NOVA’s Nobel Poll: Scientists Predict the 2013 Laureates

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 The selection process for the Nobel prizes—this year’s to be announced starting October 7—is highly secretive, but that doesn’t stop the speculation. In that spirit, we surveyed dozens of scientists in the fields of physics, chemistry, and physiology, asking who they think could win this year’s Nobel Prize.
 
<h2>
 Physics
 </h2>

 For the physics prize, almost all of our respondents predicted that it will honor the discovery of the Higgs boson,
 <a href="http://www.pbs.org/wgbh/nova/physics/higgs-boson-revealed.html">
 announced tentatively in July 2012
 </a>
 and with
 <a href="http://www.pbs.org/wgbh/nova/next/physics/higgs-boson-discovered/">
 greater confidence in March 2013
 </a>
 . But with thousands of scientists involved in the discovery,
 <a href="http://www.pbs.org/wgbh/nova/physics/blog/2012/03/a-higgs-by-any-other-name/">
 eight or more
 </a>
 contributing to the origination of the theory, and the prize allowed to go to no more than three winners, how will the Nobel committee divvy up the laurels?
 
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<figcaption>The Nobel Prize medal
 
 </figcaption>
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 Most of the physicists responding to our poll felt that the prize would go to Peter Higgs and Francois Englert, who independently invoked a new field—known today as the Higgs field—to explain why subatomic particles have mass. Their ideas were published within just weeks of each other. As Peter G. O. Freund, a theoretical physicist at the University of Chicago, wrote, “For the better part of the past half century the phenomenon discovered by Englert, Brout [Englert’s coauthor] and Higgs has been a crucial ingredient of the standard model of physics, and repeatedly verified indirectly along with this model. Now, after the phenomenon’s beautiful direct verification at the LHC, it is high time to honor its discoverers with the Nobel Prize.”
 
<h2>
 Chemistry
 </h2>

 The chemists selected David A. Evans, a synthetic organic chemist at Harvard. Evans’s work focuses on both total synthesis and stereoselectivity. Total synthesis involves creating synthetic versions of compounds found in nature. The pharmaceutical industry relies on the field’s techniques heavily, as they allow researchers to mine the natural world for compounds that may prove beneficial as treatments, even if those compounds are incredibly rare. Evans is something of a total synthesis wizard—he and his lab have synthesized over 50 natural products throughout the years.
 

 Stereoselectivity, Evans’s other speciality, is where one chemical reaction spits out different three-dimensional orientations of the same molecule, or stereoisomers. Specifically, Evans is interested in enantiomers, a specific class of stereoisomer that involves mirror images of the same molecule. Evans has been developing techniques that vary the levels of stereoselectivity in the hopes that someday we’ll be able to completely control the configuration of the final product. Like total synthesis, it’s important in the development and production of pharmaceuticals. The painkiller naproxen is a perfect example. One enantiomer relieves pain, while the other simply causes liver damage. Producing and selecting the right enantiomer is crucial.
 
<h2>
 Medicine
 </h2>

 For medicine and physiology, unfortunately our poll didn’t garner enough results to say anything conclusive, but one widely-watched Nobel prediction site, ScienceWatch, published by Thomson Reuters, has identified as possible winners A. Paul Alivisatos, Chad A. Mirkin, and Nadrian C. Seeman for their work on DNA nanotechnology, a promising and relatively new field that uses the unique properties of both DNA and nanoparticles to study biological processes and treat the human body. Mirkin’s research, for example,
 <a href="http://www.pbs.org/wgbh/nova/next/tech/nanoparticles-and-the-future-of-medicine/">
 uses gold nanoparticles studded with nucleic acids
 </a>
 to deliver drugs targeted at specific cells.
 

 It’s important to keep in mind that these predictions are just that, predictions. We’ll have to wait until next week to see if any pan out. But in the meantime, you can
 <a href="http://svy.mk/19mOIwz">
 voice your opinion in our public Nobel poll
 </a>
 and see which scientists the crowd feels are this year’s frontrunners.
 
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 Photo credit: Public domain

Welcome to The Nature of Reality

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 When I was seven, I understood relativity perfectly. I
 
 got
 
 it. At least I thought I did. And it was glorious.
 

 It all started with
 
<a href="http://en.wikipedia.org/wiki/Flight_of_the_Navigator">
 The Flight of the Navigator
 </a>

 , that movie about the kid who accidentally stumbles upon a space ship and has a grand old afternoon traversing the galaxy in the company of its cargo of friendly creatures. The problem? When he returns to Earth he finds that eight years have elapsed. He has been declared missing; when he rings the bell at his old house, a stranger answers the door.
 


 The Flight of the Navigator
 
 is a story about
 <a href="http://www.pbs.org/wgbh/nova/physics/spacetime-trip.html" target="_blank" title="A Trip Through Spacetime">
 time dilation
 </a>
 . The ship was traveling close to the speed of light, so time passed significantly more slowly for its passengers than it did for those back on Earth. That’s special relativity for you. It seemed easy, elegant, amazing.
 

