Largest cosmic structures 'too big' for theories

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.

Galaxies, clusters, and superclusters - mere local details?

We know that the universe was smooth just after its birth. Measurements of the cosmic microwave background radiation (CMB), the light emitted 370,000 light 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.

Coagulating dark energy

The result hints at some profound new physical phenomenon, perhaps involving dark energy – the mysterious entity that is accelerating the expansion of space. Dark energy is usually assumed to be uniform across the cosmos. If instead it can pool in some areas, then its repulsive force could push away nearby matter, creating these giant patterns.

Alternatively, we may need to extend our understanding of gravity beyond Einstein's general theory of relativity. "It could be that we need an even more general theory to explain how gravity works on very large scales," says Thomas.

A more mundane answer might yet emerge. Using colour to find distance is very sensitive to observational error, says David Spergel of Princeton University. Dust and stars in our own galaxy could confuse the dataset, for example. Although the UCL team have run some checks for these sources of error, Thomas admits that the result might turn out to be the effect of foreground stars either masking or mimicking distant galaxies.

Fractal structure?

"It will be essential to confirm this with another technique," says Spergel. The best solution would be to get detailed spectra of a large number of galaxies. Researchers would be able to work out their distances from Earth much more precisely, since they would know how much their light has been stretched, or red-shifted, by the expansion of space.

Sylos Labini has made such a map using a subset of Sloan data. It reveals clumpiness on unexpectedly large scales – though not as vast as these. He believes that the universe may have a fractal structure, looking similar at all scales.

A comprehensive catalogue of spectra for Sloan galaxies is being assembled in a project called the Baryon Oscillation Spectroscopic Survey. Meanwhile, the Dark Energy Survey will use a telescope in Chile to measure the colours of even more galaxies than Sloan, beginning in October. Such maps might bring hyperclusters out of the haze – or consign them to the status of monstrous mirage.

Source New Scientist

U.T. Experiment Grapples With Essence of Gravity

We have all experienced gravity, but even to the brightest minds in science, it remains largely a mystery. Gary J. Hill, an astronomer at the University of Texas at Austin, is trying to change that.

“We don’t know why there’s gravity,” said Mr. Hill, one of the lead astronomers on the Hobby-Eberly Telescope Dark Energy Experiment, or Hetdex, which could turn gravity’s time-honored laws on their head. “We have a pretty good theory of it. It may be that our observations could have a bearing on finally formulating why gravity exists.”

Sky reflects in the primary mirror of the Hobby-Eberly telescope at the McDonald Observatory. The mirror, partly obscured, is made of 91 segments. 

Mr. Hill has teamed with Karl Gebhardt, an astronomy professor at U.T., on the $36 million project, which has prevailed despite the threat of natural disasters, potential lack of financing and all the kinks that can throw off a long-term project. The experiment’s goal is to analyze our understanding of how the universe is expanding — with ramifications on gravity, the Big Bang theory and the fate of the universe.

“Not only is the universe expanding, but it’s accelerating,” Mr. Gebhardt said. “And so that’s what we call dark energy — the existence of the acceleration. And that’s the huge thing that no one can explain.”
Granted, in a time of high unemployment, crazy gas prices and water shortages, studying the swelling of the universe might seem out of touch. But when asked about its importance, Steven Weinberg, a Nobel Prize-winning physicist at U.T., said, “Do you really need a sermon on why settling questions about the fundamental laws of nature are worth pursuing?”

For Mr. Hill, 48, and Mr. Gebhardt, 46, even to be in position of rewriting the books is fortunate. The McDonald Observatory — where the dark-energy observations, made with the third-largest telescope in the world, are set to begin next spring after nearly 10 years of development — is about 425 miles west of Austin, in Fort Davis. In April, the Rock House Fire, which started 35 miles south of there, in Marfa, scorched the Davis Mountains surrounding the state-of-the-art observatory, putting it perilously close to going up in flames.
Mother Nature has not been the only threat. Lack of financing for an abstract experiment with little or no immediate pay-off has stymied several similar projects that sprang from the discovery of dark energy in 1998. Now, only a handful of those remain, and none have the proprietary will of Hetdex — a testament to the ego of the state of Texas.

Nearly a third of the money raised for Hetdex, which includes a one-of-its-kind $16 million spectrograph created by Mr. Hill called Virus (Visible Integral-Field Replicable Unit Spectrograph), came from private in-state sources. The largest donor, Harold Simmons, a Dallas investor and U.T. alumnus whom Forbes magazine ranked as the 55th-richest person in the United States, gave two gifts totaling $6.5 million. (Mr. Simmons’s family foundation is a major donor to The Texas Tribune.)
“I could see that figuring out the nature of dark energy would be of historic importance, not just in astronomy but for all science, and for all humankind,” Mr. Simmons said in an e-mail. “As a proud Texan, I wanted a Texas-based, Texas-led project to be first.”

Meanwhile, broader debate has recently emerged over the role of academic research in state universities, with some conservatives calling for a greater emphasis on teaching to improve efficiency. But many in the higher education community have argued that the benefits of research extend beyond universities’ bottom lines.
“This is helping us train the next generation of engineers and leaders in these fields of technology,” Mr. Gebhardt said of Hetdex, which derives about a quarter of its financing from U.T. and a $6 million special biennial line item in the state budget. “And that’s important because we don’t have a lot of that in the country.”
The impact on education goes even deeper, Mr. Hill said, explaining: “Kids, when they’re 5 or 6 or 7, these are the ones who get interested in science through fields like paleontology and astronomy. These are exciting areas.”

Where the education system falls short, Mr. Hill added, “is failing to take that excitement and actually train them so they remain excited through college.”
The McDonald Observatory’s history also provides a valuable lesson in collaboration.
On a recent tour, Thomas Barnes, the observatory’s superintendent, said U.T. did not even have an astronomy department in 1926, when William Johnson McDonald, a banker from Paris, Tex., bequeathed his $1.1 million fortune to start an observatory. U.T. enlisted the University of Chicago to design and build the operation under the direction of Otto Struve, a Russian-born, fourth-generation astronomer who operated the McDonald Observatory for 30 years, ushering it into the U.T.-led era.

“Better a foreigner than a damn Yankee,” one of the U.T. regents at the time said of Mr. Struve’s appointment, according to Mr. Barnes.
And now the U.T. astronomy department has a chance to enhance its history.
“There will only be one time when we figure out what is in the universe, and then it gets placed in the textbooks,” Mr. Gebhardt said. “We are basically living through that time now.”


Source The New York times

LSU researchers see an indication of a new type of neutrino oscillation at the T2K experiment

T2K experiment has first results

BATON ROUGE – LSU Department of Physics Professors Thomas Kutter and Martin Tzanov, and Professor Emeritus William Metcalf, along with graduate and undergraduate students, have been working for several years on an experiment in Japan called T2K, or Tokai to Kamioka Long Baseline Neutrino Oscillation Experiment, which studies the most elusive of fundamental subatomic particles – the neutrino. The team announced they have an indication of a new type of neutrino transformation or oscillation from a muon neutrino to an electron neutrino.

