-acquaint yourself with that child within you. You will need to pull all the stops out and allow yourself to ‘play’ with nature and the many clues that scientists have uncovered about it. You will need to do more than read books by physicists and astronomers. They speak the language of the left-brain . They can help you to see the logical development of our understanding of space and the Void, but they can not help you internalize this knowledge so that it actually means something to you. For that, you have to engage your right-brain faculties, and this requires that you see the patterns behind the words that physicists and astronomers use. To do that, you will need to think in terms of pictures and other types of images. You will need to bring something to the table to help you make sense of space in a way that you have not been able to before. You will need to expand your internal library of visual imagery to help you find analogues to what physicists and astronomers are trying to describe in words and equations. These visual analogues can be found in many common shapes and patterns, some seen under unusual and evocative circumstances. Here are some evocative images that seem to suggest how space might be put together compliments of  a diatom, the painters Miro and Mondrian, dew on a spider web, and atoms in a tungsten needle tip!

Spider web covered with dew drops

Remember, the right brain uses ALL sensory inputs to search for patterns and to understand them. It even uses imaginary information, dreams, and other free-forms to decode what it is experiencing.  

My book ‘Exploring Quantum Space’ is a guidebook that will give you some of the mental tools you will need to make sense of one of the greatest, and most subtle, discoveries in human history. Space, itself, is far from being ‘nothing’ or merely a container for matter to rattle around within. It is a landscape of hidden patterns and activity that shapes our universe and our destiny. You cannot understand it, or sense the awe and mystery of its existence, by simply reading words and following a logical exposition of ‘ifs and thens’. You also have to experience it through evocative imagery and imagination. Space is such a different medium from anything we have ever had to confront, intellectually, that we need to employ a different strategy if we wish to understand it in a personal way. Once we do this, we will be reconnected with that sense of awe we feel each time we look at the night sky.

My next blog about Nothing introduces some of the other ideas and techniques that scientists use to think about the impossible!

 

Astronomy, Physics

Misconceiving the Big Bang

The Big Bang was NOT a Fireworks Display!

Written by Sten Odenwald
Copyright (C) 1997. Published in the Washington Post Horizon education supplement on May 14, 1997.

The Big Bang wasn’t really big. Nor was it really a bang. In fact, the event that created the universe and everything in it was a very different kind of phenomenon than most people–or, at least, most nonphysicists–imagine.
Even the name “Big Bang” originally was a put-down cooked up by a scientist who didn’t like the concept when it was first put forth. He favored the idea that the universe had always existed in a much more dignified and fundamentally unchanging, steady state.

But the name stuck, and with it has come the completely wrong impression that the event was like an explosion and that the universe is expanding today because the objects in it are being flung apart like fragments of a detonated bomb.

Virtually every basic aspect of this intuitive image for the Big Bang (we ARE stuck with the name) is incorrect. To understand why, you need to understand Albert Einstein’s general theory of relativity. Or, at least, you need to have a sense of it. That may sound daunting, but general relativity is the most revolutionary scientific advance of the 20th century, and we all ought to acquire some feeling for it before the century ends.

After all, it’s been 82 years since Einstein put forth his theory. It’s been tested in scores of experiments and has always passed with flying colors and is now firmly established as our premier guide to understanding how gravity operates. Moreover, it is part of the foundation of Big Bang cosmology. And it is because of general relativity that we know the Big Bang was (and is, for the event is still going on) nothing like an explosion.

Albert Einstein developed general relativity in order to make his famous theory of special relativity include the effects of gravity. It is a better way than Sir Isaac Newton’s of understanding how gravity works. Like a hungry amoeba, general relativity ( or just GR for short) had absorbed both Einstein’s newly-minted special relativity and Newton’s physics, giving us the means to replicate ALL of the predictions from these two great theories, while extending them into unfamiliar realms of experience. One of these realms was the Black Hole. The other was the shape and evolution of the universe itself.

Big Bang cosmology says that the universe came into existence between 10 to 20 billion years ago, and that from a hot dense state has been expanding and cooling ever since, remains unassailable. Yet, Big Bang cosmology is vulnerable. It is based on GR being accurate over an enormous range of scales in time and space. Just how good is general relativity? So far, GR has made the following specific predictions:

1…The entire orbit of Mercury rotates because of the curved geometry of space near the sun. The amount of ‘perihelion shift’ each century was well known at the time Einstein provided a complete explanation for it in 1915.

2…Light at every frequency can be bent in exactly the same way by gravity. This was confirmed in the 1919 Solar Eclipse for optical light using stars near the Sun’s limb, and in 1969-1975 using radio emissions from star-like quasars also seen near the limb of the Sun. The deflection of the light was exactly as predicted by GR.

3…Clocks run slower in strong gravitational fields. This was confirmed by Robert Pound and George Rebka at Harvard University in 1959, and by Robert Vessot in the 1960’s and 70’s using high-precession hydrogen maser clocks flown on jet planes and on satellites.

4…Gravitational mass and inertial mass are identical. Most recently in 1971, Vladimir Braginsky at Moskow University confirmed GRs prediction of this to within 1 part in a trillion of the exact equality required by GR.

5…Black holes exist. Although these objects have been suspected to exist since they were first introduced to astronomers in the early 1970’s, it is only in 1992 that a critical acceptance threshold was crossed in the astronomical community. It was then that Hubble Space Telescope observations revealed monstrous, billion-sun black holes in the cores of nearby galaxies such as Messier 87, Messier 33 and NGC 4261.

6…Gravity has its own form of radiation which can carry energy. Russel Hulse and Joseph Taylor in 1975 discovered two pulsars orbiting each other, and through careful monitoring of their precise pulses during the next 20 years, confirmed that the system is loosing energy at a rate within 1 percent of the prediction by GR based on the emission of gravitational radiation.

7…A new force exists called ‘gravito-magnetism’. Just as electric and magnetic fields are linked together, according to GR, a spinning body produces a magnetism-like force called gravitomagnetism. GR predicts that rotating bodies not only bend space and time, but also make empty space spin. A NASA satellite called Gravity Probe B will be launched in the next few years to see whether this effect exists. This is a killer. If it is not found, GR is mortally wounded despite its long string of other successes.

8…Space can stretch during the expansion of the universe. This was confirmed by Edwin Hubble’s detection of the recession of the galaxies ca 1929. More recently in 1993, Astronomer Kenneth Kellerman confirmed that the angular sizes of distant radio sources shrink to a minimum then increase at greater distances exactly as expected for a dilating space. This is not predicted by any other cosmological model that does not also include the dilation of space as a real, physical phenomenon.

We have now boxed ourselves into a corner. If we accept the successes of GR, we are forced to see the world and the cosmos through its eyes, and its eyes alone, since it is the theory which satisfies all known tests to date.

So, how should we think about the Big Bang? Our mental ‘fireworks’ image of the Big Bang contains these basic elements: 1) A pre-existing sky or space into which the fragments from the explosion are injected; 2) A pre-existing time we can use to mark when the explosion happened; 3) Individual projectiles moving through space from a common center; 4) A definite moment when the explosion occurred; and 5) Something that started the Big Bang.

All of these elements to our visualization of the Big Bang are completely false according to GR!

Preexisting Space?

There wasn’t any!

The mathematics of GR state specifically and unambiguously that 3-dimensional space was created at the Big Bang itself, at ‘Time Zero’, along with everything else. It was a ‘singular’ event in which the separations between all particles everywhere, vanished. This is just another way of saying that our familiar 3-dimensional space vanished. Theorists studying various prototypes for the Theory of Everything have only modified this statement somewhat. During its earliest moments, the universe may have existed in a nearly incomprehensible state which may have had more than 4 dimensions, or perhaps none at all. Many of these theories of the earliest moments hypothesize a ‘mother space-time’ that begat our own universe, but you cannot at the same time place your minds eye both inside this Mother Spacetime to watch the Big Bang happen, and inside our universe to see the matter flying around. This is exactly what the fireworks display model demands that you do.

Preexisting Time?

There wasn’t any of this either!

Again, GR’s mathematics treats both space and time together as one object called ‘space-time’ which is indivisible. At Time Zero plus a moment, you had a well defined quantity called time. At Time Zero minus a moment, this same quantity changed its character in the mathematics and became ‘imaginary’. This is a mathematical warning flag that something dreadfully unexpected has happened to time as we know it. In a famous quote by Einstein, “…time and space are modes by which we think and not conditions in which we live”. Steven Hawking has looked at the mathematics of this state using the fledgling physics of Quantum Gravity Theory, and confirms that at the Big Bang, time was murdered in the most thorough way imaginable. It may have been converted into just another ‘timeless’ dimension of space…or so the mathematics seems to suggest.

Individual objects moving out from a common center?

Nope!

GR says specifically that space is not a passive stage upon which matter plays out its dance, but is a member of the cast. When you treat both galaxies and space-time together, you get a very different answer for what happens than if you treat them separately, which is what we instinctively always do. Curved space distorts the paths of particles, sometimes in very dramatic ways. If you stepped into a space ship and tried to travel to the edge of the universe and look beyond, it would be impossible. Not only could you not reach a supposed “edge” of the universe no matter how long or how fast you traveled, in a closed universe, you would eventually find yourself arriving where you departed. The curvature of space would bring you right back, in something like the way the curvature of Earth would bring you home if you flew west and never changed course. In other words, the universe has no edge in space. There is nothing beyond the farthest star.

As a mental anchor, many have used the expanding balloon as an analogy to the expanding universe. As seen from any one spot on the balloon’s surface, all other spots rush away from it as the balloon is inflated. There is no one center to the expansion ON THE SURFACE of the balloon that is singled out as the center of the Big Bang. This is very different than the fireworks display which does have a dramatic, common center to the expanding cloud of cinders. The balloon analogy, however, is not perfect, because as we watch the balloon, our vantage point is still within a preexisting larger arena which GR says never existed for the real universe.