 For the next few years, that was my relationship with relativity. Then came the equations, and suddenly relatively didn’t seem so easy any more. Elegant, maybe. But that first spark of intuition got lost in symbols, equations, calculations and miscalculations. So I wondered: Why can’t we have it both ways? Is it possible to be both wide-eyed and rigorous, methodical and amazed?
 

 That’s a balance even physicists struggle with. As MIT theorist Max Tegmark told NOVA, “When I was in high school, physics was my most boring subject….It was only later that I realized that physics isn’t at all about just solving some equations. It’s about figuring out what reality is all about.”
 

 That’s what we’re doing on this blog: taking on the biggest questions of all, the ones that get at the very nature of reality. What happens to information inside a black hole? What are we really talking about when we talk about teleportation? What if the laws of physics can’t be unified? Every week, we’ll have a new post from a scientist or science writer–look for James Stein, Sean Carroll, and Frank Wilczek in the coming weeks and months–with plenty of room for you to join the discussion with your own questions and ideas.
 

 We hope you’ll let us know what subjects in fundamental physics you want to hear about—the stranger, the better. Can neutrinos really go
 <a href="http://www.nature.com/news/2011/110922/full/news.2011.554.html">
 faster than the speed of light
 </a>
 ? What is this
 <a href="http://www.pbs.org/wgbh/nova/physics/spacetime-lemonade.html">
 spacetime
 </a>
 thing anyway? Is our universe just one of countless others in a
 <a href="http://www.pbs.org/wgbh/nova/physics/johnson-multiverse.html">
 multiverse
 </a>
 ? Join us as we dive deep and discover how physics is changing what we thought we knew about the nature of reality.
 
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Galaxies' Gamma Rays May Illuminate Dark Matter

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 Dark matter is a riddle: Stars can feel it, but we can’t see it. It makes up 80% of the matter in the universe, yet we can only guess at what it actually is.
 

 The puzzle began in 1933, when the Swiss astronomer
 <a href="http://www.amnh.org/education/resources/rfl/web/essaybooks/cosmic/p_zwicky.html">
 Fritz Zwicky
 </a>
 pointed out that galaxies in a group called the Coma Cluster seemed to be moving too quickly to be bound together by the cluster’s gravity. Stronger evidence followed in the 1960s and 1970s, when
 <a href="http://www.amnh.org/education/resources/rfl/web/essaybooks/cosmic/p_rubin.html">
 Vera Rubin’s studies of galactic rotation
 </a>
 revealed that stars at the outer edge of spiral galaxies were rotating just as fast as those in the center. That extra speed should have sent them flying out into intergalactic space. Gravity held them back—but gravity from what? When astronomers estimated the total mass contained in all the stars, gas, and dust in the galaxies, it didn’t add up: Either the laws of gravity were wrong, or some invisible “dark matter” was hiding in the galaxies’ dim margins.
 
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<figcaption>A computer simulation of dwarf galaxy formation. Credit: Ralf Kaehler, John Wise, Tom Abel (KIPAC/SLAC)
 
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 Since those early observations, astronomers have found a wealth of
 
 indirect
 
 evidence for dark matter. Dark matter
 <a href="http://lsst.org/lsst/science/scientist_dark_matter">
 bends light
 </a>
 from distant galaxies and
 <a href="http://map.gsfc.nasa.gov/universe/uni_matter.html">
 shapes
 </a>
 and
 <a href="http://sci.esa.int/planck/51603-planck-sees-a-cosmic-journey-13-billion-years-in-the-making/">
 distorts
 </a>
 the cosmic microwave background radiation. “It is like seeing a dancing marionette puppet (the gravitational effects), and inferring there must be strings (dark matter) to make it move,” wrote Ben Cook, an astrophysics graduate student at the Harvard-Smithsonian Center for Astrophysics, on
 <a href="http://astrobites.org/2015/03/18/a-possible-detection-of-dark-matter-in-a-dwarf-galaxy/">
 Astrobites
 </a>
 . “To prove dark matter really exists, we must actually see the strings, not just the puppet.”
 

 Today, the leading theory is that dark matter is made up of subatomic particles called weakly interacting massive particles (WIMPs), relatively heavy particles that only feel gravity and a fundamental force called the weak force. Because they don’t interact with ordinary matter via the other fundamental forces, they can pass right through walls, people, even entire planets, with just a tiny chance of actually getting close enough to a nucleus of regular matter to disturb it.
 

 But, physicists still haven’t found any
 
 direct
 
 evidence of WIMPs, or any other kind of dark matter. No one has definitively caught a dark matter particle or spotted it doing anything other than, well, gravitating—that is, invisibly exerting a force on the ordinary matter around it. It’s certainly not for lack of trying. Using detectors like the
 <a href="http://lux.brown.edu/LUX_dark_matter/Home.html">
 Large Underground Xenon
 </a>
 (LUX) and
 <a href="http://cdms.berkeley.edu/">
 Cryogenic Dark Matter Search
 </a>
 experiments, physicists have been trying to catch the subatomic slipstreams left behind by cosmic dark matter particles, and at accelerators like the
 <a href="http://www.symmetrymagazine.org/article/the-search-for-dark-matter-at-the-lhc">
 LHC
 </a>
 , they are trying to create dark matter from scratch. At the same time, astrophysicists are searching the skies for the gamma-ray lightshows that could come from dark matter particles crashing into and annihilating each other.
 

