Tag Archives: cosmology

BigBang

CDM: Cosmic Discovery Machine

We think CDM sounds much more fun than LHC, a rather dry acronym for Large Hadron Collider.

Researchers at the LHC are set to announce the latest findings in early July from the record-breaking particle smasher buried below the French and Swiss borders. Rumors point towards the discovery of the so-called Higgs boson, the particle theorized to give mass to all the other fundamental building blocks of matter. So, while this would be another exciting discovery from CERN and yet another confirmation of the fundamental and elegant Standard Model of particle physics, perhaps there is yet more to uncover, such as the exotically named “inflaton”.

[div class=attrib]From Scientific American:[end-div]

Within a sliver of a second after it was born, our universe expanded staggeringly in size, by a factor of at least 10^26. That’s what most cosmologists maintain, although it remains a mystery as to what might have begun and ended this wild expansion. Now scientists are increasingly wondering if the most powerful particle collider in history, the Large Hadron Collider (LHC) in Europe, could shed light on this mysterious growth, called inflation, by catching a glimpse of the particle behind it. It could be that the main target of the collider’s current experiments, the Higgs boson, which is thought to endow all matter with mass, could also be this inflationary agent.

During inflation, spacetime is thought to have swelled in volume at an accelerating rate, from about a quadrillionth the size of an atom to the size of a dime. This rapid expansion would help explain why the cosmos today is as extraordinarily uniform as it is, with only very tiny variations in the distribution of matter and energy. The expansion would also help explain why the universe on a large scale appears geometrically flat, meaning that the fabric of space is not curved in a way that bends the paths of light beams and objects traveling within it.

The particle or field behind inflation, referred to as the “inflaton,” is thought to possess a very unusual property: it generates a repulsive gravitational field. To cause space to inflate as profoundly and temporarily as it did, the field’s energy throughout space must have varied in strength over time, from very high to very low, with inflation ending once the energy sunk low enough, according to theoretical physicists.

Much remains unknown about inflation, and some prominent critics of the idea wonder if it happened at all. Scientists have looked at the cosmic microwave background radiation—the afterglow of the big bang—to rule out some inflationary scenarios. “But it cannot tell us much about the nature of the inflaton itself,” says particle cosmologist Anupam Mazumdar at Lancaster University in England, such as its mass or the specific ways it might interact with other particles.

A number of research teams have suggested competing ideas about how the LHC might discover the inflaton. Skeptics think it highly unlikely that any earthly particle collider could shed light on inflation, because the uppermost energy densities one could imagine with inflation would be about 10^50 times above the LHC’s capabilities. However, because inflation varied with strength over time, scientists have argued the LHC may have at least enough energy to re-create inflation’s final stages.

It could be that the principal particle ongoing collider runs aim to detect, the Higgs boson, could also underlie inflation.

“The idea of the Higgs driving inflation can only take place if the Higgs’s mass lies within a particular interval, the kind which the LHC can see,” says theoretical physicist Mikhail Shaposhnikov at the École Polytechnique Fédérale de Lausanne in Switzerland. Indeed, evidence of the Higgs boson was reported at the LHC in December at a mass of about 125 billion electron volts, roughly the mass of 125 hydrogen atoms.

Also intriguing: the Higgs as well as the inflaton are thought to have varied with strength over time. In fact, the inventor of inflation theory, cosmologist Alan Guth at the Massachusetts Institute of Technology, originally assumed inflation was driven by the Higgs field of a conjectured grand unified theory.

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]Image courtesy of Physics World.[end-div]

BigBang

The 100 Million Year Collision

Four billion, or so, years from now, our very own Milky Way galaxy is expected to begin a slow but enormous collision with its galactic sibling, the Andromeda galaxy. Cosmologists predict the ensuing galactic smash will take around 100 million years to complete. It’s a shame we’ll not be around to witness the spectacle.

[div class=attrib]From Scientific American:[end-div]

The galactic theme in the context of planets and life is an interesting one. Take our own particular circumstances. As unappealingly non-Copernican as it is, there is no doubt that the Milky Way galaxy today is ‘special’. This should not be confused with any notion that special galaxy=special humans, since it’s really not clear yet that the astrophysical specialness of the galaxy has significant bearing on the likelihood of us sitting here picking our teeth. Nonetheless, the scientific method being what it is, we need to pay attention to any and all observations with as little bias as possible – so asking the question of what a ‘special’ galaxy might mean for life is OK, just don’t get too carried away.

First of all the Milky Way galaxy is big. As spiral galaxies go it’s in the upper echelons of diameter and mass. In the relatively nearby universe, it and our nearest large galaxy, Andromeda, are the sumo’s in the room. This immediately makes it somewhat unusual, the great majority of galaxies in the observable universe are smaller. The relationship to Andromeda is also very particular. In effect the Milky Way and Andromeda are a binary pair, our mutual distortion of spacetime is resulting in us barreling together at about 80 miles a second. In about 4 billion years these two galaxies will begin a ponderous collision lasting for perhaps 100 million years or so. It will be a soft type of collision – individual stars are so tiny compared to the distances between them that they themselves are unlikely to collide, but the great masses of gas and dust in the two galaxies will smack together – triggering the formation of new stars and planetary systems.

Some dynamical models (including those in the most recent work based on Hubble telescope measurements) suggest that our solar system could be flung further away from the center of the merging galaxies, others indicate it could end up thrown towards the newly forming stellar core of a future Goliath galaxy (Milkomeda?). Does any of this matter for life? For us the answer may be moot. In about only 1 billion years the Sun will have grown luminous enough that the temperate climate we enjoy on the Earth may be long gone. In 3-4 billion years it may be luminous enough that Mars, if not utterly dried out and devoid of atmosphere by then, could sustain ‘habitable‘ temperatures. Depending on where the vagaries of gravitational dynamics take the solar system as Andromeda comes lumbering through, we might end up surrounded by the pop and crackle of supernova as the collision-induced formation of new massive stars gets underway. All in all it doesn’t look too good. But for other places, other solar systems that we see forming today, it could be a very different story.

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]Image: Composition of Milky Way and Andromeda. Courtesy of NASA, ESA, Z. Levay and R. van der Marel (STScI), T. Hallas, and A. Mellinger).[end-div]

BigBang

Mutant Gravity and Dark Magnetism

Scientific consensus states that our universe is not only expanding, but expanding at an ever-increasing rate. So, sometime in the very distant future (tens of billions of years) our Milky Way galaxy will be mostly alone, accompanied only by its close galactic neighbors, such as Andromeda. All else in the universe will have receded beyond the horizon of visible light. And, yet for all the experimental evidence, no one knows the precise cause(s) of this acceleration or even of the expansion itself. But, there is no shortage of bold new theories.

[div class=attrib]From New Scientist:[end-div]

WE WILL be lonely in the late days of the cosmos. Its glittering vastness will slowly fade as countless galaxies retreat beyond the horizon of our vision. Tens of billions of years from now, only a dense huddle of nearby galaxies will be left, gazing out into otherwise blank space.

That gloomy future comes about because space is expanding ever faster, allowing far-off regions to slip across the boundary from which light has time to reach us. We call the author of these woes dark energy, but we are no nearer to discovering its identity. Might the culprit be a repulsive force that emerges from the energy of empty spaceMovie Camera, or perhaps a modification of gravity at the largest scales? Each option has its charms, but also profound problems.

But what if that mysterious force making off with the light of the cosmos is an alien echo of light itself? Light is just an expression of the force of electromagnetism, and vast electromagnetic waves of a kind forbidden by conventional physics, with wavelengths trillions of times larger than the observable universe, might explain dark energy’s baleful presence. That is the bold notion of two cosmologists who think that such waves could also account for the mysterious magnetic fields that we see threading through even the emptiest parts of our universe. Smaller versions could be emanating from black holes within our galaxy.

It is almost two decades since we realised that the universe is running away with itself. The discovery came from observations of supernovae that were dimmer, and so further away, than was expected, and earned its discoverers the Nobel prize in physics in 2011.

Prime suspect in the dark-energy mystery is the cosmological constant, an unchanging energy which might emerge from the froth of short-lived, virtual particles that according to quantum theory are fizzing about constantly in otherwise empty space.

Mutant gravity

To cause the cosmic acceleration we see, dark energy would need to have an energy density of about half a joule per cubic kilometre of space. When physicists try to tot up the energy of all those virtual particles, however, the answer comes to either exactly zero (which is bad), or something so enormous that empty space would rip all matter to shreds (which is very bad). In this latter case the answer is a staggering 120 orders of magnitude out, making it a shoo-in for the least accurate prediction in all of physics.

This stumbling block has sent some researchers down another path. They argue that in dark energy we are seeing an entirely new side to gravity. At distances of many billions of light years, it might turn from an attractive to a repulsive force.

But it is dangerous to be so cavalier with gravity. Einstein’s general theory of relativity describes gravity as the bending of space and time, and predicts the motions of planets and spacecraft in our own solar system with cast-iron accuracy. Try bending the theory to make it fit acceleration on a cosmic scale, and it usually comes unstuck closer to home.

That hasn’t stopped many physicists persevering along this route. Until recently, Jose Beltrán and Antonio Maroto were among them. In 2008 at the Complutense University of Madrid, Spain, they were playing with a particular version of a mutant gravity model called a vector-tensor theory, which they had found could mimic dark energy. Then came a sudden realisation. The new theory was supposed to be describing a strange version of gravity, but its equations bore an uncanny resemblance to some of the mathematics underlying another force. “They looked like electromagnetism,” says Beltrán, now based at the University of Geneva in Switzerland. “We started to think there could be a connection.”

So they decided to see what would happen if their mathematics described not masses and space-time, but magnets and voltages. That meant taking a fresh look at electromagnetism. Like most of nature’s fundamental forces, electromagnetism is best understood as a phenomenon in which things come chopped into little pieces, or quanta. In this case the quanta are photons: massless, chargeless particles carrying fluctuating electric and magnetic fields that point at right angles to their direction of motion.

Alien photons

This description, called quantum electrodynamics or QED, can explain a vast range of phenomena, from the behaviour of light to the forces that bind molecules together. QED has arguably been tested more precisely than any other physical theory, but it has a dark secret. It wants to spit out not only photons, but also two other, alien entities.

The first kind is a wave in which the electric field points along the direction of motion, rather than at right angles as it does with ordinary photons. This longitudinal mode moves rather like a sound wave in air. The second kind, called a temporal mode, has no magnetic field. Instead, it is a wave of pure electric potential, or voltage. Like all quantum entities, these waves come in particle packets, forming two new kinds of photon.

As we have never actually seen either of these alien photons in reality, physicists found a way to hide them. They are spirited away using a mathematical fix called the Lorenz condition, which means that all their attributes are always equal and opposite, cancelling each other out exactly. “They are there, but you cannot see them,” says Beltrán.

