Tom is a professor at Rutgers and UC Santa Cruz, an extremely accomplished researcher in field theory and string theory, and the author of a textbook on quantum field theory. In collaboration with Fischler, Shenker, and Susskind, he proposed the (M)atrix Theory non-perturbative formulation of string theory. Most recently, he (often working with Willy Fischler) has been exploring the connections between holography and cosmology, developing a detailed model of the evolution of the universe that is compatible with the holographic principle. Here is video of a lecture Tom recently gave on holographic cosmology.
This post is at a more technical level than most of our entries here at CV, and we’re going to try to keep the discussion useful for workers in the field. Sincere questions are welcome, but we’ll be deleting any unproductive philosophical gripes or advertisements for anyone’s personal outsider theories.
Why I Don’t Believe in Eternal Inflation
A lot of research in high energy theory has been devoted to the topic of eternal inflation. More and more, over the last few years, I’ve come to regard this as an enormous waste of intellectual resources and I’ve chosen Cosmic Variance as a very public way to make my objections to this theoretical mistake clear. The theory was developed in the 1980s, when it seemed plausible that quantum field theory in curved space-time was a good approximation to a real theory of quantum gravity whenever the energy densities and curvatures of the background geometry were small in Planck units. This idea is simply wrong. The fact that its falsification came through a back door, the rather philosophical discussion of whether black hole evaporation violates the rules of quantum mechanics, has led to a widespread but unfortunate tendency to ignore this FACT.
There are two other psychological reasons for the widespread interest in Eternal Inflation, which I will discuss below. They have led even the inventors of the resolution of the black hole information paradox through the notion of holography, to try to find a sensible holographic theory which incorporates the notion of EI. While this attempt itself is subject to a number of objections, I will not go into them here. Instead, I’ll concentrate on evidence from the seminal Coleman-De Luccia (CDL) theory of tunneling in quantum gravity, which is one of the two biggest clues to what the theory of quantum gravity really is.
There are, in my opinion, two serious conceptual errors behind the theory of EI. The first is the notion that space-time geometry is a fluctuating quantum variable. The second is that de Sitter (dS) space is a system with an ever increasing number of quantum degrees of freedom. The increase is supposed to take place as the global dS time coordinate, or the time coordinate in flat coordinates, goes to future infinity. I’ll end this post with a brief discussion of the formalism of Holographic Space Time (HST), in which both of these ideas are seen to be false, in a very explicit manner. The fact that the HST formalism is able to give an approximate description of particle physics in a curved space-time background is by itself enough to falsify any claim that the semi-classical ideas that lead to EI are inevitable consequences of ANY sensible theory of quantum gravity. For this purpose, it’s not even necessary that HST be right, only that it have a limit in which it reduces to QFT in curved space-time.
There are two flavors of EI. Read More
Lisa Randall is a friend and collaborator, as well as a science superstar. She is one of the most highly cited physicists of all time, for a variety of contributions to field theory and particle physics, especially her work with Raman Sundrum on warped extra dimensions. Her first book, Warped Passages, was a major success, which naturally raises the question of what one does next. (Besides writing papers, I mean.)
So we’re very happy to welcome Lisa aboard to guest blog about her new book, just out today: Knocking on Heaven’s Door: How Physics and Scientific Thinking Illuminate the Universe and the Modern World. (Among other virtues, this book has the single most impressive collection of blurbers of any book ever written, from Bill Clinton to Carlton Cuse.) From personal experience I can verify that writing a book doesn’t just happen; it’s a tremendous commitment over an extended period of time, and once it’s done there’s not much chance to go back and change it. So deciding to write a book at all, and more importantly how exactly to target the writing, is a delicate and critical process.
While Lisa hasn’t yet become a regular blogger, she is active on Twitter, where you can follow her at @lirarandall.
In conjunction with the publication of Knocking on Heaven’s Door, I thought I’d take advantage of Sean’s kind invitation to post on Cosmic Variance to explain my motivations in writing my book. I haven’t done a lot of blogging myself but I am impressed at the care and interest that go into science blogs. They are a way of sharing developments as they happen and an opportunity to have meaningful discussion of results.
I talk about a lot of science in my book. So I thought rather than summarizing it all—at least in this post—I’d focus on the question of why I wrote this particular book. I waited several years before even considering embarking on a second book project. I certainly didn’t want to simply repeat the content of my previous book, and my own personal goal is always to branch out into new arenas—in this case into new types of writing–while still remaining true to my physics roots. I didn’t know the exact book I was after but I did know some of the topics I considered important and timely.
