Double Negative Kelvin

Reports that researchers elicited a temperature “lower than absolute zero” might make one question the meaning of the word absolute.  On Built on Facts, Matt Springer writes “temperature is a relationship between energy and entropy, and you can do some weird things to entropy and energy and get the formal definition of temperature to come out negative.”  Usually collisions between atoms ensure that less than 50% of atoms in a sample are excited, no matter how much heat you add.  But Springer analogizes “What if I start with a huge pile of ground-state atoms, and one by one I whack them with a hammer to get them excited and then throw my collection of excited atoms into a jar?”  In this case, as more than 50% of the atoms are excited, physical equations yield a negative temperature.  Chad Orzel explains that the smallest negative temperature (i.e. -.01 K) reflects the highest concentration of excited atoms, while larger negative temperatures (i.e. -100K) actually approach lukewarm.  In his latest post, Chad Orzel breaks down the highly technical details of the researchers’ accomplishment.


Making Waves

On Built on Facts, Matt Springer writes that “there’s really no such thing as a purely continuous monochromatic light wave” and “any pulse of light that lasts a finite amount of time will actually contain a range of frequencies.” Pass this pulse of light through a medium such as glass, which “can have a different refractive index for each frequency,” and some very weird things start to happen. On Life at the SETI Institute, Dr. Lori Fenton explains her study of “aeolian geomorphology – how wind shapes a planetary surface.” As it does on Earth, weather makes wave patterns in the dunes of Venus, Mars, and Saturn’s moon Titan, leaving a record of the meteorological forces at play. On Uncertain Principles, Chad Orzel takes a step back from wave-particle duality. Researchers have observed wave interference in molecules that “contain up to 430 atoms, and are several nanometers across, making them by far the largest objects anybody has ever seen displaying wave behavior.” This brings the “quantum-classical boundary” a little closer to the human scale. But for now, we still behave a lot like particles.

Reaching for the Moon

The moon entrances us—it is near yet far away, familiar, yet unremittingly mysterious. In synchronous rotation, it has a face it never shows. It pulls the oceans; it stirs the blood. It beckons into the unknown. On Universe, Claire L. Evans says that in 1969, six artists snuck “a minuscule enamel wafer inscribed with six tiny drawings” onto Apollo 12’s landing module. Claire writes, “the artistry of this ‘museum’ is as much about the gesture of sneaking it, illicitly, onto the leg of the lunar lander, as it is about the drawings themselves.” On Starts With a Bang!, Ethan Siegel explains that due to the very slight tilt of the Moon on its axis, permanently shadowed craters at the North and South poles may hold “some very, very dirty ice, mixed with normal Moon-dust and rock, possibly similar to a glacier on Earth!” Could these ice-traps help sustain a lunar colony? Or should we be content to study the Moon with the Lunar Reconnaissance Orbiter?

Olympian Physics

i-1bb7a977da8e219a8cb5e493d4c90a31-lympicbuzz.jpgEquations can hurt, although not as much as wiping out on the downhill or faceplanting in the halfpipe. On Dot Physics, Rhett Alain explains the amazing angles at which Apolo Ohno leans around the short track, writing “a skater wouldn’t have to lean at all if the skater was stopped. As the angle gets smaller (approaching zero), the skater would have to be going faster and faster.” On Built On Facts, Matt Springer investigates the somewhat more subdued sport of curling, where men with brooms lead forty pound stones to their targets. Crunching numbers, Matt concludes that “granite on vigorously swept ice” produces less friction than “teflon on teflon.” And back on Dot Physics, Rhett draws up some colorful diagrams of ski jumps, explaining that although you wouldn’t want to jump off an eleven-meter building, “you can make it survivable if you increase the time over which the change in velocity takes place.” In other words, those athletes can be thankful they’re landing on a sloped surface.

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Endless Frontiers of Science

i-c52f334d7a810c32036501d75d7e32a5-frontbuzz.jpgScience is knowledge, and knowledge can inspire certainty. But certainty, as much a fruit of science, can be its enemy. Whatever wonders may meet the eye, there has always been more to the world. On Oscillator, Christina Agapakis explores the frontiers of synthetic biology, where researchers hope to manufacture “altered proteins or entirely different biological polymers” by creating a “parallel genetic code” that uses four-letter codons instead of three. On Starts With A Bang!, Ethan Siegel recounts two centuries of paradigm shifts, and asks what the next “new” law of nature will be. Can protons decay? Does supersymmetry exist? Are quarks composed of even more elementary particles? And on The Island of Doubt, James Hrynyshyn writes that even the most fundamental tenets of our knowledge have “scientists poking around the edges, looking for flaws in the ointment.” James dismisses the idea “that the science of anthropogenic global warming is ‘settled.’ It isn’t and never will be.”

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A Few Head Scratchers

i-656d7084f310cdd541f67f152bc3eba8-physicbuzz.jpgLove it or hate it, physics is a demanding subject. It defines much of our knowledge and experience in a daunting variety of ways. But really, you do love physics, don’t you? On Uncertain Principles, Chad Orzel describes a modern implementation of “Maxwell’s Demon,” a dreamed-of 19th century device that could “cool a gas without obviously increasing entropy.” While this may smack of perpetual motion, researchers have taken first steps toward realizing Maxwell’s mechanism, using angled traps and lasers to winnow lower-energy atoms from a gas sample. On Starts With A Bang, Ethan Siegel explains the relative homogeneity of the solar system by imagining Jupiter much closer to the sun. At that distance its thick atmosphere would boil off, leaving behind “a hard, rocky core not all that different from our planet, except in terms of size and density.” And on Built on Facts, Matt Springer expounds on the dynamics of a Foucault pendulum, which can “swing freely in any direction” and give the illusion that it rotates the plane of its swing. Matt also includes pictures of a new pendulum at the beautiful George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M.

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High in the Sky

i-e2cb1b9adcafb5f0ec9a54a94624e2bf-skybuzz.jpgIt’s Friday, time to kick back and let ScienceBlogs do your homework for you. On Cognitive Daily, Dave Munger wonders how outfielders are so good at running to the right spot to catch a fly ball—are they calculating trajectories in their heads, or making optical deductions? To answer this question, researchers put virtual reality helmets on skilled ball players, then made the virtual balls break the laws of physics as the players tried to “catch” them. On Built On Facts, Matt Springer calculates the energy required to raise the mass of the world’s tallest building into the sky, all so “you can park your desk and do paperwork in what used to be blank air a thousand feet above the ground.” 3.4 trillion joules is a lot, but costs next to nothing compared to the rest of the building. And on Starts With A Bang!, Ethan Siegel sets the stage for the greatest story ever told, filling black holes in our understanding of the universe with explorations of what might have happened before the big bang. Now stick around and enjoy your weekend before Monday brings you back down to Earth.

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