Beltrán and Maroto’s theory looked like electromagnetism, but without the Lorenz condition. So they worked through their equations to see what cosmological implications that might have.

The strange waves normally banished by the Lorenz condition may come into being as brief quantum fluctuations – virtual waves in the vacuum – and then disappear again. In the early moments of the universe, however, there is thought to have been an episode of violent expansion called inflation, which was driven by very powerful repulsive gravity. The force of this expansion grabbed all kinds of quantum fluctuations and amplified them hugely. It created ripples in the density of matter, for example, which eventually seeded galaxies and other structures in the universe.

Crucially, inflation could also have boosted the new electromagnetic waves. Beltrán and Maroto found that this process would leave behind vast temporal modes: waves of electric potential with wavelengths many orders of magnitude larger than the observable universe. These waves contain some energy but because they are so vast we do not perceive them as waves at all. So their energy would be invisible, dark… perhaps, dark energy?

Beltrán and Maroto called their idea dark magnetism (arxiv.org/abs/1112.1106). Unlike the cosmological constant, it may be able to explain the actual quantity of dark energy in the universe. The energy in those temporal modes depends on the exact time inflation started. One plausible moment is about 10 trillionths of a second after the big bang, when the universe cooled below a critical temperature and electromagnetism split from the weak nuclear force to become a force in its own right. Physics would have suffered a sudden wrench, enough perhaps to provide the impetus for inflation.

If inflation did happen at this “electroweak transition”, Beltrán and Maroto calculate that it would have produced temporal modes with an energy density close to that of dark energy. The correspondence is only within an order of magnitude, which may not seem all that precise. In comparison with the cosmological constant, however, it is mildly miraculous.

The theory might also explain the mysterious existence of large-scale cosmic magnetic fields. Within galaxies we see the unmistakable mark of magnetic fields as they twist the polarisation of light. Although the turbulent formation and growth of galaxies could boost a pre-existing field, is it not clear where that seed field would have come from.

Even more strangely, magnetic fields seem to have infiltrated the emptiest deserts of the cosmos. Their influence was noticed in 2010 by Andrii Neronov and Ievgen Vovk at the Geneva Observatory. Some distant galaxies emit blistering gamma rays with energies in the teraelectronvolt range. These hugely energetic photons should smack into background starlight on their way to us, creating electrons and positrons that in turn will boost other photons up to gamma energies of around 100 gigaelectronvolts. The trouble is that astronomers see relatively little of this secondary radiation. Neronov and Vovk suggest that is because a diffuse magnetic field is randomly bending the path of electrons and positrons, making their emission more diffuse (Science, vol 32, p 73).

“It is difficult to explain cosmic magnetic fields on the largest scales by conventional mechanisms,” says astrophysicist Larry Widrow of Queen’s University in Kingston, Ontario, Canada. “Their existence in the voids might signal an exotic mechanism.” One suggestion is that giant flaws in space-time called cosmic strings are whipping them up.

With dark magnetism, such a stringy solution would be superfluous. As well as the gigantic temporal modes, dark magnetism should also lead to smaller longitudinal waves bouncing around the cosmos. These waves could generate magnetism on the largest scales and in the emptiest voids.

To begin with, Beltrán and Maroto had some qualms. “It is always dangerous to modify a well-established theory,” says Beltrán. Cosmologist Sean Carroll at the California Institute of Technology in Pasadena, echoes this concern. “They are doing extreme violence to electromagnetism. There are all sorts of dangers that things might go wrong,” he says. Such meddling could easily throw up absurdities, predicting that electromagnetic forces are different from what we actually see.

The duo soon reassured themselves, however. Although the theory means that temporal and longitudinal modes can make themselves felt, the only thing that can generate them is an ultra-strong gravitational field such as the repulsive field that sprang up in the era of inflation. So within the atom, in all our lab experiments, and out there among the planets, electromagnetism carries on in just the same way as QED predicts.

Carroll is not convinced. “It seems like a long shot,” he says. But others are being won over. Gonzalo Olmo, a cosmologist at the University of Valencia, Spain, was initially sceptical but is now keen. “The idea is fantastic. If we quantise electromagnetic fields in an expanding universe, the effect follows naturally.”

So how might we tell whether the idea is correct? Dark magnetism is not that easy to test. It is almost unchanging, and would stretch space in almost exactly the same way as a cosmological constant, so we can’t tell the two ideas apart simply by watching how cosmic acceleration has changed over time.

Ancient mark

Instead, the theory might be challenged by peering deep into the cosmic microwave background, a sea of radiation emitted when the universe was less than 400,000 years old. Imprinted on this radiation are the original ripples of matter density caused by inflation, and it may bear another ancient mark. The turmoil of inflation should have energised gravitational waves, travelling warps in space-time that stretch and squeeze everything they pass through. These waves should affect the polarisation of cosmic microwaves in a distinctive way, which could tell us about the timing and the violence of inflation. The European Space Agency’s Planck spacecraft might just spot this signature. If Planck or a future mission finds that inflation happened before the electroweak transition, at a higher energy scale, then that would rule out dark magnetism in its current form.

Olmo thinks that the theory might anyhow need some numerical tweaking, so that might not be fatal, although it would be a blow to lose the link between the electroweak transition and the correct amount of dark energy.

One day, we might even be able to see the twisted light of dark magnetism. In its present incarnation with inflation at the electroweak scale, the longitudinal waves would all have wavelengths greater than a few hundred million kilometres, longer than the distance from Earth to the sun. Detecting a light wave efficiently requires an instrument not much smaller than the wavelength, but in the distant future it might just be possible to pick up such waves using space-based radio telescopes linked up across the solar system. If inflation kicked in earlier at an even higher energy, as suggested by Olmo, some of the longitudinal waves could be much shorter. That would bring them within reach of Earth-based technology. Beltrán suggests that they might be detected with the Square Kilometre Array – a massive radio instrument due to come on stream within the next decade.

If these dark electromagnetic waves can be created by strong gravitational fields, then they could also be produced by the strongest fields in the cosmos today, those generated around black holes. Beltrán suggests that waves may be emitted by the black hole at the centre of the Milky Way. They might be short enough for us to see – but they could easily be invisibly faint. Beltrán and Maroto are planning to do the calculations to find out.

One thing they have calculated from their theory is the voltage of the universe. The voltage of the vast temporal waves of electric potential started at zero when they were first created at the time of inflation, and ramped up steadily. Today, it has reached a pretty lively 1027 volts, or a billion billion gigavolts.

Just as well for us that it has nowhere to discharge. Unless, that is, some other strange quirk of cosmology brings a parallel universe nearby. The encounter would probably destroy the universe as we know it, but at least then our otherwise dark and lonely future would end with the mother of all lightning bolts.

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]Graphic courtesy of NASA / WMAP.[end-div]

BigBang

Something Out of Nothing

The debate on how the universe came to be rages on. Perhaps, however, we are a little closer to understanding why there is “something”, including us, rather than “nothing”.

[div class=attrib]From Scientific American:[end-div]

Why is there something rather than nothing? This is one of those profound questions that is easy to ask but difficult to answer. For millennia humans simply said, “God did it”: a creator existed before the universe and brought it into existence out of nothing. But this just begs the question of what created God—and if God does not need a creator, logic dictates that neither does the universe. Science deals with natural (not supernatural) causes and, as such, has several ways of exploring where the “something” came from.

Multiple universes. There are many multiverse hypotheses predicted from mathematics and physics that show how our universe may have been born from another universe. For example, our universe may be just one of many bubble universes with varying laws of nature. Those universes with laws similar to ours will produce stars, some of which collapse into black holes and singularities that give birth to new universes—in a manner similar to the singularity that physicists believe gave rise to the big bang.

M-theory. In his and Leonard Mlodinow’s 2010 book, The Grand Design, Stephen Hawking embraces “M-theory” (an extension of string theory that includes 11 dimensions) as “the only candidate for a complete theory of the universe. If it is finite—and this has yet to be proved—it will be a model of a universe that creates itself.”

Quantum foam creation. The “nothing” of the vacuum of space actually consists of subatomic spacetime turbulence at extremely small distances measurable at the Planck scale—the length at which the structure of spacetime is dominated by quantum gravity. At this scale, the Heisenberg uncertainty principle allows energy to briefly decay into particles and antiparticles, thereby producing “something” from “nothing.”

Nothing is unstable. In his new book, A Universe from Nothing, cosmologist Lawrence M. Krauss attempts to link quantum physics to Einstein’s general theory of relativity to explain the origin of a universe from nothing: “In quantum gravity, universes can, and indeed always will, spontaneously appear from nothing. Such universes need not be empty, but can have matter and radiation in them, as long as the total energy, including the negative energy associated with gravity [balancing the positive energy of matter], is zero.” Furthermore, “for the closed universes that might be created through such mechanisms to last for longer than infinitesimal times, something like inflation is necessary.” Observations show that the universe is in fact flat (there is just enough matter to slow its expansion but not to halt it), has zero total energy and underwent rapid inflation, or expansion, soon after the big bang, as described by inflationary cosmology. Krauss concludes: “Quantum gravity not only appears to allow universes to be created from noth ing—meaning … absence of space and time—it may require them. ‘Nothing’—in this case no space, no time, no anything!—is unstable.”

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]Image: There’s Nothing Out There. Courtesy of Rolfe Kanefsky / Image Entertainment.[end-div]

BigBang

Spacetime as an Emergent Phenomenon

A small, but growing, idea in theoretical physics and cosmology is that spacetime may be emergent. That is, spacetime emerges from something much more fundamental, in much the same way that our perception of temperature emerges from the motion and characteristics of underlying particles.

[div class=attrib]More on this new front in our quest to answer the most basic of questions from FQXi:[end-div]

Imagine if nothing around you was real. And, no, not in a science-fiction Matrix sense, but in an actual science-fact way.

Technically, our perceived reality is a gigantic series of approximations: The tables, chairs, people, and cell phones that we interact with every day are actually made up of tiny particles—as all good schoolchildren learn. From the motion and characteristics of those particles emerge the properties that we see and feel, including color and temperature. Though we don’t see those particles, because they are so much smaller than the phenomena our bodies are built to sense, they govern our day-to-day existence.

Now, what if spacetime is emergent too? That’s the question that Joanna Karczmarek, a string theorist at the University of British Columbia, Vancouver, is attempting to answer. As a string theorist, Karczmarek is familiar with imagining invisible constituents of reality. String theorists posit that at a fundamental level, matter is made up of unthinkably tiny vibrating threads of energy that underlie subatomic particles, such as quarks and electrons. Most string theorists, however, assume that such strings dance across a pre-existing and fundamental stage set by spacetime. Karczmarek is pushing things a step further, by suggesting that spacetime itself is not fundamental, but made of more basic constituents.