These topics fell into several categories. First, I wanted to give an accurate picture of what is happening in particle physics and cosmology today—both with experiments and with theory. Particle physicists know this to be the era of the Large Hadron Collider (LHC), the machine that is colliding together protons at unprecedented energies to test the nature of matter and forces at smaller distances than ever explored. The interactions between theorists and experimenters is more intense than it has been during the time I’ve been actively pursuing physics. That is because everyone realizes this interactions are essential with these challenging experiments to get to the right answers. I wanted to convey the excitement and implications of the research taking place there, so when discoveries are made, anyone interested can understand what was found and what it could mean.
Cosmologists too find this is an important time and I wanted to share some of the interest in that major topic as well. One arena that both particle physicists and cosmologists are excited about are experimental studies of the nature of dark matter. Many find this topic perplexing, whereas even if difficult to tackle experimentally, the underlying idea really is not. I wanted to explain a bit how I think about dark matter and how experiments are searching for its feeble and elusive effects.
But I wanted to do more than just summarize the physics. Read More
Jim Kakalios of the University of Minnesota has achieved internet demi-fame — he has a YouTube video with over a million and a half views. It’s on the science of Watchmen, the movie based on Alan Moore’s graphic novel. Jim got that sweet gig because he wrote a great book called The Science of Superheroes — what better credentials could you ask for?
More recently Jim has written another book, The Amazing Story of Quantum Mechanics. But even without superheroes in the title, everything Jim thinks about ends up being relevant to movies before too long. The new movie Source Code features a twist at the end that involves — you guessed it — quantum mechanics. Jim has applied his physicist super-powers to unraveling what it all means, and was kind enough to share his thoughts with us in this guest post.
There is an interesting discussion taking place on the internets concerning the ending of the newly released film SOURCE CODE, that suggests that the film concludes with a paradox. I believe that any such paradox can be resolved – with Physics!
This entire post is one big honkin’ SPOILER, so if you want to read about the final twist ending of a film without having seen said film – by all means, read on, MacDuff!
In SOURCE CODE, Jake Gyllenhaal plays US helicopter pilot Colter Stevens, whose consciousness is inserted into another man’s body (Sean Fentress, a school teacher in Chicago) through a procedure that requires a miracle exception from the laws of nature (involving quantum mechanics and “parabolic calculus” – by the way, there is no such thing as parabolic calculus). Thanks to some technobabble (or as Q-Bert on Futurama would describe it – weapons grade bolognium) Colter’s mind can only enter Sean’s body in the last eight minutes of Sean’s life. As Sean is sitting on a city bound Chicago commuter train, on which a bomb will explode at 7:58 AM, killing everyone aboard, the goal is for Colter to ascertain who planted the bomb. He cannot stop it from exploding, he is told, because that has already happened. He cannot affect the past, but he can bring information obtained in the past back to his present time. Learning the identity of the bomber would enable the authorities to prevent the detonation of a threatened second “dirty atomic” bomb is downtown Chicago.
While the above can be discerned from the movie trailer, what I am going to discuss next involves the actual ending of the film, and if you do not want this ending spoiled, you should stop reading now. Read More
I tell everyone I meet that we are at the dawn of the Dark Matter Decade. Usually they slowly back away, but I’m pretty persistent. Our technology has reached the point that we have an excellent chance of actually detecting most of the matter in the universe for the first time.
We’re very happy to have a guest post from Neal Weiner, one of the leading theorists working in the fast-moving area. (Don’t forget our previous guest post from one of the leading experimentalists.) Neal is responsible for some of the most imaginative models for what’s going on in the dark sector, and is excited about the upcoming experimental prospects. If you want to know what particle physicists are thinking about dark matter these days, you’ve come to the right place.
For anyone in the New York area, Neal is giving a public lecture on dark matter at AMNH on Friday the 4th (tomorrow). If you have a chance to go, I’d recommend not missing it.
The Era of Dark Matter Direct Detection
Commonly, when I speak to my friends who don’t spend their time obsessing about the prospects for dark matter discovery, I am confronted by indifference, or worse, pessimism, when I mention the next few years of dark matter experiment. The history of dark matter direct detection has largely been a string of experiments, increasingly able to better find nothing, interrupted by occasional unverified claims, they point out. Why should this era be any different?
In contrast, I remain incredibly optimistic about the coming era. I feel this level of sensitivity is special, and that if we are to discover WIMP scattering, it should be in the next few years.
Why am I so optimistic?
1)This level of sensitivity is special
When we talk about discovering dark matter through direct detection, we are typically referring to discovering WIMPs, or Weakly Interacting Massive Particles (although a variety of searches for axions are ongoing). These are particles with masses ranging from roughly the proton mass, to 1000 x the proton mass. The hope is that by putting large (~100 kg or larger) experiments underground, where cosmic rays are shielded, experiments can detect the rare scattering of one of these WIMPs as they pass through the detector. (Estimates of the local density suggest that for WIMPs 300 x the proton mass, there should be about 1000 of them in a cubic meter of space near Earth.)