The center of the Big Bang was not a point in space, but a point in time! It is a center, not in the fabric of the balloon, but outside it along the 4th dimension…time. We cannot see this point anywhere we look inside the space of our universe out towards the distant galaxies. You can’t see time afterall! We can only see it as we look back in time at the ancient images we get from the most distant objects we can observe. We see a greatly changed, early history of the universe in these images but no unique center to them in space.

It is at this point that common sense must give up its seat on the bus, and yield to the insights provided by GR. And it is at precisely this point that so many non-physicists refuse to be so courteous. And who can blame them? But there’s more to come.

Projectiles moving through space?

Sorry!

GR again has something very troubling to say about this. For millions of years we have learned from experience on the savanas of the African continent and elsewhere, that we can move through space. As we drive down the highway, we have absolutely no doubts what is happening as we traverse the distance between landmarks along the roadside. This knowledge is so primal that we are incapable of mustering much doubt about it. But science is not about confirming our prejudices. It’s about revealing how things actually are.

What if I told you that you could decrease the distance from your house and the Washington Monument by ‘standing still’ and just letting space contract the distance away? GR predicts exactly this new phenomenon, and the universe seems to be the only arena we know today in which it naturally occurs. Like spots glued to the surface of the balloon at eternally fixed latitude and longitude points, the galaxies remain where they are while space dilates between them with the passage of time. There is no reason at all we should find this kind of motion intuitive.

If space is stretching like this, where do the brand new millions of cubic light years come from, from one moment to the next? The answer in GR is that they have always been there. To see how this could happen, I like to think of the shape of our universe as a “Cosmic Watermellon”. The fact that this is only the shape for a ‘closed’ finite universe is only a technicality. Finite watermellons are also cheaper to buy than infinite ones.

GR predicts the entire past, present and future of the universe all at once, and predicts its entire 4-dimensional shape. As we slice the 4-dimensional, Cosmic Watermellon at one end of the cosmic time line, we see 3-dimensional space and its contents soon after the Big Bang. At the other end of the Cosmic Watermellon in the far future, we see the collapse of space and matter just before the Big Crunch. But in between, our slices show the shape of space (closed, spherical volumes) and the locations of galaxies ( at fixed locations) as space dilates from one extreme to the other.

As a particular slice through an ordinary watermellon, we see that its meat has always been present in the complete watermellon. The meat is present as a continuous medium, and we never ask where the meat in a particular slice came from. Cosmologically, GR ask us to please think of 3-dimensional space in the same way. Space, like the meat of the watermellon, has always existed in the complete shape of the universe in 4-dimensions. But it is only in 4-dimensions that the full shape of the universe is revealed. It is a mystery why our consciousness insists on experiencing the universe one moment at a time, and that is why we end up with the paradox of where space comes from. There really is no paradox at all.

Space is not ‘nothing’ according to Einstein, it is merely another name for the gravitational field of the universe. Einstein once said, “Space-time does not claim existence on its own but only as a structural quality of the [gravitational] field”. If you could experimentally turn-off gravity with a switch, space-time would vanish. This is the ultimate demolition experiment known to physics for which an environmental impact statement would most certainly have to be filed.

The gravitational field at one instant is wedded to itself in the next instant by the incessant quantum churnings of the myriad of individual particles that like bees in a swarm, make up the gravitational field itself. In this frothing tumult, the gravitational field is knit together, quantum by quantum, from perhaps even more elemental building blocks, and it is perhaps here that we will find the ultimate origin for the expansion of the universe and the magical stretching of space. We hope the much anticipated Theory of Everything will have more to say about this, but to actually test this theory may require technologies and human resources that we can only dimly dream of.

Was there a definite moment to the Big Bang?

GR is perfectly happy to forecast that our universe emerged from an infinite density, zero-space ‘Singularity’ at Time Zero, but physicists now feel very strongly that this instant was smeared out by any number of quantum mechanical effects, so that we can never speak of a time before about 10^-43 seconds after the Big Bang. Just as Gertrude Stein once remarked about my hometown, Oakland, California that “There is no ‘There’ there”, at 10^-43 seconds, nature may tell us that before the Big Bang, “There was no ‘When’ there” either. The moment dissolves away into some weird quantum fog, and as Steven Hawking speculates, time may actually become bent into a new dimension of space and no longer even definable in this state. Ordinary GR is unable to describe this condition and only some future theory combing GR and quantum mechanics will be able to tell us more. We hope.

Something started the Big Bang!

At last we come to the most difficult issue in modern cosmology. In the fireworks display, we can trace the events leading up to the explosion all the way back to the chemists that created the gunpowder and wrapped the explosives. GR, however, can tell us nothing about the equivalent stages leading up to the Big Bang, and in fact, among its strongest statements is the one that says that time itself may not have existed. How, then, do we speak or think about a condition, or process, that started the whole shebang if we are not even allowed to frame the event as “This happened first…then this…then kerpowie!”? This remains the essential mystery of the Big Bang which seems to doggedly transcend every mathematical description we can create to describe it.

All of the logical frameworks we know about are based on chains of events or states. All of our experiences of such chains in the physical world have been ordered in time. Even when the mathematics and the theory tell us ‘What happened before the Big Bang to start it?’ is not a logical or legitimate question, we insist on viewing this as a proper question to ask of nature, and we expect a firm answer. But like so many other things we have learned this century about the physical world, our gut instincts about which questions ought to have definite answers is often flawed when we explore the extreme limits to our physical world.

I wrote this essay before seeing the new IMAX file at the Air and Space Museum ‘Cosmic Journey”, by far one of the nicest and most heroic movies of its kind I had ever seen. But of course it showed the Big Bang as a fireworks display. No matter. It doesn’t take a rocket scientist to accept the fact that the Big Bang was a spectacular moment in history. What is amazing is that the daring audacity of humans may have demystified some of it, and revealed a universe far stranger than any could have imagined.

Still, we are haunted by our hunches and intuitions gathered over millenia, and under circumstances far removed from the greater physical world we are now exploring. No wonder it all seems so alien and maddeningly complex.

Astronomy, Physics

Before the Big Bang

Beyond the Big Bang

Written by Sten Odenwald Copyright (C) 1987, Kalmbach Publishing. Reprinted by permission

Sometime between 15 and 20 billion years ago the universe came into existence. Since the dawn of human awareness, we have grappled with the hows and whys of this event and out of this effort have sprung many ideas. An ancient Egyptian legend describes how the universe was created by Osiris Khepera out of a dark, boundless ocean called Nu and that Osiris Khepera created himself out of this ocean by uttering his own name. Human inventiveness has not stood still in the 5000 years since these ideas were popular. The modern theory of the Big Bang states that our universe evolved from an earlier phase billions of times hotter than the core of our sun and trillions of times denser than the nucleus of an atom. To describe in detail such extreme physical conditions, we must first have a firm understanding of the nature of matter and of the fundamental forces. At the high temperatures likely to have attended the Big Bang, all familiar forms of matter were reduced to their fundamental constituents. The forces of gravity and electromagnetism together with the strong and weak nuclear forces, were the essential means through which the fundamental particles of matter interacted.
The feedback between cosmology and particle physics is nowhere more clearly seen than in the study of the early history of the universe. In October, 1985 the giant accelerator at Fermilab acheived for the first time, the collision of protons and anti-protons at energies of 1.6 trillion electron volts, about 1600 times the rest mass of the proton. This was a unique event because for one split second, on a tiny planet in an undistinguished galaxy, a small window onto the Creation Event was opened for the first time in at least 15 billion years.

THE LIMITS OF CERTAINTY

The persuit by physicists of a single, all encompassing theory capable of describing the four natural forces has, as a by-product, resulted in some surprising glimpses of the Creation Event. Although such a theory remains perhaps several decades from completion, it is generally recognized that such a theory will describe physical conditions so extreme it is quite possible that we may never be able to explore them first- hand, even with the particle accelerators that are being designed today. For example, the Superconducting Supercollider to be built by the early 1990’s will cost 6 billion dollars and it will allow physicists to collide particles at energies of 40 trillion electron volts ( 40,000 GeV) matching the conditions prevailing 10 seconds after the Big Bang. The expected windfall from such an accelerator is enormous and will help to answer many nagging questions now plaguing the theoretical community, but can we afford to invest perhaps vastly larger sums of money to build machines capable of probing the quantum gravity world at 10 GeV? At these energies, the full unification of the natural forces is expected to become directly observable. How curious it is that definite answers to questions such as, ‘What was Creation like?’ and ‘Do electrons and quarks have internal structure?’ are so inextricably intertwined. Our ability to find answers to these two questions, among others, does not seem to be hampered by some metaphysical prohibition, but by the resources our civilization can afford to devote to finding the answers. Fortunatly, the situation is not quite so bleak, for you see, the ‘machine’ has already been ‘built’ and every possible experiment we can ever imagine has already been performed!

WHAT WE THINK WE KNOW

We are living inside the biggest particle accelerator ever created – the universe. Ten billion years before the sun was born, Nature’s experiment in high-energy physics was conducted and the experimental data can now be examined by studying the properties and contents of the universe itself. The collection of fundamental facts that characterize our universe is peculiar in that it derives from a variety of sources. A partial list of these ‘meta-facts’ looks like this:

1) We are here, therefore, some regions of the universe are hospitible to the creation of complex molecules and living, rational organisms.

2) Our Universe has 4 big dimensions and all are increasing in size as the universe expands in time and space.

3) There are 4 dissimilar forces acting in Nature.

4) Only matter dominates; no anti-matter galaxies exist and this matter is built out of 6 quarks and 6 types of leptons.

The task confronting the physicist and the astronomer is to create, hopefully, a single theory consistent with these metafacts that can then be used to derive the secondary characteristics of our universe such as the 2.7 K background radiation, the primordial element abundances, and galaxy formation. The interplay between the study of the macrocosm and the microcosm has now become so intense that astronomers have helped physicists set limits to the number of lepton families — No more than 4 are allowed otherwise the predicted cosmological abundance of helium would seriously disagree with what is observed. Physicists, on the other hand, use the astronomical upper limits to the current value of the cosmological constant to constrain their unification theories.

