By MICHIO KAKU
WSJ
July 24, 2009
We sometimes forget that the universe is a violent place.
This week, astronomers in Hawaii recorded an exceedingly rare event. An amazing photograph revealed a comet or asteroid, probably no more than a mile across, plowing into Jupiter’s atmosphere. The impact created a fireball roughly the size of the planet earth. The good news is that Jupiter was just doing its job, cleaning out the solar system of stray comets and asteroids. Jupiter, 318 times more massive than the earth, acts like a cosmic vacuum cleaner, sucking in or deflecting debris left over from the solar system’s birth 4.5 billion years ago. If it weren’t for Jupiter’s colossal gravitational field, we wouldn’t be here, since the earth would be hit with deadly comet and meteor impacts every month or so. Most of the U.S. would just be an empty graveyard of bleak craters.
The bad news is that a comet impact could happen to us. A black eye for Jupiter would be a body blow to the earth. We got a taste of this back in 1908, when something the size of an apartment building plowed into Tunguska, Siberia. This “city-buster” flattened 100 million trees with the force of a hydrogen bomb. But this recent Jupiter comet, much larger and coming in at perhaps 100,000 miles per hour, would have unleashed the power of hundreds of H-bombs. It might have engulfed most of the East Coast in a huge firestorm, triggering a massive tsunami and destabilizing the weather.
According to Hollywood, we can always send our astronauts on a space shuttle to intercept a comet and blow it up with H-bombs. Wrong. Blowing up a comet with nuclear bombs creates chunks of debris, increasing the area of destruction. So we are sitting ducks to a potential impact from deep space.
(snip)
But it also happened on the 40th anniversary of the moon landing. So maybe Mother Nature was reminding us that the universe is, after all, a violent place—that we may one day need a new home. The earth lies in the middle of a cosmic shooting gallery. The proof comes out every night when we gaze at the moon. When viewing the film of Neil Armstrong and Buzz Aldrin bobbing among the barren craters of the moon, we are reminded that each crater was gouged out by a titanic impact. In addition, there are more than 5,000 so-called near-earth objects, carefully tracked by telescope, that can cross near the orbit of the earth. One of them, the asteroid Apophis, is about the size of the Rose Bowl. It will graze the earth in 2029 and again in 2036, passing below some of our satellites.
(snip)
So in the long term, perhaps we should look at the space program as an insurance policy. Not only has the space program given us a bonanza of benefits (such as weather satellites, the Global Positioning System, telecommunications, etc.), it also provides a gateway to the stars. Over the course of the next few centuries, maybe we should use that gateway to plan to be a “two planet species.” Life is too precious to place in one basket. In August, President Barack Obama will receive a major report from the U.S. human space flight plans committee about the future of space travel, which could be a turning point for NASA in the 21st century. He should remember the Jupiter hit as he considers the report.
—Mr. Kaku is the author of “Physics of the Impossible: a Scientific Exploration into the World of Phasers, Force Fields, Teleportation, and Time Travel” (Doubleday, 2008).
Printed in The Wall Street Journal, page A13
http://online.wsj.com/article/SB20001424052970203517304574306131239654294.html
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