Is our universe the only universe?
Category Archives: Physics
Enormous hole in the universe may not be the only one
By Carole Mundell, University of Bath
Astronomers have found evidence of a giant void that could be the largest known structure in the universe. The “supervoid” solves a controversial cosmic puzzle: it explains the origin of a large and anomalously cold region of the sky. However, future observations are needed to confirm the discovery and determine whether the void is unique.
The so-called cold spot can be seen in maps of the Cosmic Microwave Background (CMB), which is the radiation left over from the birth of the universe. It was first discovered by NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) in 2004 and confirmed by ESA’s Planck Satellite. For more than a decade, astronomers have failed to explain its existence. But there has been no shortage of suggestions, with unproven and controversial theories being put forward including imprints of parallel universes, called the multiverse theory, and exotic physics in the early universe.
Now an international team of astronomers led by Istvan Szapudi of the Institute for Astronomy at The University of Hawaii at Manoa have found evidence for one of the theories: a supervoid, in which the density of galaxies is much lower than usual in the known universe.
Explainer: The mysterious dark energy that speeds the universe’s rate of expansion
By Robert Scherrer, Vanderbilt University
The nature of dark energy is one of the most important unsolved problems in all of science. But what, exactly, is dark energy, and why do we even believe that it exists?
Step back a minute and consider a more familiar experience: what happens when you toss a ball straight up into the air? It gradually slows down as gravity tugs on it, finally stopping in mid-air and falling back to the ground. Of course, if you threw the ball hard enough (about 25,000 miles per hour) it would actually escape from the Earth entirely and shoot into space, never to return. But even in that case, gravity would continue to pull feebly on the ball, slowing its speed as it escaped the clutches of the Earth.
But now imagine something completely different. Suppose that you tossed a ball into the air, and instead of being attracted back to the ground, the ball was repelled by the Earth and blasted faster and faster into the sky. This would be an astonishing event, but it’s exactly what astronomers have observed happening to the entire universe!
Dark matter discovery may open a new frontier in physics
Christian Science Monitor reports: A quartet of colliding galaxies in a vast cluster 1.4 billion light-years away may prompt scientists to rethink their notions about the nature of dark matter – a hidden form of matter that makes up some 85 percent of all the matter in the universe.
Dark matter forms cocoons in which galaxies and clusters of galaxies form. Its gravity holds galaxies together. It’s “dark” because, as currently conceived, it rarely, if ever, interacts with ordinary matter, or even itself, other than through gravity.
Out at the cluster, known as Abell 3827, hints have emerged that dark matter may be less reclusive than previously believed. Three of the four merging galaxies appear to be sitting in the middle of their own dark-matter halos, as theory predicts. The fourth halo, however, appears to be trailing its galaxy like a reluctant retriever tugging at the end of a 5,000-light-year-long leash.
Unless astrophysicists can come up with and verify a more prosaic reason for the offset, which still could happen, this could be the first hint that dark matter does interact with other dark matter and by a means other than gravity.
If dark matter turns out to interact with itself, the implications could be profound, researchers say.
It would provide confirmation at the cosmic level that a new physics frontier lies beyond the standard model of physics, which describes a zoo of subatomic particles and their interactions. The standard model has no candidates for dark-matter particles, explains Dan Hooper, an astrophysicist at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill.
Confronted with self-interacting dark matter, physics then would have to do more than identify the subatomic particle associated with dark matter itself. They also would have to propose particles that in effect govern the interactions.
“There is a huge difference between zero interactions and even teeny tiny interactions,” explains Richard Massey, an astrophysicist at the Institute for Computational Cosmology at Durham University in Britain and the lead author of a formal description of the Abell 3827 observation, published this week in the Monthly Notices of the Royal Astronomical Society. [Continue reading…]
The quantum mechanics of fate
George Musser writes: The objective world simply is, it does not happen,” wrote mathematician and physicist Hermann Weyl in 1949. From his point of view, the universe is laid out in time as surely as it is laid out in space. Time does not pass, and the past and future are as real as the present. If your common sense rebels against this idea, it is probably for a single reason: the arrow of causality. Events in the past cause events in the present which cause events in the future. If time really is like space, then shouldn’t events from the future influence the present and past, too?
They actually might. Physicists as renowned as John Wheeler, Richard Feynman, Dennis Sciama, and Yakir Aharonov have speculated that causality is a two-headed arrow and the future might influence the past. Today, the leading advocate of this position is Huw Price, a University of Cambridge philosopher who specializes in the physics of time. “The answer to the question, ‘Could the world be such that we do have a limited amount of control over the past,’ ” Price says, “is yes.” What’s more, Price and others argue that the evidence for such control has been staring at us for more than half a century.