Having carried out early research in atomic, molecular and optical physics, Karczmarek shifted into string theory because she “was more excited by areas where less was known”—and looking for the building blocks from which spacetime arises certainly fits that criteria. The project, funded by a $40,000 FQXi grant, is “high risk but high payoff,” Karczmarek says.

Although one of only a few string theorists to address the issue, Karczmarek is part of a growing movement in the wider physics community to create a theory that shows spacetime is emergent. (See, for instance, “Breaking the Universe’s Speed Limit.”) The problem really comes into focus for those attempting to combine quantum mechanics with Einstein’s theory of general relativity and thus is traditionally tackled directly by quantum gravity researchers, rather than by string theorists, Karczmarek notes.

That may change though. Nathan Seiberg, a string theorist at the Institute for Advanced Study (IAS) in Princeton, New Jersey, has found good reasons for his stringy colleagues to believe that at least space—if not spacetime—is emergent. “With space we can sort of imagine how it might work,” Sieberg says. To explain how, Seiberg uses an everyday example—the emergence of an apparently smooth surface of water in a bowl. “If you examine the water at the level of particles, there is no smooth surface. It looks like there is, but this is an approximation,” Seiberg says. Similarly, he has found examples in string theory where some spatial dimensions emerge when you take a step back from the picture (arXiv:hep-th/0601234v1). “At shorter distances it doesn’t look like these dimensions are there because they are quantum fluctuations that are very rapid,” Seiberg explains. “In fact, the notion of space ceases to make sense, and eventually if you go to shorter and shorter distances you don’t even need it for the formulation of the theory.”

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]Image courtesy of Nature.[end-div]

BigBang

So Where Is Everybody?

Astrobiologist Caleb Scharf brings us up to date on Fermi’s Paradox — which asks why, given that our galaxy is so old, haven’t other sentient intergalactic travelers found us. The answer may come from a video game.

[div class=attrib]From Scientific American:[end-div]

Right now, all across the planet, millions of people are engaged in a struggle with enormous implications for the very nature of life itself. Making sophisticated tactical decisions and wrestling with chilling and complex moral puzzles, they are quite literally deciding the fate of our existence.

Or at least they are pretending to.

The video game Mass Effect has now reached its third and final installment; a huge planet-destroying, species-wrecking, epic finale to a story that takes humanity from its tentative steps into interstellar space to a critical role in a galactic, and even intergalactic saga. It’s awfully good, even without all the fantastic visual design or gameplay, at the heart is a rip-roaring plot and countless backstories that tie the experience into one of the most carefully and completely imagined sci-fi universes out there.

As a scientist, and someone who will sheepishly admit to a love of videogames (from countless hours spent as a teenager coding my own rather inferior efforts, to an occasional consumer’s dip into the lushness of what a multi-billion dollar industry can produce), the Mass Effect series is fascinating for a number of reasons. The first of which is the relentless attention to plausible background detail. Take for example the task of finding mineral resources in Mass Effect 2. Flying your ship to different star systems presents you with a bird’s eye view of the planets, each of which has a fleshed out description – be it inhabited, or more often, uninhabitable. These have been torn from the annals of the real exoplanets, gussied up a little, but still recognizable. There are hot Jupiters, and icy Neptune-like worlds. There are gassy planets, rocky planets, and watery planets of great diversity in age, history and elemental composition. It’s a surprisingly good representation of what we now think is really out there.

But the biggest idea, the biggest piece of fiction-meets-genuine-scientific-hypothesis is the overarching story of Mass Effect. It directly addresses one of the great questions of astrobiology – is there intelligent life elsewhere in our galaxy, and if so, why haven’t we intersected with it yet? The first serious thinking about this problem seems to have arisen during a lunchtime chat in the 1940?s where the famous physicist Enrico Fermi (for whom the fundamental particle type ‘fermion’ is named) is supposed to have asked “Where is Everybody?” The essence of the Fermi Paradox is that since our galaxy is very old, perhaps 10 billion years old, unless intelligent life is almost impossibly rare it will have arisen ages before we came along. Such life will have had time to essentially span the Milky Way, even if spreading out at relatively slow sub-light speeds, it – or its artificial surrogates, machines – will have reached every nook and cranny. Thus we should have noticed it, or been noticed by it, unless we are truly the only example of intelligent life.

The Fermi Paradox comes with a ton of caveats and variants. It’s not hard to think of all manner of reasons why intelligent life might be teeming out there, but still not have met us – from self-destructive behavior to the realistic hurdles of interstellar travel. But to my mind Mass Effect has what is perhaps one of the most interesting, if not entertaining, solutions. This will spoil the story; you have been warned.

Without going into all the colorful details, the central premise is that a hugely advanced and ancient race of artificially intelligent machines ‘harvests’ all sentient, space-faring life in the Milky Way every 50,000 years. These machines otherwise lie dormant out in the depths of intergalactic space. They have constructed and positioned an ingenious web of technological devices (including the Mass Effect relays, providing rapid interstellar travel) and habitats within the Galaxy that effectively sieve through the rising civilizations, helping the successful flourish and multiply, ripening them up for eventual culling. The reason for this? Well, the plot is complex and somewhat ambiguous, but one thing that these machines do is use the genetic slurry of millions, billions of individuals from a species to create new versions of themselves.

It’s a grand ol’ piece of sci-fi opera, but it also provides a neat solution to the Fermi Paradox via a number of ideas: a) The most truly advanced interstellar species spends most of its time out of the Galaxy in hibernation. b) Purging all other sentient (space-faring) life every 50,000 years puts a stop to any great spreading across the Galaxy. c) Sentient, space-faring species are inevitably drawn into the technological lures and habitats left for them, and so are less inclined to explore.

These make it very unlikely that until a species is capable of at least proper interplanetary space travel (in the game humans have to reach Mars to become aware of what’s going on at all) it will have to conclude that the Galaxy is a lonely place.

[div class=attrib]Read more after the jump.[end-div]

[div class=attrib]Image: Intragalactic life. Courtesy of J. Schombert, U. Oregon.[end-div]

BigBang

The More Things Stay the Same, the More They Change?

[div class=attrib]From Scientific American:[end-div]

Some things never change. physicists call them the constants of nature. Such quantities as the velocity of light, c, Newton’s constant of gravitation, G, and the mass of the electron, me, are assumed to be the same at all places and times in the universe. They form the scaffolding around which the theories of physics are erected, and they define the fabric of our universe. Physics has progressed by making ever more accurate measurements of their values.

And yet, remarkably, no one has ever successfully predicted or explained any of the constants. Physicists have no idea why constants take the special numerical values that they do (given the choice of units). In SI units, c is 299,792,458; G is 6.673 × 10–11; and me is 9.10938188 × 10–31 —numbers that follow no discernible pattern. The only thread running through the values is that if many of them were even slightly different, complex atomic structures such as living beings would not be possible. The desire to explain the constants has been one of the driving forces behind efforts to develop a complete unified description of nature, or “theory of everything.” Physicists have hoped that such a theory would show that each of the constants of nature could have only one logically possible value. It would reveal an underlying order to the seeming arbitrariness of nature.

In recent years, however, the status of the constants has grown more muddied, not less. Researchers have found that the best candidate for a theory of everything, the variant of string theory called M-theory, is self-consistent only if the universe has more than four dimensions of space and time—as many as seven more. One  implication is that the constants we observe may not, in fact, be the truly fundamental ones. Those live in the full higher-dimensional space, and we see only their three-dimensional “shadows.”

Meanwhile physicists have also come to appreciate that the values of many of the constants may be the result of mere happenstance, acquired during random events and elementary particle processes early in the history of the universe. In fact, string theory allows for a vast number—10500 —of possible “worlds” with different self-consistent sets of laws and constants. So far researchers have no idea why our combination was selected. Continued study may reduce the number of logically possible worlds to one, but we have to remain open to the unnerving possibility that our known universe is but one of many—a part of a multiverse—and that different parts of the multiverse exhibit different solutions to the theory, our observed laws of nature being merely one edition of many systems of local bylaws.

No further explanation would then be possible for many of our numerical constants other than that they constitute a rare combination that permits consciousness to evolve. Our observable uni verse could be one of many isolated oases surrounded by an infinity of lifeless space—a surreal place where different forces of nature hold sway and particles such as electrons or structures such as carbon atoms and DNA molecules could be impossibilities. If you tried to venture into that outside world, you would cease to be.

Thus, string theory gives with the right hand and takes with the left. It was devised in part to explain the seemingly arbitrary values of the physical constants, and the basic equations of the theory contain few arbitrary parameters. Yet so far string theory offers no explanation for the observed values of the constants.

[div class=attrib]Read the entire article here.[end-div]

BigBang

A Theory of Everything? Nah

A peer-reviewed journal recently published a 100-page scientific paper describing a theory of everything that unifies quantum theory and relativity (a long sought-after goal) with the origin of life, evolution and cosmology. And, best of all the paper contains no mathematics.

The paper written by a faculty member at Case Western Reserve University raises interesting issues about the peer review process and the viral spread of information, whether it’s correct or not.

[div class=attrib]From Ars Technica:[end-div]

Physicists have been working for decades on a “theory of everything,” one that unites quantum mechanics and relativity. Apparently, they were being too modest. Yesterday saw publication of a press release claiming a biologist had just published a theory accounting for all of that—and handling the origin of life and the creation of the Moon in the bargain. Better yet, no math!

Where did such a crazy theory originate? In the mind of a biologist at a respected research institution, Case Western Reserve University Medical School. Amazingly, he managed to get his ideas published, then amplified by an official press release. At least two sites with poor editorial control then reposted the press release—verbatim—as a news story.

Gyres all the way down

The theory in question springs from the brain of one Erik Andrulis, a CWRU faculty member who has a number of earlier papers on fairly standard biochemistry. The new paper was accepted by an open access journal called Life, meaning that you can freely download a copy of its 105 pages if you’re so inclined. Apparently, the journal is peer-reviewed, which is a bit of a surprise; even accepting that the paper makes a purely theoretical proposal, it is nothing like science as I’ve ever seen it practiced.

The basic idea is that everything, from subatomic particles to living systems, is based on helical systems the author calls “gyres,” which transform matter, energy, and information. These transformations then determine the properties of various natural systems, living and otherwise. What are these gyres? It’s really hard to say; even Andrulis admits that they’re just “a straightforward and non-mathematical core model” (although he seems to think that’s a good thing). Just about everything can be derived from this core model; the author cites “major phenomena including, but not limited to, quantum gravity, phase transitions of water, why living systems are predominantly CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur), homochirality of sugars and amino acids, homeoviscous adaptation, triplet code, and DNA mutations.”