For dark matter to scatter off of the nucleus, it must interact with it. In the standard model, there are only a limited number of possibilities, and for “renormalizable” interactions, there are only two. It can scatter by exchanging a Z-boson, or by exchanging a Higgs boson.
If the interaction is through a Z-boson, the strength is completely calculable. While a “weak” interaction, the Z-boson provides a relatively strong interaction as far as weak interactions go. Indeed, a WIMP exchanging a Z-boson to elastically scatter off a nucleus would have been seen already about a decade ago, and is excluded by about four orders of magnitude by present experiments (i.e., current experiments would have seen roughly 10^4 events, instead of few or none).
However there is a second possibility – that the WIMP interacts through a Higgs boson. The coupling of the Higgs to ordinary matter is orders of magnitude weaker, with a strength 10 – 100 times weaker than the current generation of experiments, but within reach of the next decade’s experiments. This is not something just pointed out now – Burgess, Pospelov and ter Veldhuis pointed this out a decade ago.
While other force carriers appear in new physics models, such as supersymmetry, even there, the Higgs is often the dominant one. Thus, if you had asked me twenty years ago* what the most interesting levels of sensitivity to think about were, I’d have told you to look for the Z and the Higgs exchange. We know it’s not the Z, and we’re about to know about the Higgs.
*OK, twenty years ago I’d actually have said “huh?”, but that misses the point.
2) If anomalies mean anything, we should find out soon
A great deal of thinking and excitement on the theoretical side has come from considering dark matter anomalies. The DAMA collaboration has reported an annual modulation in the flashes of light in a NaI(Tl) experiment for a decade. This modulation signature was pointed out by Drukier, Freese and Spergel in 1986. When the Earth orbits the sun, sometimes we move with the galactic rotation and sometimes we move against it, consequently the flux of WIMPs should change seasonally, and events in the detector should as well. This is precisely what the DAMA collaboration has observed.
Competing experiments, such as XENON, CDMS, Edelweiss, ZEPLIN and others have seen no such evidence, however, excluding the most conventional scenarios. This has prompted a variety of new ideas: light dark matter, inelastic dark matter, resonant dark matter, luminous dark matter… All of these allow a signal at DAMA consistent with other searches. When compelled by a novel result, theorists begin to see a wider range of possibilities. But even these possibilities make predictions.
More recently, the CoGeNT experiment has seen event rates in their detector above what is expected from background. While no claim has been made of discovery, it is in a range where light dark matter should be expected to be found. XENON and CDMS (and in particular a recent low-energy analysis of the CDMS data, who use the same target) do not see what would have been expected, but a clear background explanation is lacking.
These may be signs of dark matter, and they may not be. If they are, we may already have guessed the correct model, or we may not have, but enough upcoming experiments have sensitivity that almost any scenario should be tested.
What should we be looking for this year?
Going forward, improvements to established detector technologies (such as CDMS) and the maturation of the liquid nobles (such as XENON, but also LUX, DEAP/CLEAN, WARP, DarkSide and more) promise an era of rapid progress, with sensitivity improving by orders of magnitude over the next decade. If WIMPs are there, this coming era is our best opportunity to see them. When coupled with the LHC and new data from astrophysics experiments (Fermi, and PLANCK among others), our attitudes of what dark matter is – or at least what it is not – will soon be entirely different.
It’s a big universe out there — maybe bigger that we think. A lot of people these days are contemplating the possibility that the wider world isn’t just more of the same; it could be that there are regions very different from ours, even with different low-energy laws of physics, outside our observable universe. It’s an old idea, which we now label the “multiverse,” even though we’re talking about regions of space connected to ours. A lot of other people are aghast that this is considered science. Personally I think science talks about unobservable things all the time, and this question is going to be resolved by people doing hard work to make sense of multiverse scenarios rather than by pronouncements about what is or is not science.
We’re very happy to have a guest post from one of the people who is doing exactly that hard work — Matt Johnson, who guest-blogged for us before. He and his collaborators just come out two papers that examine the cosmic microwave background, looking for evidence of “bubble collisions.”
First Observational Tests of Eternal Inflation
Stephen M. Feeney (UCL), Matthew C. Johnson (Perimeter Institute), Daniel J. Mortlock (Imperial College London), Hiranya V. Peiris (UCL)
First Observational Tests of Eternal Inflation: Analysis Methods and WMAP 7-Year Results
Stephen M. Feeney (UCL), Matthew C. Johnson (Perimeter Institute), Daniel J. Mortlock (Imperial College London), Hiranya V. Peiris (UCL)
The hope is that these other “universes” might not be completely separate from our own — maybe we collided in the past. They’ve done a very careful job going through the data, with intriguing but inconclusive results. (See also Backreaction.)