That evidence, they say, is something called entanglement, a signature feature of quantum mechanics. The word “entanglement” has the same connotations as a romantic entanglement: a special, and potentially troublesome, relationship. Entangled particles start off in close proximity when they are produced in the laboratory. Then, when they are separated, they behave like a pair of magic dice. You can “roll” one in Las Vegas (or make a measurement on it), your friend can roll the other in Atlantic City, N.J., and each die will land on a random side. But whatever those two sides are, they will have a consistent relationship to each other: They could be identical, for example, or always differ by one. If you ever saw this happen, you might assume the dice were loaded or fixed before they were rolled. But no crooked dice could behave this way. After all, the Atlantic City die changes its behavior depending on what is going on with the Las Vegas die and vice versa, even if you roll them at the same moment.
The standard interpretation of entanglement is that there is some kind of instant communication happening between the two particles. Any communication between them would have to travel the intervening distance instantaneously—that is, infinitely fast. That is plainly faster than light, a speed of communication prohibited by the theory of relativity. According to Einstein, nothing at all should be able to do that, leading him to think that some new physics must be operating, beyond the scope of quantum mechanics itself. [Continue reading…]
Too many worlds
Philip Ball writes: In July 2011, participants at a conference on the placid shore of Lake Traunsee in Austria were polled on what they thought the meeting was about. You might imagine that this question would have been settled in advance, but since the broad theme was quantum theory, perhaps a degree of uncertainty was to be expected. The title of the conference was ‘Quantum Physics and the Nature of Reality’. The poll, completed by 33 of the participating physicists, mathematicians and philosophers, posed a range of unresolved questions about the relationship between those two things, one of which was: ‘What is your favourite interpretation of quantum mechanics?’
The word ‘favourite’ speaks volumes. Isn’t science supposed to be decided by experiment and observation, free from personal preferences? But experiments in quantum physics have been obstinately silent on what it means. All we can do is develop hunches, intuitions and, yes, cherished ideas. Of these, the survey offered no fewer than 11 to choose from (as well as ‘other’ and ‘none’).
The most popular (supported by 42 per cent of the very small sample) was basically the view put forward by Niels Bohr, Werner Heisenberg and their colleagues in the early days of quantum theory. Today it is known as the Copenhagen Interpretation. More on that below. You might not recognise most of the other alternatives, such as Quantum Bayesianism, Relational Quantum Mechanics, and Objective Collapse (which is not, as you might suppose, just saying ‘what the hell’). Maybe you haven’t heard of the Copenhagen Interpretation either. But in third place (18 per cent) was the Many Worlds Interpretation (MWI), and I suspect you do know something about that, since the MWI is the one with all the glamour and publicity. It tells us that we have multiple selves, living other lives in other universes, quite possibly doing all the things that we dream of but will never achieve (or never dare). Who could resist such an idea?
Yet resist we should. We should resist not just because MWI is unlikely to be true, or even because, since no one knows how to test it, the idea is perhaps not truly scientific at all. Those are valid criticisms, but the main reason we should hold out is that it is incoherent, both philosophically and logically. There could be no better contender for Wolfgang Pauli’s famous put-down: it is not even wrong. [Continue reading…]
Stunning astronomical discovery vanishes in cloud of dust
Space.com reports: It is the announcement no one wanted to hear: The most exciting astronomical discovery of 2014 has vanished. Two groups of scientists announced today (Jan. 30) that a tantalizing signal — which some scientists claimed was “smoking gun” evidence of dramatic cosmic expansion just after the birth of the universe — was actually caused by something much more mundane: interstellar dust.
In the cosmic inflation announcement, which was unveiled in March 2014, scientists with the BICEP2 experiment, claimed to have found patterns in light left over from the Big Bang that indicated that space had rapidly inflated at the beginning of the universe, about 13.8 billion years ago. The discovery also supposedly confirmed the existence of gravitational waves, theoretical ripples in space-time.
But in a statement today, scientists with the European Space Agency said that data from the agency’s Planck space observatory has revealed that interstellar dust caused more than half of the signal detected by the Antarctica-based BICEP2 experiment. The Planck spacecraft observations were not yet available last March when the BICEP2 science team made its announcement. [Continue reading…]
Ancient planets are almost as old as the universe
New Scientist reports: The Old Ones were already ancient when the Earth was born. Five small planets orbit an 11.2 billion-year-old star, making them about 80 per cent as old as the universe itself. That means our galaxy started building rocky planets earlier than we thought.
