All posts by StenBlog

Hohmann’s Tyrany

It really is a shame. When all you have is a hammer, everything else looks like a nail. This also applies to our current, international space programs.

We have been using chemical rockets for centuries, but since the advent of V2s and the modern space age, these brute-force and cheap work horses have been the main propulsion technology we use to go just about everywhere in the solar system. But this amounts to thinking that one technology can span all of our needs, and the trillions of cubic miles that encompass interplanetary space.

We pay a huge price for this belief.

Chemical rockets have their place in space travel. They are fantastic ways of delivering HUGE thrusts quickly; the method par excellance for getting us off this planet and paying the admission ticket to space.  No other known propulsion technology is as cheap, simple, and technologically elegant as chemical propulsion in this setting.  Applying this same technology to interplanetary travel beyond the moon is quite another thing, and sets in motion an escalating series of difficult problems.

Every interplanetary spacecraft launched so far to travel to each of the planets in our solar system works on the exact same principle. Give the spacecraft a HUGE boost to get it off the launch pad, and with enough velocity to reach the distant planet, then cut the engines off after a few minutes so the spacecraft can literally coast the whole way. With a few more ‘Delta-V’ changes, this is called the minimum –energy trajectory or for rocket scientists the Hohmann Transfer orbit. It is designed to get you there, not in the shortest time, but using the least amount of energy. In propulsion, energy is money. We use souped-up Atlas rockets at a few hundred million dollars a pop to launch space craft to the outer planets. We don’t use  even larger and expensive Saturn V rockets that deliver even more energy for a dramatically-shorter ride.

If you bank on taking the slow-boat to Mars rather than a more energetic ride, this leads to all sorts of problems. The biggest of these is that the inexpensive 220-day journeys let humans build up all sorts of nasty medical problems that short 2-week trips would completely eliminate. In fact, the entire edifice of the $150 billion International Space Station is there to explore the extended human stays in space that are demanded by Hohmann Transfer orbits and chemical propulsion. We pay a costly price to keep using cheap chemical rockets that deliver long stays in space, and cause major problems that are expensive to patch-up afterwards. The entire investment in the ISS could have been eliminated if we focused on getting the travel times in space down to a few weeks.

You do not need Star Trek warp technology to do this!

Since the 1960s, NASA engineers and academic ‘think tanks’ have designed nuclear rocket engines and ion rocket engines, both show enormous promise in breaking the hegemony of chemical transportation. The NASA nuclear rocket program began in the e arly-1960s and built several operational prototypes, but the program was abandoned in the late 1960s because nuclear rockets were extremely messy, heavy, and had a nasty habit of slowly vaporizing the nuclear reactor and blowing it out the rocket engine!  Yet, Wernher  Von Braun designed a Mars expedition for the 1970s in which several,  heavy 100-ton nuclear motors would be placed in orbit by a Saturn V and then incorporated into an set of three interplanetary transports. This program was canceled when the Apollo program was ended and there was no longer a conventional need for the massive Saturn V rockets. But ion rockets continued to be developed and today several of these have already been used on interplanetary spacecraft like Deep Space 1 and Dawn. The plans for humans on Mars in 2030s rely on ion rocket propulsion powered by massive solar panels.

Unlike chemical rockets, which limit spacecraft speeds to a few kilometers/sec, ion rockets can be developed with speeds up to several thousand km/sec. All that they need is more thrust, and to get that they need low-mass power plants in the gigawatt range. ‘Rocket scientists’ gauge engine designs based on their Specific Impulse, which is the exhaust speed divided by the acceleration of gravity on Earth. Chemical rockets can only provide SIs of 300 seconds, but ion engine designs can reach 30,000 seconds or more! With these engine designs, you can travel to Mars in SIX DAYS, and a jaunt to Pluto can take a neat 2 months! Under these conditions, most of the problems and hazards of prolonged human travel in space are eliminated.

But instead of putting our money into perfecting these engine designs, we keep building chemical rockets and investing billions of dollars trying to keep our long-term passengers alive.

Go figure!!!

Check back here on Friday, March 17 for a new blog!

 

The Mystery of Gravity

In grade school we learned that gravity is an always-attractive force that acts between particles of matter. Later on, we learn that it has an infinite range through space, weakens as the inverse-square of the distance between bodies, and travels exactly at the speed of light.

But wait….there’s more!

 

It doesn’t take a rocket scientist to remind you that humans have always known about gravity! Its first mathematical description as a ‘universal’ force was by Sir Isaac Newton in 1666. Newton’s description remained unchanged until Albert Einstein published his General Theory of Relativity in 1915. Ninety years later, physicists, such as Edward Witten, Steven Hawkings, Brian Greene and Lee Smolin among others, are finding ways to improve our description of ‘GR’ to accommodate the strange rules of quantum mechanics. Ironically, although gravity is produced by matter, General Relativity does not really describe matter in any detail – certainly not with the detail of the modern quantum theory of atomic structure. In the mathematics, all of the details of a planet or a star are hidden in a single variable, m, representing its total mass.

 

The most amazing thing about gravity is that is a force like no other known in Nature. It is a property of the curvature of space-time and how particles react to this distorted space. Even more bizarrely, space and time are described by the mathematics of  GR as qualities of the gravitational field of the cosmos that have no independent existence. Gravity does not exist like the frosting on a cake, embedded in some larger arena of space and time. Instead, the ‘frosting’ is everything, and matter is embedded and intimately and indivisibly connected to it. If you could turn off gravity, it is mathematically predicted that space and time would also vanish! You can turn off electromagnetic forces by neutralizing the charges on material particles, but you cannot neutralize gravity without eliminating spacetime itself.  Its geometric relationship to space and time is the single most challenging aspect of gravity that has prevented generations of physicists from mathematically describing it in the same way we do the other three forces in the Standard Model.

Einstein’s General Relativity, published in 1915, is our most detailed mathematical theory for how gravity works. With it, astronomers and physicists have explored the origin and evolution of the universe, its future destiny, and the mysterious landscape of black holes and neutron stars. General Relativity has survived many different tests, and it has made many predictions that have been confirmed. So far, after 90 years of detailed study, no error has yet been discovered in Einstein’s original, simple theory.

Currently, physicists have explored two of its most fundamental and exotic predictions: The first is that gravity waves exist and behave as the theory predicts. The second is that a phenomenon called ‘frame-dragging’ exists around rotating massive objects.

Theoretically, gravity waves must exist in order for Einstein’s theory to be correct. They are distortions in the curvature of spacetime caused by accelerating matter, just as electromagnetic waves are distortions in the electromagnetic field of a charged particle produced by its acceleration. Gravity waves carry energy and travel at light-speed. At first they were detected indirectly. By 2004, astronomical bodies such as the  Hulse-Taylor orbiting pulsars were found to be losing energy by gravity waves emission at exactly the predicted rates. Then  in 2016, the  twin  LIGO gravity wave detectors detected the unmistakable and nearly simultaneous pulses of geometry distortion created by colliding black holes billions of light years away.