Looking for this kind of signature in the CMB is certainly reminiscent of the concentric circles predicted by Gurzadyan and Penrose. But despite the similarities, it’s different in crucial ways — different theory, different phenomenon leading to the signal, different analysis, different conclusions. The road to sorting out this multiverse stuff is long and treacherous, but our brave cosmological explorers will eventually guide us through.
Observing other universes: is this science fiction?
Perhaps not. Stephen Feeney, Daniel Mortlock, Hiranya Peiris and I recently performed an observational search for the signatures of colliding bubble universes in the cosmic microwave background. Before getting to our results, let me explain some of the back-story.
The idea that there might be other universes is taken quite seriously in high energy physics and cosmology these days. This is mainly due to the fact that the laws of physics, and the various “fundamental” constants appearing in them, could have been otherwise. More technically worded, there is no unique vacuum in theories of high energy physics that involve spontaneous symmetry breaking, extra dimensions, or supersymmetry. Having a bunch of vacua around is interesting, but to what extent are they actually realized in nature? Surprisingly, when a spacetime region undergoing inflation is metastable, there are cases when all of the vacua in a theory can be realized in different places and at different times. This phenomenon is known as eternal inflation. In an inflating universe, if a region is in a metastable vacuum, bubbles containing different vacua will form. These bubbles then expand, and eat into the original vacuum. However, if the space between bubbles is expanding fast enough, they never merge completely. There is always more volume to convert into different vacua through bubble formation, and the original vacuum never disappears: inflation becomes eternal. In the theory of eternal inflation, our entire observable universe resides inside one of these bubbles. Other bubbles will contain other universes. In this precise sense, many theories of high energy physics seem to predict the existence of other universes.
A little while back we advertised that Eugene Lim had volunteered to visit Haiti to teach in a university there over the summer, and would be reporting back about the experience. Here’s Eugene’s write-up — a powerful and affecting look into conditions there, and the spirit of the students.
I noticed a puzzled look on Vicky’s face — she was squinting at the blackboard filled with equations describing how the subtitution rule in integral calculus works. She is one of my better students whom I know to be following my lectures well. I took it as a cue that I have not made a point clear, and I knew I must fallen back into speaking as though as my students are native English speakers. They are not — they speak Haitian Creole, and I was trying to teach them basic intro to mathematics in English and and a smattering of Creole.
Hello from Fondwa, Haiti, elevation 850m, Population 8000. For the past twenty days, I have been teaching a group of enthusiastic Haitian university students at the University of Fondwa. As I mentioned in my previous post, the university lost all its buildings during the Jan 12 quake. At the moment, we are using an abandoned warehouse as a temporary campus. It has no roof, so we put a tin roof over to keep the rain out. We use tarps (thank you USAID) for our windows to keep the rain out. There are 3 classrooms and an office. Some of the students have lost their homes in the Jan 12 earthquake, so the university allowed them to stay inside the warehouse.
We have no running water and a few solar panels for power. Water is obtained from wells, from a spring (about 15 minutes walk up hill), and from the regular rain showers we have been getting — hurricane season is upon us after all. This often led to me wondering whether I should be wishing for rain so we can fill up our water tank, or for the sun so we can charge up our batteries.
Many of the students are extremely enthusiastic. In my first full day, when I was just waiting for a teaching assignment, Deb, Vicky and Everest approached me and asked me in halting English what I would be teaching. I told them I would probably be teaching them math, and they said they have not had a math professor for the entire semester, and oh would you help us with some of these problems. So I ended up working with them right there and then. Turns out that these vanguard of students have been trying to teach themselves math from some books. They have had some confusion with concepts that one would expect from being self-taught, but they were sharp and intelligent. I found it a joy to work with them. Deb in particular, is especially strong and spoke some English, so I hired him as my Teaching Assistant who can also translate for me. Given his mathematical acumen, I started teaching him more advanced topics in a special class.
I was assigned to teach two classes in four weeks — an Intro to mathematics (for first years) and the vaguely titled “Business Mathematics” class to the 4th years. After a quick evaluation of the students’ ability, I ended up deciding that I am going to teach the first years differential and integral calculus — useful things to know whether you are going to be an agronomist or a manager. For the “business math” class, I chose to teach them some basic statistics — with the goal that they should be able to deal with frequency and probability distribution functions when completed.
English is not a widely spoken language in Haiti, so it was a challenge to teach the classes. However, I find that we can make a lot of headway with a mixture of my rudimentary Creole and the combined English knowledge of my students, assisted by a dictionary. The classes understandably proceed slower than usual, but that is not always a bad thing in pedagogy. After a hesitant start, we settled on a good system where some of the more capable English speakers would translate for the other students in real time. Sometimes, some of the more advanced students would volunteer to teach a difficult concept which they have grasped to the class in Creole. The students are generally attentive, and eager — I am often asked to teach extra classes.