In the T2K experiment in Japan, a beam of muon neutrinos – one of the three types of neutrinos, which also include the electron and tau – was produced in the Japan Proton
Accelerator Research Complex, or J-PARC, located in Tokai village, Ibaraki prefecture, on the east coast of Japan. The beam was aimed at the gigantic Super-Kamiokande underground detector in Kamioka, near the west coast of Japan, 295 km, or 185 miles away from Tokai. An analysis of the detected neutrino-induced events in the Super-Kamiokande detector indicated that a small number of muon neutrinos traveling from Tokai to Kamioka transformed themselves into electron neutrinos.

As part of the experiment, high energy protons were directed onto a carbon target, where their collisions produced charged particles called pions, which travelled through a helium-filled volume where they decayed to produce a beam of the elusive neutrinos. These neutrinos then flew about 200 meters through the earth to a sophisticated detector system capable of making detailed measurements of their energy, direction and type.
"It took the international collaboration about ten years to realize the project and bring it from first idea to first results," said Kutter, leader of the T2K project at LSU. "The entire LSU team is honored to be part of the collaboration and proud to contribute to the experiment. We expect many more results in the near future and look forward to the new research opportunities which are likely to arise from the tantalizing indication of this new neutrino oscillation."

LSU physicists have been part of a number of measurements over the last decade, which include Super Kamiokande, SNO, KamLAND that have shown that neutrinos possess the strange property of neutrino oscillations – one flavor of neutrino can transform into another as it travels through space. This is significant because neutrinos were first predicted theoretically in 1930, first actually detected in 1956 and for 50 years were assumed to have zero mass. But neutrino oscillations require mass.
With mysterious linkage between the three types, neutrinos challenge the understanding of the fundamental forces and basic constituents of matter. They may be related to the mystery of why there is more matter than anti-matter in the universe, and are the focus of intense study worldwide.

Precision measurements of neutrino oscillations can be made using artificial neutrino beams. This was pioneered in Japan by the K2K neutrino experiment in which neutrinos were produced at the KEK accelerator laboratory near Tokyo and were detected using the Super-Kamiokande neutrino detector, a 50,000 ton tank of ultra-pure water located more than half a mile underground in a laboratory 183 miles away near Toyama.
T2K is a more powerful and sophisticated version of the K2K experiment, with a more intense neutrino beam derived from the newly-built main ring synchrotron at the J-PARC accelerator laboratory. The beam was built by physicists from KEK in cooperation with other Japanese institutions and with assistance from American, Canadian, UK and French T2K institutes. The beam is aimed once again at Super-Kamiokande, which has been upgraded for this experiment with new electronics and software.

Before the neutrinos leave the J-PARC facility, their properties are determined by a sophisticated "near" detector, partly based on a huge magnet donated from the CERN accelerator laboratory in Geneva. The CERN magnet was earlier used for the UA1 experiment, which won the Nobel Prize for the discovery of the W and Z bosons which are the basis of neutrino interactions. The LSU team was responsible for building major components of the "near" detector, which provided an important ingredient to the oscillation analysis.
During the next several years, the search will be improved, with the hope that the three-mode oscillation will allow a comparison of the oscillations of neutrinos and anti-neutrinos, probing the asymmetry between matter and anti-matter in the universe.

Source  EurekaAlert!

X-ray telescope finds new voracious black holes in early universe

ANN ARBOR, Mich.—Using the deepest X-ray image ever taken, a University of Michigan astronomer and her colleagues have found the first direct evidence that massive black holes were common in the early universe. This discovery from NASA's Chandra X-ray Observatory shows that very young black holes grew more aggressively than previously thought, in tandem with the growth of their host galaxies.

 This is an artist's impression of a growing supermassive black hole located in the early universe, showing a disk of gas rotating around the central object that generates copious amounts of radiation. This gas is destined to be consumed by the black hole.

By pointing Chandra at a patch of sky for over six weeks, astronomers obtained what is known as the Chandra Deep Field South (CDFS). When combined with very deep optical and infrared images from NASA's Hubble Space Telescope, the new Chandra data allowed astronomers to search for black holes in 200 distant galaxies, from when the universe was between about 800 million and 950 million years old.

"We had reason to expect that black holes existed in many of the very first galaxies, but they had evaded our searches until now. When I compared Chandra's data to my theoretical models I was stunned by their agreement. It's the dream of any theoretician," said Marta Volonteri, a U-M associate professor of astronomy and co-author of the study that appears in this week's Nature.

The super-sized growth means that the black holes in the CDFS are related to quasars, very luminous, rare objects powered by material falling onto supermassive black holes. However, the sources in the CDFS are about a hundred times fainter, and the black holes are about a thousand times less massive than the ones in quasars.

It was found that between 30 percent and 100 percent of the distant galaxies contain growing supermassive black holes. Extrapolating these results from the small observed field to the full sky, there are at least 30 million supermassive black holes in the early Universe. This is a factor of 10,000 larger than the estimated number of quasars in the early Universe.

 This composite image from NASA's Chandra X-ray Observatory and Hubble Space Telescope combines the deepest X-ray, optical and infrared views of the sky. Using these images, astronomers have obtained the first direct evidence that black holes are common in the early universe and shown that very young black holes grew more aggressively than previously thought

"It appears we've found a whole new population of baby black holes," said co-author Kevin Schawinski of Yale University. "We think these babies will grow by a factor of about a hundred or a thousand, eventually becoming like the giant black holes we see today almost 13 billion years later."

A population of baby black holes in the early universe had been predicted, but not yet observed. Detailed calculations show that the total amount of black hole growth observed by this team is about a hundred times higher than recent estimates.

"Until now, we had no idea what the black holes in these early galaxies were doing—or if they even existed," said Ezequiel Treister of the University of Hawaii, lead author of the study. "Now we know they are there and they are growing like gangbusters."

Because these baby black holes are nearly all enshrouded in thick clouds of gas and dust, optical telescopes frequently cannot detect them. However, the high energies of X-ray light can penetrate these veils, allowing the black holes inside to be studied.

Two critical issues in black hole physics are how the first supermassive black holes were formed and how they grow. Although evidence for parallel growth of black holes and galaxies has been established at closer distances, the new Chandra results show that this connection starts earlier than previously thought, perhaps right from the origin of both.

"Most astronomers think in the present-day universe, black holes and galaxies are somehow symbiotic in how they grow," said Priya Natarajan, a co-author from Yale University. "We have shown that this codependent relationship has existed from very early times."

It has been suggested that early black holes would play an important role in clearing away the cosmic "fog" of neutral (uncharged) hydrogen that pervaded the early universe when temperatures cooled down after the Big Bang. However, the Chandra study shows that blankets of dust and gas stop ultraviolet radiation generated by the black holes from traveling outwards to perform this "reionization." Therefore, stars and not growing black holes are likely to have cleared this fog at cosmic dawn.

Chandra is capable of detecting extremely faint objects at vast distances, but these black holes are so obscured that relatively few photons can escape and hence they could not be individually detected. Instead, the team used a technique that relied on Chandra's ability to very accurately determine the direction from which the X-rays came to add up all the X-ray counts near the positions of distant galaxies and find a statistically significant signal.

