Science Tuesday - Tetrahedrons, Wine, Lizards, Exercise, and Climate Change

Researchers have been using Dungeons & Dragons dice to learn how to pack tetrahedrons. The record density recently hit 85.63 percent.

Packing Tetrahedrons, and Closing in on a Perfect Fit
By KENNETH CHANG, The New York Times, January 5, 2010

More than 2,300 years ago, Aristotle was wrong.

Now, in the past year, a flurry of academic activity is suddenly zooming in on an answer to a problem akin to wondering how many people can fit into a Volkswagen Beetle or a phone booth. Except here mathematicians have been thinking not about the packing of people, but of geometric solids known as tetrahedrons.

“It’s pretty remarkable how many papers have been written on this in the past year,” said Henry Cohn, a mathematician at Microsoft Research New England.

A tetrahedron is a simple construct — four sides, each a triangle. For the packing problem, researchers are looking at so-called regular tetrahedrons, where each side is an identical equilateral triangle. Players of Dungeons & Dragons recognize the triangular pyramid shape as that of some dice used in the game.

Aristotle mistakenly thought that identical regular tetrahedrons packed together perfectly, as identical cubes do, leaving no gaps in between and filling 100 percent of the available space. They do not, and 1,800 years passed before someone pointed out that he was wrong. Even after that, the packing of tetrahedrons garnered little interest. More centuries passed.

A similar conundrum for how to best pack identical spheres has a more storied history. There, the answer was obvious. They should be stacked like oranges at a supermarket (with a packing density of 74 percent), and that is what Johannes Kepler conjectured in 1611. But proving the obvious took almost four centuries until Thomas C. Hales, a mathematician at the University of Pittsburgh, succeeded in 1998 with the help of a computer.

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OBSERVATORY: Much-Maligned Mother of Many Beloved Wines
By HENRY FOUNTAIN, The New York Times, January 5, 2010

About a decade ago, researchers had some startling news for wine lovers. Some of their beloved grape varieties, including chardonnay and gamay noir, were the offspring of a third-rate parent, gouais blanc. In fact, the research showed that at least a dozen varieties were a result of crosses, a long time ago, between pinot noir and gouais blanc, which had such a bad reputation that its cultivation was at times outlawed.

The news just got a bit more startling. Looking at the DNA in chloroplasts in the 12 varieties, Harriet V. Hunt and Matthew C. Lawes of the University of Cambridge in England and colleagues set out to determine which was the paternal parent (supplying the pollen) and which was the maternal one (supplying the egg cells). Gouais blanc, they write in Biology Letters, was the mother of nine of the varieties: aligoté, auxerrois, franc noir, melon, bachet, sacy and romorantin, in addition to chardonnay and gamay noir.

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Several lizard species that are dark have developed white skin in the White Sands of New Mexico.

OBSERVATORY: White Lizards Evolve in New Mexico Dunes
By HENRY FOUNTAIN, The New York Times, January 5, 2010

The White Sands of New Mexico are a good place to study evolution in progress. One reason is that the terrain, gypsum dunes white as a sheet of paper, is so different from the surrounding area. Another is that the dunes formed only about 6,000 years ago.

“From an evolutionary perspective, that’s really the blink of an eye,” said Erica Bree Rosenblum, a professor at the University of Idaho who has been studying evolution at White Sands for much of the past decade. Her focus has been on three lizard species that elsewhere are dark skinned but in White Sands have each evolved a white-skinned variety that makes them hard to find. “It’s really obvious what’s happened,” Dr. Rosenblum said. “Everybody got white so that they could better escape from their predators.” It’s a great example of convergent evolution, of species independently acquiring the same traits.

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Q & A: Temperature and Exercise
By C. CLAIBORNE RAY, The New York Times, January 5, 2010

Q. Does a person tend to burn more fat exercising outdoors in colder weather or in hotter weather? I am leaning to the colder weather side, since the body has to work harder to keep the body temperature near normal.

A. “Contrary to conventional wisdom, the combination of exercise and cold exposure does not act synergistically to enhance metabolism of fats,” according to a study published in 1991 in the journal Sports Medicine.

The study, done at the Hyperbaric Environmental Adaptation Program of the Naval Medical Research Institute in Bethesda, Md., found that some of the bodily processes involved in fat metabolism were actually slowed down by the effects of relatively cold temperatures on human tissue.

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A satellite image of the East Siberian Sea from 1999-2008. This image has been degraded to hide the satellite’s true capabilities.

C.I.A. Is Sharing Data With Climate Scientists
By William J. Broad, The New York Times, January 5, 2010

The nation’s top scientists and spies are collaborating on an effort to use the federal government’s intelligence assets — including spy satellites and other classified sensors — to assess the hidden complexities of environmental change. They seek insights from natural phenomena like clouds and glaciers, deserts and tropical forests.

The collaboration restarts an effort the Bush administration shut down and has the strong backing of the director of the Central Intelligence Agency. In the last year, as part of the effort, the collaborators have scrutinized images of Arctic sea ice from reconnaissance satellites in an effort to distinguish things like summer melts from climate trends, and they have had images of the ice pack declassified to speed the scientific analysis.

The trove of images is “really useful,” said Norbert Untersteiner, a professor at the University of Washington who specializes in polar ice and is a member of the team of spies and scientists behind the effort.

Scientists, Dr. Untersteiner said, “have no way to send out 500 people” across the top of the world to match the intelligence gains, adding that the new understandings might one day result in ice forecasts.

“That will be very important economically and logistically,” Dr. Untersteiner said, arguing that Arctic thaws will open new fisheries and sea lanes for shipping and spur the hunt for undersea oil and gas worth hundreds of billions of dollars.

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