 Now, astrophysicists may finally be closing in on dark matter. In 2009, researchers Lisa Goodenough and Dan Hooper found
 <a href="http://www.nature.com/news/2009/091019/full/news.2009.1018.html">
 surprisingly bright gamma ray emission
 </a>
 coming from the center of the Milky Way. Right away, they noticed that the emission was “bumpy,” says Hooper, meaning that it was concentrated within a narrow energy band rather than being smoothly spread out across the gamma-ray spectrum. The peaked spectrum was unusual for known gamma ray sources, but it squared up well with predictions for dark matter annihilation. While Hooper and others continue to consider other possible explanations for these homegrown gamma rays—a mob of exotic pulsars, an outburst from our central supermassive black hole—Hooper thinks dark matter is the likeliest culprit. “It’s pretty easy to explain with dark matter, and pretty difficult to explain with other stuff,” says Hooper.
 

 When it comes to picking up gamma ray signals, the galactic center has the advantage of proximity. But, “things are notoriously messy and complicated” in there, says Hooper. So researchers have turned their attention to dwarf galaxies, which are rich in dark matter and not much else. “The ratio of dark matter to ordinary matter in dwarfs is very, very high,” explains Hooper; dwarf galaxies may contain thousands of dark matter particles for every one ordinary particle. Otherwise placid, they make ideal hunting grounds for unusual gamma ray emission.
 

 “Dwarfs are what everyone’s got their eye on,” says Hooper. But, though they are probably the commonest galaxy type in the cosmos, they are difficult to find, and a
 <a href="https://www.quantamagazine.org/20141025-dwarf-galaxies-dim-dark-matter-hopes/">
 recent search for excess gamma ray emission
 </a>
 from the few known nearby dwarfs came up empty-handed.
 

 Now, that story may be changing. Combing through data from the Fermi spacecraft’s Large Area Telescope (LAT),
 <a href="http://arxiv.org/abs/1503.06209">
 two
 </a>
<a href="http://arxiv.org/abs/1503.02320">
 groups
 </a>
 of researchers found surprisingly bright gamma-ray emission coming from a newly-discovered dwarf galaxy called Reticulum 2. While the teams can’t rule out the possibility that the gamma rays are coming from a more mundane source or that they’re random background noise, they think that the gamma-ray signal matches what you’d expect from dark matter particles crashing into and annihilating each other.
 

 A
 <a href="http://arxiv.org/abs/1503.02632">
 third analysis
 </a>
 , which was based on nearly identical raw data processed with a newer algorithm, turned up more gamma ray photons than expected, but not enough to make the case for a meaningful signal. It isn’t clear yet whether these apparently clashing results are truly contradictory, says Alex Geringer-Sameth of Carnegie Mellon University, lead author on the first paper to claim a detection of excess gamma rays. Once the new data set, called “Pass 8,” is made public, researchers like Hooper and Geringer-Sameth will comb through it trying to understand the source of the disagreement.
 

 If the signal is real (“a HUGE if” emphasizes Garinger-Sameth), it will be a major advance for particle physics. Finally, physicists will be able to get a fix on dark matter’s mass and its annihilation process. “If the Reticulum 2 signal holds up, other groups will have a specific target to shoot for,” said Geringer-Sameth in an email. “Imagine an underground detector finding new particles streaming through the Earth that have the same properties as the new particles a hundred thousand light years away in a dwarf galaxy. It would be a very strong case that what both groups are seeing is actually the dark matter.”
 

 If the observation does not hold up, though, astrophysicists will have a fresh puzzle on their hands. Fermilab physicist Alex Drlica-Wagner, who led up the team that measured the smallest gamma-ray excess, points out that a succession of gamma-ray no-shows from dwarf galaxies could scuttle the notion that galactic center gamma rays are really due to dark matter. “If the excess emission from galactic center comes from dark matter annihilation, then we should start seeing a similar gamma-ray signal coming from the dwarf galaxies. So far, we have not,” he wrote in an email.
 

 “I believe that the most important question to answer in this analysis is, ‘How much dark matter is in Reticulum 2?’” says Drlica-Wagner. To find out, astronomers will be tracking the motion of stars within Reticulum 2 with optical telescopes to reveal how their velocity is being affected by dark matter’s gravity.
 

 Reticulum 2 is one of nine dwarf galaxies just discovered by the
 <a href="http://www.fnal.gov/pub/presspass/press_releases/2015/DES-Dwarf-Galaxies-20150310.html">
 Dark Energy Survey
 </a>
 (DES) and is still the only dwarf galaxy from which astronomers have detected a gamma-ray excess. “Before 2006 there were only about 10 dwarf companions of the Milky Way that were known,” says Geringer-Sameth. Now, we are on the brink of a “tsunami” of new discoveries, he says, with data flooding in from the DES and a sky survey called the Panoramic Survey Telescope &amp; Rapid Response System (Pan-STARRS). In the next decade our census of dwarf galaxies may triple, Hooper estimates: “That could totally change the game.”
 

 As new dwarf discoveries come in, astrophysicists can immediately begin searching for their gamma-ray counterparts in Fermi’s rich data archive. “We have data,” says Geringer-Sameth. “We just don’t know where to look.”
 

