Science News and Notes
Thursday, May 20, 2004
Cosmos 'a billion years older'
By Dr David Whitehouse - BBC News Online science editor
The Universe could be a billion years older than was thought, according to Italian and German scientists. Measurements made in an underground laboratory suggest an atomic reaction that produces energy inside stars is slower than was believed. It means that estimates of stellar lifetimes are too short. A readjustment gives the Universe an age of 14.7 instead of 13.7 billion years. The results are to be published in the journal Physics Review Letters.
The new result comes from Luna - the Laboratory for Underground Nuclear Astrophysics - situated underneath Gran Sasso mountain in Italy. In Luna scientists from the Italian Institute of Nuclear Physics and the University of Bochum in Germany are reproducing one of the energy-producing nuclear reactions that takes place inside the Sun. "In an ordinary laboratory on the surface the effects of the reaction studied by Luna would be hidden by similar, but much more abundant, effects. Because our laboratory is under 1,400m of rock we have an isolated base to make these delicate measurements," says Luna co-ordinator Dr Carlo Broggini.
The cycle they are studying - the carbon-nitrogen-oxygen cycle - only supplies a tiny fraction of our Sun's energy. It is far more important in larger stars. The result obtained suggests that the carbon-nitrogen-oxygen cycle takes place at half the rate as was believed. The implications are that massive stars live longer than was believed, a factor that affects estimates of the age of the Universe based on the ages of the oldest stars.
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Tuesday, May 18, 2004
Evidence Of Meteor Impact Found Off Australian Coast
Wybung Head, Australia PTB
Arlington VA (SPX) May 14, 2004
An impact crater believed to be associated with the "Great Dying," the largest extinction event in the history of life on Earth, appears to be buried off the coast of Australia. NASA and the National Science Foundation (NSF) funded the major research project headed by Luann Becker, a scientist at the University of California, Santa Barbara (UCSB). Science Express, the electronic publication of the journal Science, published a paper describing the crater today.
Most scientists agree a meteor impact, called Chicxulub, in Mexico's Yucatan Peninsula, accompanied the extinction of the dinosaurs 65 million years ago. But until now, the time of the Great Dying 250 million years ago, when 90 percent of marine and 80 percent of land life perished, lacked evidence and a location for a similar impact event.
Becker and her team found extensive evidence of a 125-mile- wide crater, called Bedout, off the northwestern coast of Australia. They found clues matched up with the Great Dying, the period known as the end-Permian. This was the time period when the Earth was configured as one primary land mass called Pangea and a super ocean called Panthalassa. During recent research in Antarctica, Becker and her team found meteoric fragments in a thin claystone "breccia" layer, pointing to an end-Permian event. The breccia contains the impact debris that resettled in a layer of sediment at end- Permian time. They also found "shocked quartz" in this area and in Australia. "Few Earthly circumstances have the power to disfigure quartz, even high temperatures and pressures deep inside the Earth's crust," Becker said. Quartz can be fractured by extreme volcanic activity, but only in one direction. Shocked quartz is fractured in several directions and is therefore believed to be a good tracer for the impact of a meteor.
Becker discovered oil companies in the early 70's and 80's had drilled two cores into the Bedout structure in search of hydrocarbons. The cores sat untouched for decades. Becker and co-author Robert Poreda went to Australia to examine the cores held by the Geological Survey for Australia in Canberra. "The moment we saw the cores, we thought it looked like an impact breccia," Becker said. Becker's team found evidence of a melt layer formed by an impact in the cores. In the paper, Becker documented how the Chicxulub cores were very similar to the Bedout cores. When the Australian cores were drilled, scientists did not know exactly what to look for in terms of evidence of impact craters. Co-author Mark Harrison, from the Australian National University in Canberra, determined a date on material obtained from one of the cores, which indicated an age close to the end-Permian era. While in Australia on a field trip and workshop about Bedout, funded by the NSF, co-author Kevin Pope found large shocked quartz grains in end-Permian sediments, which he thinks formed as a result of the Bedout impact. Seismic and gravity data on Bedout are also consistent with an impact crater.