The title of the Nature paper describing these results is "Black hole growth in the early Universe is self-regulated and largely hidden from view." The other co-author is Eric Gawiser from Rutgers University in New Jersey.

Source University of Michigan

Why the universe wasn't fine-tuned for life

IF THE force of gravity were a few per cent weaker, it would not squeeze and heat the centre of the sun enough to ignite the nuclear reactions that generate the sunlight necessary for life on Earth. But if it were a few per cent stronger, the temperature of the solar core would have been boosted so much the sun would have burned out in less than a billion years - not enough time for the evolution of complex life like us.

In recent years many such examples of how the laws of physics have been "fine-tuned" for us to be here have been reported. Some religious people claim these "cosmic coincidences" are evidence of a grand design by a Supreme Being. In The Fallacy of Fine-tuning, physicist Victor Stenger makes a devastating demolition of such arguments.

A general mistake made in search of fine-tuning, he points out, is to vary just one physical parameter while keeping all the others constant. Yet a "theory of everything" - which alas we do not yet have - is bound to reveal intimate links between physical parameters. A change in one may be compensated by a change in another, says Stenger.

In addition to general mistakes, Stenger deals with specifics. For instance, British astronomer Fred Hoyle discovered that vital heavy elements can be built inside stars only because a carbon-12 nucleus can be made from the fusion of three helium nuclei. For the reaction to proceed, carbon-12 must have an energy level equal to the combined energy of the three helium nuclei, at the typical temperature inside a red giant. This has been touted as an example of fine-tuning. But, as Stenger points out, in 1989, astrophysicist Mario Livio showed that the carbon-12 energy level could actually have been significantly different and still resulted in a universe with the heavy elements needed for life.

The most striking example of fine-tuning appears to be the dark energy - or energy of the vacuum - that is speeding up the expansion of the universe. Calculations show it to be 10¹²⁰ bigger than quantum theory predicts. But Stenger stresses that this prediction is made in the absence of a quantum theory of gravity, when gravity is known to orchestrate the universe.
Even if some parameters turn out to be fine-tuned, Stenger argues this could be explained if ours is just one universe in a "multiverse" - an infinite number of universes, each with different physical parameters. We would then have ended up in the one where the laws of physics are fine-tuned to life because, well, how could we not have? (For a related philosophical discussion read this article.)

Religious people say that, by invoking a multiverse, physicists are going to extraordinary lengths to avoid God. But physicists have to go where the data lead them. And, currently, there are strong hints from string theory, the standard picture of cosmology and fine-tuning itself to suggest that the universe we can see with our biggest telescopes is only a small part of all that is there.

Source New Scientist

New insights into the 'hidden' galaxies of the universe

A unique example of some of the lowest surface brightness galaxies in the universe have been found by an international team of astronomers lead by the Niels Bohr Institute. The galaxy has lower amounts of heavier elements than other known galaxies of this type. The discovery means that small low surface brightness galaxies may have more in common with the first galaxies formed shortly after the Big Bang than previously thought. The results have been published in Monthly Notices of the Royal Astronomical Society.

 The galaxy ESO 546G-34 is small faint and unevolved low surface brightness galaxy of dwarf-type, which makes it somewhat similar to the Small Magellanic Cloud (companion galaxy to the Milky Way) in appearance. ESO 546G-34 has an extremely low abundance of heavier elements and contains at least 50 percent gas, which also makes it similar to the small galaxies that were abundant in the early universe.

As the name implies, the galaxies are faint and therefore difficult to find and challenging to observe. The galaxy called ESO 546-G34 is a nearly 20 year old observation that no one had previously taken much notice of. The observation has now been analysed using new methods and it is only now that astronomers have realised how special it is.
"The galaxy gives us an idea of how the galaxies must have looked before star formation really got going", explains Lars Mattsson, an astrophysicist at the Dark Cosmology Centre at the Niels Bohr Institute, University of Copenhagen. The discovery was made in collaboration with astronomers at Uppsala University and the Astronomical Observatory in Kiev.


The evolution of galaxies

A galaxy consists of many millions or billions of stars. Stars are formed when giant gas clouds condense and form a ball of glowing gas – a star. A star produces energy through the fusion of hydrogen into helium, which fuses into carbon and oxygen and further into heavier and heavier elements. The process of conversion from gases to heavier elements takes anywhere from hundreds of thousands of years to billions of years.
Most of the known galaxies that have only formed small amounts of the heavy elements are young galaxies that are undergoing gigantic outbursts of star formation. This makes them incredibly bright and easier to observe. One type of galaxy with bursts of star formation is called blue compact galaxies, as newly formed stars emit a bluish light.

'Unevolved' dwarf galaxy The galaxy that has been observed is small and contains only extremely small amounts of the heavier elements. That it consists mostly of the gases hydrogen and helium and is so faint means that it has only just begun to form stars.

 Compared to other galaxies of this type the ESO 546G-34 has a very low content of oxygen, nitrogen and an extremely small amounts of heavier elements. It contains at least 50 percent gas, which is several times higher than the corresponding values for a large evolved galaxy like the Milky Way. Also the amount of stars is lower.

"Our analysis shows that while a large, mature galaxy like our own galaxy, the Milky Way, is comprised of around 15-20 percent gas, this faint little galaxy is comprised of up to 50 percent gas and is very poor in heavier elements. This means that it is very unevolved", explains Lars Mattsson.
The theory is that the very small faint galaxies collide with each other and the greater concentration of gas material and dynamical disturbance boosts star formation and thereby form the larger blue, compact galaxies.
"ESO 546-G34 is a left over dwarf galaxy that doesn't seem to have collided with other galaxies. This gives us unique insight into how the earliest galaxies in the universe may have looked", explains Lars Mattsson.

Source EurekaAlert!

When the multiverse and many-worlds collide

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.

To explain why we never seem to see cats that are both dead and alive, and yet can detect atoms in a superposition of states, physicists have in recent years replaced the idea of superpositions collapsing with the idea that quantum objects inevitably interact with their environment, allowing information about possible superpositions to leak away and become inaccessible to the observer. All that is left is the information about a single state.

Physicists call this process "decoherence". If you can prevent it - by tracking all the information about all possible states - you can preserve the superposition.

In the case of something as large as a cat, that may be possible in Schrödinger's theoretical sealed box. But in the real world, it is very difficult to achieve. So everyday cats decohere rapidly, leaving behind the single state that we observe. By contrast, small things like photons and electrons are more easily isolated from their environment, so they can be preserved in a superposition for longer: that's how we detect these strange states.

The puzzle is how decoherence might work on the scale of the entire universe: it too must exist in a superposition of states until some of the information it contains leaks out, leaving the single state that we see, but in conventional formulations of the universe, there is nothing else for it to leak into.

What Bousso and Susskind have done is to come up with an explanation for how the universe as a whole might decohere. Their trick is to think of the volume of space that encompasses all the information in our universe and everything it might possibly interact with in the future. In previous work, Susskind has dubbed this region a causal patch. The new idea is that our universe is just one causal patch among many others in a much bigger multiverse.

