The easiest way to spot a supermassive black hole (SMBH) is when it expels a huge jet of matter in one of the most energetic displays in the Universe. While astronomers have spotted these huge black holes at the centers of most galaxies, not all are active—meaning the jet isn't there, and the SMBH is hiding. However, even inactive black holes may give themselves away if we can spot them eating stars: the disruption of a star by gravitational forces can produce a burst of light.

As reported in Nature, the Pan-STARRS1 (PS1) galaxy survey spotted a burst of intense ultraviolet and visible light from the center of a galaxy with no known SMBH. S. Gezari et al. performed a spectral analysis on the flare, and determined it to be consistent with the destruction of a red giant star with a helium-rich core. The likely culprit for the star's disruption is a black hole with a mass between 2.7 and 2.9 million times that of our Sun.







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Recent changes in the Earth's climate are primarily being driven by the burning of fossil fuels—that is, taking carbon from deep in the Earth, and dumping it into the atmosphere at breakneck speed. Wouldn’t it be nice if we could just sort of… put it back?

That’s roughly the idea behind carbon capture and sequestration (CCS). Carbon dioxide is captured from the effluent of a large generator, like a coal power plant, and compressed into a supercritical liquid. That liquid is then transported via pipeline to an injection station where it’s pumped deep underground.

But the technique requires some very specific rock formations if we expect the carbon to stay there. Two new studies have looked at how much CO2 we could hope to store, and how that storage may be affected by another process that's booming: fracking.






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As record temperatures swept through the Midwest and trees bloomed early across the Northeast, lots of talk focused on what an unusually warm start spring was having. The folks at the National Oceanic and Atmospheric Administration have now crunched the numbers, and found that it wasn't just unusually warm—March was bizarrely hot. With 15,000 record high temperatures set in the US, it was far and away the warmest March in the nation's history, and only a single month—January of 2006—was as far off from the monthly average.

Only one of the 48 contiguous states (Washington) was below normal, and a huge slice down the center of the country was bathed in bright red in NOAA's map, indicative of record high temperatures. The heatwave was partly responsible for moving the first quarter of the year into the top slot of the US record books. The high temperatures also kicked off an unusually early spring cluster of tornadoes in the Midwest.

Neither NASA nor NOAA have managed to do the global monthly averages yet, so it's not clear if our experience was shared by much of the rest of the planet (the US occupies a relatively small fraction of its surface). So far this year, the global means have been pretty mundane. They're above last century's average, but not by a lot, and every month has been above that average since early 1994.

NOAA indicates that it was a specific weather pattern that pushed heat into the central US. One of the key drivers of global temperature, the tropical Pacific's surface temperatures, remain in a cooler, La Niña state, so it's unlikely the rest of the world shared in our warmth.





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It was a genuine small-town mystery that briefly put Clintonville, Wisconsin in the national spotlight. Late on March 18, folks in the city of 4,700 just west of Green Bay (and a couple hours north of my current base of operations) suddenly flooded 911 with reports of unsettling booms and shaking. Callers described the noises as being similar to jackhammers, rattling pipes, rumbling thunder, or slamming doors. Authorities scrambled to identify the source. Gas lines were checked for signs of leaks or other anomalies, the same for sewers and water mains. Planes surveyed the county for plumes of smoke. The landfill was checked for signs of a methane explosion. The dam was inspected for structural damage. The military was asked about exercises. Everything checked out, and there were no reports of industrial accidents, either.

Thoughts naturally turned to earthquakes, even though Wisconsin is about as seismically active as a sloth is fast. The United States Geological Survey (USGS) wasn’t reporting any events in the region, so that route of inquiry didn't go far. The reports stopped coming around in 10:00 am, but the booms returned with nightfall like the mysterious assailants in The 13th Warrior.







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In 1961 Rolf Landauer linked information and thermodynamic entropy by showing that erasing or combining bits of memory must be accompanied by an increase in entropy. For the first time since then, a team of physicists have experimentally verified this principle.

According to Landauer’s principle, any logically irreversible transformation of information results in, at best, some small dissipation of heat. The specific amount depends on the operating temperature—per bit, it amounts to around 3×10-21 joules at room temperature. This energy is the Landauer limit, and controls the maximum energy efficiency of computers (it's similar to the Carnot efficiency in heat engines, both of which are related to entropy).