An extention to the standard Big Bang model called the Inflationary Universe (see The Decay of the False Vacuum) was created by MIT physicist Alan Guth in 1981. This theory combined Grand Unification Theory with cosmology and, if correct, allows astronomers to trace the history of the universe all the way back to 10 seconds after the Big Bang when the strong, weak and electromagnetic forces were unified into a single ‘electro-nuclear’ force. During the 4 years since the Inflationary Universe model was proposed, other theoretical developments have emerged that may help us probe events occurring at an even earlier stage, perhaps even beyond the Creation Event itself. Ten years ago, theoreticians discovered a new class of theories called Supersymmetric Grand Unified Theories ( SUSY GUTs). These theories, of which there are several competing types, have shown great promise in providing physicists with a unified framework for describing not just the electro-nuclear force but also gravity, in addition to the particles they act on (see The Planck Era: March 1984). Unfortunately, as SUSY GUTs were studied more carefully, it was soon discovered that even the most promising candidates for THE Unified Field Theory suffered from certain fundamantal deficiencies. For instance:

1) There were not enough basic fields predicted to accomodate the known particles.

2) Left and right-hand symmetry was mandated so that the weak force, which breaks this symmetry, had to be put in ‘by hand’.

3) Anomalies exist which include the violation of energy conservation and charge.

4) The Cosmological Constant is 10 times larger than present upper limits suggest.

In recent years, considerable effort has gone into extending and modifying the postulates of SUSY GUTs in order to avoid these problems. One avenue has been to question the legitimacy of a very basic premise of the field theories developed heretofore. The most active line of theoretical research in the last 25 years has involved the study of what are called ‘point symmetry groups’. For example, a hexagon rotated by 60 degrees about a point at its center is indistinguishable from one rotated by 120, 180, 240, 300 and 360 degrees. These 6 rotation operations form a mathematical group so that adding or subtracting any two operations always result in a rotation operation that is already a member of the group ( 180 = 120 + 60 etc). The Grand Unification Theories of the electro-nuclear interaction are based on point symmetry groups named SU(3), SU(2) and U(1) which represent analogous ‘rotations’ in a more complex mathematical space. In the context of ponderable matter, point symmetry groups are also the mathematical statement of what we believe to be the structure of the fundamental particles of matter, namely, that particles are point-like having no physical size at all. But what if this isn’t so? The best that experimental physics has to offer is that the electron which is one of a family of 6 known Leptons, behaves like a point particle at scales down to 10 cm, but that’s still an enormous distance compared to the gravitational Planck scale of 10 cm where complete unification with gravity is expected to occur.

By assuming that fundamental particles have internal structure, Michael Green at Queen Mary College and John Schwartz at Caltech made a remarkable series of discoveries which were anounced in the journal NATURE in April 1985. They proposed that, if a point particle were replaced by a vibrating ‘string’ moving through a 10-dimensional spacetime, many of the problems plaguing SUSY GUTs seemed to vanish miraculously. What’s more, of all the possible kinds of ‘Superstring’ theories, there were only two ( called SO(32) and E8 x E8′) that were: 1) Consistent with both the principles of relativity and quantum mechanics,2) Allowed for the asymmetry between left and right-handed processes and, 3) Were free of anomalies. Both versions were also found to have enough room in them for 496 different types of fields; enough to accomodate all of the known fundamental particles and then some! Superstring theories also have very few adjustable parameters and from them, certain quantum gravity calculations can be performed that give finite answers instead of infinite ones. In spite of their theoretical successes, Superstring theories suffer from the difficulty that the lightest Superstring particles will be completely massless while the next more massive generation will have masses of 10 GeV. It is not even clear how these supermassive string particles are related to the known particles which are virtually massless by comparison (a proton has a mass of 1 GeV!). It is also not known if the 496 different particles will cover the entire mass range between 0 and 10 GeV. It is possible that they may group themselves into two families with masses clustered around these two extreems. In the later instance, experimental physicists may literally run out of new particles to discover until accelerators powerful enough to create supermassive particles can be built.

An attractive feature of the SO(32) model, which represents particles as open-ended strings, is that gravity has to be included from the start in order to make the theory internally consistent and capable of yielding finite predictions. It is also a theory that reduces to ordinary point field theories at energies below 10 GeV. The complimentary theory, E8 x E8′, is the only other superstring theory that seems to work as well as SO(32) and treats particles as though they were closed strings without bare endpoints. This model is believed to show the greatest promise for describing real physical particles. It also includes gravity, but unlike SO(32), E8 x E8′ does seem to reduce at low energy, to the symmetry groups associated with the strong, weak and electromagnetic interactions, namely, SU(3), SU(2) and U(1).

If E8 x E8′ is destined to be the ‘ultimate, unified field theory’, there are some additional surprises in store for us. Each group, E8 and E8′, can be reduced mathematically to the products of the groups that represent the strong, weak and electromagnetic forces; SU(3) x SU(2) x U(1). If the E8 group corresponds to the known particles what does E8′ represent? In terms of its mathematical properties, symmetry considerations alone seem to require that the E8′ group should be a mirror image of E8. If E8 contains the groups SU(3), SU(2) and U(1) then E8′ contains SU(3)’, SU(2)’ and U(1)’. The primed fields in E8′ would have the same properties as those we ascribe to the strong, weak and electromagnetic forces. The E8′ particle fields may correspond to a completly different kind of matter, whose properties are as different from matter and anti-matter as ordinary matter is from anti-matter! ‘Shadow Matter’ as it has been called by Edward Kolb, David Seckel and Michael Turner at Fermilab, may actually co-exist with our own – possibly accounting for the missing mass necessary to close the universe. Shadow matter is only detectable by its gravitational influence and is totally invisible because the shadow world electromagnetic force (shadow light) does not interact with any of the particles in the normal world.

BEYOND SPACE AND TIME

The quest for a mathematical description of the physical world uniting the apparent differences between the known particles and forces, has led physicists to the remarkable conclusion that the universe inhabits not just the 4 dimensions of space and time, but a much larger arena whose dimensionality may be enormous (see Does Space Have More Than 3 Dimensions?). Both the Superstring theories and SUSY GUTs agree that our physical world has to have more than the 4 dimensions we are accustomed to thinking about. A remarkable feature of Superstring theory is that of all the possible dimensionalities for spacetime, only in 10-dimensions ( 9 space dimensions and 1 time dimension) will the theory lead to a computationally finite and internally consistent model for the physical world that includes the weak interaction from the outset, and where all of the troublesome anomalies cancil exactly. In such a 10-dimensional world, it is envisioned that 6 dimensions are now wrapped-up or ‘compactified’ into miniscule spheres that accompany the 4 coordinates of every point in spacetime. What would a description of the early universe look like from this new viewpoint? The 6 internal dimensions are believed to have a size of order 10 cm.

As we follow the history of the universe back in time, the 3 large dimensions of space rapidly shrink until eventually they become only 10 cm in extent. This happened during the Planck Era at a time, 10 seconds after the Creation Event. The appearance of the universe under these conditions is almost unimaginable. Today as we look out at the most distant quasar, we see them at distances of billions of lightyears. During the Planck Era, the matter comprising these distant systems was only 10 cm away from the material that makes-up your own body!

What was so special about this era that only 4 of the 10 dimensions were singled-out to grow to their enormous present size?. Why not 3 ( 2 space + 1 time) or 5 ( 4 space + 1 time)? Physicists have not as yet been able to develope an explanation for this fundamental mystery of our plenum, on the other hand, it may just be that had the dimensional breakdown of spacetime been other than ‘4 + 6’, the physical laws we are the products of, would have been totally inhospitable to life as we know it.

As we relentlessly follow the history of the universe to even earlier times, the universe seems to enter a progressively more and more symmetric state. The universe at 10 seconds after the Big Bang may have been populated by supermassive particles with masses of 10^15 GeV or about 10^-13 grams each. These particles ultimatly decayed into the familiar quarks and leptons once the universe had grown colder as it expanded. In addition, there may only have been a single kind of ‘superforce’ acting on these particles; a force whose character contained all of the individual attributes we now associate with gravity, electromagnetism and the strong and weak nuclear forces. Since the particles carrying the ‘superforce’ had masses similar to those of the supermassive particles co-existing then, the distinction between the force-carriers and the particles they act on probably broke-down completely and the world became fully supersymmetric.

To go beyond the Planck Era may require a radical alteration in our conventional way of thinking about time and space. Only glimpses of the appropriate way to think about this multidimensional landscape can be found in the equations and theories of modern-day physics. Beyond the Planck Era, all 10 dimensions (and perhaps others) become co-equal at least in terms of their physical size. The supermassive Superstring particles begin to take-on more of the characteristics of fluctuations in the geometry of spacetime than as distinguishable, ingredients in the primordial, cosmological ‘soup’. There was no single, unique geometry for spacetime but, instead, an ever-changing quantum interplay between spacetimes with an unlimited range in geometry. Like sound waves that combine with one another to produce interference and reinforcement, the spacetime that emerged from the Planck Era is thought to be the result of the superposition of an infin ite number of alternate spacetime geometries which, when added together, produced the spacetime that we are now a part of.

Was there light? Since the majority of the photons were probably not created in large numbers until at least the beginning of the Inflationary Epoc, 10^-36 seconds after the Big Bang, it is not unthinkable that during its earliest moments, the universe was born out of darkness rather than in a blinding flash of light. All that existed in this darkness before the advent of light, was an empty space out of which our 10-dimensional spacetime would later emerge. Of course, under these conditions it is unclear just how we should continue to think about time itself.