Many physicists have toyed with the idea that the cosmos is made up of regions which differ so profoundly that they can be thought of as different universes inside a bigger multiverse. Bousso and Susskind suggest that information can leak from our causal patch into others, allowing our part of the universe to decohere into one state or another, resulting in the universe that we observe.

But while decoherence explains why we don't see cats that are dead and alive at the same time, or our own universe in a huge superposition of states, it does not tell us which state the cat, or the universe, should eventually end up in. So Bousso and Susskind have also linked the idea of a multiverse of causal patches to something known as the "many worlds" interpretation of quantum mechanics, which was developed in the 1950s and 60s but has only become popular in the last 10 years or so.

According to this strange idea, when a superposition of states occurs, the cosmos splits into multiple parallel but otherwise identical universes. In one universe we might see the cat survive and in another we see it die. This results in an infinite number of parallel universes in which every conceivable outcome of every event actually happens.

Bousso and Susskind's contention is that the alternative realities of the many worlds interpretation are the additional causal patches that make up the multiverse. Most of these patches would have split from other universes, perhaps even ancestors of our own. "We argue that the global multiverse is a representation of the many-worlds in a single geometry," they say. They call this idea the multiverse interpretation of quantum mechanics and in a paper now available online they have proposed the mathematical framework behind it (arxiv.org/abs/1105.3796).

One feature of their framework is that it might explain puzzling aspects of our universe, such as the value of the cosmological constant and the apparent amount of dark energy.

The paper has caused flurry of excitement on physics blogs and in the broader physics community. "It's a very interesting paper that puts forward a lot of new ideas," says Don Page, a theoretical physicist at the University of Alberta in Edmonton, Canada. Sean Carroll, a cosmologist at the California Institute of Technology in Pasadena and author of the Cosmic Variance blog, thinks the idea has some merit. "I've gone from a confused skeptic to a tentative believer," he wrote on his blog. "I realized that these ideas fit very well with other ideas I've been thinking about myself!"

However, most agree that there are still questions to iron out. "It's an important step in trying to understand the cosmological implications of quantum mechanics but I'm sceptical that it's a final answer," says Page.

For example, one remaining question is how information can leak from a causal patch, a supposedly self-contained volume of the multiverse.

Susskind says it will take time for people to properly consider their new approach. And even then, the ideas may have to be refined. "This is not the kind of paper where somebody does a calculation and confirms that we're correct," says Bousso. "It's the sort of thing that will take a while to digest."

Source New Scientist

NASA's Swift finds most distant gamma-ray burst yet

On April 29, 2009, a five-second-long burst of gamma rays from the constellation Canes Venatici triggered the Burst Alert Telescope on NASA's Swift satellite. As with most gamma-ray bursts, this one -- now designated GRB 090429B -- heralded the death of a star some 30 times the sun's mass and the likely birth of a new black hole.

 The afterglow of GRB 090429B (red dot, center) stands out in the in this optical and infrared composite from Gemini Observatory images. The red color results from the absence of visible light, which has been absorbed by hydrogen gas in the distant universe.
 
"What's important about this event isn't so much the 'what' but the 'where,'" said Neil Gehrels, lead scientist for Swift at NASA's Goddard Space Flight Center in Greenbelt, Md. "GRB 090429B exploded at the cosmic frontier, among some of the earliest stars to form in our universe."
Because light moves at finite speed, looking farther into the universe means looking back in time. GRB 090429B gives astronomers a glimpse of the cosmos as it appeared some 520 million years after the universe began.

Now, after two years of painstaking analysis, astronomers studying the afterglow of the explosion say they're confident that the blast was the farthest explosion yet identified -- and at a distance of 13.14 billion light-years, a contender for the most distant object now known.
Swift's discoveries continue to push the cosmic frontier deeper back in time. A gamma-ray burst detected on Sept. 4, 2005, was shown to be 12.77 billion light-years away. Until the new study dethroned it, GRB 090423, which was detected just six days before the current record-holder, reigned with a distance of about 13.04 billion light-years.

Gamma-ray bursts are the universe's most luminous explosions, emitting more energy in a few seconds than our sun will during its energy-producing lifetime. Most occur when massive stars run out of nuclear fuel. When such a star runs out of fuel, its core collapses and likely forms a black hole surrounded by a dense hot disk of gas. Somehow, the black hole diverts part of the infalling matter into a pair of high-energy particle jets that tear through the collapsing star.

The jets move so fast -- upwards of 99.9 percent the speed of light -- that collisions within them produce gamma rays. When the jets breach the star's surface, a gamma-ray burst is born. The jet continues on, later striking gas beyond the star to produce afterglows.
"Catching these afterglows before they fade out is the key to determining distances for the bursts," Gehrels said. "Swift is designed to detect the bursts, rapidly locate them, and communicate the position to astronomers around the world." Once word gets out, the race is on to record as much information from the fading afterglow as possible.

In certain colors, the brightness of a distant object shows a characteristic drop caused by intervening gas clouds. The farther away the object is, the longer the wavelength where this sudden fade-out begins. Exploiting this effect gives astronomers a quick estimate of the blast's "redshift" -- a color shift toward the less energetic red end of the electromagnetic spectrum that indicates distance.
The Gemini-North Telescope in Hawaii captured optical and infrared images of GRB 090429B's quickly fading afterglow within about three hours of Swift's detection. "Gemini was the right telescope, in the right place, at the right time," said lead researcher Antonino Cucchiara at the University of California, Berkeley. "The data from Gemini was instrumental in allowing us to reach the conclusion that the object is likely the most distant GRB ever seen."

The team combined the Gemini images with wider-field images from the United Kingdom Infrared Telescope, which is also located on Mauna Kea in Hawaii, to narrow estimates of the object's redshift.
Announcing the finding at the American Astronomical Society meeting in Boston on Wednesday, May 25, the team reported a redshift of 9.4 for GRB 090429B. Other researchers have made claims for galaxies at comparable or even larger redshifts, with uncertain distance estimates, and the burst joins them as a candidate for the most distant object known.

Studies by NASA's Hubble Space Telescope and the Very Large Telescope in Chile were unable to locate any other object at the burst location once its afterglow had faded away, which means that the burst's host galaxy is so distant that it couldn't be seen with the best existing telescopes. "Because of this, and the information provided by the Swift satellite, our confidence is extremely high that this event happened very, very early in the history of our universe," Cucchiara said.

Swift, launched in November 2004, is managed by Goddard. It was built and is being operated in collaboration with Penn State University, University Park, Pa., the Los Alamos National Laboratory in New Mexico, and General Dynamics of Gilbert, Ariz., in the U.S. International collaborators include the University of Leicester and Mullard Space Sciences Laboratory in the United Kingdom, Brera Observatory and the Italian Space Agency in Italy, and additional partners in Germany and Japan.

Source EurekaAlert!