Measuring such a tiny amount of energy in a memory storage devices is, to say the least, challenging. But now, a team from École Normale Supérieure, the University of Kaiserslautern, and the University of Augsburg has managed to do so.






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Like his buddy Richard Dawkins, the evolutionary biologist who wrote the Afterward to his book, physicist Lawrence Krauss does not have a ton of patience for theology. Or American schools. Or God. Krauss seems totally unimpressed by deities in general.

In 2009, Krauss gave a lecture entitled "A Universe from Nothing" for the Atheist Alliance International Conference. It became a YouTube sensation, with over a million hits. His book is essentially a transcript of the talk; it has the same quotes, the same jokes, the same disparaging remarks about religion. 
But the talk loses something in translation. Online, the figures are in color, whereas in the book they are in black and white, and Krauss has a speaking style that many find compelling. If you like seeing things in print, or want to underline them and review them over and over, read the book; if you are more of an oral learner, or only have an hour to devote to the subject, watch the video. But be warned that Dr. Krauss is wearing a shirt that is the exact same color as the wall behind him, which is kind of disconcerting—like his torso is transparent or something.






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Long Beach, California—Harvard's Atul Gawande says that the solution to our expensive (and growing) healthcare problems is simple. What we need, he told the TED audience, is a system—a real system that emphasizes the importance of simplicity. How could the complexities of our healthcare system possibly be handled by increased simplicity?

Gawande, who specializes in reducing risks in medical contexts, is in a position to appreciate the advantages of simplicity. A big challenge in medicine today starts at the doors of medical school. While we may be eager to blame governments or insurers, the cause of our health care troubles is the complexity that science has given us, which in turn dictates how we train our doctors. We end up with doctors that take on specializations, nurses that take on specializations, and drugs that are increasingly specialized as well.


This produces doctors that are trained to be cavalier and strongly individualist—cowboys of a sort. And thanks to movies and television, we idealize the arrogant cowboys, doctors who are capable of spotting the 1-in-1,000 exception to a standard diagnosis. But that, according to Gawande, is the wrong model to idealize.  "We have trained, hired, and rewarded people to be cowboys," he said. "But it’s pit crews that we need."






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Those of you who know my writing will know that I don't use many analogies. Analogies have a very useful place in helping people understand difficult concepts, but they also have a tendency to be a end up strained beyond their limits. Now, imagine how I would react to a whole new field of physics that might be best described as "physics by analogy."

The whole field is based on the premise that, when two physically very different situations can be described using the same mathematical model, the conclusions drawn from one situation can be applied to the other. Unfortunately, this is usually applied in situations where the physics in one situation—black holes, for instance—are so extreme that it is difficult, if not impossible, to test any of the conclusions.

It appears I must adjust my attitude and admit that the field as a whole is not useless. I reached this conclusion after reading a paper that uses sound propagation in Bose Einstein condensates (BEC) to throw light on the origin of the largest discrepancy between two calculations ever seen.







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Last week, several documents that purportedly came from the Heartland Institute appeared on the Web, laying out the organization's financial efforts to undercut the mainstream understanding of climate science. Although the Heartland admitted that most of the materials were genuine, it claims they had been obtained via deception, and that one of the documents (the most inflammatory) was a fake. Now, a prominent environmental researcher has admitted that he impersonated a Heartland board member in order to obtain the documents, but claims they are all genuine.

Peter Gleick is the founder and current president of the Pacific Institute, where he specializes in research on the water cycle. His research can be provocative—some of it suggested that the US has already passed peak water—but has been considered important enough to get him elected to the National Academies of Science.







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One of the key concepts in physics is that of a phase transition. Ice melting to form water is one example; another is the transition between magnetic and non-magnetic forms of iron. The underlying physics of these transitions is a story about correlations. Understanding a phase transition and, indeed, a phase of matter, is all about understanding the growth of correlations.

You would think that one of the cleanest and best understood physical systems wouldn't have a lot to offer physicists in terms of understanding correlations that develop through a phase transition. However, physicists got a bit of a surprise when they looked at particular correlations that arise as a dilute gas is cooled down until it forms a Bose Einstein condensate (BEC).






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During the middle of the 19th century, a star system known as Eta Carinae
suddenly became the second-brightest star in the night sky, then
gradually faded again. Known as the Great Eruption, this event
released about 10 percent of the energy that would have been liberated if the star had gone
supernova, and caused the star to shed approximately 10 Suns' worth of mass. Yet somehow, Eta Carinae
survives to this day. Understanding the behavior of Eta Carinae (which is
estimated to still hold at least 100 times the mass of our Sun) will provide
astronomers with knowledge of the end-stages of very
massive stars, and allow them to distinguish between
eruptions and supernova explosions.

