Clocking an Accelerating Universe: First Results from BOSS

Some six billion light years ago, almost halfway from now back to the big bang, the universe was undergoing an elemental change. Held back until then by the mutual gravitational attraction of all the matter it contained, the universe had been expanding ever more slowly. Then, as matter spread out and its density decreased, dark energy took over and expansion began to accelerate.

Today BOSS, the Baryon Oscillation Spectroscopic Survey, the largest component of the third Sloan Digital Sky Survey (SDSS-III), announced the most accurate measurement yet of the distance scale of the universe during the era when dark energy turned on.

"We've made precision measurements of the large-scale structure of the universe five to seven billion years ago -- the best measure yet of the size of anything outside the Milky Way," says David Schlegel of the Physics Division at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), BOSS's principal investigator. "We're pushing out to the distances when dark energy turned on, where we can start to do experiments to find out what's causing accelerating expansion."

How to measure expansion in an accelerating universe

Accelerating expansion was announced less than 14 years ago by both the Supernova Cosmology Project (SCP) based at Berkeley Lab and the competing High-z Supernova Search Team, a discovery that resulted in 2011 Nobel Prizes for the SCP's Saul Perlmutter and High-z Team members Brian Schmidt and Adam Riess. Acceleration may result from an unknown something dubbed "dark energy" -- or, dark energy may be just a way of saying we don't understand how gravity really works.

The first step in finding out is to establish a detailed history of expansion. Unlike supernova searches, which depend on the brightness of exploding stars, BOSS uses a technique called baryon acoustic oscillation (BAO) to determine the distances to faraway galaxies.

Baryon acoustic oscillation measures the angle across the sky of structures of known size, the peaks where galaxies cluster most densely in the network of filaments and voids that fill the universe. Since these density peaks recur regularly, the angle between appropriate pairs of galaxies as precisely measured from Earth reveals their distance -- the narrower the apparent angle, the farther away they are.

Knowing the distance to an object tells its age as well, since its light travels from there to here at known speed. And the redshift of the light reveals how the universe has expanded since that time, as expansion stretches space itself; the wavelength of light traveling through space toward Earth stretches proportionally, becoming redder and revealing the expansion of the universe since the light left its source.

"BOSS's first major cosmological results establish the accurate three-dimensional positions of 327,349 massive galaxies across 3,275 square degrees of the sky, reaching as far back as redshift 0.7 -- the largest sample of the universe ever surveyed at this high density," says Martin White of Berkeley Lab's Physics Division, a professor of physics and astronomy at the University of California at Berkeley and chair of the BOSS science survey teams. "BOSS's average redshift is 0.57, equivalent to some six billion light-years away. BOSS gives that distance to within 1.7 percent -- 2,094 megaparsecs plus or minus 34 megaparsecs -- the most precise distance constraint ever obtained from a galaxy survey."

The origin of BAO, the regular clustering of ordinary matter (called "baryons" by astronomical convention), was the pressure of sound waves (thus "acoustic") moving through the universe when it was still so hot that light and matter were mixed together in a kind of soup, in which the sound waves created areas of regularly varying density ("oscillation"). By 380,000 years after the big bang, expansion had cooled the soup enough for ordinary matter to condense into hydrogen atoms (invisible dark matter was also part of the soup) and for light to go its separate way.

At that moment variations in density were preserved as variations in the temperature of the cosmic microwave background (CMB), a phenomenon first measured by Berkeley Lab astrophysicist George Smoot, for which he shared the 2006 Nobel Prize. The warmer regions of the CMB signal areas where the density of matter was greater; these regions seeded the galaxies and clusters of galaxies that form the large-scale structure of the universe today. Thus the cosmic microwave background establishes the basic scale of baryon acoustic oscillation used to measure the expansion history of the universe.

BOSS's data on galaxy clustering and redshifts can be applied not only to BAO but also to a separate technique called "redshift space distortions" -- a direct test of gravity that measures how fast neighboring galaxies are moving together to form galaxy clusters.

