An Eye on the Sky

One of the few advantages of advanced age is the ability to torture the young. It's easy when there's a young designer in your office who has something of the worrisome nature I had at his age, a quality I admire in a generation that tends to be rather unreflective to say the least. So occasionally in passing I'll call out, "Hey, J----, don't make any plans for April 19th."

While he knows I'm kidding, he also knows that I religiously monitor NASA's Near Earth Object website (http://neo.jpl.nasa.gov/ca/), a veritable font of tantilizing end-of-the-world scenarios for a fatalist like myself -- disaster porn at its finest. It lists every known asteroid, comet, meteor, or foreign body currently being tracked in the shooting gallery that is our solar system. The intention, I suppose, is to alert us to any potential collision prior to the fact, but given the dearth of options available to us at present, it would function more as a countdown to extermination. Still, it's a fascinating site.

The objects are tracked six to nine months ahead, and a quick scan of the list shows that there are days when we're threatened by as many as four or five at a time. The site estimates the size of each object as well as its relative magnitude as viewed from the earth, and speculates on the distance by which each will miss our planet. Misses are given in moon units, the distance between the earth and our moon, about 240,000 miles. So an object with a "2" rating should miss us by about half a million miles -- a hair's breadth in celestial terms.

The object I mentioned to my young friend, who is probably digging a shelter in his back yard at this moment, is an asteroid that may be a quarter mile wide. It's slated to miss us on April 19th by 5.9 units, or much more than a million miles. The site allows you to click on the object to see its trajectory through the solar system, and the tiny margin by which it will slide by the earth. July 31st looks like a pretty busy day for space traffic as well; there are three known objects passing us at a safe distance, although one of them may be more than a half-mile wide.

But for every near Earth object being tracked, there are likely to be ten more we haven't spotted. There's something powerfully exciting about the inevitability of a collision of the type that wiped out the dinosaurs 65 million years ago. It's a reminder of the grand scale of the universe, and the tiny role we have in it on a minute blue dot at the edge of the galaxy.