Astronomers also detected by 1997 the ‘frame-dragging’ phenomenon in  X-ray studies of distant black holes. As a black hole (or any other body) rotates, it actually ‘drags’ space around with it. This means that you cannot have stable orbits around a rotating body, which is something totally unexpected in Newton’s theory of gravity. The  Gravity Probe-B satellite orbiting Earth also confirmed in 2011 this exotic spacetime effect at precisely the magnitude expected by the theory for the rotating Earth.

Gravity also doesn’t care if you have matter or anti-matter; both will behave identically as they fall and move under gravity’s influence. This quantum-scale phenomenon was searched for at the Large Hadron Collider ALPHA experiment, and in 2013 researchers placed the first limits on how matter and antimatter ‘fall’ in Earth’s gravity. Future experiments will place even more stringent limits on just how gravitationally similar matter and antimatter are. Well, at least we know that antimatter doesn’t ‘fall up’!

There is only one possible problem with our understanding of gravity known at this time.

Applying general relativity, and even Newton’s Universal Gravitation, to large systems like galaxies and the universe leads to the discovery of a new ingredient called Dark Matter. There do not seem to be any verifiable elementary particles that account for this gravitating substance. Lacking a particle, some physicists have proposed modifying Newtonian gravity and general relativity themselves to account for this phenomenon without introducing a new form of matter. But none of the proposed theories leave the other verified predictions of general relativity experimentally intact. So is Dark Matter a figment of an incomplete theory of gravity, or is it a here-to-fore undiscovered fundamental particle of nature? It took 50 years for physicists to discover the lynchpin particle called the Higgs boson. This is definitely a story we will hear more about in the decades to come!

There is much that we now know about gravity, yet as we strive to unify it with the other elementary forces and particles in nature, it still remains an enigma. But then, even the briefest glance across the landscape of the quantum world fills you with a sense of awe and wonderment at the improbability of it all. At its root, our physical world is filled with improbable and logic-twisting phenomena and it simply amazing that they have lent themselves to human logic to the extent that they have!

 

Return here on Monday, March 13 for my next blog!

A Family Resurrection

When someone tells you that they are a family geneaologist, your first reaction is to gird yourself for a boring conversation about begats that will sound something like a chapter out of the Old Testament Genesis. What you probably don’t understand is the compulsion that drives us in this task.

A pretty little scene from one of my ancestral places near Uddevalla!

5,176 – That’s the number of people I have helped bring back from oblivion through my labors. There is an ineffable feeling of deep satisfaction in having tracked them down through the countless Swedish church records spanning over 600 years of  history. Every one recovered and named was a personal victory for me against the forgetfulness of time and history. Ancient Egyptians believed that if you removed a person’s name from monuments, or ceased to speak it, that the person’s spirit would actually cease to exist.  That is why so many pharaoh’s defaced their predecessor’s monuments by removing their names. To counter this eternal death, all you have to do is again speak their name!

I, personally, have resurrected over 15 families who I never knew existed. I can now name their parents, their children, when and where they were born and died, how often they pulled up roots in one town and moved to another. I know where and when they lived among the countless towns and farms in rural Sweden. I can also anticipate what major stories and geopolitical issues must have been the small talk around dinner tables and among their fellow farm laborers in the fields.

Everyone loves the thrill of the hunt, the stalking of prey, and the final moment of satisfaction at the completion of the pursuit. For a genealogist, we hunt through historical records in pursuit of a single  individual. Pouring through a record containing a thousand names, we spot the birth of an ancestor. The accompanying census record tips us off about his family unit captured in hand-written names, birth dates and places. A bit more work among the records of that moment clinches the number of children and where the family had last been in its travels. Looking forward, we recover the names of the grandparents, the birth and death dates and places of the parents, marriages, when the children left home, and where they later wound up as their own lives played out in the course of time.

Countess ‘Aha’ moments reward you as you meticulously slog through these records, and step-by-step recover a parent, a child, a place, a history. In doing so, you enter the acute fogginess of an alternate state of mind. The reward for this compulsion carries you on for many days until at last your labors are completed and you sit back and admire what you have just accomplished. There on your pages of notes, an entire family has been brought back from the depths of time. Like a diadem recovered from the soil, you can now admire the texture of this family and see it as an organic and living thing in space and time. As little as two weeks ago, you never even knew they existed. For years and even centuries before that, these ancestors lay buried in time and utterly forgotten by the living. They slumbered in the many fragmented pages of a hundred church books spread across countless square miles of Sweden until you, one day, decided to resurrect them and tell their story.

The curious, but typical story of Eric Juhlin!

Eric Ulric Juhlin, my second great great uncle, was born on July 4, 1823 to my third great grandfather Magnus Juhlin and his wife Britta Ulrica Gadd, in the town of Tutaryd, Sweden.

In 2010 I only knew Eric existed from the town’s census record that revealed the 11 children of my distant grandfather Magnus Juhlin, which were listed neatly in their own little rows of data. Eric was the twin to Petrus Juhlin who, sadly, died three months later as was a common risk for young children and infants in 18th century rural Sweden.

Well, Eric eventually met Eva Cajsa Svensdotter from Ljungby, Sweden; The exact details of how they met are obscure. But they settled for a time in the town of Halmstad, where on March 6, 1855 they had their first child Clara. Returning to Tutaryd in 1856, for the next 22 years they gave birth to six more children: Ida Regina, Ferdinand, Hedvig, Davida, Ulrica, and Gustaf Adolph. By the time their seventh-and- last child Carl Leonard was born in 1878, Eric was by that time 55 years old and Eva Caisa had turned 48 only 5 months later.

This family was singularly unlucky in raising their children to adulthood. Ferdinand died at the age of only five years. Carl Leonard made it to age 3, and Gustav Adolph, with an impressive King’s name, died at age 8. But there were also some hopeful stories too among their more fortunate siblings who they barely got to know.

Ida Regina did survive childhood and went on to marry Magnus Adolph Persson. Settling in the southern town of Hjämarp, they raised three sons and three daughters who all grew up and lived to old age. Magnus eventually died in 1930 at the age of 69 followed by Ida ten years later at the age of 83. Ida’s 16-year-old sister Ulrica, decided for whatever reason to emmigrate to the United States, where she eventually met and married her husband Fredrick William Picknell in 1893. Settling in Champaign, Illinois, they raised three sons: Percy Gordon, Frederick and Charles. Sadly, Ulrica died in 1915 at the age of 45. Her husband survived her another 30 years. Their three sons went on to form their own families until they, themselves, passed into history; the last of them, Frederick exiting this world in Toledo, Ohio on Halloween Day, 1986. But each of them managed to cast yet another generation into futurity, and through their children, colonized the years between 1920 and 2012. One of them, Harry Gene Picknell lived in Bethesda, Maryland only a stone’s throw from my own front door…but I never got to meet him.