Even though the Great Eruption first became visible in 1838,
astronomers are still able to observe its effects today
through light echoes: light that has bounced off particles inside the
nebula surrounding Eta Carinae for a while, and has reached Earth long after the
initial eruption has faded. A new study of the light echoes, performed by
A. Rest et al., reveals that
Eta Carinae was relatively cool at the time of its brightening. While eruptions observed in other galaxies seem to be driven by thick, opaque clouds
of matter being driven away from their progenitor star, the analysis published in
the February 16 edition of Nature seems to show that the
Great Eruption may actually have been triggered by a blast
wave emanating from the surface of Eta Carinae.







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An essential part of science involves finding correlations between two sets of measurements and seeking explanations for those correlations. However, relationships can be suggested by data even when they don't actually exist, and correlations may occur due to random fluctuations rather than a deep underlying principle (as the infamous "correlation does not equal causation" cliché suggests). These errors are easy to make, and the scientific literature is full of them.

So how can researchers establish if a correlation is both real and meaningful? In a Perspective in the February 10 issue
of Science, Michael P.H. Stumpf and Mason A. Porter
examine the type of correlation known as a power law, where one set of measurements is related to a second via an exponent. They argue that two things must be in place for a power law
to be valid as a predictive model: it must hold over a wide range of data to eliminate chance associations, and it must have a plausible mechanism to explain why the correlation showed up in the data.






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Understanding dunes is important, since he who controls the Spice controls the Universe… That’s the last Dune joke, I promise.

Understanding the mechanisms behind desert sand dune formation and evolution actually is useful, since migrating dune fields threaten agricultural areas and human habitats. At the edges of dune fields, habitats can transition from lifeless deserts to areas covered in vegetation over fairly short distances. Various factors, such as the supply and transport rates of sand and groundwater, along with vegetation density, have all been proposed as key influences on this transition point, but nobody has come up with a model describing the evolution of dune fields.

Until now, that is. A team led by Douglas Jerolmack, joined by others at the Universities of Pennsylvania, Alabama, and Temple University, published a paper in a recent issue of Nature Geoscience that focused on the gypsum dunes of White Sands National Monument, New Mexico. The team came up with a model describing both the transport of the sand that forms the dunes and the changes in vegetation, relating to the levels of groundwater underneath the sand.






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Richard Feynman on imagining electromagnetic waves:

I’ll tell you what I see. I see some kind of vague showy, wiggling lines  — here and there an E and a B written on them somehow, and perhaps some of the lines have arrows on them — an arrow here or there which disappears when I look too closely at it. When I talk about the fields swishing through space, I have a terrible confusion between the symbols I use to describe the objects and the objects themselves. I cannot really make a picture that is even nearly like the true waves. So if you have difficulty making such a picture, you should not be worried that your difficulty is unusual.

From The Feynman Lectures on Physics, volume II.

Other Feynman posts:

Richard Feynman and Captain Picard try to prove Fermat’s Last Theorem
Most important event of the 19th century
God is in the details

African naked mole rats never cease to amaze. Not only are they exceedingly ugly, but they are the longest living rodents. Moreover, none have ever been observed to get cancer. And they are the only known vertebrates that are not bothered by acid. A report in this week’s Science explains the molecular basis underlying this acid insensitivity, and suggests that it might be an adaptation to their oxygen-poor living conditions..

Acid causes pain by activating nociceptors, proton-triggered ion channels that activate neurons. This recent study compared acid receptors from naked mole rats and mice, and found that they were not all that different. Similar numbers of each receptor were found in the respective animals, and acid evoked similar levels of current through them.







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Hydraulic fracturing (more commonly referred to as “fracking”) involves the injection of fluid at high pressure into a well, opening or widening fractures in the rock below that free up the flow of natural gas. Domestic natural gas production has been booming as a result, but opponents claim the technique contaminates drinking water, causing serious health effects.

Rigorous studies on fracking have been sparse, and the impassioned debate has raged on. A new investigation by the US Environmental Protection Agency (EPA) at a site in Wyoming is one of the first to look thoroughly at the potential link between fracking operations and groundwater contamination. The agency's report was released yesterday—and it provides a clear link between fracking and water supply problems.