In terms of the theories available today, it may well be that the particular dimension we call Time had a definite zero point so that we can not even speak logically about what happened before time existed. The concept of ‘before’ is based on the presumption of time ordering. A traveler standing on the north pole can never move to a position on the earth that is 1 mile north of north! Nevertheless, out of ingrained habit, we speak of the time before the genesis of the universe when time didn’t exist and ask, “What happened before the Big Bang?”. The list of physicists investigating this ‘state’ has grown enormously over the last 15 years. The number of physicists, worldwide, that publish research on this topic is only slightly more than 200 out of a world population of 5 billion!

QUANTUM COSMOLOGY

In the early 1970’s Y. Zel’dovitch and A. Starobinski of the USSR along with Edward Tryon at Hunter College proposed that the universe emerged from a fluctuation in the vacuum. This vacuum fluctuation ‘ran away’ with itself, creating all the known particles out of empty space at the ‘instant’ of no-time. To understand what this means requires the application of a fundamental fact of relativistic quantum physics discovered during the latter half of the 1920’s. Vacuum fluctuations are a direct consequence of Heisenberg’s Uncertainty Principle which limits how well we can simultaneously know a particle’s momentum and location (or its total energy and lifetime). What we call empty space or the physical vacuum is a Newtonian fiction like absolute space and time. Rather than a barren stage on which matter plays-out its role, empty space is known to be filled with ‘virtual particles’ that spontaneously appear and disappear beyond the ability of any physical measurement to detect directly. From these ghost particles, a variety of very subtle phenomena can be predicted with amazing accuracy. Depending on the total rest mass energy of the virtual particles created in the vacuum fluctuation, they may live for a specific lifetime before Heisenberg’s Uncertainty Principle demands that they vanish back into the nothingness of the vacuum state. In such a quantum world, less massive virtual particles can live longer than more massive ones. Edward Tyron proposed that the universe is just a particularly long-lived vacuum fluctuation differing only in magnitude from those which occur imperceptably all around us. The reason the universe is so long lived in spite of its enormous mass is that the positive energy latent in all the matter in the universe is offset by the negative potential energy of the gravitational field of the universe. The total energy of the universe is, therefore, exactly zero and its maximum lifetime as a ‘quantum fluctuation’ could be enormous and even infinite! According to Tryon, “The Universe is simply one of those things which happens from time to time.”

This proposal by Tryon was regarded with some scepticism and even amusement by astronomers, and was not persued much further. This was a fate that had also befallen the work on 5-dimensional general relativity by Theodore Kaluza and Oskar Klein during the 1920’s which was only resurrected in the late 1970’s as a potent remedy for the ills plaguing supersymmetry theory.

In 1978, R. Brout, P. Englert, E. Gunzig and P. Spindel at the University of Brussels, proposed that the fluctuation that led to the creation of our universe started out in an empty, flat, 4-dimensional spacetime. The fluctuation in space began weakly, creating perhaps a single matter- antimatter pair of supermassive particles with masses of 10^19 GeV. The existence of this ‘first pair’ stimulated the creation from the vacuum of more particle-antiparticle pairs which stimulated the production of still others and so on. Space became highly curved and exploded, disgorging all of the superparticles which later decayed into the familiar leptons, quarks and photons.

Heinz Pagels and David Atkatz at Rockefeller University in 1981 proposed that the triggering agent behind the Creation Event was a tunneling phenomenon of the vacuum from a higher-energy state to a lower energy state. Unlike the Brout-Englert-Gunzig-Spindel model which started from a flat spacetime, Pagels and Atkatz took the complimentary approach that the original nothingness from which the universe emerged was a spatially closed, compact empty space, in other words, it had a geometry like the 2-D surface of a sphere. but the dimensionality of its surface was much higher than 2. Again this space contained no matter what-so-ever. The characteristics (as yet unknown) of the tunneling process determined, perhaps in a random way, how the dimensionality of spacetime would ‘crystallize’ into the 6+4 combination that represents the plenum of our universe.

Alex Vilenkin at Tufts University proposed in 1983 that our spacetime was created out of a ‘nothingness’ so complete that even its dimensionality was undefined. In 1984, Steven Hawkings at Cambridge and James Hartle at UCSB came to a similar conclusion through a series of quantum mechanical calculations. They described the geometric state of the universe in terms of a wavefunction which specified the probability for spacetime to have one of an infinite number of possible geometries. A major problem with the ordinary Big Bang theory was that the universe emerged from a state where space and time vanished and the density of the universe became infinite; a state called the Singularity. Hawkings and Hartle were able to show that this Big Bang singularity represented a specific kind of geometry which would become smeared-out in spacetime due to quantum indeterminacy. The universe seemed to emerge from a non-singular state of ‘nothingness’ similar to the undefined state proposed by Vilenkin. The physicist Frank Wilczyk expresses this remarkable situation the best by saying that, ” The reason that there is Something rather than Nothing is that Nothing is unstable.”

PERFECT SYMMETRY

Theories like those of SUSY GUTS and Superstrings seem to suggest that just a few moments after Creation, the laws of physics and the content of the world were in a highly symmetric state; one superforce and perhaps one kind of superparticle. The only thing breaking the perfect symmetry of this era was the definite direction and character of the dimension called Time. Before Creation, the primordial symmetry may have been so perfect that, as Vilenkin proposed, the dimensionality of space was itself undefined. To describe this state is a daunting challenge in semantics and mathematics because the mathematical act of specifying its dimensionality would have implied the selection of one possibility from all others and thereby breaking the perfect symmetry of this state. There were, presumably, no particles of matter or even photons of light then, because these particles were born from the vacuum fluctuations in the fabric of spacetime that attended the creation of the universe. In such a world, nothing happens because all ‘happenings’ take place within the reference frame of time and space. The presence of a single particle in this nothingness would have instantaneously broken the perfect symmetry of this era because there would then have been a favored point in space different from all others; the point occupied by the particle. This nothingness didn’t evolve either, because evolution is a time-ordered process. The introduction of time as a favored coordinate would have broken the symmetry too. It would seem that the ‘Trans-Creation’ state is beyond conventional description because any words we may choose to describe it are inherently laced with the conceptual baggage of time and space. Heinz Pagels reflects on this ‘earliest’ stage by saying, “The nothingness ‘before’ the creation of the universe is the most complete void we can imagine. No space, time or matter existed. It is a world without place, without duration or eternity…”

A perusal of the scientific literature during the last 20 years suggests that we may be rapidly approaching a major crossroad in physics. One road seems to be leading to a single unification theory that is so unique among all others that it is the only one consistent with all the major laws we know about. It is internally consistent; satisfies the principles of relativity and quantum mechanics and requires no outside information to describe the particles and forces it contains . A prototype of this may be superstring theory with its single adjustable parameter, namely, the string tension. The other road is much more bleak. It may also turn out that we will create several theoretical systems that seem to explain everything but have within them hard to detect flaws. These flaws may stand as barracades to further logical inquiry; to be uncovered only through experiments that may be beyond our technological reach. It is possible that we are seeing the beginning of this latter process even now, with the multiplicity of theories whose significant deviations only occur at energies near 10^19 GeV.

I find it very hard to resist the analogy between our current situation and that of the Grecian geometers. For 2000 years the basic postulates of Eulidean geometry and the consequences of this logical system, remained fixed. It became a closed book with only a few people in the world struggling to find exceptions to it such as refutations of the parallel line postulate. Finally during the 19th century, non-euclidean geometry was discovered and a renaissance in geometry occurred. Are physicists on the verge of a similar great age, finding themselves hamstrung by not being able to devise new ways of thinking about old problems? Egyptian cosmology was based on motifs that the people of that age could see in the world around them; water, sky, land, biological reproduction. Today we still use motifs that we find in Nature in order to explain the origin of the universe; the geometry of space, virtual particles and vacuum fluctuations. We can probably expect that in the centuries to follow, our descendents will find still other motifs and from them, fashion cosmologies that will satisfy the demands of that future age with, possibly, much greater accuracy and efficiency than ours do today. Perhaps, too, in those future ages, scientists will marvel at the ingenuity of modern physicists and astronomers, and how in the space of only 300 years, we had managed to create our own quaint theory as the Egyptians had before us.

In the meantime, physicists and astronomers do the best they can to fashion a cosmology that will satisfy the intellectual needs of our age. Today, as we contemplate the origin of the universe we find ourselves looking out over a dark, empty void not unlike the one that our Egyptian predecessors might have imagined. This void is a state of exquisite perfection and symmetry that seems to defy description in any linguistic terms we can imagine. Through our theories we launch mathematical voyages of exploration, and watch the void as it trembles with the quantum possibilities of universes unimaginable.

Astronomy, Physics

What is Space? Part I

Does Space Have More Than 3 Dimensions?
Written by Sten Odenwald
Copyright (C) 1984 Kalmbach Publishing. Reprinted by permission

The intuitive notion that the universe has three dimensions seems to be an irrefutable fact. After all, we can only move up or down, left or right, in or out. But are these three dimensions all we need to describe nature? What if there aree, more dimensions ? Would they necessarily affect us? And if they didn’t, how could we possibly know about them? Some physicists and mathematicians investigating the beginning of the universe think they have some of the answers to these questions. The universe, they argue, has far more than three, four, or five dimensions. They believe it has eleven! But let’s step back a moment. How do we know that our universe consists of only three spatial dimensions? Let’s take a look at some “proofs.”

On a 2-dimensional piece of paper you can draw an infinite number of polygons.  But when you try this same trick in 3-dimensions you run up against a problem.There are five and only five regular polyhedra. A regular polyhedron is defined as a solid figure whose faces are identical polygons – triangles, squares, and pentagons – and which is constructed so that only two faces meet at each edge. If you were to move from one face to another, you would cross over only one edge. Shortcuts through the inside of the polyhedron that could get you from one face to another are forbidden. Long ago, the mathematician Leonhard Euler demonstrated an important relation between the number of faces (F), edges (E), and corners (C) for every regular polyhedron: C – E + F = 2. For example, a cube has 6 faces, 12 edges, and 8 corners while a dodecahedron has 12 faces, 30 edges, and 20 corners. Run these numbers through Euler’s equation and the resulting answer is always two, the same as with the remaining three polyhedra. Only five solids satisfy this relationship – no more, no less.

