In medieval European cathedrals, the glass sometimes looks odd. Some panes are thicker at the bottom than they are at the top. The seemingly solid glass appears to have melted. This is evidence, say tour guides, Internet rumors and even high school chemistry teachers, that glass is actually a liquid. And, because glass is hard, it must be a supercooled liquid.
Glass, however, is actually neither a liquid - supercooled or otherwise - nor a solid. It is an amorphous solid - a state somewhere between those two states of matter. And yet glass's liquidlike properties are not enough to explain the thicker-bottomed windows, because glass atoms move too slowly for changes to be visible.
Jon Cartwright
PhysicsWebThu, 08 Mar 2007 04:37 UTC
Astronomers in the US and Europe have proved that sunlight plays a key role in how fast asteroids rotate. The rotation is caused by the small torque given to an asteroid when previously absorbed solar radiation is re-emitted. This mechanism -- known as the "YORP" effect -- has now been seen for the first time in two asteroids, and could be the reason behind the odd distribution of rotations seen in asteroid families.
Large asteroids rotate at a range of different speeds, roughly following a bell-shaped "Gaussian" distribution in which most rotate at a speed close to some average, with only a small proportion rotating much faster or much slower then the norm. However, the distribution for asteroids with a diameter less than 10 km is rather different - their families have a large excess of asteroids rotating at the fast and slow extremes.
Researchers had thought that the odd distributions could be a result of infrared photons from the Sun warming an asteroid's near surface as they are absorbed. These absorbed photons are re-emitted once the surface turns away from the Sun, making the asteroid recoil a tiny amount each time they depart. Although a symmetrical asteroid would be unaffected by these recoils, an irregularly-shaped asteroid would experience a net torque that increases the speed of its rotation over millions of years - the so-called "YORP" effect (named after its originators Yarkovsky, O'Keefe, Radzievskii and Paddack). However, the torque would be so small that it would only cause a significant rotation in small asteroids.
XinhuaWed, 07 Mar 2007 13:56 UTC
A killer asteroid whose target is Earth will likely go undetected because NASA doesn't have the funds to find it, media reported Tuesday.
NASA officials say the space agency is capable of finding nearly all the asteroids that might destroy Earth, but the price to find at least 90 percent of the 20,000 potentially hazardous asteroids and comets by 2020 would be about 1 billion U.S. dollars, according to a report NASA will release later this week.
The report was previewed Monday at a Planetary Defense Conference in Washington.
Comment: Defending against one asteroid that might hit us is one thing, defending against hundreds or thousands is another. In any case, we suspect that those Powers That Be are well aware of the real danger and have prepared their underground bunkers leaving the Rest Of Us to face the music. And it is a funeral dirge...
Check out Laura Knight Jadczyk's article
Independence Day for details. Coming to a reality near you....
A US man awaiting trial on firearms offences is suing Microsoft after FBI technicians found self-made sex videos and evidence that he frequented porn sites on his PC.
Michael Alan Crooker, currently on remand in a Connecticut jail on charges of selling illegally modified firearms and possessing bomb-making equipment, is inflamed that security settings on his PC failed to prevent Federal agents from finding out about his smut-surfing habits. He's suing Microsoft in Massachusetts Superior Court for privacy violations that he claims caused him "great embarrassment" in a lawsuit that seeks $200,000 in damages in compensatory and punitive damages.
Tiny lab versions of 12-foot tall snow spikes that form naturally on some high mountain glaciers may someday help scientists mitigate the effects of global warming in the Andes, according to a University of Colorado at Boulder professor.
CU-Boulder physics Assistant Professor Meredith Betterton said the spikes, known as penitentes, are shaped when concentrated rays of sunlight evaporate snow from low spots on glacier fields in a process known as sublimation. The lab studies confirm that the low spots, or troughs, deepen as intense sunlight strikes them, sculpting penitentes by the hundreds of thousands on some glaciers, she said.