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Anybody who follows basketball has seen it before: a player hits a momentum-changing three point shot. His team gets the ball back and tears down the court. Will the same player feel he (or she) has a hot hand and try another long-distance shot? Chances are he will. And chances are he'll miss. And chances are he'll do the same exact thing the next game.

That's the conclusion of a statistical analysis of a few hundred professional basketball players (291 from the NBA, 41 from the WNBA). The goal was not only to find out whether the frequently discussed "hot hand"—a shooter who's connecting on most of the shots he takes—exists, but also to find out whether players could identify when they're more likely to be hot, and adjust their behavior accordingly. The answer to both appears to be no, but there may be some other learning going on on the court.







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In a recent interview, Gary Taubes calls picking data that support your conclusion “Bing Crosby science.” This comes from a song by Bing Crosby that begins “You’ve got to accentuate the positive, eliminate the negative.”

Taubes uses the phrase to refer specifically to epidemiology, though it applies to all science. He credits “a Scottish researcher” with coining the phrase, but doesn’t say any more about who this researcher was.

Related post:

Amputating reality

In March, the platform-agnostic research management tool, Mendeley, announced an API Battle, held in conjunction with the Public Library of Science. The goal was to spur the community into developing neat apps that use the database that powers Mendeley. Apps were judged by a panel that included Tim O'Reilly (of O'Reilly Media) and Amazon CTO Werner Vogels, based on the following criteria: API key usage, whether or not it goes viral, how much the app contributes to collaboration and transparency, and general coolness.

Late last week (December 1st) the winners were announced, and 1st place went to openSNP, a community-driven project for publicly sharing personal genetic data (such as an individual's 23andMe results). You can read an interview with the winners over at Mendeley's blog. PaperCritic and rOpenSci were the runners-up.




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The release of a series of e-mails apparently stolen from the University of East Anglia's Climatic Research Unit was timed so that they would hit the news immediately before the Copenhagen climate conference. They didn't seem to affect the conference itself (where deals appear to have collapsed under their own weight), but they did spawn over a half-dozen inquiries, all of which cleared the researchers of anything other than a cavalier attitude towards the UK's Freedom of Information Act. Nevertheless, whoever was behind that original release has loosed another batch in advance of this year's Durban climate meeting.

The last time out, only Saudi Arabia seemed to reference the contents of the e-mails at the Copenhagen meeting itself. And this time, indications are that a significant agreement is very unlikely, so it's not obvious that the e-mail release will even register. This is especially true because the e-mails have come from the same stash as the original batch. And, in the mean time, multiple inquiries have concluded that the e-mails didn't raise questions about the validity of climate science, although individual researchers displayed a cavalier attitude towards sharing data and Freedom of Information Act requests.







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It has been a busy week in the world of particle physics, with attention focused on the home of the LHC: CERN. This year, the LHC generated five inverse femtobarns worth of data—nearly half the amount generated during the entire lifetime of the Tevatron—before shutting down the proton program a few weeks ago. From now until its scheduled winter shutdown, the LHC will be doing lead ion collisions to examine the quark-gluon interactions that dominated the Universe immediately after the Big Bang.

In the mean time, analysis of the data has continued, and some significant news has come out this week. A further dissection of last year's data has placed tighter limits on where the Higgs boson, which provides mass to other particles, might be hiding (assuming it exists). Meanwhile, the LHCb detector, which studies particles that contain heavy quarks, has found an anomalous behavior that might hint at physics beyond the Standard Model. And the LHC accelerator chain has sent some more neutrinos to detectors at Italy's Gran Sasso, which has helped them eliminate some potential sources of error in their faster-than-light findings. We'll take a look at each of these in turn.







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How high are we willing to let the temperature of the planet get? Many governments have signed on to international agreements that would limit greenhouse gas emissions to targets that will keep the Earth from exceeding a 2°C increase over preindustrial levels. However, two studies that came out in recent weeks suggest we're rapidly running out of time to do so. Both suggest we could be locked in to changes above 2°C before the decade is out, and perhaps in as little as five years.

Estimates of future warming are based on a term called the climate sensitivity, which is usually expressed in terms of the expected temperature rise caused by a doubling of atmospheric CO2 concentrations. (The impact of each incremental increase goes down as the concentration rises, since there's a greater chance that some other CO2 molecule will have already absorbed a given infrared photon.) The IPCC's best estimate is that the climate sensitivity is about 3°C per doubling, with uncertainties of about a degree in either direction.