He’s serious about the “not limited to” part; one of the sections describes how gyres could cause the Moon to form.

Is this a viable theory of everything? The word “boson,” the particle that carries forces, isn’t in the text at all. “Quark” appears once—in the title of one of the 800 references. The only subatomic particle Andrulis describes is the electron; he skips from there straight up to oxygen. Enormous gaps exist everywhere one looks.

[div class=attrib]Read more here.[end-div]

BigBang

From Nine Dimensions to Three

Over the last 40 years or so physicists and cosmologists have sought to construct a single grand theory that describes our entire universe from the subatomic soup that makes up particles and describes all forces to the vast constructs of our galaxies, and all in between and beyond. Yet a major stumbling block has been how to bring together the quantum theories that have so successfully described, and predicted, the microscopic with our current understanding of gravity. String theory is one such attempt to develop a unified theory of everything, but it remains jumbled with many possible solutions and, currently, is beyond experimental verification.

Recently however, theorists in Japan announced a computer simulation which shows how our current 3-dimensional universe may have evolved from a 9-dimensional space hypothesized by string theory.

[div class=attrib]From Interactions:[end-div]

A group of three researchers from KEK, Shizuoka University and Osaka University has for the first time revealed the way our universe was born with 3 spatial dimensions from 10-dimensional superstring theory1 in which spacetime has 9 spatial directions and 1 temporal direction. This result was obtained by numerical simulation on a supercomputer.

[Abstract]

According to Big Bang cosmology, the universe originated in an explosion from an invisibly tiny point. This theory is strongly supported by observation of the cosmic microwave background2 and the relative abundance of elements. However, a situation in which the whole universe is a tiny point exceeds the reach of Einstein’s general theory of relativity, and for that reason it has not been possible to clarify how the universe actually originated.

In superstring theory, which is considered to be the “theory of everything”, all the elementary particles are represented as various oscillation modes of very tiny strings. Among those oscillation modes, there is one that corresponds to a particle that mediates gravity, and thus the general theory of relativity can be naturally extended to the scale of elementary particles. Therefore, it is expected that superstring theory allows the investigation of the birth of the universe. However, actual calculation has been intractable because the interaction between strings is strong, so all investigation thus far has been restricted to discussing various models or scenarios.

Superstring theory predicts a space with 9 dimensions3, which poses the big puzzle of how this can be consistent with the 3-dimensional space that we live in.

A group of 3 researchers, Jun Nishimura (associate professor at KEK), Asato Tsuchiya (associate professor at Shizuoka University) and Sang-Woo Kim (project researcher at Osaka University) has succeeded in simulating the birth of the universe, using a supercomputer for calculations based on superstring theory. This showed that the universe had 9 spatial dimensions at the beginning, but only 3 of these underwent expansion at some point in time.

This work will be published soon in Physical Review Letters.

[The content of the research]

In this study, the team established a method for calculating large matrices (in the IKKT matrix model4), which represent the interactions of strings, and calculated how the 9-dimensional space changes with time. In the figure, the spatial extents in 9 directions are plotted against time.

If one goes far enough back in time, space is indeed extended in 9 directions, but then at some point only 3 of those directions start to expand rapidly. This result demonstrates, for the first time, that the 3-dimensional space that we are living in indeed emerges from the 9-dimensional space that superstring theory predicts.

This calculation was carried out on the supercomputer Hitachi SR16000 (theoretical performance: 90.3 TFLOPS) at the Yukawa Institute for Theoretical Physics of Kyoto University.

[The significance of the research]

It is almost 40 years since superstring theory was proposed as the theory of everything, extending the general theory of relativity to the scale of elementary particles. However, its validity and its usefulness remained unclear due to the difficulty of performing actual calculations. The newly obtained solution to the space-time dimensionality puzzle strongly supports the validity of the theory.

Furthermore, the establishment of a new method to analyze superstring theory using computers opens up the possibility of applying this theory to various problems. For instance, it should now be possible to provide a theoretical understanding of the inflation5 that is believed to have taken place in the early universe, and also the accelerating expansion of the universe6, whose discovery earned the Nobel Prize in Physics this year. It is expected that superstring theory will develop further and play an important role in solving such puzzles in particle physics as the existence of the dark matter that is suggested by cosmological observations, and the Higgs particle, which is expected to be discovered by LHC experiments.

[div class=attrib]Read the entire article here.[end-div]

[div class=attrib]Image: A visualization of strings. Courtesy of R. Dijkgraaf / Universe Today.[end-div]

BigBang

Pulsars Signal the Beat

Cosmology meets music. German band Reimhaus samples the regular pulse of pulsars in its music. A pulsar is the rapidly spinning remains of an exploded star — as the pulsar spins it emits a detectable beam of energy that has a very regular beat, sometimes sub-second.

[div class=attrib]From Discover:[end-div]

Some pulsars spin hundreds of times per second, some take several seconds to spin once. If you take that pulse of light and translate it into sound, you get a very steady thumping beat with very precise timing. So making it into a song is a natural thought.
But we certainly didn’t take it as far as the German band Reimhaus did, making a music video out of it! They used several pulsars for their song “Echoes, Silence, Pulses & Waves”. So here’s the cosmic beat:

[tube]86IeHiXEZ3I[/tube]

BigBang

A Great Mind Behind the Big Bang

Davide Castelvecchi over at Degrees of Freedom visits with one of the founding fathers of modern cosmology, Alan Guth.

Now professor of physics at MIT, Guth originated the now widely accepted theory of the inflationary universe. Guth’s idea, with subsequent supporting mathematics, was that the nascent universe passed through a phase of exponential expansion. In 2009, he was awarded the 2009 Isaac Newton Medal by the British Institute of Physics.

[div class=attrib]From Scientific American:[end-div]

On the night of December 6, 1979–32 years ago today–Alan Guth had the “spectacular realization” that would soon turn cosmology on its head. He imagined a mind-bogglingly brief event, at the very beginning of the big bang, during which the entire universe expanded exponentially, going from microscopic to cosmic size. That night was the birth of the concept of cosmic inflation.

Such an explosive growth, supposedly fueled by a mysterious repulsive force, could solve in one stroke several of the problems that had plagued the young theory of the big bang. It would explain why space is so close to being spatially flat (the “flatness problem”) and why the energy distribution in the early universe was so uniform even though it would not have had the time to level out uniformly (the “horizon problem”), as well as solve a riddle in particle physics: why there seems to be no magnetic monopoles, or in other words why no one has ever isolated “N” and “S” poles the way we can isolate “+” and “-” electrostatic charges; theory suggested that magnetic monopoles should be pretty common.

In fact, as he himself narrates in his highly recommendable book, The Inflationary Universe, at the time Guth was a particle physicist (on a stint at the Stanford Linear Accelerator Center, and struggling to find a permanent job) and his idea came to him while he was trying to solve the monopole problem.

Twenty-five years later, in the summer of 2004, I asked Guth–by then a full professor at MIT and a leading figure of cosmology– for his thoughts on his legacy and how it fit with the discovery of dark energy and the most recent ideas coming out of string theory.

The interview was part of my reporting for a feature on inflation that appeared in the December 2004 issue of Symmetry magazine. (It was my first feature article, other than the ones I had written as a student, and it’s still one of my favorites.)

To celebrate “inflation day,” I am reposting, in a sligthly edited form, the transcript of that interview.

DC: When you first had the idea of inflation, did you anticipate that it would turn out to be so influential?

AG: I guess the answer is no. But by the time I realized that it was a plausible solution to the monopole problem and to the flatness problem, I became very excited about the fact that, if it was correct, it would be a very important change in cosmology. But at that point, it was still a big if in my mind. Then there was a gradual process of coming to actually believe that it was right.

DC: What’s the situation 25 years later?

AG: I would say that inflation is the conventional working model of cosmology. There’s still more data to be obtained, and it’s very hard to really confirm inflation in detail. For one thing, it’s not really a detailed theory, it’s a class of theories. Certainly the details of inflation we don’t know yet. I think that it’s very convincing that the basic mechanism of inflation is correct. But I don’t think people necessarily regard it as proven.

[div class=attrib]Read the entire article here.[end-div]

[div class=attrib]Image: Alan Guth. Courtesy of Scientific American.[end-div]

BigBang

The Universe and Determinism

General scientific consensus suggests that our universe has no pre-defined destiny. While a number of current theories propose anything from a final Big Crush to an accelerating expansion into cold nothingness the future plan for the universe is not pre-determined. Unfortunately, our increasingly sophisticated scientific tools are still to meager to test and answer these questions definitively. So, theorists currently seem to have the upper hand. And, now yet another theory puts current cosmological thinking on its head by proposing that the future is pre-destined and that it may even reach back into the past to shape the present. Confused? Read on!

[div class=attrib]From FQXi:[end-div]

The universe has a destiny—and this set fate could be reaching backwards in time and combining with influences from the past to shape the present. It’s a mind-bending claim, but some cosmologists now believe that a radical reformulation of quantum mechanics in which the future can affect the past could solve some of the universe’s biggest mysteries, including how life arose. What’s more, the researchers claim that recent lab experiments are dramatically confirming the concepts underpinning this reformulation.

Cosmologist Paul Davies, at Arizona State University in Tempe, is embarking on a project to investigate the future’s reach into the present, with the help of a $70,000 grant from the Foundational Questions Institute. It is a project that has been brewing for more than 30 years, since Davies first heard of attempts by physicist Yakir Aharonov to get to root of some of the paradoxes of quantum mechanics. One of these is the theory’s apparent indeterminism: You cannot predict the outcome of experiments on a quantum particle precisely; perform exactly the same experiment on two identical particles and you will get two different results.

While most physicists faced with this have concluded that reality is fundamentally, deeply random, Aharonov argues that there is order hidden within the uncertainty. But to understand its source requires a leap of imagination that takes us beyond our traditional view of time and causality. In his radical reinterpretation of quantum mechanics, Aharonov argues that two seemingly identical particles behave differently under the same conditions because they are fundamentally different. We just do not appreciate this difference in the present because it can only be revealed by experiments carried out in the future.

“It’s a very, very profound idea,” says Davies. Aharonov’s take on quantum mechanics can explain all the usual results that the conventional interpretations can, but with the added bonus that it also explains away nature’s apparent indeterminism. What’s more, a theory in which the future can influence the past may have huge—and much needed—repercussions for our understanding of the universe, says Davies.

[div class=attrib]More from theSource here.[end-div]

BigBang

Science: A Contest of Ideas

[div class=attrib]From Project Syndicate:[end-div]

It was recently discovered that the universe’s expansion is accelerating, not slowing, as was previously thought. Light from distant exploding stars revealed that an unknown force (dubbed “dark energy”) more than outweighs gravity on cosmological scales.