What if dark energy isn't an unknown force or substance, but instead a shortcoming of Albert Einstein's General Theory of Relativity, our best-yet theory of gravity? General Relativity predicts how fast galaxies should be moving toward one another in galaxy clusters, and, in the aggregate, how fast the structure of the universe should be growing. Any departure from its predictions would mean the theory is flawed.

"We depend on redshift to know expansion rates and how structure was growing at different times in the past," says Beth Reid, a Hubble Fellow at Lawrence Berkeley National Laboratory who directed the BOSS study of redshift space distortions. "But redshifts aren't uniform. Galaxies are carried along in the Hubble flow as the universe expands, but they also have their own velocities. They tend to fall toward denser regions, for example. Because the ones on the far side of a dense region are coming toward us, their redshift makes them look closer than they really are; the opposite is true for the galaxies on the near side, which are falling away from us -- they look farther away."

Statistical analysis of the redshifts of the hundreds of thousands of galaxies in the BOSS dataset can take into account the peculiarities of local variation and still produce a dependable measure of distance, the Hubble expansion rate, and the growth rate of structure in the universe. With these techniques, Reid and her colleagues have measured gravity on a scale of 100 million light years, far larger than the most accurate gravity measure yet, which is based on the distance from Earth to the moon. Their conclusion: Einstein was right.

Read more at Science Daily

Crocodiles Trump T. Rex as Heavyweight Bite-Force Champions, New Study Shows

Paul M. Gignac, Ph.D., Instructor of Research, Department of Anatomical Sciences, Stony Brook University School of Medicine, and colleagues at Florida State University and in California and Australia, found in a study of all 23 living crocodilian species that crocodiles can kill with the strongest bite force measured for any living animal. The study also revealed that the bite forces of the largest extinct crocodilians exceeded 23,000 pounds, a force two-times greater than the mighty Tyrannosaurus rex.

Their data, reported online in PLoS One, contributes to the understanding of performance in animals from the past and provides unprecedented insight into how evolution has shaped that performance.

In "Insights into the Ecology and Evolutionary Success of Crocodilians Revealed through Bite-Force and Tooth-Pressure Experimentation," the researchers detail their examination of the bite force and tooth pressure of every species of alligator, crocodile, caiman, and gharial. Led by Project Director Gregory Erickson, Ph.D., Professor of Biological Science at Florida State University, the study took more than a decade to complete and required a diverse team of croc handlers and scientists.

"Crocodiles and alligators are the largest, most successful reptile hunters alive today, and our research illustrates one of the key ways they have maintained that crown," says Dr. Gignac.

The team roped 83 adult alligators and crocodiles and placed a force meter between their back teeth and recorded the bite force. They found that gators and crocs have pound-for-pound comparable maximal bite forces, despite different snouts and teeth. Contrary to previous evolutionary thinking, they determined that bite force was correlated with body size but showed surprisingly little correlation with tooth form, diet, jaw shape, or jaw strength.

Dr. Gignac emphasizes that the study results suggest that once crocodilians evolved their remarkable capacity for force-generation, further adaptive modifications involved changes in body size and the dentition to modify forces and pressures for different diets.

The team has been contacted by editors of the "Guinness Book of World Records" inquiring about the data.

Among living crocodilians, the bite-force champion is a 17-foot saltwater croc, with a force measured at 3,700 pounds.

"This kind of bite is like being pinned beneath the entire roster of the New York Knicks," says Dr. Gignac, illustrating the tremendous force displayed by the living creatures. "But with bone-crushing teeth."

Read more at Science Daily

How to Become a Planet Hunter

This last month saw a boom in planetary sightings across the world. Wherever you observed the night sky from you couldn't fail to have seen, and been impressed by, the view of Venus and Jupiter dancing around in the twilight after the sun had set.

While these two planets were setting, Mars and Saturn were rising in the East, continuing the celestial show. It's easy enough to still spot these planets with the naked eye, but to really get the most out of them a telescope or powerful binoculars are needed.

There is no better time than now to learn about how to get the most out of your equipment for planet spotting.

First things first: magnification. To be able to see any decent level of detail, a magnification of at least 20 is needed. Anything less than this and you'll just see the planets as bright stars.