What became of Clara, Hedvig and Davida? Well, between the ages of 20-22, they moved from their family homes in Tutaryd to the far-flung towns of  Hesslunda and  Mörarp. Their younger sister Davida followed suit on August 10, 1883 and moved to the Big City of Halmstad. The census for this town spans thousands of pages and is a daunting challenge to study. Perhaps Davida will turn up somewhere among them, but it will be a long while before I muster up the courage to dive into THAT archive.

Or perhaps like so many other ancestors, Davida Juhlin’s story will remain the silent gold of history!

Check back here on Wednesday, March 8 for a new blog!

Martian Swamp Gas?

Thanks to more than a decade of robotic studies, the surface of Mars is becoming a place as familiar to some of us as similar garden spots on Earth such as the Atacama Desert in Chile, or Devon Island in Canada. But this rust-colored world still has some tricks up its sleave!

Back in 2003, NASA astronomer Michael Mumma and his team discovered traces of methane in the dilute atmosphere of Mars. The gas was localized to only a few geographic areas in the equatorial zone in the martian Northern Hemisphere, but this was enough to get astrobiologists excited about the prospects for sub-surface life. The amount being released in a seasonal pattern was about 20,000 tons during the local summer months.


The discovery using ground-based telescopes in 2003 was soon confirmed a year later by other astronomers and by the Mars Express Orbiter, but the amount is highly variable. Ten years later, the Curiosity rover also detected methane in the atmosphere from its location many hundreds of miles from the nearest ‘plume’ locations. It became clear that the hit-or-miss nature of these detections had to do with the source of the methane turning on and off over time, and it was not some steady seepage going on all the time. Why was this happening, and did it have anything to do with living systems?

On Earth, there are organisms that take water (H2O) and combine it with carbon dioxide in the air (CO2) to create methane (CH3) as a by-product, but there are also inorganic processes that create methane too. For instance, electrostatic discharges can ionize water and carbon dioxide and can produce trillions of methane molecules per discharge. There is plenty of atmospheric dust in the very dry Martian atmosphere, so this is not a bad explanation at all.

This diagram shows possible ways that methane might make it into Mars’ atmosphere (sources) and disappear from the atmosphere (sinks). (Credit: NASA/JPL-Caltech/SAM-GSFC/Univ. of Michigan)

Still, the search for conclusive evidence for methane production and removal is one of the high frontiers in Martian research these days. New mechanisms are being proposed every year that involve living or inorganic origins. There is even some speculation that the Curiosity rover’s chemical lab was responsible for the rover’s methane ‘discovery’. Time will tell if some or any of these ideas ultimately checks out. There seem to be far more geological ways to create a bit of methane compared to biotic mechanisms. This means the odds do not look so good that the fleeting traces of methane we do see are produced by living organisms.

What does remain very exciting is that Mars is a chemically active place that has more than inorganic molecules in play. In 2014, the Curiosity rover took samples of mudstone and tested them with its on-board spectrometer. The samples were rich in organic molecules that have chlorine atoms including chlorobenzene (C6H4Cl2) , dichloroethane (C2H4Cl2), dichloropropane (C3H6Cl2) and dichlorobutane (C4H8Cl2). Chlorobenzene is not a naturally occurring compound on Earth. It is used in the manufacturing process for pesticides, adhesives, paints and rubber. Dichloropropane is used as an industrial solvent to make paint strippers, varnishes and furniture finish removers, and is classified as a carcinogen. There is even some speculation that the abundant perchlorate molecules (ClO4) in the Martian soil, when heated inside the spectrometer with the mudstone samples, created these new organics.

Mars is a frustratingly interesting place to study because, emotionally, it holds out hope for ultimately finding something exciting that takes us nearer to the idea that life once flourished there, or may still be present below its inaccessible surface. But all we have access to for now is its surface geology and atmosphere. From this we seem to encounter traces of exotic chemistry and perhaps our own contaminants at a handful of parts-per-billion. At these levels, the boring chemistry of Mars comes alive in the statistical noise of our measurements, and our dreams of Martian life are temporarily re-ignited.

Meanwhile, we will not rest until we have given Mars a better shot at revealing traces of its biosphere either ancient or contemporary!

Check back here on Thursday, March 2 for the next essay!

Near Death Experiences

A CBS News Survey in 2014  found that 3 in 4 Americans believe in an afterlife. A similar survey in the UK in 2009 found 1 in 2 believe in life after death and 70% believe in the existence of a human soul.

So pervasive is this belief that, amazingly, more Britons believe in life after death than believe in God! This belief in life-after-death is so fundamental to how humans see the world that a 2013 Pew Poll of Americans  found that 13% of athiests also believed in an afterlife!

Luigi Schiavonetti’s 1808 engraving of a soul leaving a body. (Credit: National Gallery of Victoria, Melbourne)

Of course, many will argue that once you are gone you are gone, but in that twilight moment in the minutes and seconds before death, people have been revived through heroic medical interventions and some but not all declare they have experienced ‘something’ absolutely remarkable.

Called Near Death Experiences, entire shelves of books have been written on this subject over the decades since the ground-breaking work of Ceila Green in 1968 and then popularized in 1975 by psychiatrist Raymond Moody. Extensive eye-witness accounts were recorded, classified and sorted into a small number of apparently archetypical scenarios such as tunnels of pure light; out of body experiences; meeting loved ones; indescribable love. According to a Gallup Poll about 3% of Americans claim to have had them.  There were early attempts by Duncan MacDougall in 1901 at detecting the exit of the soul from the body by carefully weighing the patient, but all failed, and were immediately explained by denying that the soul had any weight at all.

Scientists have largely refused to wade into this area of inquiry because, like many other human beliefs, there is enormous public resistance to scientists meddling in such cherished and highly personal ideas shared by virtually all humans, even some athiests! In a classic case of what psychologists call confirmation bias, there is nothing that science can say about this matter that would be trusted unless it lines up exactly to confirm what we have all made up our minds about, literally for millennia. That said, I myself, must tread very carefully as I write this blog because, frankly, those of you reading it have also made up your mind about the subject and I do not want to slap you in the face by disrespecting your fundamental core beliefs, which will always trump anything a scientist can tell you. Even my simple uttering of this disclaimer will be interpreted as me being a condescending scientist…or worse!

But I cannot help myself! I have been curious about this subject all my life, and any new insights I come across in my readings are like candy to my brain. So here goes!

NDEs are not a feature of any other organ than the brain because they involve visual perceptions, bodily sensations, and the knitting together of a story that is later told by the ‘traveler’. All of these are brain functions, so it is no wonder that those who study the clinical aspects of NDEs begin with what the brain is doing. Amazingly, you do not even have to be clinically ‘near death’ to experience them. All that is required is a deep conviction that you ARE dying to trigger them.

