Telescopes could save the planet

by Jacquelyn Olson

The work of the Hubble telescope in examining space could be easily outdone within 10 to 15 years by something cheaper, lighter and more effective at predicting the paths of asteroids, meteorites and comets, Freeman Dyson, Princeton physics professor, said Wednesday.
As the scientist told an audience of more than 300 at the Tate Laboratory of Physics, celestial objects do occasionally hit the earth. The Ukatan Peninsula comet of 65 million years ago was the size of downtown Minneapolis, and is commonly cited as the main reason dinosaurs became extinct. Comet Shoemaker-Levy 9, which struck Jupiter two years ago, changed the face of that planet.
The Jupiter comet, and the heightened awareness that something like it could hit the earth, has renewed interest in creating devises to detect Earth impacting objects, Dyson said.
“What makes the detection of comets difficult is that sunlight is very faint farther out in the solar system. That’s the bad news. The good news is that they move slowly, only a few kilometers per second … so we always have about 15 years’ warning,” Dyson said.
Improved equipment should increase the warning time to about 30 years. Using an automated, wide-field telescope whose only function is scanning the sky, Dyson said, is the best way to detect objects that might collide with the Earth.
Knowing how often objects collide with Earth is determined mostly from astronomical evidence, such as estimating the age of craters by examining sedimentary rock layers, Dyson said.
University Physics and Astronomy Professor Robert D. Gehrz said he agrees a telescope capable of detecting Earth-impacting objects could be made in 10 years.
“From what I heard today I think that it is technologically feasible to both detect and deflect large objects that would threaten the Earth.”
Celestial billiards is one way to prevent objects from hitting Earth, Dyson said.
“Rather than deflecting the object directly, we can arrange a collison between this object and a smaller one.”
Because the rate of collisions is measured per millions of years, however, their frequency is actually sporadic. The next time a celestial body hits the earth “could be five minutes. Or it could be a million years,” Gehrz said.
Dyson’s speech was part of the 21st Abigail and John Van Vleck Lecture Series, sponsored by the physics and astronomy departments.