Some scientists have predicted that penitentes might help put the brakes on shrinking glaciers in a warming climate by blocking sunlight that might otherwise be absorbed by glacial surfaces, said Betterton. She gave a presentation on penitentes at the March Meeting of the American Physical Society in Denver March 5-9, which hosted more than 7,000 scientists.
Scientists and engineers remain on course in their efforts to determine what caused the twin Pioneer spacecraft to apparently drift off course by hundreds of thousands of kilometres during their three-decade missions. Within a year, they expect to be able to decide whether this drift was caused by a fault on the spacecraft.
Launched 35 years ago on Friday, Pioneer 10 was the first spacecraft to reach the outer solar system and return pictures of Jupiter. It was followed by Pioneer 11, which launched on 5 April 1973 and also visited Saturn.
After these historic encounters, NASA kept track of the drifting spacecraft, finally losing contact with Pioneer 11 in 1995 and Pioneer 10 in 2003.
When humans first trekked from Asia to North America, perhaps as long as 25,000 years ago, the continent was gripped by ice sheets and glaciers. Those hardy immigrants probably traveled by boat or along the shore, where finding food and shelter would have been easier. The trouble for archaeologists is that as the ice melted, the seas rose and covered any traces of this early migration. Now marine geologists and archaeologists are hunting for underwater clues in the Gulf of Mexico.
This morning, a research expedition steamed out of the Port of Galveston, Texas, for the Flower Garden Banks National Marine Sanctuary, about 180 kilometers off the coast of Texas and Louisiana. Led by Robert Ballard, president of the Institute for Exploration at Mystic Aquarium in Mystic, Connecticut, and Kevin McBride of the Mashantucket Pequot Museum and Research Center in Connecticut, the expedition consists of a 44-meter-long Navy research submarine, two ships, and a remotely operated vehicle (ROV).
Jon Cartwright
PhysicsWebWed, 07 Mar 2007 06:34 UTC
Physicists analyzing data taken by the HyperCP experiment at Fermilab in the US claim they may have glimpsed the first Higgs boson -- the particle many think is responsible for all mass in the universe. However, for their claim to be correct our current 30-year-old Standard Model of particle physics would have to be set aside in favour of an alternative "supersymmetric" model.
The great triumph of the Standard Model is that it unites two of the fundamental forces - the weak and electromagnetic force - into a single, symmetric "electroweak" force at high energies. But at low energies, a symmetric electroweak theory would imply that particles have no mass, which is clearly wrong.
A new study is raising questions about whether a suspect fingered by scientists is as big a driver of human aging as previously thought. For years, researchers believed that small DNA mutations in the energy-producing parts of our cells lead us down the road to aching bodies and wrinkled skin. But mice engineered to have hundreds of times more of these mutations than average showed no signs of premature aging, indicating that scientists are going to have to look elsewhere for their culprit.
Cells contain thousands of tiny structures called mitochondria, which generate energy and harbor their own DNA distinct from the cell's nucleus. Scientists suspect this DNA, called mitochondrial DNA, or mtDNA, may be more vulnerable to mutations from errors in DNA replication. Over the last five years, several studies in mice pointed to a link between these mutations in mtDNA and the decline of tissue function that occurs as humans and animals age.
Scientists have delivered proof of what many have suspected for years - the weather is always worse at weekends.
Saturdays are colder and wetter than any other day, a major study of weather patterns has revealed.
And the researchers insist people themselves are to blame for the trend - because they drive more during the week and increase dust pollution.
Meteorologists looked at 6.3million pieces of climate data from across Europe between 1991 and 2005.
It's thought to be the most comprehensive weather study ever.
They found Wednesdays have the highest average temperatures and Mondays are the driest. Saturdays were worst on both counts.
Comment: Defending against one asteroid that might hit us is one thing, defending against hundreds or thousands is another. In any case, we suspect that those Powers That Be are well aware of the real danger and have prepared their underground bunkers leaving the Rest Of Us to face the music. And it is a funeral dirge...
Check out Laura Knight Jadczyk's article Independence Day for details. Coming to a reality near you....