Physics and the Immortality of the Soul

The topic of "life after death" raises disreputable connotations of past-life regression and haunted houses, but there are a large number of people in the world who believe in some form of persistence of the individual soul after life ends. Clearly this is an important question, one of the most important ones we can possibly think of in terms of relevance to human life. If science has something to say about, we should all be interested in hearing.
Adam Frank thinks that science has nothing to say about it. He advocates being "firmly agnostic" on the question. (His coblogger Alva Noë resolutely disagrees.) I have an enormous respect for Adam; he's a smart guy and a careful thinker. When we disagree it's with the kind of respectful dialogue that should be a model for disagreeing with non-crazy people. But here he couldn't be more wrong.

Adam claims that there "simply is no controlled, experimental[ly] verifiable information" regarding life after death. By these standards, there is no controlled, experimentally verifiable information regarding whether the Moon is made of green cheese. Sure, we can take spectra of light reflecting from the Moon, and even send astronauts up there and bring samples back for analysis. But that's only scratching the surface, as it were. What if the Moon is almost all green cheese, but is covered with a layer of dust a few meters thick? Can you really say that you know this isn't true? Until you have actually examined every single cubic centimeter of the Moon's interior, you don't really have experimentally verifiable information, do you? So maybe agnosticism on the green-cheese issue is warranted. (Come up with all the information we actually do have about the Moon; I promise you I can fit it into the green-cheese hypothesis.)

Obviously this is completely crazy. Our conviction that green cheese makes up a negligible fraction of the Moon's interior comes not from direct observation, but from the gross incompatibility of that idea with other things we think we know. Given what we do understand about rocks and planets and dairy products and the Solar System, it's absurd to imagine that the Moon is made of green cheese. We know better.

We also know better for life after death, although people are much more reluctant to admit it. Admittedly, "direct" evidence one way or the other is hard to come by -- all we have are a few legends and sketchy claims from unreliable witnesses with near-death experiences, plus a bucketload of wishful thinking. But surely it's okay to take account of indirect evidence -- namely, compatibility of the idea that some form of our individual soul survives death with other things we know about how the world works.

Claims that some form of consciousness persists after our bodies die and decay into their constituent atoms face one huge, insuperable obstacle: the laws of physics underlying everyday life are completely understood, and there's no way within those laws to allow for the information stored in our brains to persist after we die. If you claim that some form of soul persists beyond death, what particles is that soul made of? What forces are holding it together? How does it interact with ordinary matter?
Everything we know about quantum field theory (QFT) says that there aren't any sensible answers to these questions. Of course, everything we know about quantum field theory could be wrong. Also, the Moon could be made of green cheese.

Among advocates for life after death, nobody even tries to sit down and do the hard work of explaining how the basic physics of atoms and electrons would have to be altered in order for this to be true. If we tried, the fundamental absurdity of the task would quickly become evident.
Even if you don't believe that human beings are "simply" collections of atoms evolving and interacting according to rules laid down in the Standard Model of particle physics, most people would grudgingly admit that atoms are part of who we are. If it's really nothing but atoms and the known forces, there is clearly no way for the soul to survive death. Believing in life after death, to put it mildly, requires physics beyond the Standard Model. Most importantly, we need some way for that "new physics" to interact with the atoms that we do have.

Very roughly speaking, when most people think about an immaterial soul that persists after death, they have in mind some sort of blob of spirit energy that takes up residence near our brain, and drives around our body like a soccer mom driving an SUV. The questions are these: what form does that spirit energy take, and how does it interact with our ordinary atoms? Not only is new physics required, but dramatically new physics. Within QFT, there can't be a new collection of "spirit particles" and "spirit forces" that interact with our regular atoms, because we would have detected them in existing experiments. Ockham's razor is not on your side here, since you have to posit a completely new realm of reality obeying very different rules than the ones we know.

But let's say you do that. How is the spirit energy supposed to interact with us? Here is the equation that tells us how electrons behave in the everyday world:

Don't worry about the details; it's the fact that the equation exists that matters, not its particular form. It's the  Dirac equation -- the two terms on the left are roughly the velocity of the electron and its inertia -- coupled to electromagnetism and gravity, the two terms on the right.

As far as every experiment ever done is concerned, this equation is the correct description of how electrons behave at everyday energies. It's not a complete description; we haven't included the weak nuclear force, or couplings to hypothetical particles like the Higgs boson. But that's okay, since those are only important at high energies and/or short distances, very far from the regime of relevance to the human brain.

If you believe in an immaterial soul that interacts with our bodies, you need to believe that this equation is not right, even at everyday energies. There needs to be a new term (at minimum) on the right, representing how the soul interacts with electrons. (If that term doesn't exist, electrons will just go on their way as if there weren't any soul at all, and then what's the point?) So any respectable scientist who took this idea seriously would be asking -- what form does that interaction take? Is it local in spacetime? Does the soul respect gauge invariance and Lorentz invariance? Does the soul have a Hamiltonian? Do the interactions preserve unitarity and conservation of information?

Nobody ever asks these questions out loud, possibly because of how silly they sound. Once you start asking them, the choice you are faced with becomes clear: either overthrow everything we think we have learned about modern physics, or distrust the stew of religious accounts/unreliable testimony/wishful thinking that makes people believe in the possibility of life after death. It's not a difficult decision, as scientific theory-choice goes.

We don't choose theories in a vacuum. We are allowed -- indeed, required -- to ask how claims about how the world works fit in with other things we know about how the world works. I've been talking here like a particle physicist, but there's an analogous line of reasoning that would come from evolutionary biology. Presumably amino acids and proteins don't have souls that persist after death. What about viruses or bacteria? Where upon the chain of evolution from our monocellular ancestors to today did organisms stop being described purely as atoms interacting through gravity and electromagnetism, and develop an immaterial immortal soul?

There's no reason to be agnostic about ideas that are dramatically incompatible with everything we know about modern science. Once we get over any reluctance to face reality on this issue, we can get down to the much more interesting questions of how human beings and consciousness really work.

Sean Carroll is a physicist and author. He received his Ph.D. from Harvard in 1993, and is now on the faculty at the California Institute of Technology, where his research focuses on fundamental physics and cosmology. Carroll is the author of From Eternity to Here: The Quest for the Ultimate Theory of Time, and Spacetime and Geometry: An Introduction to General Relativity. He has written for Discover, Scientific American, New Scientist, and other publications. His blog Cosmic Variance is hosted by Discover magazine, and he has been featured on television shows such as The Colbert Report, National Geographic's Known Universe, and Through the Wormhole with Morgan Freeman. His Twitter handle is  @seanmcarroll
Cross-posted on Cosmic Variance.
The views expressed are those of the author and are not necessarily those of Scientific American.

Source  Scientific American

All Eyes on Large Hadron Collider in Dark Matter Hunt

Researchers from a number of overlapping disciplines are awaiting a big boost from the world's largest particle collider.

BALTIMORE—Dark matter pervades the universe, giving shape to the cosmos on the grandest scales. So perhaps it is fitting that physicists are turning to a large-scale physics experiment to uncover what dark matter is made of.

LEADER OF THE PARTICLE PACK: CMS, one of two general-purpose particle physics experiments at the Large Hadron Collider in Europe, could soon tell astronomers what dark matter is made of. Image: © CERN

Dark matter helps mold galaxy formation and accounts for five times the mass of all the ordinary, visible matter in the universe, but it has eluded direct detection for decades. Astronomers can see its gravitational effects—galaxies and galaxy clusters behave as if they have far more mass than ordinary matter alone can provide—but the particle nature of the stuff remains a mystery.

