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- THE WEEK, Page 27HEALTH & SCIENCEHeads Up
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- A comet may strike the earth in mid-August . . . of the year
- 2126
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- Every August the Earth passes through the orbital path of
- Comet Swift-Tuttle. If the comet ever happened to be there, the
- 10-km-wide (6-mile) chunk of ice and rock could slam into the
- planet, carving an enormous crater, generating tidal waves and
- throwing up a worldwide pall of dust that could block sunlight
- for months. Plants would be largely wiped out, and so would many
- species that ultimately depend on plants for food -- including,
- perhaps, the human race. Just such a disaster, many scientists
- believe, killed off the dinosaurs 65 million years ago. A
- smaller strike in the Atlantic 35 million years ago, described
- in a U.S. Geological Survey report released last week, sent a
- 300-m-high (1,000-ft.) wall of water over much of the U.S. East
- Coast.
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- Luckily, planet and comet have never been in the same
- place at the same time. The only visible effect of the crossed
- paths is the annual Perseid meteor shower, caused when lingering
- comet dust burns up in the earth's atmosphere. But humanity may
- not be so lucky for long: there is a chance that the next time
- Swift-Tuttle comes around, probably in the year 2126, it will
- fall to earth. The odds are small -- 10,000 to 1 against --
- according to the International Astronomical Union's Brian
- Marsden. But the downside is so great that Marsden has urged his
- colleagues to keep careful track of Swift-Tuttle so its orbit
- can be more precisely calculated. If it really is on a collision
- course, the only answer may be to blast it from afar with
- nuclear warheads.
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