Not content to restrict themselves to only three dimensions, mathematicians have generalized Euler’s relationship to higher dimensional spaces and, as you might expect, they’ve come up with some interesting results. In a world with four spatial dimensions, for example, we can construct only six regular solids. One of them – the “hypercube” – is a solid figure in 4-D space bounded by eight cubes, just as a cube is bounded by six square faces. What happens if we add yet another dimension to space? Even the most ambitious geometer living in a 5-D world would only be able to assemble thee regular solids. This means that two of the regular solids we know of – the icosahedron and the dodecahedron – have no partners in a 5-D universe.
For those of you who successfully mastered visualizing a hypercube, try imagining what an “ultracube” looks like. It’s the five- dimensional analog of the cube, but this time it is bounded by one hypercube on each of its 10 faces! In the end, if our familiar world were not three-dimensional, geometers would not have found only five regular polyhedra after 2,500 years of searching. They would have found six (with four spatial dimension,) or perhaps only three (if we lived in a 5-D universe). Instead, we know of only five regular solids. And this suggests that we live in a universe with, at most, three spatial dimensions.

All right, let’s suppose our universe actually consists of four spatial dimensions. What happens? Since relativity tells us that we must also consider time as a dimension, we now have a space-time consisting of five dimensions. A consequence of 5-D space-time is that gravity has freedom to act in ways we may not want it to.

To the best available measurements, gravity follows an inverse square law; that is, the gravitational attraction between two objects rapidly diminishes with increasing distance. For example, if we double the distance between two objects, the force of gravity between them becomes 1/4 as strong; if we triple the distance, the force becomes 1/9 as strong, and so on. A five- dimensional theory of gravity introduces additional mathematical terms to specify how gravity behaves. These terms can have a variety of values, including zero. If they were zero, however, this would be the same as saying that gravity requires only three space dimensions and one time dimension to “give it life.” The fact that the Voyager space- craft could cross billions of miles of space over several years and arrive vithin a few seconds of their predicted times is a beautiful demonstration that we do not need extra-spatial dimensions to describe motions in the Sun’s gravitational field.

From the above geometric and physical arguments, we can conclude (not surprisingly) that space is three-dimensional – on scales ranging from that of everyday objects to at least that of the solar system. If this were not the case, then geometers would have found more than five regular polyhedra and gravity would function very differently than it does – Voyager would not have arrived on time. Okay, so we’ve determined that our physical laws require no more than the three spatial dimensions to describe how the universe works. Or do they? Is there perhaps some other arena in the physical world where multidimensional space would be an asset rather than a liability?

Since the 1920s, physicists have tried numerous approaches to unifying the principal natural interactions: gravity, electromagnetism, and the strong and weak forces in atomic nuclei. Unfortunately, physicists soon realized that general relativity in a four-dimensional space-time does not have enough mathematical “handles” on which to hang the frameworks for the other three forces. Between 1921 and 1927, Theodor Kaluza and Oskar Klein developed the first promising theory combining gravity and electromagnetism. They did this by extending general relativity to five dimensions. For most of us, general relativity is mysterious enough in ordinary four-dimensional space-time. What wonders could lie in store for us with this extended universe?

General relativity in five dimensions gave theoreticians five additional quantities to manipulate beyond the 10 needed to adequately define the gravitational field. Kaluza and Klein noticed that four of the five extra quantities could be identified with the four components needed to define the electromagnetic field. In fact, to the delight of Kaluza and Klein, these four quantities obeyed the same types of equations as those derived by Maxwell in the late 1800s for electromagnetic radiationl Although this was a promising start, the approach never really caught on and was soon buried by the onrush of theoretical work on the quantum theory of electromagnetic force. It was not until work on supergravity theory began in 1975 that Kaluza and Klein’s method drew renewed interest. Its time had finally come.

What do theoreticians hope to gain by stretching general relativity beyond the normal four dimensions of space-time? Perhaps by studying general relativity in a higher-dimensional formulation, we can explain some of the constants needed to describe the natural forces. For instance, why is the proton 1836 times more massive than the electron? Why are there only six types of quarks and leptons? Why are neutrinos massless? Maybe such a theory can give us new rules for calculating the masses of fundamental particles and the ways in which they affect one another. These higher-dimensional relativity theories may also tell us something about the numbers and properties of a mysterious new family of particles – the Higgs bosons – whose existence is predicted by various cosmic unification schemes. (See “The Decay of the False Vacuum,” ASTRONOMY, November 1983.)

These expectations are not just the pipedreams of physicists – they actually seem to develop as natural consequences of certain types of theories studied over the last few years. In 1979, John Taylor at Kings College in London found that some higher- dimensional formalisms can give predictions for the maximum mass of the Higgs bosons (around 76 times that of the proton.) As they now stand, unification theories can do no more than predict the existence of these particles – they cannot provide specific details about their physical characteristics. But theoreticians may be able to pin down some of these details by using extended theories of general relativity. Experimentally, we know of six leptons: the electron, the muon, the tauon, and their three associated neutrinos. The most remarkable prediction of these extended relativity schemes, however, holds that the number of leptons able to exist in a universe is related to the number of dimensions of space-time. In a 6-D space-time, for example, only one lepton – presumably the electron – can exist. In a 10-D space-time, four leptons can exist – still not enough to accommodate the six we observe. In a 12-D space- time, we can account for all six known leptons – but we also acquire two additional leptons that have not yet been detected. Clearly, we would gain much on a fundamental level if we could increase the number of dimensions in our theories just a little bit.

How many additional dimensions do we need to consider in order to account for the elementary particles and forces that we know of today? Apparently we require at least one additional spatial dimension for every distinct “charge” that characterizes how each force couples to matter. For the electromagnetic force, we need two electric charges: positive and negative. For the strong force that binds quarks together to form, among other things, protons and neutrons, we need three “color” charges – red, blue, and green. Finally, we need two “weak” charges to account for the weak nuclear force. if we add a spatial dimension for each of these charges, we end up with a total of seven extra dimensions. The properly extended theory of general relativity we seek is one with an 11 -dimensional space-time, at the very least. Think of it – space alone must have at least 10 dimensions to accomodate all the fields known today.

Of course, these additional dimensions don’t have to be anything like those we already know about. In the context of modern unified field theory, these extra dimensions are, in a sense, internal to the particles themselves – a “private secret,” shared only by particles and the fields that act on them! These dimensions are not physically observable in the same sense as the three spatial dimensions we experience; they’stand in relation to the normal three dimensions of space much like space stands in relation to time.

With today’s veritable renaissance in finding unity among the forces and particles that compose the cosmos, some by methods other than those we have discussed, these new approaches lead us to remarkably similar conclusions. It appears that a four-dimensional space-time is simply not complex enough for physics to operate as it does.

We know that particles called bosons mediate the natural forces. We also know that particles called fermions are affected by these forces. Members of the fermion family go by the familiar names of electron, muon, neutrino, and quark; bosons are the less well known graviton, photon, gluon, and intermediate vector bosons. Grand unification theories developed since 1975 now show these particles to be “flavors” of a more abstract family of superparticies – just as the muon is another type of electron. This is an expression of a new kind of cosmic symmetry – dubbed supersymmetry, because it is all-encompassing. Not only does it include the force-carrying bosons, but it also includes the particles on which these forces act. There also exists a corresponding force to help nature maintain supersymmetry during the various interactions. It’s called supergravity. Supersymmetry theory introduces two new types of fundamental particles – gravitinos and photinos. The gravitino has the remarkable property of mathematically moderating the strength, of various kinds of interactions involving the exchange of gravitons. The photino, cousin of the photon, may help account for the “missing mass” in the universe.

Supersymmetry theory is actually a complex of eight different theories, stacked atop one another like the rungs of a ladder. The higher the rung, the larger is its complement of allowed fermion and boson particle states. The “roomiest” theory of all seems to be SO(8), (pronounced ess-oh-eight), which can hold 99 different kinds of bosons and 64 different kinds of fermions. But SO(8) outdoes its subordinate, SO(7), by only one extra dimension and one additional particle state. Since SO(8) is identical to SO(7) in all its essential features, we’ll discuss SO(7) instead. However, we know of far more than the 162 types of particles that SO(7) can accommodate, and many of the predicted types have never been observed (like the massless gravitino). SO(7) requires seven internal dimensions in addition to the four we recognize – time and the three “every day” spatial dimensions. If SO(7) at all mirrors reality, then our universe must have at least 11 dimensions! Unfortunately, it has been demonstrated by W. Nahm at the European Center for Nuclear Research in Geneva, Switzerland that supersymmetry theories for space-times with more than 11 dimensions are theoretically impossible. SO(7) evidently has the largest number of spatial dimensions possible, but it still doesn’t have enough room to accommodate all known types of particles.

It is unclear where these various avenues of research lead. Perhaps nowhere. There is certainly ample historical precedent for ideas that were later abandoned because they turned out to be conceptual dead-ends. Yet what if they turn out to be correct at some level? Did our universe begin its life as some kind of 11-dimensional “object” which then crystallized into our four- dimensional cosmos?

Although these internal dimensions may not have much to do with the real world at the present time, this may not always have been the case. E. Cremmer and J. Scherk of I’Ecole Normale Superieure in Paris have shown that just as the universe went through phase transitions in its early history when the forces of nature became distinguishable, the universe may also have gone through a phase transition when mensionality changed. Presumably matter has something like four external dimensions (the ones we encounter every day) and something like seven internal dimensions. Fortunately for us, these seven extra dimensions don’t reach out into the larger 4-D realm where we live. If they did, a simple walk through the park might become a veritable obstacle course, littered with wormholes in space and who knows what else!