When classes are not in session, I am kept busy with students who wanted to learn more, or have questions about math or English. I find these impromptu discussion sessions the most rewarding — I can teach the students at the pace at which they are learning. As a personal bonus, I have the luxury of having the students teach *me* Creole. Although I am assigned a very good Creole teacher, I learned most of my Creole from such constant interaction with the students.
Living conditions in Fondwa are rough. I am staying in a semi-collapsed building with a couple of volunteers from the US (Rohan Mahy and Reuben Grandon), and a rotating roster of Haitian teachers, most who live outside Fondwa : unfortunately qualified teachers and lecturers are extremely scarce in Haiti. Our quake damaged building has no running water, no power, and red “X” marks on parts of the buildings that are unstable — a non-trivial indicator since we are still experiencing aftershocks (I personally felt three so far). On the other hand, we have a great view — on a clear day, we can see distant Leogane northward and the Gulf of Mexico, 80 km away.
Nevertheless, our humble abode is a palace compared to the conditions that most Haitians live in. Many of them have lost homes in the quake; some of hem are still living in tents. Ironically, many of the stone buildings collapsed, while the wooden ones survived. I visited one of the tent cities of Port-au-Prince — they are hot, dusty, crowded and so incredibly unsanitary that they seems like epidemic timebombs waiting to go off. Every single building left standing suffered some form of damage from the quake — sometimes looking past the intact facade will reveal a completely collapsed back portion of the house. This does not stop Haitians from living in them. There is a strong sense of communal spirit among rural Haitians, more than once, I was told by the tenants that their house was “kraze” (destroyed) in the gudu-gudu (quake) and they are living in that “kind madame’s” house. Our neighbouring house, a wooden structure no bigger than the size of a school bus, is home to thirty men, women and children.
The Haitians are very friendly. After getting past the initial bemusement (and amusement) of being called “blan” (white man) in the first few days, I find the Haitians incredibly hospitable, and resilient in the face of such hardship. Wherever I go, it is easy to smile and call out a “bonjou” or “bonswa”, or “komen ou ye” (how are you?) to people passing me or just doing chores in front of their houses. I have a special love for the Haitian children — they are the most energetic and playful bunch of kids I have ever met. A group of them would show up at our house from time to time, screaming the names of us *blan* volunteers, and we would end up playing with them until we are exhausted. It is poignant for me to know that some of them have lost siblings and parents in the quake.
I will be leaving Haiti in a few days. Personally, I found the teaching experience and my interactions with the Haitians incredibly fulfilling and rewarding. But it was also very sobering to see the damage, destruction and human misery caused by the quake. There is a lingering sense of not having done enough, and that there is so much more left to be done. I do plan to come back again, and perhaps learn enough Creole to teach in it next time.
Eugene Lim was one of my first graduate students at the University of Chicago. We violated Lorentz invariance together (it’s not as dirty as it sounds), and he’s since gone on to think about bubble collisions and eternal inflation at prestigious places like Yale, Columbia, and Cambridge.
But Eugene always cared about other things in addition to physics, and today he’s bringing us a guest post about a heart-wrenching topic: education in Haiti in the aftermath of their devastating earthquake. Not content to agitate for support from the comfort of his computer, Eugene is actually hopping on a plane this weekend to spend a month teaching math at a poor rural university. Here’s his introduction, and we hope to have a follow-up post after he returns from his travels.
On Tuesday, January 12, 2010 at 4:53pm, a massive quake hit Haiti, killing an approximate quarter of a million people, injuring another quarter of a million, and causing massive infrastructure damage. Today, more than five months later, as the news cycle has moved on, Haitians are still pulling themselves out of the disaster, with 1.5 million people still homeless.
Fondwa is the 10th Communal Section of Leogane situated about 60 km south of the Haitian capital, Port-au-Prince, near the epicenter of the quake. It is a rural community with big dreams, the peasants banded together in 1988 to form the APF (Association of Peasants of Fondwa) to create a model community, not just with the aim of providing basic services but to empower the people of Haiti by providing them with the education and knowledge to improve their own lives.
One of their amazing achievement is the founding of a university, the University of Fondwa (UNIF) in 2004 in the mountains of Haiti, offering majors in Management, Agricultural Engineering and Veterinary Science — skills necessary for a rural community to survive and thrive — with about 40 students from all over Haiti. They graduated their first class last year.
The quake destroyed all the buildings of UNIF : the main building, the dorms and the lecture halls. Remarkably, classes continued after the quake, first in tents, and hopefully soon in temporary shelters. Final exams were given and graded, and the new semester began on schedule, May 5.