The Bedout impact crater is also associated in time with extreme volcanism and the break-up of Pangea. "We think that mass extinctions may be defined by catastrophes like impact and volcanism occurring synchronously in time," Becker said. "This is what happened 65 million years ago at Chicxulub but was largely dismissed by scientists as merely a coincidence. With the discovery of Bedout, I don't think we can call such catastrophes occurring together a coincidence anymore," she added.
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Saturday, May 15, 2004
Impact Crater Labeled Clue to Mass Extinction
By Guy Gugliotta - Washington Post Staff Writer - Friday, May 14, 2004; Page A03
Scientists said yesterday they have found evidence that a huge meteorite or comet plunged into the coastal waters of the Southern Hemisphere 251 million years ago, possibly triggering the most catastrophic mass extinction in Earth's history.
The researchers said that geological evidence suggests that an object about six miles in diameter crashed at the shoreline of what is now Australia's northwestern coast, creating climate changes and other natural catastrophes that wiped out 90 percent of marine species and 70 percent of land species. This "extinction event" marks the boundary between the Permian and Triassic periods of geologic time. Another extinction that wiped out the dinosaurs and other species 65 million years ago is generally attributed to a similar-size meteor that punched an enormous crater in what is now Mexico's Yucatan Peninsula.
"What we found [is] the top of this very large feature buried under sediments," said Luann Becker, a University of California at Santa Barbara geochemist and leader of the research team reporting in the journal Science. "We have a date consistent with end-Permian [and] impact debris [minerals]. I think we have a pretty strong story." Yesterday's report is the third published by Science documenting the Becker team's work. Nevertheless, the extraterrestrial impact theory remains controversial, because the extinction is also contemporaneous with a huge outpouring of volcanic "flood basalts" in Northern Siberia, perhaps also capable of triggering global climatic change. "The evidence for impact has been growing over the last few years," said National Museum of Natural History paleontologist Douglas H. Erwin. "This isn't a slam-dunk yet for impact, but it sure makes it a stronger contender." However, he added, "scientists don't like coincidences, and we have the complication of Siberia."
The Permian-Triassic extinction is one of five such events known to have occurred through geological history, and is estimated to have caused twice as many species of plants and animals to become extinct as any of the others. The trigger -- either an extraterrestrial impact or volcanism -- caused massive amounts of debris and dust to fly into the atmosphere, either creating a sudden greenhouse effect that led to radical global warming or obscuring the sun to such a degree that Earth was embraced by the prehistoric equivalent of "nuclear winter." A meteoric impact could also cause massive tidal waves and other disturbances. Since 2001, Becker and her team, funded by NASA and the National Science Foundation, had reported finding evidence of impact debris in the southern reaches of what used to be the massive prehistoric continent Pangea. They described their latest work in a telephone news conference.
Team member Robert Poreda, an Earth scientist from the University of Rochester, said an Australian colleague tipped off the researchers about an underwater geological formation called the Bedout High that resembled Yucatan's Chicxulub Crater. The Permian deposits lay beneath almost two miles of ocean sediment. After examining core samples taken from the formation by oil exploration firms, "we were absolutely flabbergasted," Poreda said. What had been described by the oil geologists as "volcanic rock" showed that bits of the crystalline mineral feldspar had been transformed into glass by the shock of the impact. "This never occurs in volcanic debris," Poreda said. "This was absolutely convincing proof of an impact formation." Using dating techniques based on radioactive decay, the team found that a grain of material from the bottom of one of the Bedout oil exploration wells was 250.2 million years old -- close to the target date.
Finally, Poreda noted that last year, the team reported finding fragments of quartz and other minerals that had been similarly "shocked" by an extraterrestrial impact and spewed into the atmosphere to land 3,000 to 4,000 miles away in a pattern suggesting they came from the Bedout High. In all, Poreda said, Bedout "happened at the right time, in the right place and had the right features" to match up with the extinction, "so, yes, this is a really good candidate." Erwin acknowledged that the Becker team had provided additional evidence of an extraterrestrial impact, but "perhaps not yet compelling -- what's going to happen is that geologists and paleontologists will investigate this far more thoroughly and find more evidence to support or refute this interpretation." He said the key task is to resolve the apparent conflict between the impact theory and the view that Siberian flood basalts caused the extinction. Scientists must make further efforts to accurately date both events to determine whether they are truly contemporaneous, he said. If they are, he added, scientists must then determine whether the impact might somehow have caused the Siberian volcanism.