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If you're a cyclist training for competition or just want to burn more fat during exercise when biking, it's good to know whether you should pedal quickly or at slower cadences. Active.com explains why pedaling at fast rates is more efficient. More »

Relativity is the reigning theory of gravity. In situations where we can measure it directly, such as binary neutron stars, its predictions match the real world with remarkable precision. And, when supplemented with inflation and dark matter, relativity nicely reproduces the large-scale structure of the Universe. But this reliance on other models like dark matter means that we don't have a direct, large-scale test of relativity. Now, scientists have measured the redshifting of light by galaxy clusters to give use the biggest test of relativity yet. Their results show that relativity passes muster, while modified forms of Newtownian gravity fall short.

Light emitted by distant objects rarely makes it to Earth at the same wavelength that it started out at. The fabric of the Universe is expanding, which causes a redshift. Most objects are also moving relative to the Earth, which adds a Doppler shift to the light. Finally, light that has to climb out of a large gravity well on its way to Earth also gets red-shifted.

In theory, it should be easy to account for the distance and Doppler shift; anything that's left over should be the effect of gravity. Unfortunately, even with something as massive as a galaxy cluster, the gravity-induced redshift is about two orders of magnitude smaller than a typical Doppler shift. On top of that, the motion of galaxies within clusters should be random relative to the Earth, creating a broad, Gaussian distribution of color shifts. Picking a gravitational signal out of that curve would require a large data set to help cut down on the statistical noise.







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The US Supreme Court’s criticism of significance testing has been in the news lately. Here’s a criticism of significance testing involving the US Congress. Consider the following syllogism.

If a person is an American, he is not a member of Congress.
This person is a member of Congress.
Therefore he is not American.

The initial premise is false, but the reasoning is correct if we assume the initial premise is true.

The premise that Americans are never members of Congress is clearly false. But it’s almost true! The probability of an American being a member of Congress is quite small, about 535/309,000,000. So what happens if we try to salvage the syllogism above by inserting “probably” in the initial premise and conclusion?

If a person is an American, he is probably not a member of Congress.
This person is a member of Congress.
Therefore he is probably not American.

What went wrong? The probability is backward. We want to know the probability that someone is American given he is a member of Congress, not the probability he is a member of Congress given he is American.

Science continually uses flawed reasoning analogous to the example above. We start with a “null hypothesis,” a hypothesis we seek to disprove. If our data are highly unlikely assuming this hypothesis, we reject that hypothesis.

If the null hypothesis is correct, then these data are highly unlikely.
These data have occurred.
Therefore, the null hypothesis is highly unlikely.

Again the probability is backward. We want to know the probability of the hypothesis given the data, not the probability of the data given the hypothesis.

We can’t reject a null hypothesis just because we’ve seen data that are rare under this hypothesis. Maybe our data are even more rare under the alternative. It is rare for an American to be in Congress, but it is even more rare for someone who is not American to be in the US Congress!

I found this illustration in The Earth is Round (p < 0.05) by Jacob Cohen (1994). Cohen in turn credits Pollard and Richardson (1987) in his references.

Related posts:

How insignificant is significance testing?
Five criticisms of significance testing
Most published research results are false
Classical statistics in a nutshell

U.S.-record-holding memory champ Joshua Foer explains how anyone with an average memory can significantly boost her memory by creating visual, spatial "memory palaces" to store information. He used these methods to memorize the order of a shuffled deck of cards in a minute and forty-one seconds; you can use it for any number of more practical memory applications. More »

About a year and a half ago, we reported on a Nature venture that was a bit far afield from its general focus on scientific publishing. Scitable aims to provide online, open access educational materials in the sciences. Anyone can browse the content or follow predefined courses, currently limited to the life sciences. But one thing that you won't generally spot is ads. Can a resource like this stay free indefinitely? It seems like a lot of scientific publishers are betting that it can, since a number of other free services have launched in the intervening time.

According to Scitable's Vikram Savkar, the answer is yes, although it's not there yet. Within the past year, the company has gotten some sponsors on board. Some of these are biotech and pharmaceutical companies, which are very focused on the current bioscience material (New England Biolabs, for example, has sponsored a series on the restriction enzymes they sell). Presumably, this roster will expand as Scitable grows into more subject areas. But a couple of existing sponsors—Intel and Tata Consultancy—are involved simply because they apparently think they're promoting a valuable resource.