Unexpected by researchers, such a force had nevertheless been predicted in 1915 by a modification that Albert Einstein proposed to his own theory of gravity, the general theory of relativity. But he later dropped the modification, known as the “cosmological term,” calling it the “biggest blunder” of his life.

So the headlines proclaim: “Einstein was right after all,” as though scientists should be compared as one would clairvoyants: Who is distinguished from the common herd by knowing the unknowable – such as the outcome of experiments that have yet to be conceived, let alone conducted? Who, with hindsight, has prophesied correctly?

But science is not a competition between scientists; it is a contest of ideas – namely, explanations of what is out there in reality, how it behaves, and why. These explanations are initially tested not by experiment but by criteria of reason, logic, applicability, and uniqueness at solving the mysteries of nature that they address. Predictions are used to test only the tiny minority of explanations that survive these criteria.

The story of why Einstein proposed the cosmological term, why he dropped it, and why cosmologists today have reintroduced it illustrates this process. Einstein sought to avoid the implication of unmodified general relativity that the universe cannot be static – that it can expand (slowing down, against its own gravity), collapse, or be instantaneously at rest, but that it cannot hang unsupported.

This particular prediction cannot be tested (no observation could establish that the universe is at rest, even if it were), but it is impossible to change the equations of general relativity arbitrarily. They are tightly constrained by the explanatory substance of Einstein’s theory, which holds that gravity is due to the curvature of spacetime, that light has the same speed for all observers, and so on.

But Einstein realized that it is possible to add one particular term – the cosmological term – and adjust its magnitude to predict a static universe, without spoiling any other explanation. All other predictions based on the previous theory of gravity – that of Isaac Newton – that were testable at the time were good approximations to those of unmodified general relativity, with that single exception: Newton’s space was an unmoving background against which objects move. There was no evidence yet, contradicting Newton’s view – no mystery of expansion to explain. Moreover, anything beyond that traditional conception of space required a considerable conceptual leap, while the cosmological term made no measurable difference to other predictions. So Einstein added it.

[div class=attrib]More from theSource here.[end-div]

[div class=attrib]Image courtesy of Wikipedia / Creative Commons.[end-div]

BigBang

Dark Matter: An Illusion?

Cosmologists and particle physicists have over the last decade or so proposed the existence of Dark Matter. It’s so called because it cannot be seen or sensed directly. It is inferred from gravitational effects on visible matter. Together with it’s theoretical cousin, Dark Energy, the two were hypothesized to make up most of the universe. In fact, the regular star-stuff — matter and energy — of which we, our planet, solar system and the visible universe are made, consists of only a paltry 4 percent.

Dark Matter and Dark Energy were originally proposed to account for discrepancies in calculations of the mass of large objects such as galaxies and galaxy clusters, and calculations derived from the mass of smaller visible objects such as stars, nebulae and interstellar gas.

The problem with Dark Matter is that it remains elusive and for the most part a theoretical construct. And, now a new group of theories suggest that the dark stuff may in fact be an illusion.

[div class=attrib]From National Geographic:[end-div]

The mysterious substance known as dark matter may actually be an illusion created by gravitational interactions between short-lived particles of matter and antimatter, a new study says.

Dark matter is thought to be an invisible substance that makes up almost a quarter of the mass in the universe. The concept was first proposed in 1933 to explain why the outer galaxies in galaxy clusters orbit faster than they should, based on the galaxies’ visible mass.

(Related: “Dark-Matter Galaxy Detected: Hidden Dwarf Lurks Nearby?”)

At the observed speeds, the outer galaxies should be flung out into space, since the clusters don’t appear to have enough mass to keep the galaxies at their edges gravitationally bound.

So physicists proposed that the galaxies are surrounded by halos of invisible matter. This dark matter provides the extra mass, which in turn creates gravitational fields strong enough to hold the clusters together.

In the new study, physicist Dragan Hajdukovic at the European Organization for Nuclear Research (CERN) in Switzerland proposes an alternative explanation, based on something he calls the “gravitational polarization of the quantum vacuum.”

(Also see “Einstein’s Gravity Confirmed on a Cosmic Scale.”)

Empty Space Filled With “Virtual” Particles

The quantum vacuum is the name physicists give to what we see as empty space.

According to quantum physics, empty space is not actually barren but is a boiling sea of so-called virtual particles and antiparticles constantly popping in and out of existence.

Antimatter particles are mirror opposites of normal matter particles. For example, an antiproton is a negatively charged version of the positively charged proton, one of the basic constituents of the atom.

When matter and antimatter collide, they annihilate in a flash of energy. The virtual particles spontaneously created in the quantum vacuum appear and then disappear so quickly that they can’t be directly observed.

In his new mathematical model, Hajdukovic investigates what would happen if virtual matter and virtual antimatter were not only electrical opposites but also gravitational opposites—an idea some physicists previously proposed.

“Mainstream physics assumes that there is only one gravitational charge, while I have assumed that there are two gravitational charges,” Hajdukovic said.

According to his idea, outlined in the current issue of the journal Astrophysics and Space Science, matter has a positive gravitational charge and antimatter a negative one.

That would mean matter and antimatter are gravitationally repulsive, so that an object made of antimatter would “fall up” in the gravitational field of Earth, which is composed of normal matter.

Particles and antiparticles could still collide, however, since gravitational repulsion is much weaker than electrical attraction.

How Galaxies Could Get Gravity Boost

While the idea of particle antigravity might seem exotic, Hajdukovic says his theory is based on well-established tenants in quantum physics.

For example, it’s long been known that particles can team up to create a so-called electric dipole, with positively charge particles at one end and negatively charged particles at the other. (See “Universe’s Existence May Be Explained by New Material.”)

According to theory, there are countless electric dipoles created by virtual particles in any given volume of the quantum vacuum.

All of these electric dipoles are randomly oriented—like countless compass needles pointing every which way. But if the dipoles form in the presence of an existing electric field, they immediately align along the same direction as the field.

According to quantum field theory, this sudden snapping to order of electric dipoles, called polarization, generates a secondary electric field that combines with and strengthens the first field.

Hajdukovic suggests that a similar phenomenon happens with gravity. If virtual matter and antimatter particles have different gravitational charges, then randomly oriented gravitational dipoles would be generated in space.

[div class=attrib]More from theSource here.[end-div]

BigBang

So the Universe is Flat?


Having just posted an article that described the universe in terms of holographic principles – a 3-D projection on a two dimensional surface, it’s timely to put the theory in context, of other theories of course. There’s a theory that posits that the universe is a bubble wrought from the collision of high-dimensional branes (membrane that is). There’s a theory that suggests that our universe is one of many in a soup of multi-verses. Other theories suggest that the universe is made up of 9, 10 or 11 dimensions.

There’s another theory that the universe is flat, and that’s where Davide Castelvecchi (mathematician, science editor at Scientific American and blogger) over at Degrees of Freedom describes the current thinking.

[div class=attrib]What Do You Mean, The Universe Is Flat? (Part I), from Degrees of Freedom:[end-div]

In the last decade—you may have read this news countless times—cosmologists have found what they say is rather convincing evidence that the universe (meaning 3-D space) is flat, or at least very close to being flat.

The exact meaning of flat, versus curved, space deserves a post of its own, and that is what Part II of this series will be about. For the time being, it is convenient to just visualize a plane as our archetype of flat object, and the surface of the Earth as our archetype of a curved one. Both are two-dimensional, but as I will describe in the next installment, flatness and curviness make sense in any number of dimensions.

What I do want to talk about here is what it is that is supposed to be flat.

When cosmologists say that the universe is flat they are referring to space—the nowverse and its parallel siblings of time past. Spacetime is not flat. It can’t be: Einstein’s general theory of relativity says that matter and energy curve spacetime, and there are enough matter and energy lying around to provide for curvature. Besides, if spacetime were flat I wouldn’t be sitting here because there would be no gravity to keep me on the chair. To put it succintly: space can be flat even if spacetime isn’t.

Moreover, when they talk about the flatness of space cosmologists are referring to the large-scale appearance of the universe. When you “zoom in” and look at something of less-than-cosmic scale, such as the solar system, space—not just spacetime—is definitely not flat. Remarkable fresh evidence for this fact was obtained recently by the longest-running experiment in NASA history, Gravity Probe B, which took a direct measurement of the curvature of space around Earth. (And the most extreme case of non-flatness of space is thought to occur inside the event horizon of a black hole, but that’s another story.)

On a cosmic scale, the curvature created in space by the countless stars, black holes, dust clouds, galaxies, and so on constitutes just a bunch of little bumps on a space that is, overall, boringly flat.

Thus the seeming contradiction:

Matter curves spacetime. The universe is flat

is easily explained, too: spacetime is curved, and so is space; but on a large scale, space is overall flat.

[div class=attrib]More from theSource here.[end-div]

[div class=attrib]Image of Cosmic Microwave Background temperature fluctuations from the 7-year Wilkinson Microwave Anisotropy Probe data seen over the full sky. Courtesy of NASA.[end-div]

BigBang

Are You Real, Or Are You a Hologram?

The principle of a holographic universe, not to be confused with the Holographic Universe, an album by swedish death metal rock band Scar Symmetry, continues to hold serious sway among a not insignificant group of even more serious cosmologists.

Originally proposed by noted physicists Gerard ‘t Hooft, and Leonard Susskind in the mid-1990s, the holographic theory of the universe suggests that our entire universe can described as a informational 3-D projection painted in two dimensions on a cosmological boundary. This is analogous to the flat hologram printed on a credit card creating the illusion of a 3-D object.

While current mathematical theory and experimental verification is lagging, the theory has garnered much interest and forward momentum — so this area warrants a brief status check, courtesy of the New Scientist.

[div class=attrib]From the New Scientist:[end-div]

TAKE a look around you. The walls, the chair you’re sitting in, your own body – they all seem real and solid. Yet there is a possibility that everything we see in the universe – including you and me – may be nothing more than a hologram.

It sounds preposterous, yet there is already some evidence that it may be true, and we could know for sure within a couple of years. If it does turn out to be the case, it would turn our common-sense conception of reality inside out.

The idea has a long history, stemming from an apparent paradox posed by Stephen Hawking’s work in the 1970s. He discovered that black holes slowly radiate their mass away. This Hawking radiation appears to carry no information, however, raising the question of what happens to the information that described the original star once the black hole evaporates. It is a cornerstone of physics that information cannot be destroyed.