 Meanwhile, Hooper and his colleagues continue to analyze gamma rays coming from the galactic center. The first study, back in 2009, was based on a single year of data from the Fermi spacecraft; now Hooper has six and a half years of measurements to work with, and he and his team can perform a more discriminating analysis of the data. Last year, a team that included Hooper and a half-dozen colleagues from around the country
 <a href="http://arxiv.org/pdf/1402.6703v2.pdf">
 showed
 </a>
 that the spectrum’s “bumpy” shape was consistent across the galactic center, and that the emission got progressively brighter closing in on the heart of the galaxy, just as predicted. Again and again, says Hooper, it “passes the test.”
 

 Will the gamma ray signals stand up to the next round of scrutiny? We’ll have to wait to find out if we’re finally seeing the light at the end of the dark matter tunnel—or if there are still unknown miles of darkness ahead.
 


 Go Deeper
 
 

 Editor’s picks for further reading
 


 The Nature of Reality:
 <a href="http://www.pbs.org/wgbh/nova/blogs/physics/2014/01/journey-into-the-dark-realm/">
 Journey Into the Dark Realm
 </a>
 
 What if dark matter isn’t just one particle, but a diverse realm of dark matter particles that experience forces that don’t affect ordinary matter? Don Lincoln explores the “dark realm.”
 

 NOVA Next:
 <a href="http://www.pbs.org/wgbh/nova/next/physics/hunt-for-dark-matter/">
 Pursuing Dark Matter, Hundreds of Miles Above Earth
 </a>
 
 The Alpha Magnetic Spectrometer, aboard the International Space Station, has been searching for evidence of dark matter since 2011. Veronique Greenwood reports on what it has found.
 

 NOVA scienceNOW:
 <a href="http://www.pbs.org/wgbh/nova/physics/dark-matter.html">
 Dark Matter
 </a>
 
 In this video, Neil deGrasse Tyson reports from a half mile underground in an abandoned mine, where scientists are using special detectors to look for dark matter particles.
 

 The New York Times:
 <a href="http://www.nytimes.com/2015/03/11/us/gamma-rays-may-be-clue-on-dark-matter.html?_r=1">
 Gamma Rays May Be Clue on Dark Matter
 </a>
 
 Dennis Overbye reports on new gamma ray studies of Reticulum 2.
 
</section>

Gamma rays from a dwarf galaxy may help astronomers solve the riddle of dark matter.

First Direct Evidence of Cosmic Inflation

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 When Alan Guth proposed the theory of
 <a href="http://www.amazon.com/The-Inflationary-Universe-Alan-Guth/dp/0201328402">
 cosmic inflation
 </a>
 almost 35 years ago, he wondered whether it would ever be possible to prove his hypothesis that the universe ballooned up exponentially in the first moments after the Big Bang. There was ample
 <a href="http://wmap.gsfc.nasa.gov/universe/bb_cosmo_infl.html">
 indirect evidence
 </a>
 : the universe’s surprisingly uniform temperature, the apparent “flatness” of spacetime, and the conspicuous absence of magnetic monopoles. In the years that followed, astronomers used satellites like
 <a href="http://www.skyandtelescope.com/news/3311206.html">
 WMAP
 </a>
 and
 <a href="http://www.nature.com/news/planck-snaps-infant-universe-1.12671">
 Planck
 </a>
 to search for echoes of the inflationary era in the cosmic microwave background radiation. Their results lined up with many inflationary predictions, but fell short of being the “smoking gun” that would have had Guth and other theorists popping their champagne.
 
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 Well, bring on the bubbly: Using a telescope called
 <a href="http://www.cfa.harvard.edu/CMB/bicep2/">
 BICEP2
 </a>
 , a team of astronomers led by John Kovac (Harvard-Smithsonian Center for Astrophysics) has
 <a href="http://bicepkeck.org/b2_respap_arxiv_v1.pdf">
 detected a polarization pattern
 </a>
 in the microwave background radiation that is the first direct evidence for cosmic inflation. This “B-mode” polarization is a “twisty” pattern created by gravitational waves. The discovery is also the first direct image of gravitational waves.
 
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<figcaption>The 10-meter South Pole Telescope and the BICEP (Background Imaging of Cosmic Extragalactic Polarization) Telescope at Amundsen-Scott South Pole Station. Credit: Keith Vanderlinde, National Science Foundation
 
 </figcaption>
</figure>

 The news is generating plenty of buzz. Here are our picks from some of the best coverage we’ve seen so far:
 


 Nature
 
 :
 <a href="http://www.nature.com/news/how-astronomers-saw-gravitational-waves-from-the-big-bang-1.14885">
 How astronomers saw gravitational waves from the Big Bang
 </a>
 
 A suite of special coverage, including an explainer on gravitational waves and an interview with John Kovac, who maintains that he, for one, has held off on the champagne:
 
<blockquote>

 My role in this process has been to remain calm at all times. The time to celebrate, I think, will be once we have published our results and presented them to the scientific community.
 