“Now that we know that these planets can be twice as old as Earth, this opens the possibility for the existence of ancient life in the galaxy,” says Tiago Campante at the University of Birmingham in the UK.
NASA’s Kepler space telescope spotted the planets around an orange dwarf star called Kepler 444, which is 117 light years away and about 25 per cent smaller than the sun.
Orange dwarfs are considered good candidates for hosting alien life because they can stay stable for up to 30 billion years, compared to the sun’s 10 billion years, the time it takes these stars to consume all their hydrogen. For context, the universe is currently 13.8 billion years old.
Since, as far as we know, life begins by chance, older planets would have had more time to allow life to get going and evolve. But it was unclear whether planets around such an old star could be rocky – life would have a harder time on gassy planets without a solid surface. [Continue reading…]
Did physics get sucked down a wormhole?
Bryan Appleyard writes: The greatest story of our time may also be the greatest mistake. This is the story of our universe from the Big Bang to now with its bizarre, Dickensian cast of characters – black holes, tiny vibrating strings, the warped space-time continuum, trillions of companion universes and particles that wink in and out of existence.
It is the story told by a long list of officially accredited geniuses from Isaac Newton to Stephen Hawking. It is also the story that is retold daily in popular science fiction from Star Trek to the latest Hollywood sci-fi blockbuster Interstellar. Thanks to the movies, the physicist standing in front of a vast blackboard covered in equations became our age’s symbol of genius. The universe is weird, the TV shows and films tell us, and almost anything can happen.
But it is a story that many now believe is pointless, wrong and riddled with wishful thinking and superstition.
“Stephen Hawking,” says philosopher Roberto Mangabeira Unger, “is not part of the solution, he is part of the problem.”
The equations on the blackboard may be the problem. Mathematics, the language of science, may have misled the scientists.
“The idea,” says physicist Lee Smolin, “that the truth about nature can be wrestled from pure thought through mathematics is overdone… The idea that mathematics is prophetic and that mathematical structure and beauty are a clue to how nature ultimately works is just wrong.”
And in an explosive essay published last week in the science journal Nature astrophysicists George Ellis and Joe Silk say that the wild claims of theoretical physicists are threatening the authority of science itself.
“This battle for the heart and soul of physics,” they write, “is opening up at a time when scientific results — in topics from climate change to the theory of evolution — are being questioned by some politicians and religious fundamentalists. Potential damage to public confidence in science and to the nature of fundamental physics needs to be contained by deeper dialogue between scientists and philosophers….The imprimatur of science should be awarded only to a theory that is testable. Only then can we defend science from attack.”
Unger and Smolin have also just gone into print with a monumental book – The Singular Universe and the Reality of Time – which systematically takes apart contemporary physics and exposes much of it as, in Unger’s words, “an inferno of allegorical fabrication.” The book says it is time to return to real science which is tested against nature rather than constructed out of mathematics. Physics should no longer be seen as the ultimate science, underwriting all others. The true queen of the sciences should be history – the biography of the cosmos. [Continue reading…]
Before any physicists stop by to question whether I really understand what a wormhole is, I will without hesitation make it clear: I have no idea. It just seems like a suitable metaphor — better, say, than rabbit hole.
A battle for the heart and soul of physics has opened up
George Ellis and Joe Silk write: This year, debates in physics circles took a worrying turn. Faced with difficulties in applying fundamental theories to the observed Universe, some researchers called for a change in how theoretical physics is done. They began to argue — explicitly — that if a theory is sufficiently elegant and explanatory, it need not be tested experimentally, breaking with centuries of philosophical tradition of defining scientific knowledge as empirical. We disagree. As the philosopher of science Karl Popper argued: a theory must be falsifiable to be scientific.
Chief among the ‘elegance will suffice’ advocates are some string theorists. Because string theory is supposedly the ‘only game in town’ capable of unifying the four fundamental forces, they believe that it must contain a grain of truth even though it relies on extra dimensions that we can never observe. Some cosmologists, too, are seeking to abandon experimental verification of grand hypotheses that invoke imperceptible domains such as the kaleidoscopic multiverse (comprising myriad universes), the ‘many worlds’ version of quantum reality (in which observations spawn parallel branches of reality) and pre-Big Bang concepts.