Telescopes can easily handle this magnification, but if you are using hand-held binoculars you might want to think about getting a tripod to mount them on. Not only will the binoculars magnify the object under study by 20 times, but any tiny movement caused by hand shake will also be magnified leading to a very wobbly and unpleasant view.

Binoculars usually have a fixed magnification, which is described by a set of numbers -- for example, "7x50" means "7 times magnification" and "a lens diameter of 50 millimeters."

To work out the magnification of a telescope, you divide the focal length of telescope by the focal length of the eyepiece -- for example 1000 millimeters (telescope) divided by 15 millimeters (eyepiece) would give a magnification of 67 times.

If you are using a telescope, and magnifying the planets much more than a set of binoculars are capable of, you may still find that you get a very disappointing view. This is caused by a few factors.

The most common cause of poor-detailed images is atmospheric conditions. If the atmosphere is very turbulent (i.e. the 'seeing' is poor) then the incoming light from the planet will get bounced around as it passes through the atmosphere, leading to a 'bubbly' or rapidly changing image.

You may get moments of good seeing but you'll require some patience. There is nothing you can do about poor atmospheric seeing and you can tell if this is the case as the stars are 'twinkling' more than usual.

Another cause of poor image quality may be the result of not letting your telescope cool down. Telescopes can take quite some time to cool (sometimes hours) so it's worth setting up your telescope outside before nightfall to let it cool -- but be careful about dew forming on the optics!

Another cause of poor image quality is collimation, particularly in reflecting telescopes that use mirrors. Make sure the optics are all aligned properly and you can be sure you are getting the best out of your telescope.

Now that you have a nice sharp image of your favorite planet you might like to try enhancing the view you can see through the use of color filters:

•     Venus is generally quite bland and seemingly featureless but a deep blue filter can enhance subtle detail in its thick atmosphere.
•     Mars has lots of detail accessible to the amateur astronomer, but more can be seen. Try an orange/red filter to increase the contrast between dark and light areas like the popular Syrtis Major region or perhaps a green/blue filter to enhance the polar ice caps.
•     Jupiter is a great target and detail in the bright areas of the gas giant's belts can be enhanced with a light blue filter and the darker belts like the northern and southern equatorial belts can be enhanced by a green or blue filter.
•     Saturn's stunning ring system can be enhanced by a light green filter, which will also pull out detail in the belts of the planet's atmosphere.

Read more at Discovery News

Martial Arts Celeb Recruited for Ancient Roman Army

Millennia before modern-day military recruiters talked up potential soldiers in shopping malls or put up posters, one Roman city took a rather different approach to recruiting soldiers for the emperor's army.

A newly translated inscription, dating back about 1,800 years, reveals that Oinoanda, a Roman city in southwest Turkey, turned to a mixed martial art champion to recruit for the Roman army and bring the new soldiers to a city named Hierapolis, located hundreds of miles to the east, in Syria.

His name was Lucius Septimius Flavianus Flavillianus and he was a champion at wrestling and pankration, the latter a bloody, and at times lethal, mixed martial art where contestants would try to pound each other unconscious or into submission.

Flavillianus proved to be so successful as a military recruiter that it was decreed that he be made a "cult figure in the band of heroes" after he died, with each tribe of the city erecting statues in his honor. The inscription, written in Greek, was engraved on the base of a statue found in Oinoanda's agora (a central public space) and would have been erected by the people of the city. Discovered by a team in 2002, it wasn't until now that researchers translated and published it.

"This is a very unusual piece of evidence that has come to light," said Nicholas Milner, a researcher with the British Institute at Ankara, who published the translation in the most recent edition of the journal Anatolian Studies.

Milner explained that in the Roman Empire, this sort of "heroisation" is very rare.

Champion athlete

The inscription hails Flavillianus as being a "champion athlete," and, from other inscriptions found at Oinoanda, researchers know that the two sports he won championships in were wrestling and pankration.

Pankration was such a bloody sport that it had only two known rules: no eye-gouging and no biting. Aside from these restrictions, anything was fair game. Philostratos, an ancient writer who lived around the same time as Flavillianus, wrote that pankration competitors are skillful in different types of strangulation. "They bend ankles and twist arms and throw punches and jump on their opponents," (Translation from the book "Arete: Greek sports from ancient sources," Stephen Gaylord Miller, 2004).