What could be a more compelling and simple idea than putting a dying person in a functional magnetic resonance imager (fMRI) or strapping an EEG net to their heads, and literally watching what the brain is doing during one of these events? Well, it would be a heinous experiment and an unwelcomed intrusion on a patient’s privacy, but nevertheless these things do happen accidentally. Cardiac patients who are more likely to die suddenly and be recovered are often monitored for other reasons prior to their NDE, and there are many other indirect ways to snoop on the brain to see what happens too.

We have already learned from fMRI studies that there is a specific brain region that allows you to have a sense of where your body is located in space. In an earlier blog I discussed how removing the stimulation of this normally very active region causes meditators to have the sensation of being ‘at-one’ with the universe. This state can also be reproduced at will through chemical manipulation. The region, when stimulated with an electrode, or during temporal lobe epilepsy, also produces the aura sensation that your Self is no longer anchored to your body in space during so-called Out-of-Body (OBE) events. So, an essential element of your body sense during an NDE can be traced to one specific brain region and whether it’s activity is stimulated or depressed. This region wins both ways because when its electrical activity is gone, you have one ‘cosmic’ sensation of leaving your body, and when it is over-stimulated you have the OBE sensation. As we know, death is the ultimate event that lowers brain activity, or temporarily elevates it in other places as blood flow catastrophically changes. We all have the same brains, so the real question is, why is it that EVERYONE doesn’t have a NDE?

It all seems to depend on how close you get to the precipice of never returning from the journey, and it is the closeness of your brain to this physiological edge that seems to trigger the events leading to this NDE experience. But we do not know for certain.

A 2011 Scientific American article summarized some of these elements announced by brain researchers Dean Mobbs and Caroline Watt.

OBE experiences can be artificially triggered by stimulating the right temporoparietal junction in the brain. Patients with Cotard or “walking corpse” syndrome believe they are dead. This is a condition caused by trauma to the parietal cortex and the prefrontal cortex. Parkinson’s disease patients have reported visions of ghosts. This condition involves abnormal functioning of dopamine, a neurotransmitter that can sometimes but not all the time evoke hallucinations. The common experience of reliving moments from one’s life can be tied to a neural circuit involving the locus coeruleus, which releases noradrenaline during stress and trauma. The locus coeruleus (shown below) is connected to brain regions that are involved with emotion and memory, such as the amygdala and hypothalamus. Finally, a number of medicinal and recreational drugs can mirror the euphoria often felt during NDEs, such as the anesthetic ketamine, which can trigger out-of-body experiences and hallucinations. These discussions of the neural basis for many of the separate elements to NBEs are now part of the official medical explanation in places such as the one found in Tim Newman’s 2016 article in Medical News Today.

Norepinephrine system (Credit: Patricia Brown, University of Cincinnati)

Beware, however, of other articles like the one in The Atlantic called ‘The Science of Near Death Experiences’. This 2015 popularization, written in the typical breezy style of newspaper reporters, also purported to summarize what we know about this condition. Sadly, the reporter spent most of the article interviewing those who experienced it and hardly any column space on actual scientific research. It was a typical ‘puff piece’ that offered nothing more than speculation and very self-serving and bias-affirming pseudoscience, along-side free plugs for many recent, lurid, books and movies about first-person accounts.

The bottom line is that NDEs are by no means common to people who think they are dying, and their incidence crosses many religious boundaries. They remain enormously powerful events that actually change the lives and even personalities of the survivors, and so they are not merely will-o-the-whisp hallucinations. We do know that their detailed descriptions follow specific cultural expectations for what the afterlife is like: a New Guinee tribesman will not describe the event the same way as a southern Evangelical.

We are only beginning to understand how our brains synthesize what we experience into the on-going story that is our personal reality, but we know from the evidence of numerous brain pathologies that this is a highly plastic process in which imagination and emotion blend with hard facts in a sometimes inseparable tapestry. Our senses are objectively known to be fallible in countless ways if left unattended, and how we interpret what we experiences is as much a logical process as a process of out-right confabulation. Like many other events in our lives, NDEs are seen as one experience that our brains work very hard to incorporate into a plausible story of our world. It is this story that through millions of years of evolution allows us to function as an integrated Self,  avoid being injured or eaten, and  propagate our genes to the next generation.

Isn’t it amazing that, against this backdrop of cognitive dissonance, sensory bias, emotional chaos, and evolutionary hard-wiring  we can create a workable story of who we are in the first place?

Check back here on Monday February 28 for my next blog!

Death By Vacuum

As an astrophysicist, this has GOT to be one of my favorite ‘fringe’ topics in physics. There’s a long preamble story behind it, though!

The discovery of the Higgs Boson with a mass of 126 GeV, about 130 times more massive than a proton, was an exciting event back in 2012. By that time we had a reasonably complete Standard Model of how particles and fields operated in Nature to create everything from a uranium atom and a rainbow, to lighting the interior of our sun. A key ingredient was a brand new fundamental field in nature, and its associated particle called the Higgs boson. The Standard Model says that all fundamental particles in Nature have absolutely no mass, but they all interact with the Higgs field. Depending on how strong this interaction, like swimming through a container of molasses, they gain different amounts of mass. But the existence of this Higgs field has led to some deep concerns about our world that go well beyond how this particle creates the physical property we call mass.

In a nutshell, according to the Standard Model, all particles interact with the ever-present Higgs field, which permeates all space. For example, the W-particles interact very strongly with the Higgs field and gain the most mass, while photons interact not at all, remain massless.

The Higgs particles come from the Higgs field, which as I said is present in every cubic centimeter of space in our universe. That’s why electrons in the farthest galaxy have the same mass as those here on Earth. But Higgs particles can also interact with each other. This produces a very interesting effect, like the tension in a stretched spring. A cubic centimeter of space anywhere in the universe is not at all perfectly empty, and actually has a potential energy ‘stress’ associated with it. This potential energy is  related to just how massive the Higgs boson is. You can draw a curve like the one below that shows the vacuum energy  and how it changes with the Higgs particle mass:

Now the Higgs mass actually changes as the universe expands and cools. When the universe was very hot, the curve looked like the one on the right, and the mass of the Higgs was zero at the bottom of the curve. As the universe expanded and cooled, this Higgs interaction curve turned into the one on the left, which shows that the mass of the Higgs is now X0 or 126 GeV. Note, the Higgs mass represented by the red ball used to be zero, but ‘rolled down’ into the lower-energy pit as the universe cooled.

The Higgs energy curve shows a very stable situation for ‘empty’ space at its lowest energy (green balls) because there is a big energy wall between where the field is today, and where it used to be (red ball). That means that if you pumped a bit of energy into empty space by colliding two particles there, it would not suddenly turn space into the roaring hot house of the Higgs field at the top of this curve.

We don’t actually know exactly what the Higgs curve looks like, but physicists have been able to make models of many alternative versions of the above curve to test out how stable the vacuum is. What they  found is something very interesting.

The many different kinds of Higgs vacuua can be defined  by using two masses: the Higgs mass and the mass of the top quark. Mathematically, you can then vary the values for the Higgs boson and the Top quark and see what happens to the stability of the vacuum. The results are summarized in the plot below.