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Although it's easy to calculate the impact of additional greenhouse gasses on the temperature, these simple calculations don't capture the potential for feedbacks in the system. The easiest feedback to understand is the ice-albedo response. As temperatures rise, ice melts; that ice normally reflects back most of the sunlight that hits it, so its loss leads to increased absorption of sunlight and hence, a further increase in temperature. Ice is hardly the only feedback, however, so researchers use climate models to try to incorporate as many of these feedbacks as possible.

Unfortunately, there's often disagreement and uncertainty as to how some of the feedbacks operate. In the past week, a couple of papers have come out that address these uncertainties. In one, an author analyzes the impact of clouds on climate, one of the largest uncertainties in current models. In the other paper, the authors argue that past attempts at figuring out the response of plants to climate change have gotten it all wrong.







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One of the things that isn't widely advertised in science is that progress often looks a bit like this video—things get done, but the results are rarely quite what you expect. A recent example of this two steps forward, one step back progress may be the study of the recently observed excess positrons coming from the center of our galaxy.

Although there are many possible astrophysical explanations, none of them were that clean or appealing, leaving one alternative attractive: dark matter. Dark matter is thought to be made up of weakly interacting massive particles, which every now and again collide and annihilate. One particular pathway for the annihilation results in positrons with about the same energy of those seen coming from the core of the galaxy. Hey, presto! thought some scientists. We may have seen dark matter decays, which then allow us to pin down dark matter. Oh and incidentally, the medal should be pinned on my left—that's your right—lapel.

But, as a recent Physical Review Paper shows, the excess may be real, but if it comes from dark matter, we have some serious cosmological problems on the horizon.






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Since Facebook has become a pretty serious mainstay of social media, researchers have become interested in using it to find out which types of social interaction people prefer. A study done at the University of Missouri used physiological data to determine that Facebook users enjoy seeking out specific information and interactions, like Facebook wall posts, far more than more general and passive uses, like browsing the newsfeed or other aggregated sections.

In the experiment, 36 participants were tracked while they browsed Facebook from their own accounts. Researchers monitored physical outputs that correspond to emotional and motivational responses, such as skin conductance and eye movement; they also took screen shots and timed how long participants spend on each page. They broke down Facebook use into two categories: social browsing—looking at newsfeeds, invites pages, and so on—and social searching, such as seeking a friend's profile page or writing on a friends' wall.

The results showed that users spent the most time on activities that were classified as social searching, and had stronger responses to them. Ocular monitoring suggested they also experienced more "pleasantness" during those interactions. Over time, social searching remained more interesting, according to eye movements, while social browsing was a bit boring, and became more so as time elapsed.

The researchers say the data suggests that social searching, or interacting with an individual's more complete information rather than a sea of informational clips, stimulates an appetitive response. Appetitive responses are typically initiated when a person encounters something that promotes species survival, according to the authors. Taking steps to make friends contributes to survival, so this doesn't seem terribly surprising.

However, the results pose an interesting paradox for Facebook, as it seems the things we're most interested in are buried a level deep in searches or menus. Furthermore, the newsfeed, a flagship feature that's intended to combine Twitterlike aggregation and extensive content controls, is the one we care far less about than in-depth knowledge about our friends. It seems we'd rather use Facebook for its more unique feature—interactions and profiles that tell us where our friends work and what movies they like.

Researchers note that they did not study some secondary features of Facebook, such as games like Farmville or Facebook Marketplace, but that they might be worth looking into.




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Epsilon Aurigae was first given serious, systematic, scientific
scrutiny in 1821. Early modern astronomers correctly classified it as
an eclipsing binary variable star, with an invisible partner that will periodically dim the
light as it eclipses the main star from the perspective of Earth. This happens every 27 years, and Epsilon Aurigae's apparent brightness drops for a period of more than a year. The
nature of this partner has remained a mystery, even though we've been observing the star for nearly two centuries.