I met the founder of the University, Fr. Joseph Phillipe in New York a few weeks ago (he also founded Haiti’s biggest microfinance bank, FONKOZE, but that’s another story) — a series of hopeful email inquiries inspired by the watching a documentary about Fondwa led to having coffee with him in uptown New York City. Despite the challenges that his community is facing, he was full of energy, focusing on what to do for the future. I was impressed. I told him I want to help out.
I told him I wanted to volunteer to teach in UNIF, but I was not sure what I need to do. He said “We are waiting for you in Fondwa.”
This week, I am headed down to Fondwa to teach math for a month. I was told to be prepared to be caught unprepared. Internet permitting, I hope to post a follow-up to this when I get to Fondwa with more pictures from the ground.
A month is not exactly a long time. But I hope that any help is better than no help at all — they are short on teaching staff after the quake. Personally, I have been inspired by humanitarian groups like Doctors without Borders and Paul Farmer’s Partners in Health. I can’t save lives as a doctor, but I can teach! A long term hope is to be able to build ties in Fondwa, and perhaps do this on a yearly basis. I believe that academics have a lot to contribute in making this world a better place beyond hanging out in our ivory towers.
I asked Fr. Joseph what else I can do to help, he said “Tell your friends about us, and ask your friends to come too”.
Sean has kindly allowed me to use this blog to publicize the plight of the community at Fondwa. They are still trying to get basic services in. Their main needs are monetary donations, temporary housing, clean water and volunteers! They are especially looking for long term volunteers for six months of longer. They are also looking for a President for UNIF — I am serious — if you are interested or know anybody who might be interested, email APF below.
If you like want to volunteer, the best way is to contact APF directly at email@example.com or go to the APF homepage. If you like to donate directly to APF click on the link to my blog for the bank information. If you want help out Haitians to help themselves : support Fonkoze’s microfinancing efforts by helping out here.
We’ve been talking about life quite a bit here recently at Cosmic Variance, and it’s always fun to talk about areas in which one has absolutely no professional expertise. But it’s also fun to bring in experts, which is why we’re happy to welcome Caleb Scharf as a guest blogger. Caleb is Director of Astrobiology at Columbia University, author of a textbook on the subject, an recently jumped into blogging. In this post he reminds us that we’re still learning a lot about the forms of life right here on Earth — knowledge that will be invaluable as we search for it elsewhere.
It’s a real privilege to be able to write a guest blog for Cosmic Variance and to take a little side trip from my regular postings to Life, Unbounded – the science of origins.
The modern search for life in the universe encompasses everything from exoplanets and astrochemistry to geophysics and paleontology. Underlying and motivating the investigations in these fields – collectively labeled astrobiology – there are some fundamental assumptions, but do they make sense?
In recent weeks one might be forgiven for thinking that a shadowy biosphere surrounds us, aliens are poised to dismantle civilization, and that time traveling species are flitting in and out of view like barflies on a Saturday night. It’s a little disconcerting, does the Kool Aid have something special in it this Spring?
Unfortunately I think that all of these headline grabbing items miss the real story of what life is, here on Earth and potentially further afield. The idea of ‘shadow biospheres’ or multiple origins of terrestrial life sounds intriguing, and certainly helps bring focus to the fact that we can be very blinkered in our outlook. It also steers attention away from a more interesting and demonstrably real point.
In the past couple of decades we have found a shadow biosphere, except that far from lurking in the cracks it turns out to be the biggest, most critical, biosphere on the planet. An astonishing 99.9% of life on Earth cannot be coerced to grow in a lab, and so we have overlooked it. Microbial life – single-celled bacteria and our ancient cousins the Archaea – is not just the stuff under your fingernails, it is what makes multi-cellular life like us function, and it helps govern the grand chemical cycles of our planet, from the continents to the oceans to the atmosphere. Such organisms have, over three to four billion years, evolved into an eye popping array of microscopic machines, the ultimate nano-bots. They can extract energy and raw materials from, it seems, almost any environment. A particularly good example is Desulforudis audaxviator – discovered 2.8 km down in a South African gold mine in a pocket of isolated water. Little audaxviator lives all alone when the vast majority of microbial life is utterly reliant on colonial symbiosis. It earns a living by mopping up the molecular detritus left after radioactive decay in the uranium rich rocks dissociates water and bicarbonates. That’s a very, very neat trick.