These unprovable hypotheses are quite different from those that relate directly to the real world and that are testable through observations — such as the standard model of particle physics and the existence of dark matter and dark energy. As we see it, theoretical physics risks becoming a no-man’s-land between mathematics, physics and philosophy that does not truly meet the requirements of any.
The issue of testability has been lurking for a decade. String theory and multiverse theory have been criticized in popular books and articles, including some by one of us (G.E.). In March, theorist Paul Steinhardt wrote in this journal that the theory of inflationary cosmology is no longer scientific because it is so flexible that it can accommodate any observational result. Theorist and philosopher Richard Dawid and cosmologist Sean Carroll have countered those criticisms with a philosophical case to weaken the testability requirement for fundamental physics.
We applaud the fact that Dawid, Carroll and other physicists have brought the problem out into the open. But the drastic step that they are advocating needs careful debate. This battle for the heart and soul of physics is opening up at a time when scientific results — in topics from climate change to the theory of evolution — are being questioned by some politicians and religious fundamentalists. Potential damage to public confidence in science and to the nature of fundamental physics needs to be contained by deeper dialogue between scientists and philosophers. [Continue reading…]
Thousands of Einstein documents now accessible online
The New York Times reports: They have been called the Dead Sea Scrolls of physics. Since 1986, the Princeton University Press and the Hebrew University of Jerusalem, to whom Albert Einstein bequeathed his copyright, have been engaged in a mammoth effort to study some 80,000 documents he left behind.
Starting on Friday, when Digital Einstein is introduced, anyone with an Internet connection will be able to share in the letters, papers, postcards, notebooks and diaries that Einstein left scattered in Princeton and in other archives, attics and shoeboxes around the world when he died in 1955.
The Einstein Papers Project, currently edited by Diana Kormos-Buchwald, a professor of physics and the history of science at the California Institute of Technology, has already published 13 volumes in print out of a projected 30. [Continue reading…]
A universal logic of discernment
Natalie Wolchover writes: When in 2012 a computer learned to recognize cats in YouTube videos and just last month another correctly captioned a photo of “a group of young people playing a game of Frisbee,” artificial intelligence researchers hailed yet more triumphs in “deep learning,” the wildly successful set of algorithms loosely modeled on the way brains grow sensitive to features of the real world simply through exposure.
Using the latest deep-learning protocols, computer models consisting of networks of artificial neurons are becoming increasingly adept at image, speech and pattern recognition — core technologies in robotic personal assistants, complex data analysis and self-driving cars. But for all their progress training computers to pick out salient features from other, irrelevant bits of data, researchers have never fully understood why the algorithms or biological learning work.
Now, two physicists have shown that one form of deep learning works exactly like one of the most important and ubiquitous mathematical techniques in physics, a procedure for calculating the large-scale behavior of physical systems such as elementary particles, fluids and the cosmos.
The new work, completed by Pankaj Mehta of Boston University and David Schwab of Northwestern University, demonstrates that a statistical technique called “renormalization,” which allows physicists to accurately describe systems without knowing the exact state of all their component parts, also enables the artificial neural networks to categorize data as, say, “a cat” regardless of its color, size or posture in a given video.
“They actually wrote down on paper, with exact proofs, something that people only dreamed existed,” said Ilya Nemenman, a biophysicist at Emory University. “Extracting relevant features in the context of statistical physics and extracting relevant features in the context of deep learning are not just similar words, they are one and the same.”
As for our own remarkable knack for spotting a cat in the bushes, a familiar face in a crowd or indeed any object amid the swirl of color, texture and sound that surrounds us, strong similarities between deep learning and biological learning suggest that the brain may also employ a form of renormalization to make sense of the world. [Continue reading…]
Complex life may be possible in only 10% of all galaxies
Science: The universe may be a lonelier place than previously thought. Of the estimated 100 billion galaxies in the observable universe, only one in 10 can support complex life like that on Earth, a pair of astrophysicists argues. Everywhere else, stellar explosions known as gamma ray bursts would regularly wipe out any life forms more elaborate than microbes. The detonations also kept the universe lifeless for billions of years after the big bang, the researchers say.
“It’s kind of surprising that we can have life only in 10% of galaxies and only after 5 billion years,” says Brian Thomas, a physicist at Washburn University in Topeka who was not involved in the work. But “my overall impression is that they are probably right” within the uncertainties in a key parameter in the analysis.