The big surprise is that, from the observed mass of the Higgs boson and our top quark shown in the small box, their values are consistent with our space being inside a very narrow zone of what is called meta-stability. We do not seem to be living in a universe where we can expect space to be perfectly stable. What does THAT mean? It does sound rather ominous that empty space can be unstable!

What it means is that, at least in principle, if you collided particles with enough energy that they literally blow-torched a small region of space, this could change the Higgs mass enough that the results could be catastrophic. Even though the collision region is smaller than an atom, once created, it could expand at the speed of light like an inflating bubble. The interior would be a region of space with new physics, and new masses for all of the fundamental particles and forces. The surface of this bubble would be a maelstrom of high-energy collisions leaking out of empty space! You wouldn’t see the wall of this bubble coming. The walls can contain a huge amount of energy, so you would be incinerated as the bubble wall ploughed through you.

Of course the world is not that simple. These are all calculations based on the Standard Model, which may be incomplete. Also, we know that cosmic rays collide with Earth’s atmosphere at energies far beyond anything we will ever achieve…and we are still here.

So sit back and relax and try not to worry too much about Death By Vacuum.

Then again…

 

Return here on Wednesday, February 22 for my next blog!

The Next Sunspot Cycle

Forecasters are already starting to make predictions for what might be in store as our sun winds-down its current sunspot cycle (Number 24) in a few years. Are we in for a very intense cycle of solar activity, or the beginning of a century-long absence of sunspots and a rise in colder climates?

Figure showing the sunspot counts for the past few cycles. (Credit:www.solen.info)

Ever since Samuel Schwabe discovered the 11-year ebb and flow of sunspots on the sun in 1843, predicting when the next sunspot cycle will appear, and how strong it will be, has been a cottage industry among scientists and non-scientists alike. For solar physicists, the sunspot cycle is a major indicator of how the sun’s magnetic field is generated, and the evolution of various patterns of plasma circulation near the solar surface and interior. Getting these forecasts bang-on would be proof that we indeed have a ‘deep’ understanding of how the sun works that is a major step beyond just knowing it is a massive sphere of plasma heated by thermonuclear fusion in its core.

So how are we doing?

For over a century, scientists have scrutinized the shapes of dozens of individual sunspot cycles to glean features that could be used for predicting the circumstances of the next one. Basically, we know that 11-years is an average and some cycles are as short as 9 years or as long as 14. The number of sunspots during the peak year, called sunspot maximum, can vary from as few as 50 to as many as 260. The speed with which sunspot numbers rise to a maximum can be as long as 80 months for weaker sunspot cycles, and as short as 40 months for the stronger cycles. All of these features, and many other statistical rules-of-thumb, lead to predictive schemes of one kind or another, but they generally fail to produce accurate and detailed forecasts of the ‘next’ sunspot cycle.

Prior to the current sunspot cycle (Number 24), which spans the years 2008-2019, NASA astronomer Dean Pesnell collected 105 forecasts for Cycle 24 . For something as simple as how many sunspots would be present during the peak year, the predictions varied from as few as 40 to as many as 175 with an average of 106 +/-31. The actual number at the 2014 peak was 116. Most of the predictions were based on little more than extrapolating statistical patterns in older data. What we really want are forecasts that are based upon the actual physics of sunspot formation, not statistics. The most promising physics-based models we have today actually follow magnetic processes on the surface of the sun and below and are called Flux Transport Dynamo models.

Solar polar magnetic field trends (Credit: Wilcox Solar Observatory)

The sun’s magnetic field is much more fluid than the magnetic field of a toy bar magnet. Thanks to the revolutionary work by helioseismologists using the SOHO spacecraft and the ground-based GONG program, we can now see below the turbulent surface of the sun. There are vast rivers of plasma wider than a dozen Earths, which wrap around the sun from east to west. There is also a flow pattern that runs north and south from the equator to each pole. This meridional current is caused by giant convection cells below the solar surface and acts like a conveyor belt for the surface magnetic fields in each hemisphere. The sun’s north and south magnetic fields can be thought of as waves of magnetism that flow at about 60 feet/second from the equator at sunspot maximum to the poles at sunspot minimum, and back again to the equator at the base of the convection cell. At sunspot minimum they are equal and opposite in intensity at the poles, but at sunspot maximum they vanish at the poles and combine and cancel at the sun’s equator. The difference in the polar waves during sunspot minimum seems to predict how strong the next sunspot maximum will be about 6 years later as the current returns the field to the equator at the peak of the next cycle. V.V Zharkova at Northumbria University in the UK uses this to predict that Cycle 25 might continue the declining trend of polar field decrease seen in the last three sunspot cycles, and be even weaker than Cycle 24 with far fewer than 100 spots. However, a recent paper by NASA solar physicists David Hathaway and Lisa Upton  re-assessed the trends in the polar fields and predict that the average strength of the polar fields near the end of Cycle 24 will be similar to that measured near the end of Cycle 23, indicating that Cycle 25 will be similar in strength to the current cycle.

But some studies such as those by Matthew Penn and William Livingston at the National Solar Observatory seem to suggest that  sunspot magnetic field strengths have been declining since about 2000 and are already close to the minimum needed to sustain sunspots on the solar surface.  By Cycle 25 or 26, magnetic fields may be too weak to punch through the solar surface and form recognizable sunspots at all, spelling the end of the sunspot cycle phenomenon, and the start of another Maunder Minimum cooling period perhaps lasting until 2100. A quick GOOGLE search will turn up a variety of pages claiming that a new ‘Maunder Minimum’ and mini-Ice Age are just around the corner! An interesting on-the-spot assessment of these disturbing predictions was offered back in 2011 by NASA solar physicist C. Alex Young, concluding from the published evidence that these conclusions were probably ‘Much Ado about Nothing’.

What can we bank on?

The weight of history is a compelling guide, which teaches us that tomorrow will be very much like yesterday. Statistically speaking, the current Cycle 24 is scheduled to draw to a close about 11 years after the previous sunspot minimum in January 2008, which means sometime in 2019. You can eyeball the figure at the top of this blog and see that that is about right. We entered the Cycle 24 sunspot minimum period in 2016 because in February and June, we already had two spot-free days. As the number of spot-free days continues to increase in 2017-2018, we will start seeing the new sunspots of Cycle 25 appear sometime in late-2019. Sunspot maximum is likely to occur in 2024, with most forecasts predicting about half as many sunspots as in Cycle 24.

None of the current forecasts suggest Cycle 25 will be entirely absent. A few forecasts even hold out some hope that a sunspot maximum equal to or greater than Cycle 24 which was near 140 is possible, while others place the peak closer to 60 in 2025.

It seems to be a pretty sure bet that there will be yet-another sunspot cycle to follow the current one. If you are an aurora watcher, 2022-2027 would be the best years to go hunting for them. If you are a satellite operator or astronaut, this next cycle may be even less hostile than Cycle 24 was, or at least no worse!