By the time he took up duties recruiting soldiers Flavillianus would have been a mature man who had fought and prevailed in many of these contests. His father even boasted about his son's success in an inscription on his own mausoleum writing that Flavillianus, "who having trained at pankration won crowns for victories in sacred games."

This experience as a champion fighter, and the fame that came with it, would have helped Flavillianus in his task. "He would have been able to judge suitable recruits, and he probably knew lots of suitable recruits," said Milner.  Also "being a top athlete was a kind of celebrity status in Roman times," he said. "A celebrity would have a greater ability to drum up support and large numbers of volunteers than somebody who was not a celebrity." It is possible, however, that some of the soldiers Flavillianus recruited were conscripted against their will.

Man of mystery

Flavillianus would have personally escorted his recruits to Hierapolis, but beyond that, Milner said, scholars don't know if the champion joined the Roman army himself.

Milner isn't sure why Flavillianus became an army recruiter, though he suggests he was likely motivated by honor. If he hadn’t done the job it would have fallen to the community at large (especially those who were wealthy) to drum up recruits.

"This was a society that was driven by the competition for honor, particularly at the top of the city," Milner explained. "They were competing to outshine one another in the eyes of their local community and hopefully also in the eyes of the Roman authorities."

Read more at Discovery News

Cows Almost Impossible To Domesticate, DNA Reveals

Cattle aren't known for their intelligence. Perhaps it's because their family tree has a very skinny trunk.

Genetic evidence suggests all "taurine" cattle (the most commonly recognized breed) descend from only about 80 females and came from a single region in what is now Iran about 10,500 years ago. A study in the journal Molecular Biology and Evolution traced the modern global herd's heritage back to its ancestral home on the range.

The study compared mitochondrial DNA extracted from 15 preserved ancient cattle's bones to modern cattle and found little variation. Little variation meant the founding population didn't have many different versions of the mitochondrial genes to start with.

Earlier research published in PloS ONE suggested that taurine cattle may have later received a small genetic boost from European aurochs. Aurochs were the super-sized ancestors of our modern hamburger on the hoof.

The size and nasty disposition of the wild auroch (Bos primigenius) would have made it a formidable beast to tame for the ancient Iranians. That difficulty is possibly why domestication only occurred with a small number of animals. The authors of the paper in Molecular Biology and Evolution suggested that only humans who had settled down into villages would have had the ability to domesticate the auroch.

"Importantly, the two sites showing the earliest signs of the wild auroch's domestication -- Dja´de and Çayönü -- are less than 250 kilometers (155 miles) apart," wrote the multinational group of authors led by Ruth Bollongino of the University of Mainz, Germany.

"Interestingly, archaeological signs of sedentism during the 9th millennium B.C. are restricted to the same region," according to the paper. "It is conceivable that the management of wild cattle was too challenging for the mobile population of the surrounding mountainous areas where goat was the preferred domestic species."

Read more at Discovery News

Take a Hike for Earth Hour

For Earth Hour on Saturday, March 31, at 8:30 p.m. the world will see a little less glitz and more natural glamor as lights go out for an hour. I recommend taking the day and going for a hike - somewhere flashlights shine rather than street lights and when you turn off the lights the stars are so bright they feel like they are just beyond the edge of Earth's horizon.

Just make sure you turn off the lights at home before you go.

The International Space Station will be observing city lights around the globe as we observe Earth Hour. The best time to observe the ISS from the United States, however is in the early hours of the morning on Saturday and Sunday. You can track its progress here.



Read more at Discovery News

Age of oldest rocks off by millions of years

Two of the solar system's best natural timekeepers have been caught misbehaving, suggesting that the accepted ages for the oldest known rock samples are off by a million years or more.

According to two new studies, a radioactive version of the element samarium decays much more quickly than previously thought, and different versions of uranium don't always appear in the same relative quantities in earthly rocks.

Both elements are used by geologists to date rocks and chart the history of events on our planet and in the solar system.