At a recent dark matter symposium at the Space Telescope Science Institute here, hopes for a solution via the Large Hadron Collider loomed large. The LHC, essentially a 27-kilometer particle racetrack buried 100 meters belowground near Geneva, started up in 2009 and quickly became the most powerful particle collider in the world. At a series of controlled impact points, protons boosted to near the speed of light collide head-on, and physicists sift through the outflying debris to look for hints of new physics.

Astronomers and cosmologists have their fingers crossed that a positive ID on a dark matter particle will be among the new phenomena that should soon come streaming out of the LHC. After all, astronomical probes that have sought out the signature of dark matter particles have come up empty, as have experiments on the ground designed to detect the stuff.

"I'm feeling a little pessimistic," astronomer Sandra Faber of the University of California, Santa Cruz, said during a panel discussion at the symposium. "As every speaker in the last two days gave their talk, I thought to myself, 'How can I make a case here that astronomy is going to answer the nature of dark matter?' I think it's pretty thin. I think we have to turn to the physicists to actually discover this particle—or particles—and tell us what it is."

One ongoing possibility is that one of many specialized dark matter detectors—such as Xenon100 in Italy or CoGeNT in Minnesota—could catch a whiff of the stuff as Earth passes through an ambient haze of dark matter. But many researchers hold out more hope for the LHC, which could produce dark matter in its particle collisions.

That would light the way toward other complementary detections. Many researchers, for instance, have used the Fermi Gamma-Ray Space Telescope to look for the signature of dark matter particles crashing into one another, mutually annihilating, and giving off gamma rays. Dan Hooper of Fermilab and Lisa Goodenough of New York University published a study in Physics Letters B in March showing that Fermi observations of the center of the Milky Way Galaxy seem to show a gamma-ray excess indicative of dark matter annihilations there.

But the data are somewhat ambiguous, U.C. Santa Cruz physicist and Fermi team member Robert Johnson said in a talk at the dark matter symposium. "You don't see any residuals at the galactic center that would suggest something extra going on there," he said. "I think it's an open question whether there is a dark matter source at the galactic center. It's very difficult to disentangle it from the other stuff going on there."

In an interview Johnson noted that the LHC should be able to clarify things considerably. "We're kind of looking blind at the data now," he said. If the LHC could pin down the attributes of a promising dark matter particle, the Fermi data would come into much tighter focus. "The LHC has a much greater reach in the parameter space for looking for something like supersymmetric dark matter," Johnson said. Supersymmetry is a popular hypothetical model for particle physics that posits that each elementary particle—quarks, electrons and so on—has a hidden counterpart particle just waiting to be discovered. One such supersymmetric partner might provide an ideal candidate for the dark matter particle.

Looking for supersymmetry is one of the LHC's primary tasks, along with discovering the long-sought Higgs boson, which is theorized to lend other elementary particles mass. And depending on the traits of the supposed supersymmetric particles, the LHC may be close to finding them. "By this summer or this winter we may have something to say if there are supersymmetric particles living out there," physicist Albert de Roeck of CERN, the European particle physics lab that operates the LHC, said at the symposium.

Even if it takes a bit longer than that—as it may if supersymmetry resides in a regime less accessible to the LHC's detectors—astronomers are willing to wait. "Give us about three years for the LHC to reach maximum luminosity," astrophysicist Joe Silk of the University of Oxford said in the panel discussion. "If they find evidence of supersymmetry, I think this would give a fantastic boost to the field."

Astronomers are counting on the LHC to break new ground in the dark matter search, but in an interview de Roeck said their expectations were not putting significant added pressure on CERN. "Supersymmetry is good—it will satisfy many customers," he said. But compared with the race to find the Higgs and the political pressure to deliver returns on such an ambitious and expensive experiment, the added pressure to find dark matter is "peanuts," de Roeck said.

Source Scientific American

Life and the Cosmos - interview with Prof. Hawkins this week

At the age of 21, the British physicist Stephen Hawking was found to have amyotrophic lateral sclerosis, Lou Gehrig’s disease. While A.L.S. is usually fatal within five years, Dr. Hawking lived on and flourished, producing some of the most important cosmological research of his time.

In the 1960s, with Sir Roger Penrose, he used mathematics to explicate the properties of black holes. In 1973, he applied Einstein’s general theory of relativity to the principles of quantum mechanics. And he showed that black holes were not completely black but could leak radiation and eventually explode and disappear, a finding that is still reverberating through physics and cosmology.

Dr. Hawking, in 1988, tried to explain what he knew about the boundaries of the universe to the lay public in “A Brief History of Time: From Big Bang to Black Holes.” The book sold more than 10 million copies and was on best-seller lists for more than two years.

Today, at 69, Dr. Hawking is one of the longest-living survivors of A.L.S., and perhaps the most inspirational. Mostly paralyzed, he can speak only through a computerized voice simulator.

On a screen attached to his wheelchair, commonly used words flash past him. With a cheek muscle, he signals an electronic sensor in his eyeglasses to transmit instructions to the computer. In this way he slowly builds sentences; the computer transforms them into the metallic, otherworldly voice familiar to Dr. Hawking’s legion of fans.

It’s an exhausting and time-consuming process. Yet this is how he stays connected to the world, directing research at the Center for Theoretical Cosmology at the University of Cambridge, writing prolifically for specialists and generalists alike and lecturing to rapt audiences from France to Fiji.

Dr. Hawking came here last month at the invitation of a friend, the cosmologist Lawrence Krauss , for a science festival sponsored by the Origins Project of Arizona State University. His lecture, “My Brief History,” was not all quarks and black holes. At one point, he spoke of the special joys of scientific discovery.

“I wouldn’t compare it to sex,” he said in his computerized voice, “but it lasts longer.” The audience roared.

The next afternoon, Dr. Hawking sat with me for a rare interview. Well, a kind of interview, actually.

Ten questions were sent to his daughter, Lucy Hawking, 40, a week before the meeting. So as not to exhaust her father, who has grown weaker since a near-fatal illness two years ago, Ms. Hawking read them to him over a period of days.

During our meeting, the physicist played back his answers. Only one exchange, the last, was spontaneous. Yet despite the limitations, it was Dr. Hawking who wanted to do the interview in person rather than by e-mail.

Some background on the second query, the one about extraterrestrials. For the past year, Lucy Hawking was writer in residence at the Origins Project at Arizona State University. As part of her work, she and Paul Davies, a physicist at Arizona State, started a contest, “Dear Aliens,” inviting Phoenix schoolchildren to write essays about what they might say to space beings trying to contact Planet Earth.

Q. Dr. Hawking, thank you so much for taking time to talk to Science Times. I’m wondering, what is a typical day like for you?

A. I get up early every morning and go to my office where I work with my colleagues and students at Cambridge University. Using e-mail, I can communicate with scientists all over the world.

Obviously, because of my disability, I need assistance. But I have always tried to overcome the limitations of my condition and lead as full a life as possible. I have traveled the world, from the Antarctic to zero gravity. (Pause.) Perhaps one day I will go into space.