</blockquote>


 The New York Times
 
 :
 <a href="http://www.nytimes.com/2014/03/18/science/space/detection-of-waves-in-space-buttresses-landmark-theory-of-big-bang.html">
 Detection of Waves in Space Buttresses Landmark Theory of Big Bang
 </a>


 Dennis Overbye talks (or emails) with everyone-who’s-anyone as he traces the history of inflationary theory from its inception in 1979 to its greatest confirmation yet today, closing with the possibility that inflation is continuing elsewhere in the cosmos:
 
<blockquote>

 Most of the hundred or so models that have been spawned by Dr. Guth’s original vision suggest that inflation, once started, is eternal. Even as our own universe settled down to a comfortable homey expansion with atoms, stars and planets, the rest of the cosmos will continue blowing up, spinning off other bubbles here and there endlessly, a concept known as the multiverse.
 
</blockquote>


 WIRED
 
 :
 <a href="http://www.wired.com/wiredscience/2014/03/gravitational-waves-b-mode-inflation/">
 Cosmologists Finally Capture an Elusive Signal From the Beginning of Time
 </a>


 Adam Mann explains “how primordial B-modes could be so important if you’ve never heard of them” and highlights the need for followup observations to confirm the result:
 
<blockquote>

 In fact, BICEP’s data is somewhat at odds with other experiments, such as the Planck space telescope, which have carefully mapped the CMB but not seen primordial B-modes. But it’s also possible that these other teams simply missed what BICEP is seeing and, now that they know how to look for the primordial B-modes, can confirm the results fairly quickly using already existing datasets, perhaps within a matter of weeks. No doubt, other collaborations will begin taking new data to try and detect the primordial B-modes on their own.
 
</blockquote>


 Sky and Telescope
 
 :
 <a href="http://www.skyandtelescope.com/news/Proof-of-Inflationary-Universe-To-Be-Announced-Monday-250522521.html">
 Proof of Inflationary Universe To Be Announced Today?
 </a>


 In advance of today’s announcement, Sky and Telescope’s Alan MacRobert rounded up coverage of the search for B-modes and explained what B-modes are and how gravitational waves create them.
 
</section>

Is Information Fundamental?