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Tuesday, May 11, 2004
Using Caffeine The Wrong Way?
CBS The Early Show - New York, May 12, 2004
(CBS) There may be a better way of utilizing caffeine to stay awake and alert, according to a new study.Researchers from Rush University Medical Center, Brigham and Women's Hospital and Harvard Medical School say they discovered low doses of caffeine throughout the day is more effective than the traditional method of having a large dose in the morning.
The Early Show medical correspondent Dr. Emily Senay is scheduled Wednesday to explain the results of the study and discuss its implications.The study discovered that caffeine works by thwarting one of two interacting physiological systems that govern the human sleep-wake cycle. The researchers reported in the journal Sleep that shift workers, medical residents, truck drivers and others who need to stay awake are better serve by low doses of caffeine to get a bigger boost from their tea or coffee.
Senay explains the caffeine taken in a large amount in the morning may be useless in keeping a person alert for the entire day. The research, which was funded by the United States Air Force Office of Scientific Research, wanted to examine how military pilots dealt with work duty hours that went longer than 16 hours and at night. The study kept the subject awake for 28 hours and they sleep for 14 hours. Subjects who took the low-dose caffeine performed better on cognitive tests. They also exhibited fewer accidental sleep onsets compared to placebo subjects.
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Sunday, May 02, 2004
Quantum Computers Are A Quantum Leap Closer, Say Purdue Physicists
Date: 30 April 2004 - A new breed of faster, more powerful computers based on quantum mechanics may be a step closer to reality, report scientists from Purdue and Duke universities. By linking a pair of tiny "puddles" of a few dozen electrons sandwiched inside a semiconductor, researchers have enabled these two so-called "quantum dots" to become parts of a transistor - the vital switching component in computer chips. Future computers that use quantum dots to store and process digital information might outperform conventional computer circuits because of both the new transistors' smaller size and their potential to solve problems that would take centuries on today's machines.
"This is a very promising candidate for quantum computation," said Albert M. Chang, who is an adjunct professor of physics in Purdue's School of Science. "We believe this research will allow large numbers of quantum-dot switches to work together as a group, which will be necessary if they are ever to function as a computer's brain, or memory. "For the market, quantum computers mean better encryption methods and heightened data security. For science, our research may help address the longstanding mystery of the relationship between the classical physics of the world we see every day, and the peculiar world of quantum physics that governs the tiny particles inside atoms." The research will appear in the current (April 30) issue of Physical Review Letters. The lead author is Jeng-Chung Chen, who received his doctorate at Purdue and is now at the University of Tokyo. Co-authors are Chang, who in 2003 relocated from Purdue to Duke University, where he is a professor of physics, and Michael. R. Melloch, a professor in Purdue's School of Electrical and Computer Engineering.
As computer circuits grow ever smaller, manufacturers draw nearer to the time when their chips' tiny on-off switches - representing the 1's and 0's of binary information, or bits - can be made comparable in size to a single molecule. At smaller scales, the laws of classical physics will no longer apply to the switches, but will be replaced by the laws of the subatomic world. These laws, described by quantum physics, can appear strange to the uninitiated. "An electron, for example, can behave like a particle or a wave at times, and it has the odd ability to seemingly be in two different states at once," Chang said. "Physicists need a different set of words and concepts to describe the behavior of objects that can do such counterintuitive things. One concept we use is the 'spin' of an electron, which we loosely imagine as being similar to the way the Earth spins each day on its axis. But it also describes a sort of ordering electrons must obey in one another's presence: When two electrons occupy the same space, they must pair with opposite spins, one electron with 'up' spin, the other 'down.'"