Over the years, different ideas have come and gone. Early hypotheses as to the nature of Epsilon Aurigae was that it is a F-type supergiant star with a mass
of over 15 solar masses. For the darker companion, people have proposed that it is an infrared star, a black
hole complete with accretion disk, or (most recently) a disk of opaque
material orbiting the companion star. The difficulty with the most recent interpretation is the improbability
of the orbits. 
For the latter case to be correct, then the
orbit of the disk around the darker companion star would have to be in the same plane
as the orbit of the darker object (companion star) around Epsilon Aurigae,
which would in turn have to be the exact same plane as Earth's vantage
point in order to produce the sequence of events we observe here on
Earth. New, direct, observations show this is indeed the case—look at enough stars, and you'll apparently see the improbable.
(Insert something about a large number of monkeys randomly banging
away
on a large number of typewriters knocking out this exact Nobel Intent
article given enough time.)

New observations of the system are reported in a letter in last week's
edition of Nature
based on data collected using Georgia State University's Center for High
Angular Resolution Astronomy interferometer with the Michigan
Infra-Red Combiner. They've produced a series of direct images of the
2009 Epsilon Aurigae eclipse (along with a snapshot from 2008 to use as a baseline). 
Combining this data and some that is in press from
other research groups, the authors report that the main star has a mass
of 3.63±0.68 solar masses (much less massive than earlier estimates), its dark companion has a mass of
5.9±0.1 solar masses. The disk of dust that orbits around the companion has a
negligible mass, 0.07 time the mass of the Earth. From the images, they
are able to describe the disk, improbable orbit and all, as a cylinder with a radius of
3.81±0.01 AU (the distance from the Earth to the Sun) and a height
of 0.76±0.02 AU. The authors conclude that the disk is an
optically thick but geometrically thin, suggesting it is a debris
disk as opposed to a young stellar object.

Nature,
2010. DOI: 10.1038/nature08968
(About
DOIs).




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The initial images of the Eyjafjallajökull eruption showed the sort of dramatic spires of molten rock that we associate with Hawaiian volcanoes. The next time it made the news, it was because air travel throughout Northern Europe had been shut down as a huge cloud of ash spread slowly across the UK and Scandinavia—very un-Hawaiian. To get a better sense of why this Icelandic volcano was showing such a split personality, we got in touch with the American Geophysical Union, which handed us on to Dr. Jeff Karson, who's chair of the Earth Sciences department at Syracuse University. Dr. Karson patiently explained what makes volcanism in Iceland distinct.






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The people who uncovered GhostNet, an extensive cyber espionage network that targeted the Tibetan exile community, are back with a sequel. Starting with an infected machine that was found during that investigation, an international team of researchers has uncovered a completely separate network that primarily targeted the Indian government, and turned up some classified documents that had been obtained by the hackers. By reconstructing the network, the team was able to trace things back to the hacking community in Chengdu, China.

The work involved a collaboration between the Information Warfare Monitor and the Shadowserver Foundation, but, over the course of its work, involved dozens of other security groups and experts. It also benefitted from extensive cooperation with the Office of His Holiness the Dalai Lama, which had previously approached the security researchers in response to security lapses that unearthed GhostNet. The researchers take what they term a "fusion methodology," which is basically a combination of fieldwork—studying infected systems in situ—with standard security approaches.






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Over two-and-a-half billion years ago, the Earth was warm enough to have liquid water and teemed with bacterial life, even though the sun was only radiating at 70 percent of its current strength. Scientists have battled with this seeming paradox, which dates to the Archean eon—it's picked up the name the "faint young Sun" problem. Some previously thought that the relatively high temperature was a result of extra greenhouse gases, but a group of researchers published a paper in Nature this week that indicates greenhouse gasses may have been only a very small component. Instead, the high temperatures at the time may have been largely a result of the Earth's diminished albedo, or reflectivity.

Scientists know that, during the Archean, the Sun was still in the flush of youth, and yet was able to sustain an Earth's worth of liquid water. This time period predates the oxygenation of the atmosphere, so the suspected culprits were greenhouse gases that helped trap the sun's light, such as carbon dioxide and ammonia. However, according to some new evidence, there wasn't nearly enough of the two gases to keep the earth sufficiently warm.






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Despite being at the bottom of the food chain, plants may be able to significantly alter the ecological patterns in their habitats. Generally, ecosystems are studied from a "top-down" perspective: top predators limit the numbers of herbivores, which in turn allows plants to flourish. In a paper published in Science last week, researchers showed that plants can also affect these patterns from the bottom up.

Milkweeds are a family of plants fed upon by a species of aphid, and these aphids serve as prey for a range of invertebrate predators. By manipulating soil nutrient levels and predator access in 16 species of milkweeds, the researchers tried to determine whether milkweed success—here measured via plant biomass—was always determined top-down, by the influence of predators.