"If you have a critical event in Earth's history, something like an extinction event or a climate change shift or a meteorite impact, you need to know the absolute age with the most confidence," says Joe Hiess of the British Geological Survey, who led one of the studies. "In Earth sciences there's a need to be able to define what happened first and what happened second."

Chronometer shortage

Geochemists age rocks by measuring the ratio of radioactive isotopes – versions of the same element with different atomic masses – in them. Because the elements decay from one isotope, or element, to another at a constant rate, knowing the ratio in a particular rock gives its age.

Different elements and isotopes decay at vastly different rates. Scientists pick one that suits the timescale of interest. One of the favourites for tracing events in the early solar system, such as when the Earth's crust differentiated from its mantle or when the lava oceans on the moon solidified, is samarium-146, a hard shiny metal found in many minerals in the Earth's crust.

"In this time window, there are not many other chronometers," says Michael Paul of the Hebrew University in Jerusalem.

Scientists have measured samarium-146's half-life – the time taken for exactly half of a sample of atoms to decay radioactively - four times over the past 60 years, and got different answers each time. The two most recent measurements seemed to converge on a half-life of 103 million years, plus or minus 5 million years. But Paul and colleagues suspected that that number wasn't quite right. So they used a technique called accelerator mass spectrometry, which Paul says is less likely to be skewed by experimental errors.

Youthful meteorites

They found that the half-life is just 68 million years, 30 per cent shorter than thought. That means that every rock dated by samarium-146 decay – which include some of the oldest on Earth and the moon, and even some Martian meteorites – formed 20 million to 80 million years earlier than thought.

In a solar system that's 4.5 billion years old, tens of millions of years "is a lot", Paul says. "It means everything was forming more quickly."

There was a second, separate hiccup. Earth's oldest rocks are also aged using isotopes of uranium, which decay into isotopes of lead. Until a few years ago, geochemists assumed that the ratio of uranium-238 to uranium-235 was constant – 137.88 – in all rocks, and therefore the ratio of lead isotopes was the only measurement needed to date the rocks. But high-precision measurements of early materials found in meteorites or rocks formed in oceans showed differences.

Hiess and colleagues made the most wide-ranging study of uranium isotope ratios yet, using 45 samples of zircon from all over the world (pictured, above right). Zircon was one of the first minerals to solidify on Earth, it resists weathering and melting, and it holds on to uranium well, so it's a good candidate for dating old rocks.

Read more at New Scientist

One Person Adds 37 Million Bacteria to a Room

Just one person in a room adds 37 million bacteria to the air every hour, according to a study published in the journal Indoor Air.

Most of the bacteria is stirred up from the floor, left behind by the room's prior occupants.

"We live in this microbial soup, and a big ingredient is our own microorganisms," Jordan Peccia, associate professor of environmental engineering at Yale and the principal investigator of the study, said in a press release.

"Mostly people are re-suspending what's been deposited before. The floor dust turns out to be the major source of the bacteria that we breathe."

Not long ago research revealed what lives in your belly button, so the overall amount of bacteria is astounding.

This latest study is the first to quantify how much a lone human presence affects the level of indoor biological aerosols (microorganisms).

Peccia and his team measured and analyzed biological particles in a single, ground floor university classroom over a period of eight days: four days when the room was periodically occupied, and four days when the room was continuously vacant. At all times the windows and doors were kept closed.

The HVAC system was operated at normal levels. Researchers sorted the particles by size.

The scientists found that "human occupancy was associated with substantially increased airborne concentrations" of bacteria and fungi of various sizes. Occupancy resulted in especially large spikes for larger-sized fungal particles and medium-sized bacterial particles.

The size of bacteria and fungi-bearing particles is important, because size affects the degree to which they are likely to be filtered from the air or linger and recirculate.

"Size is the master variable," Peccia said.

Read more at Discovery News

Neanderthals Were Dying Out Before Humans Arrived

Neanderthals in Western Europe started disappearing long before Homo sapiens showed up, suggesting that cold weather, and not cold-hearted humans, might have been responsible for the species' ultimate demise.

The findings, published in the journal Molecular Biology and Evolution, suggest that at least one population of Neanderthals was vulnerable to climate change.