In 1972 Jacob Bekenstein at the Hebrew University of Jerusalem, Israel, showed that the information content of a black hole is proportional to the two-dimensional surface area of its event horizon – the point-of-no-return for in-falling light or matter. Later, string theorists managed to show how the original star’s information could be encoded in tiny lumps and bumps on the event horizon, which would then imprint it on the Hawking radiation departing the black hole.

This solved the paradox, but theoretical physicists Leonard Susskind and Gerard ‘t Hooft decided to take the idea a step further: if a three-dimensional star could be encoded on a black hole’s 2D event horizon, maybe the same could be true of the whole universe. The universe does, after all, have a horizon 42 billion light years away, beyond which point light would not have had time to reach us since the big bang. Susskind and ‘t Hooft suggested that this 2D “surface” may encode the entire 3D universe that we experience – much like the 3D hologram that is projected from your credit card.

[div class=attrib]More from theSource here.[end-div]

[div class=attrib]Image courtesy of Computerarts.[end-div]

BigBang

When the multiverse and many-worlds collide

[div class=attrib]From the New Scientist:[end-div]

TWO of the strangest ideas in modern physics – that the cosmos constantly splits into parallel universes in which every conceivable outcome of every event happens, and the notion that our universe is part of a larger multiverse – have been unified into a single theory. This solves a bizarre but fundamental problem in cosmology and has set physics circles buzzing with excitement, as well as some bewilderment.

The problem is the observability of our universe. While most of us simply take it for granted that we should be able to observe our universe, it is a different story for cosmologists. When they apply quantum mechanics – which successfully describes the behaviour of very small objects like atoms – to the entire cosmos, the equations imply that it must exist in many different states simultaneously, a phenomenon called a superposition. Yet that is clearly not what we observe.

Cosmologists reconcile this seeming contradiction by assuming that the superposition eventually “collapses” to a single state. But they tend to ignore the problem of how or why such a collapse might occur, says cosmologist Raphael Bousso at the University of California, Berkeley. “We’ve no right to assume that it collapses. We’ve been lying to ourselves about this,” he says.

In an attempt to find a more satisfying way to explain the universe’s observability, Bousso, together with Leonard Susskind at Stanford University in California, turned to the work of physicists who have puzzled over the same problem but on a much smaller scale: why tiny objects such as electrons and photons exist in a superposition of states but larger objects like footballs and planets apparently do not.

This problem is captured in the famous thought experiment of Schrödinger’s cat. This unhappy feline is inside a sealed box containing a vial of poison that will break open when a radioactive atom decays. Being a quantum object, the atom exists in a superposition of states – so it has both decayed and not decayed at the same time. This implies that the vial must be in a superposition of states too – both broken and unbroken. And if that’s the case, then the cat must be both dead and alive as well.

[div class=attrib]More from theSource here.[end-div]

BigBang

Dark energy spotted in the cosmic microwave background

[div class=attrib]From Institute of Physics:[end-div]

Astronomers studying the cosmic microwave background (CMB) have uncovered new direct evidence for dark energy – the mysterious substance that appears to be accelerating the expansion of the universe. Their findings could also help map the structure of dark matter on the universe’s largest length scales.

The CMB is the faint afterglow of the universe’s birth in the Big Bang. Around 400,000 years after its creation, the universe had cooled sufficiently to allow electrons to bind to atomic nuclei. This “recombination” set the CMB radiation free from the dense fog of plasma that was containing it. Space telescopes such as WMAP and Planck have charted the CMB and found its presence in all parts of the sky, with a temperature of 2.7 K. However, measurements also show tiny fluctuations in this temperature on the scale of one part in a million. These fluctuations follow a Gaussian distribution.

In the first of two papers, a team of astronomers including Sudeep Das at the University of California, Berkeley, has uncovered fluctuations in the CMB that deviate from this Gaussian distribution. The deviations, observed with the Atacama Cosmology Telescope in Chile, are caused by interactions with large-scale structures in the universe, such as galaxy clusters. “On average, a CMB photon will have encountered around 50 large-scale structures before it reaches our telescope,” Das told physicsworld.com. “The gravitational influence of these structures, which are dominated by massive clumps of dark matter, will each deflect the path of the photon,” he adds. This process, called “lensing”, eventually adds up to a total deflection of around 3 arc minutes – one-20th of a degree.

Dark energy versus structure

In the second paper Das, along with Blake Sherwin of Princeton University and Joanna Dunkley of Oxford University, looks at how lensing could reveal dark energy. Dark energy acts to counter the emergence of structures within the universe. A universe with no dark energy would have a lot of structure. As a result, the CMB photons would undergo greater lensing and the fluctuations would deviate more from the original Gaussian distribution.

[div class=attrib]More from theSource here.[end-div]

BigBang

Brilliant, but Distant: Most Far-Flung Known Quasar Offers Glimpse into Early Universe

[div class=attrib]From Scientific American:[end-div]

Peering far across space and time, astronomers have located a luminous beacon aglow when the universe was still in its infancy. That beacon, a bright astrophysical object known as a quasar, shines with the luminosity of 63 trillion suns as gas falling into a supermassive black holes compresses, heats up and radiates brightly. It is farther from Earth than any other known quasar—so distant that its light, emitted 13 billion years ago, is only now reaching Earth. Because of its extreme luminosity and record-setting distance, the quasar offers a unique opportunity to study the conditions of the universe as it underwent an important transition early in cosmic history.

By the time the universe was one billion years old, the once-neutral hydrogen gas atoms in between galaxies had been almost completely stripped of their electrons (ionized) by the glow of the first massive stars. But the full timeline of that process, known as re-ionization because it separated protons and electrons, as they had been in the first 380,000 years post–big bang, is somewhat uncertain. Quasars, with their tremendous intrinsic brightness, should make for excellent markers of the re-ionization process, acting as flashlights to illuminate the intergalactic medium. But quasar hunters working with optical telescopes had only been able to see back as far as 870 million years after the big bang, when the intergalactic medium’s transition from neutral to ionized was almost complete. (The universe is now 13.75 billion years old.) Beyond that point, a quasar’s light has been so stretched, or redshifted, by cosmic expansion that it no longer falls in the visible portion of the electromagnetic spectrum but rather in the longer-wavelength infrared.

Daniel Mortlock, an astrophysicist at Imperial College London, and his colleagues used that fact to their advantage. The researchers looked for objects that showed up in a large-area infrared sky survey but not in a visible-light survey covering the same area of sky, essentially isolating the high-redshift objects. They could thus discover a quasar, known as ULAS J1120+0641, at redshift 7.085, corresponding to a time just 770 million years after the big bang. That places the newfound quasar about 100 million years earlier in cosmic history than the previous record holder, which was at redshift 6.44. Mortlock and his colleagues report their finding in the June 30 issue of Nature. (Scientific American is part of Nature Publishing Group.)

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Largest cosmic structures ‘too big’ for theories

[div class=attrib]From New Scientist:[end-div]

Space is festooned with vast “hyperclusters” of galaxies, a new cosmic map suggests. It could mean that gravity or dark energy – or perhaps something completely unknown – is behaving very strangely indeed.

We know that the universe was smooth just after its birth. Measurements of the cosmic microwave background radiation (CMB), the light emitted 370,000 years after the big bang, reveal only very slight variations in density from place to place. Gravity then took hold and amplified these variations into today’s galaxies and galaxy clusters, which in turn are arranged into big strings and knots called superclusters, with relatively empty voids in between.

On even larger scales, though, cosmological models say that the expansion of the universe should trump the clumping effect of gravity. That means there should be very little structure on scales larger than a few hundred million light years across.

But the universe, it seems, did not get the memo. Shaun Thomas of University College London (UCL), and colleagues have found aggregations of galaxies stretching for more than 3 billion light years. The hyperclusters are not very sharply defined, with only a couple of per cent variation in density from place to place, but even that density contrast is twice what theory predicts.

“This is a challenging result for the standard cosmological models,” says Francesco Sylos Labini of the University of Rome, Italy, who was not involved in the work.

Colour guide

The clumpiness emerges from an enormous catalogue of galaxies called the Sloan Digital Sky Survey, compiled with a telescope at Apache Point, New Mexico. The survey plots the 2D positions of galaxies across a quarter of the sky. “Before this survey people were looking at smaller areas,” says Thomas. “As you look at more of the sky, you start to see larger structures.”

A 2D picture of the sky cannot reveal the true large-scale structure in the universe. To get the full picture, Thomas and his colleagues also used the colour of galaxies recorded in the survey.

More distant galaxies look redder than nearby ones because their light has been stretched to longer wavelengths while travelling through an expanding universe. By selecting a variety of bright, old elliptical galaxies whose natural colour is well known, the team calculated approximate distances to more than 700,000 objects. The upshot is a rough 3D map of one quadrant of the universe, showing the hazy outlines of some enormous structures.

[div class=attrib]More from theSource here.[end-div]

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Nick Risinger’s Photopic Sky Survey

Big science covering scales from the microscopic to the vastness of the universe continues to deliver stunning new insights, now on a daily basis. I takes huge machines such as the Tevatron at Fermilab, CERN’s Large Hadron Collider, NASA’s Hubble Telescope and the myriad other detectors, arrays, spectrometers, particle smashers to probe some of our ultimate questions. The results from these machines bring us fantastic new perspectives and often show us remarkable pictures of the very small and very large.

Then there is Nick Risinger’s Photopic Sky Survey. No big science, no vast machines — just Nick Risinger, accompanied by retired father, camera equipment and 45,000 miles of travels capturing our beautiful night sky as never before.

[div class=attrib]From Nick Risinger:[end-div]

The Photopic Sky Survey is a 5,000 megapixel photograph of the entire night sky stitched together from 37,440 exposures. Large in size and scope, it portrays a world far beyond the one beneath our feet and reveals our familiar Milky Way with unfamiliar clarity.

It was clear that such a survey would be quite difficult visually hopping from one area of the sky to the next—not to mention possible lapses in coverage—so this called for a more systematic approach. I divided the sky into 624 uniformly spaced areas and entered their coordinates into the computer which gave me assurance that I was on target and would finish without any gaps. Each frame received a total of 60 exposures: 4 short, 4 medium, and 4 long shots for each camera which would help to reduce the amount of noise, overhead satellite trails and other unwanted artifacts.

And so it was with this blueprint that I worked my way through the sky, frame by frame, night after night. The click-clack of the shutters opening and closing became a staccato soundtrack for the many nights spent under the stars. Occasionally, the routine would be pierced by a bright meteor or the cry of a jackal, each compelling a feeling of eerie beauty that seemed to hang in the air. It was an experience that will stay with me a lifetime.

A truly remarkable and beautiful achievement. This is what focus and passion can achieve.