In any event, solar cycle prediction will be a rising challenge in the next few years as scientists pursue the Holy Grail of creating a reliable theory of why the sun even has such cycles in the first place!

Check back here on Friday, February 17 for my next blog!

The War on Cancer

In an earlier essay, I described how cognitive dissonance can wreak havoc with our perception of the world, especially in the case of politics. Cognitive dissonance is a psychological state in which you can believe two logically different ideas at the same time. For example, some scientists are avowed Creationists, and some people who want to help the poor, fervently vote for enormous tax breaks for the wealthy. Psychologists say that this dissonance causes internal stress and anxiety until you, yourself, create a ‘story’ that creates an acceptable way to justify the two extremes.

Depending on how you voted in 2016, you will find my earlier discussion either brilliantly insightful or insufferably condescending. But here is a topic I think we can all agree upon that suffers dramatically from this same mental affliction, namely, cancer research.
Here are the facts for 2016:

People contracting cancer……………………………. 1,685,210.

People dying from cancer…………………………………. 595,650

Cancers found in people older than 50…………………….85%

State with highest incidence rates…………………. Kentucky

State with lowest incidence rate………………………….. Arizona

Annual medical costs for cancer treatment……..$75 billion

We all agree cancer is a scary disease, and for many the mere use of this word is terrifying. Far more people die from cancer every year than from nearly all other non-disease causes of death combined. You have a one-in-two chance of getting cancer in your life and a one-in- four chance of dying from cancer in your lifetime. Your risk of dying in an airplane crash, earth quake or terrorist action is insignificant compared to your risk of dying from cancer.

Why is cognitive dissonance involved in cancer research? Because we all collectively understand the facts of cancer, but then we turn around and vote a half-hearted research budget to combat it, and then collectively shrug our shoulders that we are doing everything we can to win the war. Let’s take a look at what we are collectively doing about cancer.

The decline in NCI funding for research 2003-2014. (Credit: ASCO Connection.com)

Funding for cancer research (NCI): $5.21 billion for FY 2017. Loss of buying power since 2003: 25%. So let’s see….the annual cost for cancer treatment is $75 billion and we invest just over $5 billion to find cures. Then we have the DoD hiding $125 billion in waste at the same time they want to expand their current budget  by $2.2 billion to $524 billion in FY17.

Why is it that the case made by the DoD to increase their budget, or President Trumps  call to embark on a ‘new’ trillion-dollar arms race, are so much more compelling than the very obvious efforts to cure a major threat to the lifespans of most American voters? The polling statistics are also rather troubling.

In a new national public opinion survey commissioned by Research!America, an overwhelming majority of Americans (85%) say it is important for candidates running for national office to assign a high priority to increasing funding for medical research. The U.S. spends about five cents of each health dollar on research to prevent, cure and treat disease and disability, but only 56% say that is not enough. Yet, Vice President Joe Biden’s 2016  Cancer Moonshot   initiative to defeat cancer earns support for a tax increase to fund cancer research among only half of the respondents (50%). Only a weak majority of Democrats (67%), and few Republicans (38%) and Independents (39%) support a tax increase to engage this war. Of those who favor a tax increase, more than half (88%) say they are willing to pay up to or more than $50 per year in taxes.

The over-all NIH, FY17 budget increase of $850 million over FY16 will support an increase of 600 research projects above FY16. From this you can roughly deduce that the added $680 million for the Cancer Moonshot in FY17 will support an additional 480 cancer-related grants. But although we do NOT want to look a gift horse in the mouth, the NCI budgets since 2003 have never kept pace with inflation. By 2014 the NCI purchasing power for cancer research had fallen behind by about $1.5 billion or 30% from where they were in 2003. Have a look at this graph below. The top line shows the funded amount and the bottom line shows the inflation-adjusted purchasing power from 2003 to 2014.

In the 45 years since Mr. Nixon signed the National Cancer Act of 1971, which launched the previous War on Cancer, NCI has spent more than $100 billion on cancer research. This, buy the way is equal to the cost of NASA’s International Space Station. Since 1946, American Cancer Society has spent more than $4.5 billion to find cancer cures and forty-seven ACS-funded researchers been awarded the Nobel Prize. A relevant question is; Will the $680 million increase proposed by the Cancer Moonshot for FY17, and hopefully similar amounts after that, be enough to tip the scales towards cures in the way that VP Joe Biden has hoped?

The FY17 $6.3 billion 21st Century Cures bill was approved by the Senate in an overwhelming 94-5 vote and will doubtless be signed into law by President Barack Obama. The 10-year funding ‘Cures’ bill made its way through Congress largely because it is packed with substantial amounts of money for enough pet projects, including a batch of Medicare and mental health reforms, to keep disparate lawmakers on board.

Although other elements of President Obama’s 21st Century Cures program will receive automatic refunding in future years, Cancer Moonshot research funding is not guaranteed. It will have to be appropriated each year. Even worse, it will be paid for in part by raiding Obamacare’s Prevention and Public Health Fund, which pays for anti-smoking campaigns and other preventive health efforts. So Congress will give us a modest increase in the cancer research budget, about 10%, but will not promise this sustained support over the long haul. Again, researchers will be placed on a year-by-year leash to get their support for carrying out complex and time-consuming research. Every grant PI will have to spend time each year arguing for the refunding of their research rather than being focused on cures. Even scientists at NASA can usually count on three-year commitments for their funding!

What can you do? The odds say you should expect to contract cancer in your lifetime. The odds also say that you will probably not have a good long-term outcome. You need to accept this and do what you can to preventively temper your lifestyle and eating habits accordingly. Then, you need to decide for yourself if you are happy with the trending for cancer research. Why do we settle for $5 billion each year to fight this war when $10 billion would be far better, especially if the funding were more stable for long-term research programs? Call your Congressperson to make this case. It may actually save your life!!

Check back here on Monday, February 13 for the next installment!

By the way, check out the 2015 Ken Burns and Barak Goodman’s PBS Special Cancer:The Emperor of all Maladies about the ins and outs of cancer research. It was narrated by Edward Herrmann while he had brain cancer. He died soon after filming completed. The program will utterly change your perspective, and get you mad as hell!

My other blogs on cancer research can be found at the Huffington Post:

Our Shamefully Wimpy War Against Cancer

Our Pathetic War Against Cancer: Part III

Our Pathetic War Against Cancer: Part III

 

The Particle Desert

For the last 100 years physicists have built exotic “atom smashers” to probe the innermost constituents of matter. Along the way they created a breathtakingly elegant mathematical theory called the Standard Model that seems to explain all of the physics we see at the atomic scale. It describes how a collection of twelve fundamental matter particles (electrons, quarks neutrinos etc) generate three fundamental forces in Nature, and how these forces are related to twelve other particles called the gauge bosons. A final 25th particle, the Higgs boson, rounds out the ensemble and embues some of the 24 particles with that mystical property we call mass.