Scientists have long mused over whether a gamma ray burst could harm Earth. The bursts were discovered in 1967 by satellites designed to spot nuclear weapons tests and now turn up at a rate of about one a day. They come in two types. Short gamma ray bursts last less than a second or two; they most likely occur when two neutron stars or black holes spiral into each other. Long gamma ray bursts last for tens of seconds and occur when massive stars burn out, collapse, and explode. They are rarer than the short ones but release roughly 100 times as much energy. A long burst can outshine the rest of the universe in gamma rays, which are highly energetic photons. [Continue reading…]
Physicists prove surprising rule of threes
Natalie Wolchover writes: More than 40 years after a Soviet nuclear physicist proposed an outlandish theory that trios of particles can arrange themselves in an infinite nesting-doll configuration, experimentalists have reported strong evidence that this bizarre state of matter is real.
In 1970, Vitaly Efimov was manipulating the equations of quantum mechanics in an attempt to calculate the behavior of sets of three particles, such as the protons and neutrons that populate atomic nuclei, when he discovered a law that pertained not only to nuclear ingredients but also, under the right conditions, to any trio of particles in nature.
While most forces act between pairs, such as the north and south poles of a magnet or a planet and its sun, Efimov identified an effect that requires three components to spring into action. Together, the components form a state of matter similar to Borromean rings, an ancient symbol of three interconnected circles in which no two are directly linked. The so-called Efimov “trimer” could consist of a trio of protons, a triatomic molecule or any other set of three particles, as long as their properties were tuned to the right values. And in a surprising flourish, this hypothetical state of matter exhibited an unheard-of feature: the ability to range in size from practically infinitesimal to infinite. [Continue reading…]
In a multiverse, what are the odds?
Natalie Wolchover and Peter Byrne write: If modern physics is to be believed, we shouldn’t be here. The meager dose of energy infusing empty space, which at higher levels would rip the cosmos apart, is a trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion times tinier than theory predicts. And the minuscule mass of the Higgs boson, whose relative smallness allows big structures such as galaxies and humans to form, falls roughly 100 quadrillion times short of expectations. Dialing up either of these constants even a little would render the universe unlivable.
To account for our incredible luck, leading cosmologists like Alan Guth and Stephen Hawking envision our universe as one of countless bubbles in an eternally frothing sea. This infinite “multiverse” would contain universes with constants tuned to any and all possible values, including some outliers, like ours, that have just the right properties to support life. In this scenario, our good luck is inevitable: A peculiar, life-friendly bubble is all we could expect to observe.
Many physicists loathe the multivere hypothesis, deeming it a cop-out of infinite proportions. But as attempts to paint our universe as an inevitable, self-contained structure falter, the multiverse camp is growing.
The problem remains how to test the hypothesis. Proponents of the multiverse idea must show that, among the rare universes that support life, ours is statistically typical. The exact dose of vacuum energy, the precise mass of our underweight Higgs boson, and other anomalies must have high odds within the subset of habitable universes. If the properties of this universe still seem atypical even in the habitable subset, then the multiverse explanation fails.
But infinity sabotages statistical analysis. In an eternally inflating multiverse, where any bubble that can form does so infinitely many times, how do you measure “typical”? [Continue reading…]
The quantum edge
Johnjoe McFadden writes: The point of the most famous thought-experiment in quantum physics is that the quantum world is different from our familiar one. Imagine, suggested the Austrian physicist Erwin Schrödinger, that we seal a cat inside a box. The cat’s fate is linked to the quantum world through a poison that will be released only if a single radioactive atom decays. Quantum mechanics says that the atom must exist in a peculiar state called ‘superposition’ until it is observed, a state in which it has both decayed and not decayed. Furthermore, because the cat’s survival depends on what the atom does, it would appear that the cat must also exist as a superposition of a live and a dead cat until somebody opens the box and observes it. After all, the cat’s life depends on the state of the atom, and the state of the atom has not yet been decided.
Yet nobody really believes that a cat can be simultaneously dead and alive. There is a profound difference between fundamental particles, such as atoms, which do weird quantum stuff (existing in two states at once, occupying two positions at once, tunnelling through impenetrable barriers etc) and familiar classical objects, such as cats, that apparently do none of these things. Why don’t they? Simply put, because the weird quantum stuff is very fragile.
Quantum mechanics insists that all particles are also waves. But if you want to see strange quantum effects, the waves all have to line up, so that the peaks and troughs coincide. Physicists call this property coherence: it’s rather like musical notes being in tune. If the waves don’t line up, the peaks and troughs cancel each other out, destroying coherence, and you won’t see anything odd. When you’re dealing only with a single particle’s wave, on the other hand, it’s easy to keep it ‘in tune’ – it has to line up only with itself. But lining up the waves of hundreds, millions or trillions of particles is pretty much impossible. And so the weirdness gets cancelled out inside big objects. That’s why there doesn’t seem to be anything very indeterminate about a cat.