Alan Chocos and Steven Detweiler of Yale University have considered the evolution of a universe that starts out being five- dimensional. They discovered that while the universe eventually does evolve to a state where three of the four spatial dimensions expand to become our world at large, the extra fourth spatial dimension shrinks to a size of 10^-31 centimeter by the present time. The fifth dimension to the universe has all but vanished and is 20 powers of 10 – 100 billion billion times – smaller than the size of a proton. Although the universe appears four- dimensional in space-time, this perception is accidental due to our large size compared to the scale of the other dimensions. Most of us think of a dimension as extending all the way to infinity, but this isn’t the full story. For example, if our universe is really destined to re-collapse in the distant future, the three- dimensional space we know today is actually limited itself – it will eventually possess a maximum, finite size. It just so happens that the physical size of human beings forces us to view these three spatial dimensions as infinitely large.

It is not too hard to reconcile ourselves to the notion that the fifth (or sixth, or eleventh) dimension could be smaller than an atomic nucleus – indeed, we can probably be thankful that this is the case.

Astronomy, Physics

Einstein’s Fudge

Einstein’s Cosmic Fudge Factor

Written by Sten Odenwald
Copyright (C) 1991. Sky Publishing Corporation. Reprinted by permission. See April, 1991 issue

Black holes…quarks…dark matter. It seems like the cosmos gets a little stranger every year. Until recently, the astronomical universe known to humans was populated by planets, stars, galaxies, and scattered nebulae of dust and gas. Now, theoretists tell us it may also be inhabited by objects such as superstrings, dark matter and massive neutrinos — objects that have yet to be discovered if they exist at all!
As bizarre as these new constituents may sound, you don’t have to be a rocket scientist to appreciate the most mysterious ingredient of them all. It is the inky blackness of space itself that commands our attention as we look at the night sky; not the sparse points of light that signal the presence of widely scattered matter.

During the last few decades, physicists and astronomers have begun to recognize that the notion of empty space presents greater subtleties than had ever before been considered. Space is not merely a passive vessel to be filled by matter and radiation, but is a dynamic, physical entity in its own right.

One chapter in the story of our new conception of space begins with a famous theoretical mistake made nearly 75 years ago that now seems to have taken on a life of its own.

In 1917, Albert Einstein tried to use his newly developed theory of general relativity to describe the shape and evolution of the universe. The prevailing idea at the time was that the universe was static and unchanging. Einstein had fully expected general relativity to support this view, but, surprisingly, it did not. The inexorable force of gravity pulling on every speck of matter demanded that the universe collapse under its own weight.

His remedy for this dilemma was to add a new ‘antigravity’ term to his original equations. It enabled his mathematical universe to appear as permanent and invariable as the real one. This term, usually written as an uppercase Greek lambda, is called the ‘cosmological constant’. It has exactly the same value everywhere in the universe, delicately chosen to offset the tendency toward gravitational collapse at every point in space.

A simple thought experiment may help illustrate the nature of Lambda. Take a cubic meter of space and remove all matter and radiation from it. Most of us would agree that this is a perfect vacuum. But, like a ghost in the night, the cosmological constant would still be there. So, empty space is not really empty at all — Lambda gives it a peculiar ‘latent energy’. In other words, even Nothing is Something!

Einstein’s fudged solution remained unchallenged until 1922 when the Russian mathematician Alexander Friedmann began producing compelling cosmological models based on Einstein’s equations but without the extra quantity. Soon thereafter, theorists closely examining Einstein’s model discovered that, like a pencil balanced on its point, it was unstable to collapse or expansion. Later the same decade, Mount Wilson astronomer Edwin P. Hubble found direct observational evidence that the universe is not static, but expanding.

All this ment that the motivation for introducing the cosmological constant seemed contrived. Admitting his blunder, Einstein retracted Lambda in 1932. At first this seemed to end the debate about its existence. Yet decades later, despite the great physicist’s disavowal, Lambda keeps turning up in cosmologists’ discussions about the origin, evolution, and fate of the universe.

THEORY MEETS OBSERVATION

Friedmann’s standard ‘Big Bang’ model without a cosmological constant predicts that the age of the universe, t0, and its expansion rate (represented by the Hubble parameter, H0) are related by the equation t0 = 2/3H0. Some astronomers favor a value of H0 near 50 kilometers per second per megaparsec (one megaparsec equals 3.26 million light years). But the weight of the observational evidence seems to be tipping the balance towards a value near 100. In the Friedmann model, this implies that the cosmos can be no more than 7 billion years old. Yet some of our galaxy’s globular clusters have ages estimated by independent methods of between 12 and 18 billion years!

In what’s called the Einstein-DeSitter cosmology, the Lambda term helps to resolve this discrepancy. Now a large value for the Hubble parameter can be attributed in part to “cosmic repulsion”. This changes the relationship between t0 and H0, so that for a given size, the universe is older than predicted by the Friedmann model.

In one formulation of Einstein’s equation, Lambda is expressed in units of matter density. This means we can ask how the cosmological constant, if it exists at all, compares with the density of the universe in the forms of stars and galaxies.

So far, a careful look at the available astronomical data has produced only upper limits to the magnitude of Lambda. These vary over a considerable range – from about 10 percent of ordinary matter density to several times that density.

The cosmological constant can also leave its mark on the properties of gravitational lenses and faint galaxies. One of the remarkable features of Einstein’s theory of general relativity is its prediction that space and time become deformed or ‘warped’ in the vicinity of a massive body such as a planet, star or even a galaxy. Light rays passing through such regions of warped “space-time” have their paths altered. In the cosmological arena, nearby galaxies can deflect and distort the images of more distant galaxies behind them. Sometimes, the images of these distant galaxies can appear as multiple images surrounding the nearby ‘lensing’ galaxy.

At Kyoto University M. Fukugita and his coworkers predicted that more faint galaxies and gravitational lenses will be detected than in a Friedmann universe if Lambda is more than a few times the matter density. Edwin Turner, an astrophysicist at Princeton University also reviewed the existing, scant, data on gravitational lenses and found that they were as numerous as expected for Lambda less that a few times the matter density. By the best astronomical reconning, Lambda is probably not larger than the observed average matter density of the universe. For that matter, no convincing evidence is available to suggest that Lambda is not exactly equal to zero. So why not just dismiss it as an unnecessary complication? Because the cosmological constant is no longer, strictly, a construct of theoretical cosmology.

NOTHING AND EVERYTHING

To understand how our universe came into existence, and how its various ingredients have evolved, we must delve deeply into the fundamental constituents of matter and the forces that dictate how it will interact. This means that the questions we will have to ask will have more to do with physics than astronomy. Soon after the big bang, the universe was at such a high temperature and density that only the details of matter’s composition (quarks, electrons etc) and how they interact via the four fundamental forces of nature were important. They represented the most complex collections of matter in existence, long before atoms, planets, stars and galaxies had arrived on the scene.

For two decades now, physicists have been attempting to unify the forces and particles that make up our world – to find a common mathematical description that encompasses them all. Some think that such a Theory of Everything is just within reach. It would account not only for the known forms of matter, but also for the fundamental interactions among them: gravity, electromagnetism, and the strong and weak nuclear forces.

These unification theories are known by a variety of names: grand unification theory, supersymmetry theory and superstring theory. Their basic claim is that Nature operates according to a small set of simple rules called symmetries.

The concept of symmetry is at least as old as the civilization of ancient Greece, whos art and archetecture are masterworks of simplicity and balance. Geometers have known for a long time that a simple cube can be rotated 90 degrees without changing its outward appearance. In two dimensions, equalateral triangles look the same when they are rotated by 120 degrees. These are examples of the geometric concept of Rotation Symmetry.

There are parallels to geometric symmetry in the way that various physical phenomena and qualities of matter express themselves as well. For example, the well-known principle of the Conservation of Energy is a consequence of the fact that when some collections of matter and energy are examined at different times, they each have precisely the same total energy, just as a cube looks the same when it is rotated in space by a prescribed amount. Symmetry under a ‘shift in time’ is as closely related to the Conservation of Energy as is the symmetry of a cube when rotated by 90 degrees.

Among other things, symmetries of Nature dictate the strengths and ranges of the natural forces and the properties of the particles they act upon. Although Nature’s symmetries are hidden in today’s cold world, they reveal themselves at very high temperatures and can be studied in modern particle accelerators.

The real goal in unification theory is actually two-fold: not only to uncover and describe the underlying symmetries of the world, but to find physical mechanisms for ‘breaking’ them at low energy. After all, we live in a complex world filled with a diversity of particles and forces, not a bland world with one kind of force and one kind of particle!

Theoreticians working on this problem are often forced to add terms to their equations that represent entirely new fields in Nature. The concept of a field was invented by mathematicians to express how a particular quantity may vary from point to point in space. Physicists since the 18th century have adopted this idea to describe quantitatively how forces such as gravity and magnetism change at different distances from a body.

The interactions of these fields with quarks, electrons and other particles cause symmetries to break down. These fields are usually very different than those we already know about. The much sought after Higgs boson field, for example, was introduced by Sheldon Glashow, Abdus Salam and Steven Weinberg in their unified theory of the electromagnetic and weak nuclear forces.

Prior to their work, the weak force causing certain particles to decay, and the electromagnetic force responsible for the attraction between charged particles and the motion of compass needles, were both considered to be distinct forces in nature. By combining their mathematical descriptions into a common language, they showed that this distinction was not fundamental to the forces at all! A new field in nature called the Higgs field makes these two forces act differently at low temperature. But at temperatures above 1000 trillion degrees, the weak and electromagnetic forces become virtually identical in the way that they affect matter. The corresponding particles called the Higgs Boson not only cause the symmetry between the electromagnetic and weak forces to be broken at low temperature, but they are also responsible for confiring the property of mass on particles such as the electrons and the quarks!