During all this time, teams of physicists working in the “data dumps” of billion-dollar colliders have sifted through terabytes of information to refine the accuracy of the Standard Model and compare its predictions with the real world. The predictions always seemed to match reality and push the testing of the Standard Model to still higher energies. But at the Large Hadron Collider at CERN, among the trillions of interactions studied up to energies of 13,000 GeV, no new physics has been seen in the furthest decimal points of the Standard Model predictions since 2012; not so much as a hint that something else has to be added to bring it back in line with actual data. It is a theory that appears not to be broken at energies over 1000 times higher than it was designed for!

In the history of all previous colliders beginning in the 1950s, something new has always been found to move the development of physic’s explanatory capabilities forward. In the 1970s it was the discovery of quarks. In the 1980s it was the W and Z0 particles, and even recently in 2012 it was the Higgs boson. All these particles were found below an energy of 200 GeV. But now, as the LHC has spent the last year at 13,000 GeV, a desperate mood has set in. No new particles or forces have been discovered in this new energy landscape.

Nada. Nothing. Zippo.

Most of the theories that go beyond the Standard Model provide ways to unify the strong force with the electromagnetic and weak forces. At some very high energy, they say, all three forces have the same strength, unlike their present circumstance where the strong nuclear force is 100 times as strong as the electromagnetic force. The predicted energy where this unification happens is about 1000 trillion GeV — the so-called grand unification theory (GUT) energy.

According to popular supersymmetry theory calculations, there should be a large population of new particles above an energy of 1000 GeV. Each a partner to the known 25 particles, but far more massive. Some of these particles, such as the neutralino, are even candidates for dark matter! Above the masses of these new supersymmetry particles, however, there ought to be no new particles to discover from perhaps 100, 000 GeV to the GUT energy of 1000 trillion GeV. They say that without this energy desert, any particles there would cause the proton to decay much faster than current limits predict.

So although it is a frustrating prospect that no new particles may exist in this desert, this is a vital feature of our physical world that literally prevents all matter (protons) from disintegrating! But unlike the Sahara Desert, where we can at least drive through it to get to a different world beyond, there are apparently no easily reachable oases of new particles along the way to which physicists can target new generations of expensive colliders.

It remains to be seen whether the results from the Large Hadron Collider after 2016 will confirm our greatest hopes or validate our worst fears. Either way, stay tuned for some exciting news headlines!

 

Return here on Thursday, February 9 for my next blog!

 

Interstellar Travel?

Interstellar travel revolves around the answers to three major questions:

1) Where will we go?

2) What will we do when we get there?

3) How will it benefit folks back on Earth?

Far beyond the issue of whether interstellar travel is technologically possible is the very practical issue of answering these questions long before we turn the first screw in the hardware.

A few of the thousands of stars within 50 light years of Earth.(Credit: Atlas of the Universe)

In science fiction, finding new destinations is usually handled by either manned or unmanned expeditionary forces. Not surprisingly, the hazardous experiences of the manned expeditions are usually the exciting core of the story itself. When we create this technology ourselves, the first  trips are usually to a popular nearby star like Alpha Centauri (e.g Babylon 5). When we are co-opting alien technology, we often have to go to where the aliens previously had outposts often hundreds or thousands of light years away ( e.g Contact or Stargate). In any event, most stories assume that the travelers can select multiple destinations and hop-scotch their way around the local universe within a single human lifetime to find a habitable planet. Apparently, once you have convinced politicians to fund the first trip, the incremental cost of additional trips is very small!

The whole idea of interstellar travel was created by fiction writers, but because it has many elements of good science in it, it is a very persuasive idea. It is an idea located smack in the middle of the ‘gray area’ between fantasy and reality, and this is what goads people on to try to imagine ways to make it a reality. One thing we do know is that it will be an expensive venture requiring an investment at the level of many percent of an entire planet’s GDP.

By some estimates, the first interstellar voyage will cost many trillions of dollars, require decades to construct, and involve tens to hundreds of passengers and explorers. Assuming a project of this scope can even be sold to the bulk of humanity that will be left behind to pay the bills, how will the destination be selected? Will we just point the ship towards any star and commit these resources to a random journey and outcome, or will we know a LOT about where we are going before the fuel is loaded? Most of us will agree that the latter case for such an expensive ‘one of’ mission is more likely. By the way, let’s not talk about the human Manifest Destiny to explore the unknown. Even Christopher Columbus knew his destination in detail (India!) and traveled within a very benign biosphere, free breathable atmosphere and comfortable gravity to get there in a few months.

So…where will we go?

Contrary to popular ideas, we will know our destination in great detail long before we leave our solar system. We will know whether the star has any planets, and we will know it has at least one planet in its habitable zone (HZ) where temperature would allow liquid water to exist. We will know if the planet has an atmosphere or not. We will know its mass and size, and perhaps more importantly, whether the planet has a biosphere. We will not invest perhaps trillions of dollars to study a barren Mars or Venus-like planet. All of these issues will be worked out by astronomical remote-sensing research at far lower cost than traveling there. If a nearby star does not have detectable planets, we will most certainly NOT mount a trillion-dollar mission to just ‘go and see’!

The 10 nearest stars are: Proxima Centauri (4.24 lys), Alpha Centauri (4.36), Barnards Star (5.96), Luhman 16 (6.59), Wolf 359 (7.78), Lalande 21185 (8.29), Sirius (8.59), Luyten 726-8 (8.72), Ross 154 (9.68) and Ross 248 (10.32). This takes us out to a distance of just over 10 light years from Earth. The prospects for an interesting world to visit are not good.

Proxima Centauri has one recently-detected Earth-sized planet orbiting inside its HZ, making it a Venus-like world of no interest. Alpha Centauri B has one unverified Earth-sized planet, but not in the star’s liquid-water HZ. It orbits ten times closer than Mercury. There are no planets larger than Neptune orbiting this star closer than our planet Jupiter. Barnards Star has a no known planets, but a Jupiter-sized planet inside the orbit of Mars is exluded, so this is still a viable star for future searches for terrestrial planets in the star’s HZ. Luhman 16 is a binary system whose members orbit each other every 25 years at a distance of 3 AU. A possible companion orbits one of these stars every month at a distance closer than Mercury. As for the stars Wolf 359, Lalande 21185, Sirius, Luyten 726-8, Ross 154 and Ross 248, there have been searches for Jupiter-sized companions around these  stars, but none have ever been claimed.

So, our nearest stars within 10 light years are pretty bleak as destinations for expensive missions. There is no solid evidence for Earth-sized planets orbiting within the HZs of any of them. These would not be plausible targets because there is so little return on the high cost of getting there, even though that cost in terms of travel time is the smallest of all stars in our neighborhood. This also sets a scale for the technology required. It is not enough to visit our nearest star, but we have to trudge 2 to 3 times farther before we can find better destinations.

Better Destinations.