What if the fundamental “stuff” of the universe isn’t matter or energy, but information?That’s the idea some theorists are pursuing as they search for ever-more elegant and concise descriptions of the laws that govern our universe. Could our universe, in all its richness and diversity, really be just a bunch of bits?To understand the buzz over information, we have to start at the beginning: What is information?This is.So is an image like this:
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<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/info_booth_620.width-990_lOAtTkN.jpg"/>
<figcaption>
</figcaption>
</figure>
And an equation like this:
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<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/equation_wide.width-990_9sPTK6w.jpg"/>
<figcaption>
</figcaption>
</figure>
“It doesn’t matter whether something consists of equations, words, images or sounds—you can encode any of that in strings of zeroes and ones,” or bits, says Scott Aaronson, associate professor of electrical engineering and computer science at MIT. Your computer is doing it right now, using tiny magnets, capacitors, and transistors to store billions or trillions of binary digits. “These might have been hard concepts for people to understand a century ago, but because of the computer revolution, we deal with these concepts all the time,” says Aaronson. In an age when a USB drive dangles from every keychain and an iPhone strains the seams of every pocket, it isn’t such a leap to agree that anything can be expressed in information.
<div class="related"></div>
To some theorists, though, information is more than just a description of our universe and the stuff in it: it is the most basic currency of existence, occupying what theorist Paul Davies terms the “ontological basement” of reality.The rules of quantum information provide the most “compact” description of physics, says Vlatko Vedral, professor of quantum information theory at the University of Oxford and the National University of Singapore. “Information, it seems to me, requires fewer assumptions about anything else we could postulate. As soon as you talk about matter and energy, you have to write down the laws that govern matter and energy.”Does this mean that our universe is made of information, as some headlines claim?“It strikes me as a contentless question,” says Aaronson. “To say that matter and energy are important in physics is to say something with content.” You can imagine a universe barren of matter and energy, after all; specifying that our universe is furnished with both tells you something about it and distinguishes it from other possible universes. “But I don’t know how you could even conceive of a universe” without information, he says.Yet, as a fresh way of thinking about, well, what the universe is about, information has touched off provocative work in computer science and theoretical astrophysics, apparently disparate fields that may share a deep link manifested by that cosmic Rosetta stone, the black hole. But before we dive into the black hole, let’s step back to take a deeper look at information itself.All messages contain information, but not all messages are created equal. “Unexpected things have high information content,” says Vedral. Take a sunrise, for example. “If the sun rises tomorrow, you won’t see any newspaper writing about it. But of course if it didn’t rise, it would be a major event.”We sense intuitively that “surprises,” like a missed sunrise, carry more information than routine events. Claude Shannon, widely considered the father of information theory, formalized this intuition by defining a quantity that’s now known as “Shannon entropy.” The Shannon entropy of a message is related to the sum of the logarithm of the probability of each bit taking on a particular value. That’s a mouthful, but, Vedral explains, it mathematically captures two important features of information: the value of surprises, and the fact that information is “additive”—that is, that the total information contained in two, three, four, or a billion unrelated events is equal to the sum of the information in each one.Physicists describe entropy a little differently, often speaking in terms of the “disorder” of a system. More precisely, entropy is the number of different ways you can rearrange the littlest parts of a system and still get the same big system. A bucket full of red Legos, for instance, has high entropy. Shake it up, spin it around, and you still have what you began with: a bucket of red Legos. Assemble those same blocks into a Lego castle, though, and you’ve slashed the entropy; moving a single block nets you a different “macroscopic” system.Whichever perspective you choose, the essential result is the same. Take the paragraph you’re reading right now, for instance, with its many different letters, punctuation marks, and spaces arranged in a very particular order. It contains more information, and thus has higher entropy, than a paragraph like this one—aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaa—even though they contain the same number of characters. Entropy, then, provides a measure of not just the length but the information content of a message.Now imagine trying to build the ultimate hard drive, one that holds the maximum amount of information allowed by physics. Why should physics place a limit on the information storage capacity of this hypothetical hard drive? Thinking it over from a purely classical perspective, it seems that you could store an infinite amount of information. But when we add quantum mechanics to the mix, we introduce fundamental limits on the accuracy of our measurements. These limits cause entropy to max out at about 10 69 bits per square meter. “If you tried to pack information more densely than that,” says Aaronson, “your hard drive would collapse into a black hole.” That’s not just a whimsical footnote. Black holes, it turns out, are the universe’s very best information repositories. (Of course, Aaronson points out, they don’t make very practical hard drives, unless you’re willing to wait about 10 70 years to retrieve your data.)But there’s something odd about the way the entropy of a black hole grows. As physicists Stephen Hawking and Jacob Bekenstein discovered in the 1970s, the entropy of a black hole increases with the black hole’s two-dimensional surface area, as defined by an imaginary spherical shell with radius <a href="http://en.wikipedia.org/wiki/Schwarzschild_radius">R s</a> . This is bizarre; you would expect the amount of information you can pack into any object, like a book or a hard drive, to grow with the three-dimensional volume of the object, not its surface area.This discrepancy is more than just theoretical arcana. To physicists, it suggests that the fundamental laws of physics may have a simpler representation in two dimensions rather than the traditional three. In 1997, the Argentinian physicist Juan Maldacena, now at the Institute for Advanced Study, took advantage of this idea to work out a mathematical “duality” between our universe and one with fewer dimensions, one time dimension, and no gravity. This provides a handy mathematical back door; problems that are difficult to solve in one domain may shake out easily in the other.
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To some theorists, the duality isn’t just mathematical. The universe as we experience it, they say, may actually be the projection of information encoded on some distant cosmic boundary. Where this boundary lies and how the projection occurs are still open questions, but these theorists argue that our reality may be, in essence, a hologram analogous to the silvery images on museum store postcards.We have information theory to thank for this peculiar plot twist. But if it’s hard to imagine a practical application for this “ <a href="http://www.pbs.org/wgbh/nova/blogs/physics/2011/11/holograms-black-holes-and-the-nature-of-the-universe/">holographic principle</a> ,” it’s far easier to see how quantum information is changing computing. That’s because quantum information has different basic properties from classical information. The bits that make up classical information can be either one or zero. But the “qubits” that make up quantum information can exist in a superposition of the “one” and “zero” states; in a sense, they can take on both states at once. To maintain this superposition, though, qubits must exist in perfect isolation. As soon as that isolation is disturbed, the superposition crumbles.“Quantum information is like the information in a dream,” explained Charles Bennett, a quantum information scientist at IBM Research, in a recent talk at the annual meeting of the American Association for the Advancement of Science. “In describing it, you change you memory of it.” This may not sound like a desirable quality in a computer, but in combination with entanglement, it can be exploited to dramatically speed up certain types of calculations and to send perfectly secure encrypted messages. As Steve Girvin, a theoretical physicist at Yale University, points out, it can also be used to generate genuinely random numbers suitable for encryption keys. Quantum cryptography is already being used commercially for some bank transfers and other highly secure transmissions.“This second quantum revolution—the revolution of information—is a complete surprise,” says Girvin. “It took decades to come to grips with the weirdness and realize that the information of quantum mechanical systems is different than the information content of classical systems, and being uncertain about something can actually be good instead of bad.”
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Quantum information is useful stuff—but what is it telling us about the essential nature of our reality? Some thinkers argue that it suggests our entire universe is itself a quantum computer. “I like this image,” says Vedral, while admitting that the analogy is imperfect. “You could ask, can I treat the rest of the universe as something that I can program in the way that I program my [ordinary] computer?” No, says Vedral. “You’re still limited by the laws of physics, and you have a certain amount of resources which are finite. There are computations you will never be able to execute.” The computation at which this cosmic quantum computer is uniquely capable is that of computing its own evolution.Whether information is a useful strategy of thought or something deeper, we still don’t know. “We’re still struggling with what our theories are really telling us,” says Vedral. “You have to take a leap of imagination.”Go Deeper Editor’s picks for further readingarXiv: <a href="http://arxiv.org/abs/quant-ph/0110141">Computational capacity of the universe</a> Treating the entire universe as a computer, MIT “quantum mechanic” Seth Lloyd derives the information storage and operational limits of the universe.FQXi: <a href="http://www.fqxi.org/community/essay/winners/2013.1">It From Bit or Bit From It?</a> Read prize-winning essays from the Foundational Questions Institute’s 2013 essay contest on the theme of information and its role in reality.<a href="http://www.amazon.com/Information-Nature-Reality-Physics-Metaphysics/dp/0521762251">Information and the Nature of Reality</a> With contributions from physicists, philosophers, theologians, and biologists, this volume of essays looks at the meaning and significance of information from multiple perspectives.

