A small but growing number of astronomers are arguing that the risks of comets or meteors hitting Earth are much higher than past estimates suggest.
Some of these objects may be going unnoticed in space, the researchers say, and scientists may need to begin new studies tailored to finding them.
But advocates of the earlier estimates are shooting back that the evidence doesn't warrant revising the figures drastically.
The traditional estimates, based on sky surveys and other techniques, vary.
But in general, they conflict with the number of objects actually found to have visited Earth's neighborhood, according to David J. Asher of the Armagh Observatory in Northern Ireland and three colleagues.
Science & Technology
Last week's Quadrantid meteor shower was probably debris from a deep-space explosion that went off in the late 15th century, new observations reveal.
Bees have a much more sophisticated visual system than previously thought, according to a new UCL (University College London) study in which bees were able to solve complicated colour puzzles. The findings shed light on how brains resolve one of the most difficult challenges of vision - namely, recognizing different surfaces under different colours of illumination - by suggesting that bees solve this problem using their experience with meaningful colour relationships between objects in a scene. The findings, published in the Proceedings of the National Academy of Sciences, may one day lead to the design of autonomous robotic systems.
In the UCL study, scientists from the UCL Institute of Ophthalmology trained bumblebees to find artificial flowers of a particular colour using a nectar reward. They then tested the bees' ability to find the same flowers in scenes that were simultaneously illuminated by four differently coloured lights - UV-yellow, blue, yellow and green. To solve this puzzle, the bees had to effectively segment the scene into its different regions of illumination, and then find the correct flowers within each region.
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In the UCL study, scientists from the UCL Institute of Ophthalmology trained bumblebees to find artificial flowers of a particular colour using a nectar reward. They then tested the bees' ability to find the same flowers in scenes that were simultaneously illuminated by four differently coloured lights - UV-yellow, blue, yellow and green. To solve this puzzle, the bees had to effectively segment the scene into its different regions of illumination, and then find the correct flowers within each region.
Russia plans to participate in a European mission to investigate Jupiter's moon Europa and search for simple life forms, the Interfax news agency reported on Monday, quoting a senior researcher.
The head of the Space Research Institute, Lev Zelyony, said a project to explore the giant gaseous planet Jupiter would shortly be included in the programme of the European Space Agency (ESA) for the years 2015 to 2025.
The head of the Space Research Institute, Lev Zelyony, said a project to explore the giant gaseous planet Jupiter would shortly be included in the programme of the European Space Agency (ESA) for the years 2015 to 2025.
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| NASA satellite image of Jupiter's moon Europa. The Interfax news agency has quoted a senior researcher as saying that Moscow plans to participate in a European mission to investigate Jupiter's moon Europa and search for simple life forms. |
M.D. Anderson biochemist's work alters our view of cell division - and possibly disease.
For the first time, scientists have captured detailed images of life's essence.
The dazzling pictures reveal a key step in the process of cell division, which all organisms must undergo to survive. The moment occurs deep within a cell, as two proteins work in concert to unzip a strand of DNA to create two new cells.
For the first time, scientists have captured detailed images of life's essence.
The dazzling pictures reveal a key step in the process of cell division, which all organisms must undergo to survive. The moment occurs deep within a cell, as two proteins work in concert to unzip a strand of DNA to create two new cells.
© SVM Clube
In the meantime, a friend of mine (who is a climate scientist at a major U.S. research facility) turned me on to an interesting find, a paper addressed to the European Office of Aerospace Research and development, dated June 4, 1996, entitled: "The Hazard to Civilization from Fireballs and Comets" by S.V.M. Clube. (For the uninitiated, Clube is an astrophysicist at the University of Oxford).
In this short (4 pages) letter and summary statement, Clube writes (emphases in the original, make of them what you will):
Asteroids which pass close to the Earth have been fully recognized by mankind for only about 20 years. Previously, the idea that substantial unobserved objects might be close enough to be a potential hazard to the Earth was treated with as much derision as the unobserved aether. Scientists of course are in business to establish broad principles (eg relativity) and the Earth's supposedly uneventful, uniformitarian environment was already very much in place. The result was that scientists who paid more than lip service to objects close enough to encounter the Earth did so in an atmosphere of barely disguised contempt. Even now, it is difficult for laymen to appreciate the enormity of the intellectual blow with which most of the Body Scientific has recently been struck and from which it is now seeking to recover.
It was billed as a fond farewell to the technology industry from Bill Gates: a chance for the billionaire businessman to pay tribute to the hi-tech world one last time before he steps down from his duties at Microsoft later this year.
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| Antarctic balloon flights can last much longer than flights in other places because of the polar vortex and because there is very little atmospheric or temperature change. Constant daylight in Antarctica means no day-to-night temperature fluctuations on the balloon, which helps it stay at a nearly constant altitude during the flight. |
NASA and the National Science Foundation have achieved a new milestone in conducting scientific observations from balloons, by launching and operating three long-duration flights within a single Antarctic summer. Having three long-duration balloon science missions flying simultaneously is a record-setting event.
A Stanford scientist has spelled out for the first time the direct links between increased levels of carbon dioxide in the atmosphere and increases in human mortality, using a state-of-the-art computer model of the atmosphere that incorporates scores of physical and chemical environmental processes.
The new findings, to be published in Geophysical Research Letters, come to light just after the Environmental Protection Agency's recent ruling against states setting specific emission standards for this greenhouse gas based in part on the lack of data showing the link between carbon dioxide emissions and their health effects.
The new findings, to be published in Geophysical Research Letters, come to light just after the Environmental Protection Agency's recent ruling against states setting specific emission standards for this greenhouse gas based in part on the lack of data showing the link between carbon dioxide emissions and their health effects.
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| This study finds that the effects of carbon dioxide's warming are most significant where the pollution is already severe. Given that California is home to six of the 10 U.S. cities with the worst air quality, the state is likely to bear an increasingly disproportionate burden of death if no new restrictions are placed on carbon dioxide emissions. |
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| The Global Navigation Satellite Systems, which include the U.S.-based Global Positioning System, the Russian GLONASS system, and the upcoming European Galileo system, are used for accurately determining the geographic position of any point on Earth. |
NOAA will lead an international effort to pinpoint the locations of more than 40 global positioning satellites in Earth orbit, which is vital to ensuring the accuracy of GPS data that millions worldwide rely upon every day for safe navigation and commerce.
Comment: Continue to Part Three: Cosmic Turkey Shoot