7/24/2003:
Intermediate Word: Aricept is a popular drug for: (a)
Alzheimer's Disease (b) high blood pressure (c) Parkinson's disease (d) cancer
Difficult
Word: - bacciferous
- (a) pockeded with
hematomas (b) arrogant (c) berry-bearing
(d) characterized by clustered flowers
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Asteroid hazard revised - Nature Large meteorites are more likely to break up in the atmosphere before they hit the Earth than was previously thought. The new estimates reduce the likely frequency of potentially catastrophic impacts of large meteorites at the Earth's surface by about a factor of 50, relative to previous forecasts. They come from Philip Bland, of Imperial College in London, and Natalia Artemieva, of the Institute for Dynamics of Geospheres in Moscow1. Bland and Artemieva reckon that objects larger than 220 metres across are likely to strike the Earth every 170,000 years or so, compared with the previously claimed frequency of 3,000-4,000 years. Bodies this big would generate devastating tidal waves if they landed in the ocean. It is not clear whether this reduces the meteorite hazard to Earth, however. A shower of fragments could be just as devastating as the impact of a single large object. The realization over the past decade or so that our planet sits in a cosmic coconut shy has raised fears that we might one day share the fate of the dinosaurs, who were wiped out by the collision of a gigantic meteorite around 65 million years ago. |
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Galaxies and black holes grow together - Nature Galaxies and their central black holes grow at the same rate, astronomers have found. The discovery lays to rest the long-standing debate about which came first. "Like the chicken and the egg, neither black hole nor galaxy can be said to come first," says team member Tim Heckman of Johns Hopkins University in Baltimore, Maryland. His group presented its results at this week's International Astronomical Union meeting in Sydney, Australia. Most galaxies harbour at their heart a black hole - a pocket of space so dense that it weighs millions of times more than our Sun but is only a few times as big. Black holes' gravity is such that they act like an enormous plughole, sucking in swirls of dust that add to their mass. Astronomers have long wondered whether black holes gave rise to galaxies by pulling together dust and gas into stars, or whether galaxies - through corralling stars - harnessed enough mass to seed black holes. Heckman and other members of the Sloan Digital Sky Survey - an international collaboration to map 100 million celestial objects and their properties - studied 120,000 nearby galaxies. They saw the light signatures of the birth of stars and the destruction of matter as it is sucked into a black hole. They conclude that stars form at the same speed as black holes grow. |
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Message in a coral - Nature When local officials turned the yacht away from the white sandy beaches of Kiritimati Island in the tropical Pacific Ocean, the crew's hearts sank. But Kim Cobb and her colleagues were not hankering after long drinks in the sun. They had hoped to delve into past climate by drilling into rare deposits of fossil coral. Happily, the nearby safe haven of Palmyra Island turned out to be an unexpected goldmine. Its corals revealed that, out of five time windows between AD 928 and 1998, the largest short-term climate variability occurred between 1635 and 1670 - rather than during the global-warming-ridden twentieth century. This is interesting because Palmyra lies at the centre of Earth's most powerful climate rollercoaster, El Niņo. This cycle, which repeats every three to seven years, transfers huge amounts of heat across the equatorial Pacific Ocean. The fossils reveal the temperature and salinity at the time when |
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