Twenty or thirty years ago we barely understood that such life existed on this planet. Now we are beginning to see that the longevity of our biosphere owes itself to precisely this crowd of ‘shadowy’ organisms. A truly wonderful paper was published a couple of years ago in which Falkowski, Fenchel and Delong laid out the big picture for life on Earth. In essence, they argue that single-celled microbial life is the manifestation of an even deeper truth; the core planetary gene set. This is the set of recipes for metabolism, or how to harvest a planet for energy, and we all rely on them. The result of billions of years of natural selection, these genes are widely dispersed across the microbial biosphere. This is true to such an extent that should 99% of life be wiped out by an asteroid collision, supervolcano, or dirty telephone receiver, the information for the molecular machinery that drives all organisms will be safely preserved in the surviving 1%. The living world does not end, it just reboots. Because of this, carbon-based life is a far more robust phenomenon than we could have ever imagined. It is the ultimate, Google-like, cloud computer.
Still though, isn’t this also a blinkered view of what might constitute life? Well, sure, but there’s another fact to consider. When we look out into the universe we find that the chemistry of our life – carbon based molecular structures – is not just occasional, it’s ubiquitous. Carbon is a fabulous player; simple molecules, rings, chains, polymers, sheets, crystals, and great clumps of sooty particles abound. Some is produced directly from the huge outflows of cooling gas from old stars, much forms in the thick nebulae and proto-stellar cocoons that eventually give rise to planets. Thousands of recognizable organic molecules, including amino acids, are found in the treacly mix of some meteorites – the remains of our own ancient solar system. This is a chemical bonanza that must have played a role in setting the stage on the young planet Earth. If this is blinkered then stick a blindfold on me.
So life on Earth is tough and tenacious, and the building blocks are everywhere. Is this enough reason to think that a similar blueprint exists in other places across the universe? Well, it’s definitely motivation to go looking, and to go looking for the kind of exotica that we already know, rather than inventing new ones. Is this reason enough to think that ‘intelligent’ life exists somewhere else? That’s a tough call. Life on Earth did remarkably well for the past 3.5 billion years without us around, I don’t think there is anything that indicates we are more than an evolutionary oddity (albeit an incredible one). It’s a big universe though, with plenty of room for oddities, even if they turn out to be extremely familiar.
We’re very happy to have a guest post from Malcolm MacIver. See if you can keep this straight: Malcolm is a professor in the departments of Mechanical Engineering and Biomedical Engineering at Northwestern, with undergraduate degrees in philosophy and computer science, and a Ph.D. in neuroscience. He’s also one of the only people I know who has a doctorate but no high school diploma.
With this varied background, Malcolm studies connections between biomechanics and neuroscience — how do brains and bodies interact? This unique expertise helped land him a gig as the science advisor on Caprica, the SyFy Channel’s prequel show to Battlestar Galactica. He also blogs at Northwestern’s Science and Society blog. It’s a pleasure to welcome him to Cosmic Variance, where he’ll tell us about robots, artificial intelligence, and war.
It’s a pleasure to guest blog for CV and Sean Carroll, a friend of some years now. In my last posting back at Northwestern University’s Science and Society Blog, I introduced some issues at the intersection of robotics, artificial intelligence (AI), and morality. While I’ve long been interested in this nexus, the most immediate impetus for the posting was meeting Peter Singer, author of the excellent book ‘Wired for War’ about the rise of unmanned warfare, while simultaneously working for the TV show Caprica and a U.S. military research agency that funds some of the work in my laboratory on bio-inspired robotics. Caprica, for those who don’t know it, is a show about a time when humans invent sentient robotic warriors. Caprica is a prequel to Battlestar Galactica, and as we know from that show, these warriors rise up against humans and nearly drive them to extinction.
Here, I’d like to push the idea that as interesting as the technical challenges in making sentient robots like those on Caprica are, an equally interesting area is the moral challenges of making such machines. But “interesting” is too dispassionate—I believe that we need to begin the conversation on these moral challenges. Roboticist Ron Arkin has been making this point for some time, and has written a book on how we may integrate ethical decision making into autonomous robots.
Given that we are hardly at the threshold of building sentient robots, it may seem overly dramatic to characterize this as an urgent concern, but new developments in the way we wage war should make you think otherwise. I heard a telling sign of how things are changing when I recently tuned in to the live feed of the most popular radio station in Washington DC, WTOP. The station had commercial after commercial from iRobot (of Roomba fame), a leading builder of unmanned military robots, clearly targeting military listeners. These commercials reflect how the use of unmanned robots in the military has gone from close to zero in 2001 to over ten thousand now, with the pace of acquisition still accelerating. For more details on this, see Peter Singer’s ‘Wired for War’, or the March 23 2010 congressional hearing on The Rise of the Drones here.
Over the last few months I have had the pleasure of discussing science and science journalism with Faye Flam, who covers science for The Philadelphia Inquirer. Faye reports on all kinds of science, and a number of other topics, as you can read about on her web site. But most recently she has put a great deal of work into covering climate change; even interviewing Michael Mann, who will be visiting us at Penn for a physics colloquium in just a couple of weeks. And she has found it enough of a challenge that she has chosen to write about it as a (first of several, I hope) guest post.