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Cosmic Smoothness

Simulations based on the standard cosmological model, as shown here, indicate that on very large distance scales, galaxies should be uniformly distributed. But observations show a clumpier distribution than expected. (The length bar represents about $2.3$ billion light years.)[div class=attrib]From American Physical Society, Michael J. Hudson:[end-div]

The universe is expected to be very nearly homogeneous in density on large scales. In Physical Review Letters, Shaun Thomas and colleagues from University College London analyze measurements of the density of galaxies on the largest spatial scales so far—billions of light years—and find that the universe is less smooth than expected. If it holds up, this result will have important implications for our understanding of dark matter, dark energy, and perhaps gravity itself.

In the current standard cosmological model, the average mass-energy density of the observable universe consists of 5% normal matter (most of which is hydrogen and helium), 23% dark matter, and 72% dark energy. The dark energy is assumed to be uniform, but the normal and dark matter are not. The balance between matter and dark energy determines both how the universe expands and how regions of unusually high or low matter density evolve with time.

The same cosmological model predicts the statistics of the nonuniform structure and their dependence on spatial scale. On scales that are small by cosmological standards, fluctuations in the matter density are comparable to its mean, in agreement with what is seen: matter is clumped into galaxies, clusters of galaxies, and filaments of the “cosmic web.” On larger scales, however, the contrast of the structures compared to the mean density decreases. On the largest cosmological scales, these density fluctuations are small in amplitude compared to the average density of the universe and so are well described by linear perturbation theory (see simulation results in Fig. 1). Moreover, these perturbations can be calibrated at early times directly from the cosmic microwave background (CMB), a snapshot of the universe from when it was only 380,000 years old. Despite the fact that only 5% of the Universe is well understood, this model is an excellent fit to data spanning a wide range of spatial scales as the fluctuations evolved from the time of the CMB to the present age of the universe, some 13.8 billion years. On the largest scales, dark energy drives accelerated expansion of the universe. Because this aspect of the standard model is least understood, it is important to test it on these scales.

Thomas et al. use publicly-released catalogs from the Sloan Digital Sky Survey to select more than 700,000 galaxies whose observed colors indicate a significant redshift and are therefore presumed to be at large cosmological distances. They use the redshift of the galaxies, combined with their observed positions on the sky, to create a rough three-dimensional map of the galaxies in space and to assess the homogeneity on scales of a couple of billion light years. One complication is that Thomas et al. measure the density of galaxies, not the density of all matter, but we expect that fluctuations of these two densities about their means to be proportional; the constant of proportionality can be calibrated by observations on smaller scales. Indeed, on small scales the galaxy data are in good agreement with the standard model. On the largest scales, the fluctuations in galaxy density are expected to be of order a percent of the mean density, but Thomas et al. find fluctuations double this prediction. This result then suggests that the universe is less homogeneous than expected.

This result is not entirely new: previous studies based on subsets of the data studied by Thomas et al. showed the same effect, albeit with a lower statistical significance. In addition, there are other ways of probing the large-scale mass distribution. For example, inhomogeneities in the mass distribution lead to inhomogeneities in the local rate of expansion. Some studies have suggested that, on very large scales, this expansion too is less homogeneous than the model predictions.

Future large-scale surveys will produce an avalanche of data. These surveys will allow the methods employed by Thomas et al. and others to be extended to still larger scales. Of course, the challenge for these future surveys will be to correct for the systematic effects to even greater accuracy.

[div class=attrib]More from theSource here.[end-div]

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The Real Rules for Time Travelers

[div class=attrib]From Discover:[end-div]

People all have their own ideas of what a time machine would look like. If you are a fan of the 1960 movie version of H. G. Wells’s classic novel, it would be a steampunk sled with a red velvet chair, flashing lights, and a giant spinning wheel on the back. For those whose notions of time travel were formed in the 1980s, it would be a souped-up stainless steel sports car. Details of operation vary from model to model, but they all have one thing in common: When someone actually travels through time, the machine ostentatiously dematerializes, only to reappear many years in the past or future. And most people could tell you that such a time machine would never work, even if it looked like a DeLorean.

They would be half right: That is not how time travel might work, but time travel in some other form is not necessarily off the table. Since time is kind of like space (the four dimensions go hand in hand), a working time machine would zoom off like a rocket rather than disappearing in a puff of smoke. Einstein described our universe in four dimensions: the three dimensions of space and one of time. So traveling back in time is nothing more or less than the fourth-dimensional version of walking in a circle. All you would have to do is use an extremely strong gravitational field, like that of a black hole, to bend space-time. From this point of view, time travel seems quite difficult but not obviously impossible.

These days, most people feel comfortable with the notion of curved space-time. What they trip up on is actually a more difficult conceptual problem, the time travel paradox. This is the worry that someone could go back in time and change the course of history. What would happen if you traveled into the past, to a time before you were born, and murdered your parents? Put more broadly, how do we avoid changing the past as we think we have already experienced it? At the moment, scientists don’t know enough about the laws of physics to say whether these laws would permit the time equivalent of walking in a circle—or, in the parlance of time travelers, a “closed timelike curve.” If they don’t permit it, there is obviously no need to worry about paradoxes. If physics is not an obstacle, however, the problem could still be constrained by logic. Do closed timelike curves necessarily lead to paradoxes?

If they do, then they cannot exist, simple as that. Logical contradictions cannot occur. More specifically, there is only one correct answer to the question “What happened at the vicinity of this particular event in space-time?” Something happens: You walk through a door, you are all by yourself, you meet someone else, you somehow never showed up, whatever it may be. And that something is whatever it is, and was whatever it was, and will be whatever it will be, once and forever. If, at a certain event, your grandfather and grandmother were getting it on, that’s what happened at that event. There is nothing you can do to change it, because it happened. You can no more change events in your past in a space-time with closed timelike curves than you can change events that already happened in ordinary space-time, with no closed timelike curves.

[div class=attrib]More from theSource here.[end-div]

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Are Black Holes the Architects of the Universe?

[div class=attrib]From Discover:[end-div]

Black holes are finally winning some respect. After long regarding them as agents of destruction or dismissing them as mere by-products of galaxies and stars, scientists are recalibrating their thinking. Now it seems that black holes debuted in a constructive role and appeared unexpectedly soon after the Big Bang. “Several years ago, nobody imagined that there were such monsters in the early universe,” says Penn State astrophysicist Yuexing Li. “Now we see that black holes were essential in creating the universe’s modern structure.”

Black holes, tortured regions of space where the pull of gravity is so intense that not even light can escape, did not always have such a high profile. They were once thought to be very rare; in fact, Albert Einstein did not believe they existed at all. Over the past several decades, though, astronomers have realized that black holes are not so unusual after all: Supermassive ones, millions or billions of times as hefty as the sun, seem to reside at the center of most, if not all, galaxies. Still, many people were shocked in 2003 when a detailed sky survey found that giant black holes were already common nearly 13 billion years ago, when the universe was less than a billion years old. Since then, researchers have been trying to figure out where these primordial holes came from and how they influenced the cosmic events that followed.

In August, researchers at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University ran a supercomputer simulation of the early universe and provided a tantalizing glimpse into the lives of the first black holes. The story began 200 million years after the Big Bang, when the universe’s first stars formed. These beasts, about 100 times the mass of the sun, were so large and energetic that they burned all their hydrogen fuel in just a few million years. With no more energy from hydrogen fusion to counteract the enormous inward pull of their gravity, the stars collapsed until all of their mass was compressed into a point of infinite density.

The first-generation black holes were puny compared with the monsters we see at the centers of galaxies today. They grew only slowly at first—adding just 1 percent to their bulk in the next 200 million years—because the hyperactive stars that spawned them had blasted away most of the nearby gas that they could have devoured. Nevertheless, those modest-size black holes left a big mark by performing a form of stellar birth control: Radiation from the trickle of material falling into the holes heated surrounding clouds of gas to about 5,000 degrees Fahrenheit, so hot that the gas could no longer easily coalesce. “You couldn’t really form stars in that stuff,” says Marcelo Alvarez, lead author of the Kavli study.

[div class=attrib]More from theSource here.[end-div]

[div class=attrib]Image courtesy of KIPAC/SLAC/M.Alvarez, T. Able, and J. Wise.[end-div]

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Will Our Universe Collide With a Neighboring One?

[div class=attrib]From Discover:[end-div]

Relaxing on an idyllic beach on Grand Cayman Island in the Caribbean, Anthony Aguirre vividly describes the worst natural disaster he can imagine. It is, in fact, probably the worst natural disaster that anyone could imagine. An asteroid impact would be small potatoes compared with this kind of event: a catastrophic encounter with an entire other universe.

As an alien cosmos came crashing into ours, its outer boundary would look like a wall racing forward at nearly the speed of light; behind that wall would lie a set of physical laws totally different from ours that would wreck everything they touched in our universe. “If we could see things in ultraslow motion, we’d see a big mirror in the sky rushing toward us because light would be reflected by the wall,” says Aguirre, a youthful physicist at the University of California at Santa Cruz. “After that we wouldn’t see anything—because we’d all be dead.”

There is a sober purpose behind this apocalyptic glee. Aguirre is one of a growing cadre of cosmologists who theorize that our universe is just one of many in a “multiverse” of universes. In their effort to grasp the implications of this idea, they have been calculating the odds that universes could interact with their neighbors or even smash into each other. While investigating what kind of gruesome end might result, they have stumbled upon a few surprises. There are tantalizing hints that our universe has already survived such a collision—and bears the scars to prove it.

Aguirre has organized a conference on Grand Cayman to address just such mind-boggling matters. The conversations here venture into multiverse mishaps and other matters of cosmological genesis and destruction. At first blush the setting seems incongruous: The tropical sun beats down dreamily, the smell of broken coconuts drifts from beneath the palm trees, and the ocean roars rhythmically in the background. But the locale is perhaps fitting. The winds are strong for this time of year, reminding the locals of hurricane Ivan, which devastated the capital city of George Town in 2004, lifting whole apartment blocks and transporting buildings across streets. In nature, peace and violence are never far from each other.

Much of today’s interest in multiple universes stems from concepts developed in the early 1980s by the pioneering cosmologists Alan Guth at MIT and Andrei Linde, then at the Lebedev Physical Institute in Moscow. Guth proposed that our universe went through an incredibly rapid growth spurt, known as inflation, in the first 10-30 second or so after the Big Bang. Such extreme expansion, driven by a powerful repulsive energy that quickly dissipated as the universe cooled, would solve many mysteries. Most notably, inflation could explain why the cosmos as we see it today is amazingly uniform in all directions. If space was stretched mightily during those first instants of existence, any extreme lumpiness or hot and cold spots would have immediately been smoothed out. This theory was modified by Linde, who had hit on a similar idea independently. Inflation made so much sense that it quickly became a part of the mainstream model of cosmology.

