Yet people still believe that vulcanologists will someday predict eruptions, or that the current headline virus is gonna be the big one that matches the 1918 pandemic. Watch out! SARS is coming. Oops, that fizzled. Now it's West Nile. Oops. Okay, so watch out for the bird flu. No? Then last spring they sounded the alarm for swine flu.
Hey, I love science. But predicting future events? We don't have that down yet. What about listening to doomsayers who base their predictions on a Mayan calendar or astrology or imaginary "energy waves" from the center of the galaxy? Now you have psycho-ward reliability - like the 2012 business.
Why would anyone pay attention to any coming-disaster forecast? Is it fun? Don't they remember that zero percent of all the past predictions materialized? Why must we go through this every couple of years? Is Bill Maher right - are we a stupid country?
Fortunately, once each quarter-century or so we see some valid prognostication, usually based on Newton's reliable laws. At least in the tick-tock clockwork of the solar system, bodies really move according to plan.
This brings up Apophis. The Apophis asteroid has captured the public's interest ever since it was discovered in 2004. It's the size of two-and-a-half football fields. That's enough to do major damage - like destroy a city and create genuine tsunamis. And it's headed our way.
On Friday the 13th of April 2029, Apophis will make a record-setting close approach to Earth. It'll come nearer than any celestial body in recorded history, without hitting us: close indeed. We'll be able to watch it visibly move across the sky. Its likely track is just 22,000 miles overhead, matching that of geostationary TV satellites. We might even lose Fox News that day. But don't worry: The nearest it can possibly come is 18,300 miles above Earth's surface.
The problem up till now was figuring out how our planet's gravity will then change the asteroid's orbit. You see, Apophis will orbit the Sun a few times while we go around six times, and then - bingo, we meet again in 2036. That was the worrisome meeting. Once again the two of us meet on a Friday the 13th of April. How cool is that? But this time, there's a chance of impact.
At first, the collision odds were pinned at 2.7 percent. Then, better orbital refinements dropped it to one chance in 45,000, where it has remained the past five years. Believe it or not, this still worried a lot of people - presumably the same folks who buy lottery tickets. (For a comparison of odds, consider that the chances are one in 88 that you'll someday die in a car crash.) Anyway, now you don't have to fret: Using updated information, NASA scientists have just recalculated the path of Apophis. This shows that in 2036, its odds of collision have dropped to about one in 250,000.
Among the new findings is another close encounter with the asteroid in 2068, with chance of impact currently at three in a million. As with earlier orbital estimates, the 2068 impact odds will diminish as more information about Apophis comes in.
NASA detects and tracks asteroids and comets passing close to Earth. This program, commonly called "Spaceguard," discovers these objects and plots their orbits to determine if any could be potentially hazardous to our planet.
The reason odds always get longer over time is simple: Earth and any asteroid are like two bullets in flight, where one path is well-known but the other only approximate. As we get more information and revise the orbit, there is only one specific way that the second bullet's path can shift to create a collision. But there are 10,000 ways we can miss by an even-wider margin. Hence, the first "possible collision" headlines are always followed by later calculations that reduce or eliminate any chance of a hit.
So we're safe - for now.
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