CAPE CANAVERAL, Fla. -- Statistically speaking, a person has just as good a chance of perishing from a plummeting asteroid as he does of dying in a plane crash in his lifetime.
But the numbers are slightly misleading.
If a large enough asteroid hits Earth, as they are known to do every 100 million years or so, it could wipe out half of the planet's population. Whereas if an airplane crashes, as several do annually, it can kill hundreds of people. The odds actually even out.
"It's hard to compare the two because they're on such different time scales, . . .the consequences are so different," said asteroid hunter Jim Scotti, an astronomer with the Spacewatch group at the University of Arizona.
A November study published in the Astronomical Journal showed the odds of this planet being hit with a civilization-ending asteroid in the next 100 years are about one in 5,000. This is less likely than scientists had previously calculated.
Spread out over millions of years, astronomical odds of being killed by an asteroid can be difficult to comprehend.
"We're talking about probabilities people don't get," said Clark Chapman, institute scientist for Southwest Research Institute in Boulder, Colo. "We're not wired to understand these low probabilities, which is why state lotteries are so successful." For the record, each time a Floridian buys a state lottery ticket, he has a one in 23 million chance of winning the jackpot.
In comparison, your lifetime odds of dying from an injury are just one in 23, according to a 1998 report by the National Safety Council.
The Sloan Digital Sky Survey has software that robotically scans the skies for asteroids and found that the solar system houses about 700,000 asteroids big enough to wipe out Earth life. Earlier estimates were three times that figure. Here is how astronomers assign risk to an approaching object like an asteroid or comet:
When they spot a new asteroid, they try to observe it for as long as they can. Based upon the swath the asteroid cuts across the sky in about five minutes, astronomers try to estimate what its orbit is. But because they've only seen the orbit once, the orbit is fairly uncertain and may change as they make more observations.
"The more observations you have the better determined the orbit is in some distant date in the future," Scotti said.
If they find that its orbit around the sun may one day intersect Earth's path, then the astronomers have to figure out whether they would ever be at the same place at the same time, which could result in tsunamis, climate change or just an all-out mass extinction.
"This hazard is one element of a whole panoply of risks and hazards that people are walking around facing these days, from carcinogens, from terrorists," Chapman said. "There should be more education, informal education like through science journalism, and formal education, like through science classes" to teach people how they should respond when hearing about such hazards.
Obviously, many things in our daily lives are risky. The National Center for Statistics and Analysis reported that people faced a one-in-6,761 chance of being killed on U.S. roads in 2001. That's just for one year. The asteroid risk of one-in-5,000 is spread out over 100 years.
And besides, there's actually a chance people could survive the space rock onslaught.
Ben Affleck did.
Published under license from FLORIDA TODAY. Copyright © 2002 FLORIDA TODAY. No portion of this material may be reproduced in any way without the written consent of FLORIDA TODAY.
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