Nevertheless, wrote Schrödinger in What Is Life? (1944), some of life’s most fundamental building blocks must, like unobserved radioactive atoms, be quantum entities able to perform counterintuitive tricks. Indeed, he went on to propose that life is different from the inanimate world precisely because it inhabits a borderland between the quantum and classical world: a region we might call the quantum edge. [Continue reading…]
The grand illusion of time
Jim Holt writes: It was Albert Einstein who initiated the revolution in our understanding of time. In 1905, Einstein proved that time, as it had been understood by physicist and plain man alike, was a fiction. Our idea of time, Einstein realized, is abstracted from our experience with rhythmic phenomena: heartbeats, planetary rotations and revolutions, the swinging of pendulums, the ticking of clocks. Time judgments always come down to judgments of what happens at the same time — of simultaneity. “If, for instance, I say, ‘That train arrives here at seven o’clock,’ I mean something like this: ‘The pointing of the small hand of my watch to seven and the arrival of the train are simultaneous events,’” Einstein wrote. If the events in question are distant from each other, judgments of simultaneity can be made only by sending light signals back and forth. Einstein proved that whether an observer deems two events at different locations to be happening “at the same time” depends on his state of motion. Suppose, for example, that Jones is walking uptown on Fifth Avenue and Smith is walking downtown. Their relative motion results in a discrepancy of several days in what they would judge to be happening “now” in the Andromeda galaxy at the moment they pass each other on the sidewalk. For Smith, the space fleet launched to destroy life on earth is already on its way; for Jones, the Andromedan council of tyrants has not even decided whether to send the fleet.
What Einstein had shown was that there is no universal “now.” Whether two events are simultaneous is relative to the observer. And once simultaneity goes by the board, the very division of moments into “past,” “present,” and “future” becomes meaningless. Events judged to be in the past by one observer may still lie in the future of another; therefore, past and present must be equally definite, equally “real.” In place of the fleeting present, we are left with a vast frozen timescape — a four-dimensional “block universe.” Over here, you are being born; over there, you are celebrating the turn of the millennium; and over yonder, you’ve been dead for a while. Nothing is “flowing” from one event to another. As the mathematician Hermann Weyl memorably put it, “The objective world simply is; it does not happen.” [Continue reading…]
The thermodynamic theory of ecology
Quanta Magazine: The Western Ghats in India rise like a wall between the Arabian Sea and the heart of the subcontinent to the east. The 1,000-mile-long chain of coastal mountains is dense with lush rainforest and grasslands, and each year, clouds bearing monsoon rains blow in from the southwest and break against the mountains’ flanks, unloading water that helps make them hospitable to numerous spectacular and endangered species. The Western Ghats are one of the most biodiverse places on the planet. They were also the first testing ground of an unusual new theory in ecology that applies insights from physics to the study of the environment.
John Harte, a professor of ecology at the University of California, Berkeley, has a wry, wizened face and green eyes that light up when he describes his latest work. He has developed what he calls the maximum entropy (MaxEnt) theory of ecology, which may offer a solution to a long-standing problem in ecology: how to calculate the total number of species in an ecosystem, as well as other important numbers, based on extremely limited information — which is all that ecologists, no matter how many years they spend in the field, ever have. Five years ago, the Ghats convinced him that what he thought was possible from back-of-the-envelope calculations could work in the real world. He and his colleagues will soon publish the results of a study that estimates the number of insect and tree species living in a tropical forest in Panama. The paper will also suggest how MaxEnt could give species estimates in the Amazon, a swath of more than 2 million square miles of land that is notoriously difficult to survey.
John Harte thinks it is possible to predict the behavior of ecosystems using just a few key attributes. His method ignores nature’s small-grained complexities, which makes many ecologists skeptical of the project.If the MaxEnt theory of ecology can give good estimates in a wide variety of scenarios, it could help answer the many questions that revolve around how species are spread across the landscape, such as how many would be lost if a forest were cleared, how to design wildlife preserves that keep species intact, or how many rarely seen species might be hiding in a given area. Perhaps more importantly, the theory hints at a unified way of thinking about ecology — as a system that can be described with just a few variables, with all the complexity of life built on top. [Continue reading…]