Results show that milkweeds face an evolutionary trade-off and can adopt one of two strategies: they can invest their energy in growing quickly and taking advantage of rich soil, or in developing resistance to the aphids. Depending on which strategy was in operation, the milkweed species differed in how important top-down effects were; plants that were most responsive to changes in soil fertility were also the species in which the presence of predators had the biggest positive effect on plant biomass. In other words, the plants that sacrifice herbivore resistance for growth rely more heavily on predators for protection than plants with the alternative, aphid-resistant strategy do.

Apparently, less-resistant milkweed species still played an active role in the ecosystem, as they produce more volatile organic compounds called sesquiterpenes that can actually draw predators to the plants, providing some protection from the aphids. This study suggests that, while top-down effects are important, bottom-up effects based on evolutionary trade-offs in plants may be an underestimated source of variation in ecological communities.

Science, 2010. DOI: 10.1126/science.1184814  (About DOIs).




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Scientists are quickly putting the single-qubit system out of fashion with new setups that can simultaneously manipulate and read multiple qubits. An international collaboration recently completed an experiment involving the control of up to ten qubits at once, using hyper-entanglement and simple "cat states." While the system doesn't always read out perfectly, the approach could be further refined to produce better results.

Because qubit behavior is based in probability, it is difficult to exert a lot of control over a qubit. This problem gets a bit more significant as each additional qubit is added to the system, which has limited the number we can entangle at once. To hold down uncertainty and increase control as they add more qubits, scientists are now experimenting with hyper-entanglement, or entangling qubits on multiple levels at once. To put that another way, instead of entangling 10 different quantum objects, the authors entangled two separate properties of five items.

In this new experiment, scientists hyper-entangled sets of six, eight, and ten qubits in "cat states," or an equal superposition of two states (named after Schrodinger's cat, which occupied a superposition of the states "dead" or "alive"). The photons were entangled in two degrees of freedom: their polarization and their spatial modes. To get output from the photons once they were entangled, scientists used a special kind of interferometer that could gather information about one of the degrees of freedom without disturbing the other.

When the photons were measured, the photons produced the desired state around 60 percent of the time, with anything greater than 50% considered to be good enough to indicate that the system works at all. The eight-qubit system gave the best results, at 77.6 percent. The greatest limit of the system, according to the authors, was the photon detection efficiency, which will need to be significantly improved before implementation would be practical.

(Incidentally, the references to cat states start in the title—"Experimental demonstration of a hyper-entangled ten-qubit Schrödinger cat state"—and continue from there, with references to "ideal cat states" and "the hyper-entangled 2n-qubit cat state." "Cat" even appears as a term in some equations.

Nature Physics, 2010. DOI: 10.1038/NPHYS1603  (About DOIs).




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About 18 months ago, we discussed a mysterious "dark
flow" that was seen in early releases of the data from the
Wilkinson
Microwave Anisotropy Probe data. At that time, we remarked that it was
little more than a cosmic curiosity and possibly a statistical blip.
New research from the same group, using the more complete five-year data
set from the WMAP cosmic microwave background imager and X-ray luminosity data, reveals that the
dark flow is still there, and that it runs deeper than previously
thought.

In a paper published in the March 20th issue of The Astrophysical Journal Letters,
the authors report that they have followed the dark flow—which appears to involve matter streaming either into or out of the constellation
Centaurus/Hydra—to a distance of 2.5 billion light years. So far,
even with the full five-year data set available, the authors can detect
motion, but not whether the matter it coming towards us or moving away
from us. But they can tell that it is moving, and in a definite direction.

Relative motion of matter in the Universe is to be expected,
but motion in a preferential direction is not. According to our
best understanding of how the matter in the Universe was distributed, there's no way of
accounting for this flow. The obvious alternate explanation is a little unnerving: something
outside of our visible universe is pulling on the matter that we can see.

The researchers are currently adding more galaxies to
their catalog in order to track the dark flow to twice its current
distance. They hope that improved modeling of the motion of hot gas
within galaxy clusters will lead to further refinement of the measured speed and
direction of motion. Fortunately, we'll soon have even newer
data from the WMAP project, as well as upcoming data from the ESA's
Planck mission.

The
Astrophysical Journal Letters, 2010. DOI: 10.1088/2041-8205/712/1/L81



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