Q. Speaking of space: Earlier this week, your daughter, Lucy, and Paul Davies, the Arizona State University physicist, sent a message into space from an Arizona schoolchild to potential extraterrestrials out there in the universe. Now, you’ve said elsewhere that you think it’s a bad idea for humans to make contact with other forms of life. Given this, did you suggest to Lucy that she not do it? Hypothetically, let’s say as a fantasy, if you were to send such a message into space, how would it read?

A. Previously I have said it would be a bad idea to contact aliens because they might be so greatly advanced compared to us, that our civilization might not survive the experience. The “Dear Aliens” competition is based on a different premise.

It assumes that an intelligent extraterrestrial life form has already made contact with us and we need to formulate a reply. The competition asks school-age students to think creatively and scientifically in order to find a way to explain human life on this planet to some inquisitive aliens. I have no doubt that if we are ever contacted by such beings, we would want to respond.

I also think it is an interesting question to pose to young people as it requires them to think about the human race and our planet as a whole. It asks students to define who we are and what we have done.

Q. I don’t mean to ask this disrespectfully, but there are some experts on A.L.S. who insist that you can’t possibly suffer from the condition. They say you’ve done far too well, in their opinion. How do you respond to this kind of speculation?

A. Maybe I don’t have the most common kind of motor neuron disease, which usually kills in two or three years. It has certainly helped that I have had a job and that I have been looked after so well.

I don’t have much positive to say about motor neuron disease. But it taught me not to pity myself, because others were worse off and to get on with what I still could do. I’m happier now than before I developed the condition. I am lucky to be working in theoretical physics, one of the few areas in which disability is not a serious handicap.

Q. Given all you’ve experienced, what words would you offer someone who has been diagnosed with a serious illness, perhaps A.L.S.?

A. My advice to other disabled people would be, concentrate on things your disability doesn’t prevent you doing well, and don’t regret the things it interferes with. Don’t be disabled in spirit, as well as physically.

Q. About the Large Hadron Collider, the supercollider in Switzerland, there were such high hopes for it when it was opened. Are you disappointed in it?

A. It is too early to know what the L.H.C. will reveal. It will be two years before it reaches full power. When it does, it will work at energies five times greater than previous particle accelerators.

We can guess at what this will reveal, but our experience has been that when we open up a new range of observations, we often find what we had not expected. That is when physics becomes really exciting, because we are learning something new about the universe.

Q. I’m wondering about your book “A Brief History of Time.” Were you surprised by the enormous success of it? Do you believe that most of your readers understood it? Or is it enough that they were interested and wanted to? Or, in another way: what are the implications of your popular books for science education?

A. I had not expected “A Brief History of Time” to be a best seller. It was my first popular book and aroused a great deal of interest.

Initially, many people found it difficult to understand. I therefore decided to try to write a new version that would be easier to follow. I took the opportunity to add material on new developments since the first book, and I left out some things of a more technical nature. This resulted in a follow-up entitled “A Briefer History of Time,” which is slightly briefer, but its main claim would be to make it more accessible.

Q. Though you avoid stating your own political beliefs too openly, you entered into the health care debate here in the United States last year. Why did you do that?

A. I entered the health care debate in response to a statement in the United States press in summer 2009 which claimed the National Health Service in Great Britain would have killed me off, were I a British citizen. I felt compelled to make a statement to explain the error.

I am British, I live in Cambridge, England, and the National Health Service has taken great care of me for over 40 years. I have received excellent medical attention in Britain, and I felt it was important to set the record straight. I believe in universal health care. And I am not afraid to say so.

Q. Here on Earth, the last few months have just been devastating. What were your feelings as you read of earthquakes, revolutions, counter-revolutions and nuclear meltdowns in Japan? Have you been as personally shaken up as the rest of us?

A. I have visited Japan several times and have always been shown wonderful hospitality. I am deeply saddened for my Japanese colleagues and friends, who have suffered such a catastrophic event. I hope there will be a global effort to help Japan recover. We, as a species, have survived many natural disasters and difficult situations, and I know that the human spirit is capable of enduring terrible hardships.

Q. If it is possible to time-travel, as some physicists claim, at least theoretically, is possible, what is the single moment in your life you would like to return to? This is another way of asking, what has been the most joyful moment you’ve known?

A. I would go back to 1967, and the birth of my first child, Robert. My three children have brought me great joy.

Q. Scientists at Fermilab recently announced something that one of our reporters described as “a suspicious bump in their data that could be evidence of a new elementary particle or even, some say, a new force of nature.” What did you think when you heard about it? A. It is too early to be sure. If it helps us to understand the universe, that will surely be a good thing. But first, the result needs to be confirmed by other particle accelerators.

Q. I don’t want to tire you out, especially if doing answers is so difficult. But I’m wondering: The speech you gave the other night here in Tempe, “My Brief History,” was very personal. Were you trying to make a statement on the record so that people would know who you are?

A. (After five minutes.) I hope my experience will help other people.

Source New York Times

Sean Carroll: Distant time and the hint of a multiverse

At TEDxCaltech, cosmologist Sean Carroll attacks -- in an entertaining and thought-provoking tour through the nature of time and the universe -- a deceptively simple question: Why does time exist at all? The potential answers point to a surprising view of the nature of the universe, and our place in it.

About Sean M Carroll

A physicist, cosmologist and gifted science communicator, Sean Carroll is asking himself -- and asking us to consider -- questions that get at the fundamental nature of the universe.

'Dwarf' black holes might help explain dark matter

WE HAVE stellar-mass, intermediate and supermassive black holes. Might they also come in "dwarf" sizes too?

The controversial proposal by two researchers suggests that the lightweight objects might form when gas and dust is compressed from without rather than collapsing from within, and could account for some of the universe's dark matter.

A stellar-mass black hole forms when gravity overwhelms all other forces and crushes the core of a massive star down to a "singularity". Gravity is strong enough to do this only if the core is at least twice the mass of the sun.

But black holes of much lower mass could form in the turbulence of a supernova explosion, say Andrew Hayes and Neil Comins of the University of Maine in Orono. In the swirling cauldron of matter ejected in the blast, matter could be crushed to densities great enough to form black holes with the mass of a planet, they say (arxiv.org/abs/1104.2501).

If they exist, these black holes could contribute to the mysterious dark matter that appears to hold galaxies and galaxy clusters together. They could have evaded discovery so far if their parent supernovae pushed them out of the Milky Way's central region, where astronomers have searched for such massive dark matter candidates, says Katherine Freese of the University of Michigan in Ann Arbor.

Other researchers are not convinced that dwarf black holes could form in the first place. Stephen Hawking has suggested that the violence of the big bang created densities large enough to form "microscopic" black holes weighing as little as 10 millionths of a gram. But Hans-Thomas Janka of the Max Planck Institute for Astrophysics in Garching, Germany, doubts that supernovae could eject matter forcefully enough to create lightweight black holes today.