Could information be the fundamental &quot;stuff&quot; of the universe?

The Mistaken Assumptions That Changed Physics History

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 “Don’t assume,” they always say.
 

 Last month, Avi Loeb, an astrophysicist at Harvard, published an
 <a href="http://arxiv.org/pdf/1405.2954v1.pdf">
 essay on how mistaken assumptions have delayed the progress of astronomy
 </a>
 . In the same spirit, I wanted to find out how the course of physics has been influenced by assumptions, acknowledged or otherwise. Can lessons from the past help us be more aware of the assumptions we bring to physics today? Is it desirable—or even possible—to work without assumptions?
 

 In the years after scientists came to accept light as a wave, brilliant researchers spent untold hours chasing after the “ether,” hypothetical stuff through which light waves were thought to propagate. Water waves are disturbances in water, sound waves are disturbances in air, and so light waves must be a disturbance in
 
 something
 
 , the reasoning went. When the sophisticated experiments built to search for the ether couldn’t find it, theorists got to work trying to explain away ether’s experimental no-show. It was only when Einstein published his theory of special relativity in 1905 that the solution became clear: Ether wasn’t just hard to find. It didn’t exist.
 

 If Einstein resolved one roadblock, he set up another. He adamantly refused to accept the randomness built in to quantum mechanics, famously quipping that God doesn’t play dice with the universe, and holding fast even as experiment after experiment (including one he helped to design) showed those dice tumbling. “My instinct for physics bristles at this,” wrote Einstein.
 
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 It’s hard to imagine an astronomer dismissing observational data on the evidence of her “instinct for astronomy,” which highlights a key difference between the two fields. “The special aspect of astronomy is that we have limited information on things far away; it’s not like experiments in the laboratory where we can control conditions,” says Loeb. Astronomers therefore have to make more judgment calls than their colleagues in physics, and when they get it wrong, it’s usually because they don’t recognize the limits of their knowledge—their mistakes are failures of humility.
 

 Physicists, on the other hand, have heaps of data, but they approach that data with certain assumptions that feel like common sense: Waves need something to wave through! The universe should behave predictably! But, says David Kaiser, a physicist and historian of science at MIT, “Sticking to what feels like common sense or intuition can trip us up.”
 

 Einstein was “one of the most accomplished scientists ever—he took part in the process of discovering quantum mechanics,” says Loeb, and yet “he had a prejudice that turned out to be wrong.”
 

 To Loeb, the ideal scientific attitude is like that of the perfect detective, who brings no assumptions about the guilt or innocence of any individual to his analysis of a case. “What you want is to start with a completely blank slate,” says Loeb.
 

 But Kaiser takes a rosier view of scientific mistakes, one that suggests a somewhat different corrective. “I think we can find
 <a href="http://www.princeton.edu/history/people/data/c/creager/profile/TheRightWaytoGetItWrong.pdf">
 instances where mistakes led to productive outcomes
 </a>
 ,” says Kaiser. “It’s not always all bad.”
 

 Indeed, Kaiser points out, even though physicists were wrong about the ether, their investigations led to critical insights, like Maxwell’s equations, which are now part of the essential physics toolkit. “We still use Maxwell’s equations even though for Maxwell, there was no such thing as an elementary electric charge. He thought the world was made out of ether!” The equations stayed the same; the world changed around them.
 

 Hidden assumptions can also live at the heart of how we
 
 do
 
 science. Today, for example, most theorists expect that the deepest laws of nature will turn out to be simple and elegant. So far, that assumption has held up pretty well. But, says Kaiser, it’s possible that today’s most vexing puzzles—dark matter, dark energy, the nature of black holes—signal some breakdown of our basic assumptions about elegance and simplicity.
 

 While hindsight might lead us to brand assumptions as bald mistakes, to Kaiser, they’re more like misplaced priorities. In his 2011 book “
 <a href="http://www.hippiessavedphysics.com/">
 How the Hippies Saved Physics
 </a>
 ,” he tells the story of quantum physics’ journey from the “shut up and calculate” mode, which dominated teaching and research in the years after World War II, to a more open-minded approach that embraced “late-night speculation.” What the Cold War pragmatists never guessed was that the philosophical musings of the “hippies” would yield up a raft of cutting-edge applications based on the strange phenomenon of entanglement.
 

 “Coming out of World War II and during the war, physicists were extremely creative under tremendous time pressure,” says Kaiser. “These were extremely practical, goal-oriented applications of the Schrödinger equation. They were absolutely brilliant with world-changing impacts,” including everything from transistors to nuclear weapons. Yet a cultural resistance to “daydreaming” kept them from thinking deeply about the
 
 meaning
 
 of the equations they employed so successfully.
 