Soon after, Linde and Alex Vilenkin at Tufts University came to the startling realization that inflation may not have been a onetime event. If it could happen once, it could—and indeed should—happen again and again for eternity. Stranger still, every eruption of inflation would create a new bubble of space and energy. The result: an infinite progression of new universes, each bursting forth with its own laws of physics.

In such a bubbling multiverse of universes, it seems inevitable that universes would sometimes collide. But for decades cosmologists neglected this possibility, reckoning that the odds were small and that if it happened, the results would be irrelevant because anyone and anything near the collision would be annihilated.

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Stephen Hawking Is Making His Comeback

[div class=attrib]From Discover:[end-div]

As an undergraduate at Oxford University, Stephen William Hawking was a wise guy, a provocateur. He was popular, a lively coxswain for the crew team. Physics came easy. He slept through lectures, seldom studied, and criticized his professors. That all changed when he started graduate school at Cambridge in 1962 and subsequently learned that he had only a few years to live.

The symptoms first appeared while Hawking was still at Oxford. He could not row a scull as easily as he once had; he took a few bad, clumsy falls. A college doctor told him not to drink so much beer. By 1963 his condition had gotten bad enough that his mother brought him to a hospital in London, where he received the devastating diagnosis: motor neuron disease, as ALS is called in the United Kingdom. The prognosis was grim and final: rapid wasting of nerves and muscles, near-total paralysis, and death from respiratory failure in three to five years.

Not surprisingly, Hawking grew depressed, seeking solace in the music of Wagner (contrary to some media reports, however, he says he did not go on a drinking binge). And yet he did not disengage from life. Later in 1963 he met Jane Wilde, a student of medieval poetry at the University of London. They fell in love and resolved to make the most of what they both assumed would be a tragically short relationship. In 1965 they married, and Hawking returned to physics with newfound energy.

Also that year, Hawking had an encounter that led to his first major contribution to his field. The occasion was a talk at Kings College in London given by Roger Penrose, an eminent mathematician then at Birkbeck College. Penrose had just proved something remarkable and, for physicists, disturbing: Black holes, the light-trapping chasms in space-time that form in the aftermath of the collapse of massive stars, must all contain singularities—points where space, time, and the very laws of physics fall apart.

Before Penrose’s work, many physicists had regarded singularities as mere curiosities, permitted by Einstein’s theory of general relativity but unlikely to exist. The standard assumption was that a singularity could form only if a perfectly spherical star collapsed with perfect symmetry, the kind of ideal conditions that never occur in the real world. Penrose proved otherwise. He found that any star massive enough to form a black hole upon its death must create a singularity. This realization meant that the laws of physics could not be used to describe everything in the universe; the singularity was a cosmic abyss.

At a subsequent lecture, Hawking grilled Penrose on his ideas. “He asked some awkward questions,” Penrose says. “He was very much on the ball. I had probably been a bit vague in one of my statements, and he was sharpening it up a bit. I was a little alarmed that he noticed something that I had glossed over, and that he was able to spot it so quickly.”

Hawking had just renewed his search for a subject for his Ph.D. thesis, a project he had abandoned after receiving the ALS diagnosis. His condition had stabilized somewhat, and his future no longer looked completely bleak. Now he had his subject: He wanted to apply Penrose’s approach to the cosmos at large.

Physicists have known since 1929 that the universe is expanding. Hawking reasoned that if the history of the universe could be run backward, so that the universe was shrinking instead of expanding, it would behave (mathematically at least) like a collapsing star, the same sort of phenomenon Penrose had analyzed. Hawking’s work was timely. In 1965, physicists working at Bell Labs in New Jersey discovered the cosmic microwave background radiation, the first direct evidence that the universe began with the Big Bang. But was the Big Bang a singularity, or was it a concentrated, hot ball of energy—awesome and mind-bending, but still describable by the laws of physics?

[div class=attrib]More from theSource here.[end-div]

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A Scientist’s Guide to Finding Alien Life: Where, When, and in What Universe

[div class=attrib]From Discover:[end-div]

Things were not looking so good for alien life in 1976, after the Viking I spacecraft landed on Mars, stretched out its robotic arm, and gathered up a fist-size pile of red dirt for chemical testing. Results from the probe’s built-in lab were anything but encouraging. There were no clear signs of biological activity, and the pictures Viking beamed back showed a bleak, frozen desert world, backing up that grim assessment. It appeared that our best hope for finding life on another planet had blown away like dust in a Martian windstorm.

What a difference 33 years makes. Back then, Mars seemed the only remotely plausible place beyond Earth where biology could have taken root. Today our conception of life in the universe is being turned on its head as scientists are finding a whole lot of inviting real estate out there. As a result, they are beginning to think not in terms of single places to look for life but in terms of “habitable zones”—maps of the myriad places where living things could conceivably thrive beyond Earth. Such abodes of life may lie on other planets and moons throughout our galaxy, throughout the universe, and even beyond.

The pace of progress is staggering. Just last November new studies of Saturn’s moon Enceladus strengthened the case for a reservoir of warm water buried beneath its craggy surface. Nobody had ever thought of this roughly 300-mile-wide icy satellite as anything special—until the Cassini spacecraft witnessed geysers of water vapor blowing out from its surface. Now Enceladus joins Jupiter’s moon Europa on the growing list of unlikely solar system locales that seem to harbor liquid water and, in principle, the ingredients for life.

Astronomers are also closing in on a possibly huge number of Earth-like worlds around other stars. Since the mid-1990s they have already identified roughly 340 extrasolar planets. Most of these are massive gaseous bodies, but the latest searches are turning up ever-smaller worlds. Two months ago the European satellite Corot spotted an extrasolar planet less than twice the diameter of Earth (see “The Inspiring Boom in Super-Earths”), and NASA’s new Kepler probe is poised to start searching for genuine analogues of Earth later this year. Meanwhile, recent discoveries show that microorganisms are much hardier than we thought, meaning that even planets that are not terribly Earth-like might still be suited to biology.

Together, these findings indicate that Mars was only the first step of the search, not the last. The habitable zones of the cosmos are vast, it seems, and they may be teeming with life.

[div class=attrib]More from theSource here.[end-div]

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The Biocentric Universe Theory: Life Creates Time, Space, and the Cosmos Itself

[div class=attrib]From Discover:[end-div]

The farther we peer into space, the more we realize that the nature of the universe cannot be understood fully by inspecting spiral galaxies or watching distant supernovas. It lies deeper. It involves our very selves.

This insight snapped into focus one day while one of us (Lanza) was walking through the woods. Looking up, he saw a huge golden orb web spider tethered to the overhead boughs. There the creature sat on a single thread, reaching out across its web to detect the vibrations of a trapped insect struggling to escape. The spider surveyed its universe, but everything beyond that gossamer pinwheel was incomprehensible. The human observer seemed as far-off to the spider as telescopic objects seem to us. Yet there was something kindred: We humans, too, lie at the heart of a great web of space and time whose threads are connected according to laws that dwell in our minds.

Is the web possible without the spider? Are space and time physical objects that would continue to exist even if living creatures were removed from the scene?

Figuring out the nature of the real world has obsessed scientists and philosophers for millennia. Three hundred years ago, the Irish empiricist George Berkeley contributed a particularly prescient observation: The only thing we can perceive are our perceptions. In other words, consciousness is the matrix upon which the cosmos is apprehended. Color, sound, temperature, and the like exist only as perceptions in our head, not as absolute essences. In the broadest sense, we cannot be sure of an outside universe at all.

For centuries, scientists regarded Berkeley’s argument as a philosophical sideshow and continued to build physical models based on the assumption of a separate universe “out there” into which we have each individually arrived. These models presume the existence of one essential reality that prevails with us or without us. Yet since the 1920s, quantum physics experiments have routinely shown the opposite: Results do depend on whether anyone is observing. This is perhaps most vividly illustrated by the famous two-slit experiment. When someone watches a subatomic particle or a bit of light pass through the slits, the particle behaves like a bullet, passing through one hole or the other. But if no one observes the particle, it exhibits the behavior of a wave that can inhabit all possibilities—including somehow passing through both holes at the same time.

Some of the greatest physicists have described these results as so confounding they are impossible to comprehend fully, beyond the reach of metaphor, visualization, and language itself. But there is another interpretation that makes them sensible. Instead of assuming a reality that predates life and even creates it, we propose a biocentric picture of reality. From this point of view, life—particularly consciousness—creates the universe, and the universe could not exist without us.

[div class=attrib]More from theSource here.[end-div]

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The Great Cosmic Roller-Coaster Ride

[div class=attrib]From Scientific American:[end-div]

Could cosmic inflation be a sign that our universe is embedded in a far vaster realm

You might not think that cosmologists could feel claustrophobic in a universe that is 46 billion light-years in radius and filled with sextillions of stars. But one of the emerging themes of 21st-century cosmology is that the known universe, the sum of all we can see, may just be a tiny region in the full extent of space. Various types of parallel universes that make up a grand “multiverse” often arise as side effects of cosmological theories. We have little hope of ever directly observing those other universes, though, because they are either too far away or somehow detached from our own universe.

Some parallel universes, however, could be separate from but still able to interact with ours, in which case we could detect their direct effects. The possibility of these worlds came to cosmologists’ attention by way of string theory, the leading candidate for the foundational laws of nature. Although the eponymous strings of string theory are extremely small, the principles governing their properties also predict new kinds of larger membranelike objects—“branes,” for short. In particular, our universe may be a three-dimensional brane in its own right, living inside a nine-dimensional space. The reshaping of higher-dimensional space and collisions between different universes may have led to some of the features that astronomers observe today.

[div class=attrib]More from theSource here.[end-div]

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The Universe’s Invisible Hand

[div class=attrib]From Scientific American:[end-div]

Dark energy does more than hurry along the expansion of the universe. It also has a stranglehold on the shape and spacing of galaxies.

What took us so long? Only in 1998 did astronomers discover we had been missing nearly three quarters of the contents of the universe, the so-called dark energy–an unknown form of energy that surrounds each of us, tugging at us ever so slightly, holding the fate of the cosmos in its grip, but to which we are almost totally blind. Some researchers, to be sure, had anticipated that such energy existed, but even they will tell you that its detection ranks among the most revolutionary discoveries in 20th-century cosmology. Not only does dark energy appear to make up the bulk of the universe, but its existence, if it stands the test of time, will probably require the development of new theories of physics.

Scientists are just starting the long process of figuring out what dark energy is and what its implications are. One realization has already sunk in: although dark energy betrayed its existence through its effect on the universe as a whole, it may also shape the evolution of the universe’s inhabitants–stars, galaxies, galaxy clusters. Astronomers may have been staring at its handiwork for decades without realizing it.

[div class=attrib]More from theSource here.[end-div]