Love Dalén, lead author of the paper, told Discovery News that "even if the Neanderthals were capable of surviving periods of extreme cold, the game species they relied on likely could not, so their resource base would have been severely depleted."

Neanderthals appear to have favored hunting wooly mammoths and other big game. Neanderthals were also big-brained, with the ability to make stone tools, construct garments, control fire and find shelter.

For the study, Dalén of the Swedish Museum of Natural History and his colleagues analyzed mitochondrial DNA sequences from 13 Neanderthal individuals, including a new sequence from the site of Valdegoba cave in northern Spain.

The researchers found that Neanderthals from Western Europe, Asia and the Middle East that were older than 50,000 years showed a high degree of genetic variation, on par with what might be expected from a species that had been abundant in those areas for a long period of time.

But Neanderthals from Western Europe younger than 50,000 years ago showed an extremely reduced amount of genetic variation. The scientists believe this means the earlier population of Neanderthals there was dwindling.

"We argue that Neanderthals disappeared in Western Europe for a period of time," co-author Rolf Quam, a Binghamton University anthropologist, told Discovery News.

"Subsequently, the region was re-occupied by individuals from a surrounding region," Quam added. "It is not possible, based on the current genetic data, to determine the geographic region of this new source population."

The scientists suspect that climatic conditions were not as extreme in the surrounding areas at the time, so that Neanderthals were able to move back into Western Europe. At present, there is no clear evidence of Homo sapiens being in Europe earlier than about 35,000 to 40,000 years ago, according to Quam -- so it seems humans did not play a role in the early Neanderthal population's demise.

Read more at Discovery News

Monster Solar Tornadoes Discovered

For the first time, huge solar tornadoes have been filmed swirling deep inside the solar corona -- the sun's superheated atmosphere. But if you're imagining the pedestrian tornadoes that we experience on Earth, think again.

These solar monsters, measuring the width of several Earths and swirling at speeds of up to 300,000 kilometers (190,000 miles) per hour, aren't only fascinating structures; they may also trigger violent magnetic eruptions that can have drastic effects on our planet.

In one example observed on Sept. 25, 2011, solar researchers from the UK used the high-definition cameras onboard NASA's Solar Dynamics Observatory (SDO) to track solar gases as hot as 2 million Kelvin (3.6 million degrees Fahrenheit) getting sucked from the bottom of a solar prominence and spiral high into the corona. The solar tornado then developed for three hours, gases traveling in spiral paths for around 200,000 kilometers (120,000 miles).

"Prominences are tangled magnetic fields trapping cold and dense plasma in the solar corona," Xing Li, solar physicist at Aberystwyth University, told Discovery News. "These often erupt spectacularly and fly out into space as coronal mass ejections (CMEs), and large CMEs will impact our space weather and space technology in a significant way when they are heading toward the Earth.

"What drives these eruptions is still not clear and is very important to gain an understanding of CME initiation (so that we can possibly predict such events)."

As mankind becomes more dependent on sensitive technology, it is critical that we develop new and more sophisticated ways to predict the sun's next "temper tantrum." As it turns out, these twisted tornadoes may hold the key to predicting when the next CME will be launched.

"This unique and spectacular tornado must play a role in triggering global solar storms," said co-discoverer Huw Morgan, also at Aberystwyth University.

"These tornadoes may help to produce favorable conditions for CMEs to occur," Li added, pointing out that the tornadoes his team studied coincided with CME eruptions as observed by other instruments monitoring the wider corona.

Also, the tornadoes observed so far by Li and Morgan often occur at the root of where CMEs are initiated. As the dynamic structures wind-up magnetic fields and drag powerful electric currents high into the corona, these tornadoes could generate the conditions ripe for CME eruptions, they theorize.

But to observe the tornadoes in the first place requires a bit of luck.

Firstly, as they are magnetic structures, if the tornado is empty of radiating plasma, they will remain invisible. Only when hot plasma is being dragged high into the corona can they be seen. Conversely, should the tornado be completely flooded with plasma, you wouldn't see the motion of the material as the radiating plasma would be completely washed out.

Read more at Discovery News