 “We are not going to get to a land where we have no biases and no intuition,” says Kaiser. Scientists are human beings; their neutrality comes from the rigor of their methods rather than some superhuman ability to transcend personal biases. So, he argues, we should build “safety nets” into the scientific culture to “allow little pockets of support for crazy ideas”—that is, ideas that defy common sense and conventional wisdom and yet have some kernel of plausibility. Kaiser is optimistic that today’s scientific culture is making room for “weird” ideas, with microgrants and new research centers, like the Perimeter Institute, where “not-quite-mainstream stuff” can gain some purchase.
 

 One day, those offbeat ideas just might start to seem like common sense.
 


 Go Deeper
 
 

 Editor’s picks for further reading
 


 FQXi:
 <a href="http://fqxi.org/community/essay/winners/2012.1">
 Which of our basic physical assumptions are wrong?
 </a>
 
 Read the winning entries in FQXi’s 2012 essay competition.
 

 Hyperphysics:
 <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/mmhist.html">
 The Michelson-Morley Experiment
 </a>
 
 Learn about the 1887 experiment that helped put ether theory to rest.
 

 Wikipedia:
 <a href="http://en.wikipedia.org/wiki/Bohr%E2%80%93Einstein_debates">
 Bohr-Einstein debates
 </a>
 
 Explore the twists and turns of the ongoing dispute between Albert Einstein and Niels Bohr over the foundations of quantum mechanics.
 
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Discover how mistaken assumptions have changed the course of physics history.

Who's Afraid of Quantum Mechanics?

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Is quantum mechanics less spooky than advertised?That’s the question being mulled in the blogosphere after last month’s <a href="http://agenda.albanova.se/conferenceDisplay.py?confId=4192">three-day writers’ workshop</a> on quantum mechanics. [Disclosure: The workshop received support from the Foundational Questions Institute, which also supports this blog.] As Tushna Commissariat asks at the <a href="http://blog.physicsworld.com/2014/09/12/once-upon-a-timethe-art-of-telling-a-good-quantum-tale/">physicsworld.com blog</a> :
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Do science writers overemphasize and ultimately misconstrue the weirder, “spooky” aspects of quantum theory, or are they right to focus on these facets because they are the very things that interest people?
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“The problem, of course, is that weirdness sells, and it’s hard to find the right balance between mentioning enough of the exotic aspects to draw people in without being gratuitously confusing,” writes physicist and author Chad Orzel, blogging at <a href="http://scienceblogs.com/principles/2014/08/29/nordita-workshop-for-science-writers-day-two/">Uncertain Principles</a> .What’s the harm in emphasizing quantum “spookiness”? It could unintentionally undermine good science. Quantum mechanics may be weird, but it’s theoretically and experimentally rigorous. It isn’t mysticism or pseudoscience. By picking our adjectives from the Halloween bin, we may unintentionally cause readers to lump quantum theory with ghost stories and quasi-spiritual snake oil like the “Law of Attraction.”
But quantum weirdness isn’t just snappy branding. The rules of the quantum world are defiantly at odds with our everyday expectations, and even extensive experience with the equations of quantum theory can only go so far toward establishing a “ <a href="http://www.pbs.org/wgbh/nova/blogs/physics/2014/07/quantum-intuition/">gut feeling</a> ” about how things go in the quantum world.Quantum mechanics isn’t the only strange creature in the zoo, of course. As physicist Sabine Hossenfelder points out at her blog <a href="http://backreaction.blogspot.com/2014/08/the-ordinary-weirdness-of-quantum.html">BackReaction</a> :
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We could just discard it as headline making, a way to generate interest, but that doesn’t really explain why quantum mechanics is described as weirder or stranger as other new and often surprising effects. How is time-dilation in a gravitational field less strange than entanglement?
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Time dilation—the relativistic effect that causes time to pass more slowly when you’re in a strong gravitational field or traveling close to the speed of light—is pretty weird, and I’m not sure I agree with the assertion that writers don’t emphasize the bizarreness of this and other relativistic oddities. Yet it must mean something that even Einstein, the guy who came up with relativity, was unnerved by quantum mechanics.Because of that discomfort, Einstein rejected of some fundamentals of the quantum worldview. But for others, quantum “spookiness” is a welcome thrill. Hossenfelder quotes <a href="http://op-talk.blogs.nytimes.com/2014/08/20/why-we-love-what-we-dont-understand/?_php=true&amp;_type=blogs&amp;_r=0">Anna North’s recent Op-Talk piece</a> in the New York Times:
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“Many of us may crave that tug, the thrill of something as-yet-unexplained… We may want to get to the bottom of it, but in another way, we may not — as long as we haven’t quite figured everything out, we can keep the wonder alive.”
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North is talking about science fiction, but her point applies to science, too. Breakthrough discoveries often open more questions than they answer. That’s one of the great pleasures of science: it doesn’t snuff out wonder, it kindles it. Is that “spooky”? If spooky means supernatural, then no. But if it expresses something that lies beyond the edge of our understanding, then I’d say yes.In using the language of spookiness and mystery to describe quantum mechanics, do we do science a disservice, or are we embracing the thrill of the as-yet-undiscovered? What do you think: Is quantum mechanics spooky?
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Kate Becker

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