This is a hot topic, as we all know, and I’m hoping we get a thoughtful and respectful discussion in the comments. Nevertheless, this might be a good place to remind people that we’ll generally delete comments that are off topic or offensive.
Now, here’s Faye.
There must be some redeeming lesson to come from covering the so-called climate gate scandal that’s dragged on over the last two months. Member of the public actually care about science. They’re even passionate about it. But when that happens it’s not always pretty.
Never in my 14 years as a newspaper science writer have I found myself on the receiving end of such a powerful stream of hate mail – searing bombs of name-calling that get fired into my personal and work inboxes, as well as screaming, profanity-laced screeds landing in my voice mail. There’s much gloating about the downfall of newspapers and speculation that soon I’ll perish on the streets, begging for pennies.
I even got my first death threat following this story. It was the first of three stories I wrote on this topic for the Philadelphia Inquirer after a cache of e-mail messages were stolen from some prominent climate scientists and picked over by their worst enemies for signs of malfeasance.
Many member of the public are raging at me for failing to point out what they see as an inexcusable case of scientific fraud. For them, there’s no distinction between committing fraud and being wrong. That might worry some members of the scientific community.
I wasn’t ordered to write anything on this issue. During the same period I also wrote a nice story about the Hubble Telescope, and one about heroic cancer researchers. I could easily have skipped this whole mess and written other nice stories – on Kepler, or maybe LHC. People always like stories about planets and particles.
But instead, I returned from Thanksgiving vacation to write this quick overview, followed by the more offbeat Q and A story linked above.
Then, in a fit of masochism, I decided to profile one of the scientists involved – Michael Mann – because he works nearby at Penn State University. That gave the whole thing a local angle.
Mann’s work has been scrutinized for years, after a researcher in Canada pointed out a possible statistical flaw in some climate reconstructions done in the 1990s. That eventually led to an investigation by a National Academy panel. They concluded that Mann’s initial papers weren’t perfect but the general conclusions held up, and there was no evidence of fraud.
In other areas of science, the public can be more tolerant. Back in the 1990s, people were in some disagreement about the age of the universe. When new information came in, some were shown to be off be a few billions years, give or take, but they didn’t get carted off to Siberia.
Others had wrong ideas about the shape and fate of the universe, since nobody back then thought it was accelerating. That’s the beauty of science. It’s self-correcting – though sometimes the corrections can take a while.
The other lesson here is that many people don’t understand the role of uncertainty in science. There is uncertainty over the way water vapor changes the situation, for example, with most experts saying it will create a positive feedback but a few arguing for a negative one.
And still, some people write to inform me that the science is “settled.” These critics are not sure what’s settled but they’ve heard this and seem to think it’s important to repeat.
Others recognize the uncertainty in climate science and find it appalling. That’s particularly true of engineers, who seem pretty well-represented among self-proclaimed global warming skeptics. It’s a level of uncertainty that would never fly in modeling systems for chemical refineries, or so they tell me.
One MIT-trained engineer said his own calculations prove that the climate models can’t work because, in short: “junk in equals junk out”. It would make for a great story if a local guy who worked for a chemical refinery took down the whole climate science establishment on the back of an envelope. Unfortunately, I have to consider the possibility that he hasn’t.
The global warming skeptics also love to use the term “AGW theory”. This proved a great strategy for debating because the scientists don’t really refer to anthropogenic global warming as a theory, and many aren’t sure what AGW theory means. That gives the critics the freedom to say it means that only humans can influence the climate – and that the climate never changed at all before humans hit the scene. Then they can point to this untenable position and say, “ha ha – aren’t these scientists dumb!”
Coming from the more liberal side of things, a reader suggested that even if some fatal flaw crops up in both the climate models and the climate reconstructions, and the world does plunge into a protracted global cold spell, the scientists who had done the original work shouldn’t necessarily be thrown in prison or burned at the stake.
It might seem strange, even insane, for the public to base views of the carbon cycle and water vapor feedbacks on politics. Is it a problem of science illiteracy? I don’t think so. We could all be better educated about basic physics and chemistry and this debate would still play out the same way.
It all makes more sense, though, in light of the way differing political philosophies tolerate uncertainty – whether they’re considering government-funded scientists delivering uncertainty or the prospect of policy changes based on uncertain science. How much should we know before we start conserving energy? Classify CO2 as a pollutant? Submitting to international regulations? The best we can do as scientists and science writers is respect those political differences, state what’s known as clearly as possible, and be honest about what’s not known. People will still hate us, of course. There’s no way to escape that.