There is, however a price that must be paid for introducing new fields into the mathematical machinery. Not only do they break symmetries, but they can also give the vacuum state an enormous latent energy that, curiously, behaves just like Lambda in cosmological models.

The embarrassment of having to resurrect the obsolete quantity Lambda is compounded when unification theories are used to predict its value. Instead of being at best a vanishingly minor ingredient to the universe, the predicted values are in some instances 10 to the power of 120 times greater than even the most generous astronomical upper limits!

It is an unpleasant fact of life for physicists that the best candidates for the Theory of Everything always have to be fine-tuned to get rid of their undesirable cosmological consequences. Without proper adjustment, these candidates may give correct predictions in the microscopic world of particle physics, but predict a universe which on its largest scales looks very different from the one we inhabit.

Like a messenger from the depths of time, the smallness – or absence – of the cosmological constant today is telling us something important about how to craft a correct Theory of Everything. It is a signpost of the way Nature’s symmetries are broken at low energy, and a nagging reminder that our understanding of the physical world is still incomplete in some fundamental way.

A LIKELY STORY

Most physicists expect the Theory of Everything will describe gravity the same way we now describe matter and the strong, weak and electromagnetic forces – in the language of quantum mechanics. Gravity is, after all, just another force in Nature. So far this has proven elusive, due in part to the sheer complexity of the equations of general relativity. Scientists since Einstein have described gravity ( as well as space and time) in purely geometric terms. Thus we speak of gravity as the “curvature of space-time”.

To acheive complete unification, the dialects of quantum matter and geometric space have to be combined into a single language. Matter appears to be rather precisely described in terms of the language of quantum mechanics. Quarks and electrons exchange force-carrying particles such as photons and gluons and thereby feel the electromagnetic and strong nuclear forces. But, gravity is described by Einstein’s theory of general relativity as a purely geometric phenomenon. These geometric ideas of curvature and the dimensionality of space have nothing to do with quantum mechanics.

To unify these two great foundations of physics, a common language must be found. This new language will take some getting used to. In it, the distinction between matter and space dissolves away and is lost completely; matter becomes a geometric phenomenon, and at the same time, space becomes an exotic form of matter.

Beginning with work on a quantum theory of gravity by John Wheeler and Bryce DeWitt in the 1960’s, and continuing with the so-called superstring theory of John Schwartz and Michael Green in the 1980’s, a primitive version of such a ‘quantum-geometric’ language is emerging. Not surprisingly, it borrows many ideas from ordinary quantum mechanics.

A basic concept in quantum mechanics is that every system of elementary particles is defined by a mathematical quantity called a wave function. This function can be used, for example, to predict the probability of finding an electron at a particular place and time within an atom. Rather than a single quantity, the wave function is actually a sum over an infinite number of factors or ‘states’, each representing a possible measurement outcome. Only one of these states can be observed at a time.

By direct analogy, in quantum gravitation, the geometry of space-time, whether flat or curved, is only one of an infinite variety of geometric shapes for space-time, and therefore the universe. All of these possibilities are described as separate states in the wave function for the universe.

But what determines the probability that the universe will have the particular geometry we now observe out of the infinitude of others? In quantum mechanics, the likelihood that an electron is located somewhere within an atom is determined by the external electric field acting on it. That field is usually provided by the protons in the atomic nucleus. Could there be some mysterious field ‘outside’ our universe that determines its probability?

According to Cambridge University theorist Stephen Hawking, this is the wrong way to look at the problem. Unlike the electron acted upon by protons, our universe is completely self-contained. It requires no outside conditions or fields to help define its probability. The likelihood that our universe looks the way it does depends only on the strengths of the fields within it.

Among these internal fields, there may even be ones that we haven’t yet discovered. Could the cosmological constant be the fingerprint in our universe of a new ‘hidden’ field in Nature? This new field could affect the likelihood of our universe just as a kettle of soup may contain unknown ingredients although we can still precisely determine the kettle’s mass.

A series of mathematical considerations led Hawking to deduce that the weaker the hidden field becomes, the smaller will be the value we observe for the cosmological constant, and surprisingly, the more likely will be the current geometry of the universe.

This, in turn, implies that if Lambda were big enough to measure by astronomers in the first place, our universe would be an improbable one. Philosophically, this may not trouble those who see our cosmos as absolutely unique, but in a world seemingly ruled by probability, a counter view is also possible. There may, in fact, exist an infinite number of universes, but only a minority of them have the correct blend of physical laws and physical conditions resembling our life-nurturing one.

Hawking continued his line of speculation by suggesting that, if at the so-called Planck scale of 10 to the power of -33 centimeters the cosmos could be thought of as an effervescent landscape, or “space-time foam”, then perhaps a natural mechanism could exist for eliminating the cosmological constant for good.

One of the curiosities of combining the speed of light and Newton’s constant of gravitation from general relativity, with Planck’s constant from quantum mechanics, is that they can be made to define unique values for length, time and energy. Physicists believe that at these Planck scales represented by 10 to the power of -33 centimeters and 10 to the power of -43 seconds, general relativity and quantum mechanics blend together to become a single, comprehensive theory of the physical world: The Theory Of Everything. The energy associated with this unification, 10 to the power of 19 billion electron volts, is almost unimaginably big by the standards of modern technology.

The universe itself, soon after the Big Bang, must also have passed through such scales of space, time and energy during its first instants of existence. Cosmologists refer to this period as the Planck Era. It marks the earliest times that physicists are able to explore the universe’s physical state without having a complete Theory of Everything to guide them.

WORMHOLES

Harvard University physicist Sidney Coleman has recently pursued this thought to a possible conclusion. Instead of some mysterious new field in Nature, maybe the Lambda term appears in our theories because we are using the wrong starting model for the geometry of space at the Planck scale.

Previous thinking on the structure of space-time had assumed that it behaved in some sense like a smooth rubber sheet. Under the action of matter and energy, space-time could be deformed into a variety of shapes, each a possible geometric state for the universe. Nearly all candidates for the Theory of Everything’s embed their fields and symmetries in such a smooth geometrical arena.

But what if space-time were far more complicated? One possibility is that ‘wormholes’ exist, filling space-time with a network of tunnels. The fabric of space-time may have more in common with a piece of Swiss cheese than with a smooth rubber sheet.

According to Coleman, the addition of wormholes to space-time means that, like the ripples from many stones tossed into a pond, one geometric state for the universe could interfere with another. The most likely states ( or the biggest ripples) would win out. The mathematics suggest that quantum wormhole interference at the Planck scale makes universes with cosmological constants other than zero exceedingly unlikely.

How big would wormholes have to be to have such dramatic repurcussions? Surprisingly, the calculations suggest that small is beautiful. Wormholes the size of dogs and planets would be very rare. Universes containing even a few of them would exist with a vanishingly low probability. But wormholes smaller than 10 to the power of -33 centimeters could be everywhere. A volume the size of a sugar cube might be teeming with uncounted trillions of them flashing in and out of existence!

Coleman proposes that the action of these previously ignored mini- wormholes upon the geometric fabric of the universe that forces Lambda to be almost exactly zero. Like quantum ‘Pac Men’, they gobble up all the latent energy of space-time that would otherwise have appeared to us in the form of a measureable cosmological constant!

The addition of wormholes to the description of space-time admits the possibility that our universe did not spring into being aloof and independent, but was influenced by how other space-times had already evolved – ghostly mathematical universes with which we can never communicate directly.

The most likely of these universes had Lambda near zero, and it is these states that beat out all other contenders. In a bizarre form of quantum democracy, our universe may have been forced to follow the majority, evolving into the high probability state we now observe, without a detectable cosmological constant.

EPILOG

Wormholes? Wave functions? Hidden fields? The answer to the cosmological constant’s smallness, or absence, seems to recede into the farthest reaches of abstract thinking, faster than most of us can catch up.

As ingenious as these new ideas may seem, the final pages in this unusual story have probably not been written, especially since we can’t put any of these ideas to a direct test. It is a tribute to Einstein’s genius that even his ‘biggest blunder’ made near the beginning of this century still plagues physicists and astronomers as we prepare to enter the 21st century. Who would ever have thought that something that may not even exist would lead to such enormous problems!

Astronomy, Physics

The Planck Era

The Planck Era

Written by Sten Odenwald. Copyright (C) 1984 Kalmbach Publishing. Reprinted by permission

The Big Bang theory says that the entire universe was created in a tremendous explosion about 20 billion years ago. The enormity of this event is hard to grasp and it seems natural to ask ourselves ‘What was it like then?’ and ‘What happened before the Big Bang?’. To try to answer these queries, lets take a brief journey backwards in time.
We first see the formation of our own sun about 15 billion years after the Big Bang and then by 5 billion years, the formation of the first galaxies. By 700,000 years, the universe is awash with the fireball radiation that keeps all matter at a temperature of 4,000 degrees. Because of this, darkness is completely absent since every point in the sky glows with the brilliance of the sun. No stars, planets or even dust grains exist, just a hot dense plasma of electrons, protons and helium nuclei. By 3 minutes, we see helium form from the fusion of hydrogen atoms while the universe seeths at a temperature of nearly 1 billion degrees. The average density of matter is that of lead. By 1 second, the Lepton Era ends and the ratio of neutrons to protons has become fixed at 1 neutron for every 5 protons. The temperature is now 5 billion degrees everywhere. At about .0001 second, we watch as the Quark Era ends and the temperature of the fireball radiation rises to an incredable 1 trillion degrees. Quarks, for the first time, can combine in groups of two and three to become neutrons, protons and other types of heavy particles. The universe is now packed with matter as densly as the nucleus of an atom. A mountain like Mt. Everest could be squeezed into a volume no greater than the size of a golf ball!