Source New Scientist

52 Years and $750 Million Prove Einstein Was Right

In a tour de force of technology and just plain stubbornness spanning half a century and costing more than $750 million, a team of experimenters from Stanford University reported on Wednesday that a set of orbiting gyroscopes had detected a slight sag and an even slighter twist in space-time.

An artist’s conception of Gravity Probe B orbiting Earth to measure space-time.

“We have completed this landmark experiment of testing Einstein’s universe,” Francis Everitt, leader of the project, known as Gravity Probe B, said at a news conference at NASA headquarters in Washington. “And Einstein survives.”
That was hardly a surprise. Observations of planets, the Moon and particularly the shifting orbits of the Lageos research satellites had convinced astronomers and physicists that Einstein’s predictions were on the mark. Nevertheless, scientists said that the Gravity Probe results would live forever in textbooks as the most direct measurements, and that it was important to keep testing theories that were thought to be correct.
Clifford M. Will of Washington University in St. Louis — who was not part of the team but was chairman of a National Aeronautics and Space Administration advisory committee evaluating its work, and who wrote a book titled “Was Einstein Right?” — said that in science, “no such book is ever closed.”

Einstein’s theory relates gravity to the sagging of cosmic geometry under the influence of matter and energy, the way a sleeper makes a mattress sag. One consequence is that a massive spinning object like Earth should spin up the empty space around it, the way twirling the straw in a Frappuccino sets the drink and the whole Venti-size cup spinning around with it, an effect called frame dragging. Astronomers think this effect, although minuscule for Earth, could play a role in the black hole dynamos that power quasars.

Empty space in the vicinity of Earth is indeed turning, Dr. Everitt reported at the news conference and in a paper prepared for the journal Physical Review Letters, at the leisurely rate of 37 one-thousandths of a second of arc — the equivalent of a human hair seen from 10 miles away — every year. With an uncertainty of 19 percent, that measurement was in agreement with Einstein’s predictions of 39 milliarcseconds.
Likewise, the “sag” should alter the space-time geometry around Earth, warping it from the Euclidean ideal and cutting an inch out of the Gravity Probe’s orbit around it, so that the circumference is slightly less than the Euclidean ideal of pi times the orbit’s diameter, a fact confirmed by the Stanford gyroscopes to an accuracy of 0.3 percent.

For Dr. Everitt, who joined the Gravity Probe experiment in 1962 as a young postdoctoral fellow and has worked on nothing else since, the announcement on Wednesday capped a career-long journey.
The experiment was conceived in 1959, but the technology to make these esoteric measurements did not yet exist, which is why the experiment took so long and cost so much. The gyroscopes, for example, were made of superconducting niobium spheres, the roundest balls ever manufactured, which then had to be flown in a lead bag to isolate them from any other influences in the universe, save the subversive curvature of space-time itself.

Shortly before the probe’s launching, Dr. Francis said the project had been canceled at least seven times, “depending on what you mean by canceled.” It was finally sent into orbit in 2004 and operated for some 17 months, but not all went well. When the scientists began analyzing their data, they discovered that patches of electrical charge on the niobium balls had generated extra torque on the gyroscopes, causing them to drift.
It would take five more years to understand the spurious signals and retrieve the gravity data by dint of an effort that Dr. Will called “nothing less than heroic.”

In the meantime, the NASA grant ran out. Dr. Everitt secured another one from Richard Fairbank, a financier and son of one of the experiment’s founders, William Fairbank, that was matched by NASA and Stanford. When that ran out and NASA turned him down for a new grant, Dr. Everitt obtained a $2.7 million grant from Turki al-Saud, a Stanford graduate and vice president for research institutes at the King Abdulaziz City for Science and Technology in Saudi Arabia.

Source New York Times

Beleaguered mission measures swirling space-time at last

The beleaguered Gravity Probe B mission has finally measured a subtle effect of general relativity called frame dragging. The result comes nearly six years after it finished making measurements and years after other experiments measured the effect to greater precision.

Gravity Probe B has finally measured an effect called frame dragging (Image: Gravity Probe B/Stanford)

NASA launched the $750 million mission in 2004 and it finished collecting data in September 2005. Its goal was to test Einstein's general theory of relativity, the currently accepted theory of gravity, by measuring subtle distortions in the fabric of space-time due to the Earth's gravitational field.

To achieve this, the Gravity Probe B spacecraft contained four superconducting niobium spheres about the size of ping pong balls. They were set spinning, and it was expected that their spin axis would change slightly over time as a result of these distortions.

But the data was much noisier than expected, making it initially difficult to detect these effects.

In April 2007, after more than a year of data analysis, the team reported detecting one such phenomenon, called the geodetic effect, which is due to the dent the Earth's gravity makes in space-time.

The second effect the mission was meant to measure proved much more elusive. As the Earth rotates, it drags the surrounding space around with it – a phenomenon known as frame dragging or the Lense-Thirring effect.

Swirling honey

"Imagine the Earth as if it were immersed in honey," says Francis Everitt of Stanford University in California, the mission's chief scientist. "As the planet rotates, the honey around it would swirl, and it's the same with space and time."

A 2008 NASA review was pessimistic about the prospects for detecting frame dragging in Gravity Probe B's noisy data. But data analysis continued with private funding, some arranged by the Saudi royal family.

Now, after further analysis of the data, Gravity Probe B scientists say they have detected frame-dragging with a precision of about 20 per cent.

Earlier results

"We have managed to test two of the most profound effects of general relativity and to do so in a new way," Everitt said in a NASA press conference on Wednesday.

This is the first time frame dragging has been measured in this way. But it was measured previously in 2004 to about 10 per cent precision by its effects on the orbits of the LAGEOS I and II satellites. Tracking the motion of the moon with lasers has also measured frame dragging to a precision of 0.1 per cent.

Given these earlier results, questions are likely to remain about the value of Gravity Probe B's contribution, but Everitt defended the mission's value. "The great beauty of it is that we have complementary tests of general relativity," he said."We completed this landmark experiment testing Einstein's universe ... and Einstein survives."

Journal reference: Physical Review Letters (forthcoming)

Source New Scientist

Sky survey maps distant universe in 3D

(Image: Sloan Digital Sky Survey)
The largest-ever 3D atlas of the universe has been made, and the technique used to produce it could help shed light on dark energy, the mysterious entity that is accelerating the expansion of space.
Past surveys have relied on galaxies to map the universe (bright dots in the image's central region). Now cosmic cartographers have probed even greater distances – to about 11 billion light years away – using intergalactic gas clouds (pictured along the perimeter in blue). The gas clouds are detectable because they absorb light from even more distant objects called quasars, blazing beacons powered by supermassive black holes that are devouring surrounding matter.
The new map pinpoints the location of gas clouds backlit by 14,000 quasars studied by the Sloan Digital Sky Survey. It was unveiled on Sunday at the American Physical Society meeting in Anaheim, California, by Anže Slosar of Brookhaven National Lab in New York.
Making similar maps with larger numbers of quasars will sharpen astronomers' picture of how the large-scale structure of the universe has changed throughout its history. That will help reveal how dark energy has affected this structure, which in turn could help resolve whether dark energy is an inherent property of empty space (a cosmological constant) or a changing energy field.

Source New Scientist