Let’s take a bigger step. Out to a distance of 16 light years there are 56 normal stars, which include some promising candidate targets.

Epsilon Eridani (10.52 ly) has one known giant planet outside its HZ. It also has two asteroid belts: one at about three times Earth’s distance from our sun (3 AU) and one at about 20 AU. No one would ever risk a priceless mission by sending it to a sparse planetary system with deadly asteroid belts and no HZ candidates!

Groombridge 34 (11.62 ly) –The only suspected planet has a mass of more than five Earths. No mission would be sent to such a planet for which an atmosphere would probably be crushingly dense and probably Jupiter-like even if it was in its HZ.

Epsilon Indi (11.82 ly) – has a possible Jupiter-sized planet with a period of more than 20 years. No known smaller planets.

Artist rendering of the planets Tau Ceti e and f (Credit: PHL @ UPR Arecibo)

Tau Ceti (11.88 ly) probably has five planets between two and six times Earth’s mass, and with periods from 14 to 640 days. Planet Tau Ceti f is colder than Mars and is at the outer limit to the star’s HZ. Its atmosphere might be dense enough for greenhouse heating, so the world might be habitable after all. But this is guesswork not certainty.

Kapteyn’s Star (12.77 ly) – It has two planets, Kapteyn b and Kapteyn c, that are 5 to 8 times the mass of Earth. Kapteyn b has a period of 120 days and is a potentially habitable planet estimated to be 11 billion years old. Again, a massive planet whose surface you could never visit, so what is the point of the interstellar expedition?

Gliese 876 (15.2 ly) has four planets. All have more than 6 times the mass of Earth and orbit closer than the planet Mercury. Gliese 876 c is a giant planet like Jupiter in the star’s habitable zone. Would you bet the entire mission that 876c has habitable ‘Galilean moons’ like our Jupiter? This would be an unacceptable shot in the dark, though a tantalizing one.

So, out to 15 light years we have some interesting prospects but no confirmed Earth-sized planet in its star’s HZ whose surface you could actually visit. We also have no solid data on the atmospheres of any of these worlds. None of these candidates seem worth investing the resources of a trillion-dollar mission to reach and study. We can study them all from Earth at far less cost.

Best Destinations.

If we take an even bigger step and consider stars closer than 50 light years we have a sample of potentially 2000 stars but not all of them have been discovered and cataloged. About 130 are bright enough to be seen with the naked eye. The majority are dim and cool red dwarf stars, which are still good candidates for planetary systems. In this sample we encounter among the known planetary candidates several that would be intriguing targets:

61 Virginis (11.41 ly) – It has three planets with masses between 5 and 25 times our Earth, crowded inside the orbit of Venus. The asteroidal debris disk has at least 10 times as many comets as our solar system. There are no detected planets more massive than Saturn within 6 AU. An Earth-mass planet in the star’s habitable zone remains a possiblity, but the asteroid belts make this an unacceptable high risk target.

Gliese 667 planets (Credit: ESO )

Gliese 667 (23.2 ly) –As many as seven planets may orbit this star, but have not been confirmed. All have masses between that of Earth and Uranus. All but one are huddled inside the orbit of Mercury. Planets c and d are in the star’s HZ and are at least 3 times the mass of Earth. Their hypothetical moons may be habitable.
55 Cancri (40.3 ly)- All five planets orbiting this star are more than five times the mass of Earth. Only 55 Cancri e is located at the inner edge of the star’s HZ and its hypothetical moons could be habitable. More planets are possible within the stable zone between 0.9 to 3.8 AU if their orbits are circular. This is a system we still need to study.

HD 69830 (40.7 ly) has a debris disk produced by an asteroid belt twenty times more massive than that in our own solar system. Three detected planets have masses between 10 to 18 times that of Earth. The debris disk makes this a high-risk prospect even if there are habitable moons.

HD 40307 (41.8 ly) Five of the six planets orbit very close to the star inside the orbit of Mercury. The fifth planet orbits at a distance similar to Venus and is in the system’s habitable zone. The planets range in mass from three to ten times Earth. Again, is a planet in its HZ with a mass too great for a direct human visit a good candidate? I don’t think so.

Upsilon Andromedae (44.25 ly) The two outer planets are in orbits more elliptical than any of the planets in the Solar System. Upsilon Andromedae d is in the system’s habitable zone, has three times the mass of Jupiter, with huge temperature swings. Its hypothetical moons may be habitable.

47 Ursa Majoris (45.9 ly) The only known planet 47 Ursae Majoris b is more than twice the mass of Jupiter and orbits between Mars and Jupiter. The inner part of the habitable zone could host a terrestrial planet in a stable orbit. None yet detected.

There are still many more stars in this sample to detect, catalog and study so it is possible that a Goldilocks Planet could be found eventually. But we are now looking at destinations more than 20 light years away at a minimum. This will considerably increase the cost and duration of any interstellar mission by factors of five to ten times a simple jaunt to Alpha Centauri.

Other issues.

Would you really consider a planet with two to five times Earth’s gravity to be a candidate? Who would want to live under that crushing weight? Many of the candidates we have found so far are massive Earth’s that few colonists would consider standing upon. Their surfaces are also technologically expensive to get to and leave. But perhaps these worlds might have moons with more comfortable gravities? There is always hope, but will that be enough to risk a multi-trillion-dollar mission?

There is also the issue of atmosphere. None of the candidate planets we have discussed transit their stars, so we cannot detect their atmospheres and figure out if they have atmospheres and if their  trace gases would be  lethal. The perfect destination worth the expense of a trip would have a breathable atmosphere with oxygen. Since free oxygen is only produced by living systems, our target planet would have a biosphere. We can only hope that as the surveys of the nearby stars continue, we will find one of these. But statistics suggests we will have to search much farther than 50 light years and a few thousand stars before we encounter one. That makes the interstellar voyage even more costly, not by factors of five and ten, but potentially hundreds of times. But if the trip were to a world with a known biosphere, THAT might be worth the effort, but possibly nothing less than this would be worth the cost, the risk, and the scientific return.

So the bottom line is that the only interstellar destination worth the expense is either one in which colonists can live comfortably on the planet with a lethal atmosphere, hermetically sealed under a dome, or a similar planet with a breathable oxygen atmosphere and a biosphere. Statistically, we will find far more examples of the first kind of target than the second. But in the majority of the cases, we will not be able to detect the atmosphere of an Earth-sized world in its habitable zone before we start the trip, and will have to ‘guess’ whether it even has an atmosphere at all!

The enormous cost of an interstellar trip to a target tens or even hundreds of light years away will preclude any guess work about what we will find when we get there. Consider this: Investing $100 billion to travel to Mars, a low-risk planet we thoroughly understand in detail, is still considered a political pipe dream even with existing technology! What would we call a trip that costs perhaps 100 times as much?

For more on this topic, have a look at my book ‘Interstellar Travel:An astronomer’s guide’. Available at Amazon.com.

 

Return here for my next blog posting on Friday, February   3