Spin is one property that physicists seek to harness for memory storage. After collecting 40 to 60 paired electrons in a puddle within a semiconductor wafer of gallium arsenide and aluminum gallium arsenide, the team then added a single additional unpaired electron to the puddle. This extra electron imparted a net spin of up or down to the entire puddle, which they call a quantum dot. The team also built a second quantum dot nearby with the same net spin. "When isolated from one another, the two net spins would not seek to pair with each other," Chang said. "But we have a special method of 'tuning' the two-dot system so that, despite the similar spins, the two unpaired electrons became 'entangled' - they begin to interact with one another."
The team used eight tiny converging wires, or "gates," to deposit the electrons in the dots one by one and then electronically fine-tune the dots' properties so they would become entangled. With these gates, the team was able to slowly tune the interacting dots so they are able to exist in a mixed, down-up and up-down configuration simultaneously. In each dot, an up or down configuration would represent a 1 or 0 in a quantum bit, or "qubit," for possible use in memory chips. "Entanglement is a key property that would help give a quantum computer its power," Chang said. "Because each system exists in this mixed, down-up configuration, it may allow us to create switches that are both on and off at the same time. That's something current computer switches can't do." Large groups of qubits could be used to solve problems that have myriad potential solutions that must be winnowed down quickly, such as factoring the very large numbers used in data encryption.
"A desktop computer performs single operations one after another in series," Chang said. "It's fast, but if you could do all those operations together, in parallel rather than in series, it can be exponentially faster. In the encryption world, solving some problems could take centuries with a conventional computer." But for a quantum computer, whose bits can be in two quantum states at once - both on and off at the same time - many solutions could, in theory, be explored simultaneously, allowing for a solution in hours rather than lifetimes. "These computers would have massive parallelism built right in, allowing for the solution of many tough problems," Chang said. "But for us physicists, the possibilities of quantum computers extend beyond any single application. There also exists the potential to explore why there seem to be two kinds of reality in the universe - one of which, in everyday language, is said to stop when you cross the border 'into the interior of the atom.'" Because a quantum computer would require all its qubits to behave according to quantum rules, its processor could itself serve as a laboratory for exploring the quantum world. "Such a computer would have to exhibit 'quantum coherence,' meaning its innards would be a large-scale system with quantum properties rather than classical ones," Chang said. "When quantum systems interact with the classical world, they tend to lose their coherence and decay into classical behavior, but the quantum-dot system we have built exhibits naturally long-lasting coherence. As an entire large-scale system that can behave like a wave or a particle, it may provide windows into the nature of the universe we cannot otherwise easily explore."
The system would not have to be large; each dot has a width of only about 200 nanometers, or billionths of a meter. About 5,000 of them placed end to end would stretch across the diameter of a grain of sand. But Chang said that his group's system had another, greater advantage even than its minuscule size. "Qubits have been created before using other methods," he said. "But ours have a potential advantage. It seems possible to scale them up into large systems that can work together because we can control their behavior more effectively. Many systems are limited to a handful of qubits at most, far too few to be useful in real-world computers." For now, though, the team's qubit works too slowly to be used as the basis of a marketable device. Chang said the team would next concentrate on improving the speed at which they can manipulate the spin of the electrons.
"Essentially, what we've done is just a physics experiment, no more," he said. "In the future, we'll need to manipulate the spin at very fast rates. But for the moment, we have, for the first time, demonstrated the entanglement of two quantum dots and shown that we can control its properties with great precision. It offers hope that we can reach that future within a decade or so."
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Gravity Probe in Orbit
Date: 1 May 2004
"NASA's Gravity Probe B mission, also known as GP-B, will use four ultra-precise gyroscopes to test Einstein's theory that space and time are distorted by the presence of massive objects. To accomplish this, the mission will measure two factors -- how space and time are warped by the presence of the Earth, and how the Earth's rotation drags space-time around with it." After a 60 day test period, the Gravity Probe starts it 13-month data collection phase, followed by a 2-month final calibration. Stanford University in Stanford, Calif., developed and built the science experiment hardware and operates the science mission for NASA. (See illustration)
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