By 1 billionth of a second, the temperature is 1 thousand trillion degrees and we see the electromagnetic and weak forces merge into one force. The density of the universe has increased to the point where the entire earth could be contained in a thimble. Quarks and anti-quarks are no longer confined inside of particles like neutrons and protons but are now part of a superheated plasma of unbound particles. As the remaining history of the universe unfolds, a long period seems to pass when nothing really new happens. Then, at a time 10(-35) second after the Big Bang, a spectac ular change in the size of the universe occurs. This is the GUT Era when the strong nuclear force becomes distinguishable from the weak and electromagnetic forces. The temperature is an incredable 10 thousand trillion trillion degrees and the density of matter has sored to nearly 10(75) gm/cm3. This number is so enormous that even our analogies are almost beyond comprehension. At these densities, the entire Milky Way galaxy could easily be stuffed into a volume no larger than a single hydrogen atom! Electrons and quarks together with their anti-particles, were the major constituents of matter and very massive particles called Leptoquark Bosons caused the quarks to decay into electrons and vice versa. If we now move forward in time we would witness the vacuum of space undergoing a ‘phase transition’ from a higher energy state to a lower energy state. This is analogous to a ball rolling down the side of a mountain and coming to rest in the lowest valley. As the universe ‘rolls down hill’ it begins a brief but stupendous period of expansion. The universe swells to billions of times its former size in almost no time at all.

In addition to this, a slight excess of matter over anti-matter appears becaus of the decay of massive particles called X Higgs Bosons. As we continue to watch the universe age, the remaining pairs of particles and anti-particles find themselves and vanish in a tremendous burst of annihilation. From this paroxysm, the bulk of the fireball radiation that we now observe is born.

The GUT Era is the last stop in our fanciful journey through time. If we had asked what it was like before the GUT Era, we would immediately have entered a vast no mans land where few indisputable facts would serve to gui de us. What does seem clear is that gravity is destined to grow in importance, eventually becoming the dominant force acting between parti cles, even at the microscopic level.

G R A V I T Y

According to theories developed since the 1930’s, what we call a ‘force’ is actually a collective phenomenon caused by the exchange of innumerable, force-carrying particles called gauge bosons. The electromagnetic force, which causes like charges to attract and dissimilar ones to repel, is transmitted by gauge bosons called photons, the strong force that binds nucleii together is transmitted by gluons and the weak force which causes particles to decay is transmitted by the, recently discovered, W and Z Intermediate Vector Bosons. In an analogous way, physicists believe that gravity is transmitted by particles called Gravitons. If gravity really does have such a quantum property, its effects should appear once quarks and electrons can be forced to within 10(-33) centimeter of one another, a distance called the Planck length. To acheive these conditions, quarks and electrons will have to be collided at energies of 10(19) GeV. An accelerator patterned after the 2-mile, Stanford Linear Accelerator would have to be 1 light-year in length to push particles to these incredable energies! Fortunatly, what humans find impossible to do, Nature with its infinite resources finds less difficult. Before the universe was 10(-43) second old, matter routinely experienced collisions at these energies. This period is what we call the Planck Era.

THROUGH A LOOKING GLASS, DARKLEY

Since our technology will not allow us to physically reproduce the conditions during these ancient times, we must use our mathematical theories of how matter behaves to mentally explore what the universe was like then. We know that the appearence of the universe before 10(-43) second can only be adequatly described by modifying the Big Bang theory because this theory is, in turn, based on the General Theory of Relativity. General Relativity tells us how gravity operates on the macroscopic scale of planets, stars and galaxies. At the Planck scale, we need to extend General Relativity so that it includes not only the macroscopic properties of gravity but also is microscopic characteristics as well. The theory of ‘Quantum Gravity’ is still far from completion but physicists tend to agree that, at the very least, Quantum Gravity must combine the conceptual elements of the two great theories of modern physics: General Relativity and Quantum Mechanics.

In the language of General Relativity, gravity is a consequence of the deformati on of space caused by the presence of matter and energy. Gravity is just another name for the amount of curvature in the geometry of 3-dimensional space. In Quantum Gravity theory, gravity is produced by massless gravitons so that gravitons now represent individual packages of curved space that travel through space at the speed of light.

The appearence and dissappearence of innumerable gravitons gives the geometry of space a very lumpy and dynamic appearance. John Wheeler at Princeton University thinks of this as a foamy, sub-structure to space where the geometry of space twists and contorts so that far flung regions of space may suddenly find themselves connected by ‘wormholes’ which constantly appear and dissappear within 10(-43) seconds. Even as you are reading this article, this frenetic activity is occurring in the hyper-microscopic domain, 100 billion billion times smaller than the nucleus of an atom. For a comparison, the size of the sun and the size of a single atom stand in about this same proportion. Although Quantum Gravity effects are completely undetectable today at the atomic and nuclear scale, during the Planck Era, macroscopic and microscopic worlds merged and the Quantum Gravity of the microcosm suddenly became the Quantum Cosmology of the macrocosm!

QUANTUM COSMOLOGY

As we approach the end of the Planck Era, the random appearance and dissappearance of innumerable gravitons will eventually force us to give up the concept of a specific geometry to 3-dimensional space. Instead, the geometry at a given moment will have to be thought of as an average over all 3-dimensional space geometries that are possible. Once again, the reason for this is that particles are squeezed so closely together that we can now see individual gravitons moving around in the space between them causing space to become curved. We can no longer get away with saying that the space between two quarks, for example, is flat. This is what we mean when we say that the gravitational force between them is insignificant when compared to the other three forces of Nature.

To make matters much worse, not only will Quantum Gravity not allow us to calculate the exact 3-dimensional geometry to space but, at the Planck scale, it will not allow us to simultaneously determine its exact geometry and precise rate of change in time. What this means is that we may never be able to calculate with any certainty exactly what the history of the universe was like before 10-43 second. Today, the large-scale geometry of space is one of three possible types: flat and infinite, negatively curved and infinite or positively curved and finite. During the Planck Era, the ‘large-scale’ geometry was contorted by wormholes and and infinite number of possibilities were possible. To probe the history of the universe then would be like trying to trace your ancestral roots if every human being on earth had a possibility of being one of your parents. Now try to trace your family tree back a few generations! The farther back in time you go, the greater are the number of possible ancestors you could have had. An entirely new conception of what we mea n by ‘a history for the universe’ will have to be developed. Even the concepts of space and time will have to be completely re-evaluated in the face of the qua ntum fluctuations of spacetime at the Planck Era!

THE BIRTH OF THE UNIVERSE

The picture that seems to emerge from using our sketchy outline of what Quantum Gravity theory might look like is that as we approach the Planck Era, gravitons are exchanged between quarks and electrons with increasingly higher energy and in greater number. By the time we reach the end of the Planck Era at 10(-43) second, gravitons will begin to carry as much energy as the other force carriers (Gluons, IVBs and Photons). At still earlier times, a period of complet e symmetry and unification between all the natural forces will ensue. Only one super-unified force exists here (gravity) and only one kind of particle dominates the activity of this age(Gravitons).

During the early 70’s, the Russian physicists Ya. Zel’dovitch and A. Starobinski of the USSR Academy of Science proposed that the rapidly changing geometry of space during the Planck Era may actually have created all the matter, anti-matter and radiation that existed soon after Creation. In their picture of Creation, the rapidly changing geometry of space created particles and anti-particles with masses of 10(19) GeV. This production of matter and anti-matter removed energy from the enormous fluctuations occuring in the geometry of space and eventually succeeded in damping them out altogether by the end of the Planck Era. They also found that the rate of particle creation increased as more and more particles were created.

Several recent studies by Physicists Edward Tryon of Hunter College, R. Brout, F. Englert and E. Gunzig of the University of Brussels and david Atkatz and Heinz Pagels of the Rockefeller University have shed additional light on what Creation may have been like. Imagine if you can, nothing at all! This is the primordial vacuum of space. There is complete darkness here, no light yet exists. The number of dimensions to space was probably not the normal 3 that we are so accustomed to but may have been as high as 11 according to Supergravity theory! In this infinite emptiness, random fluctuations occurred that ever so slightly changed the energy of the vacuum at various points in space. Eventually, one of these fluctuations attained a critical energy and began to grow. As it grew, very massive particles called leptoquarks and anti-leptoquarks were created, causing the expansion to accelerate. This is much like a ball rolling down a hill that moves slowly at first and then gains momentum. The expansion of the proto-universe, in turn, caused still more leptoquarks to be created. This furious cycle continued until, at long last, the leptoquarks decayed into quarks, leptons (electrons, muons etc) and their anti-particles and the universe emerged from the Planck Era. Particle creation stopped once the fluctuations in the geometry of space subsided.

So, we are left with the remarkable possibility that, in the beginning, there ex isted quite literally, nothing at all and from it emerged nearly all of the matter and radiation that we now see. This process has been described by the physicist Frank Wilczyk at the University of California, Santa Barbara by saying, ” The reason that there is something instead of nothing is that nothing is unstable”. A ball sitting on the summit of a steep hill needs but the slightest tap to set it in motion. A random fluctuation in space was apparently all that was required to unleash the incredable latent energy of the vacuum, thus creating matter and energy and an expanding universe from ‘nothing at all’.

The universe did not spring into being instantaneously but was created a little bit at a time in a ‘bootstrap’ process. Once a few particles were created by quantum fluctuations of the empty vacuum, it became easier for a few more to appear and so, in a rapidly escalating process, the universe gushed forth from nothingness.

How long did this take? The primordial vacuum could have existed for an eternity before the particular fluctuation that gave rise to our universe happened. Physicist Edward Tryon expresses this best by saying that ” Our universe is simply one of those things that happens from time to time”.

The principles of Quantum Gravity may ultimatly force us to reconsider questions like ‘What happened before the Big Bang?’ because they imply the existence of something (time) that may not have any meaning at all. These questions may be as empty of meaning as an explorer on the north pole asking, ‘Which way is North?’. Only the complete theory of Quantum Gravity may tell us how to ask the right questions!