Liesel Cobb, age i3, of Charlotte, N.C., for her question:
What would happen if we went through the tail of a comet?
A big camet is one of the most razzle dazzle spectacles to flash across our skies. Its radiant head outshines the brightest star, and its streaming tail, fanning out as it goes, may reach over more than half the sky. Sooner or later the earth is bound to come close to such a bulky object and perhaps zoom through the tail of a passing comet.
In the spring of 1910, the famous Halley's comet swooped in to make a close U turn around the sun. Astronomers figured its path and came up with an alarming announcement. At one point on the comet's loop around the sun, its golden tail was expected to engulf the earth. There was great excitement and some people panicked. But when the amazing event occurred, only a few experts were able to observe the difference.
On May 10, 1910, Halley's comet passed directly between the earth and the sun. It was 15 million miles from the earth, and its streaming tail was far longer than this distance. What's more, its wide tail fanned out toward the earth's orbit at a point where the earth itself was traveling. The solid earth and the hazy tail of the comet occupied the same spaee.
The comet was visible in the morning skies, and the beam of its filmy tail pointed over more than half the sky. A second; wider tail pointed along the pathway of the sun. And on May l0, 1910, the earth passed through this secondary tail of Halley's comet. Those who expected disaster from this collision were disappointed. A few astronomers noticed a faint irridescent glow in the sky and nothing more.
Spanning the sky, a comet's tail may look like a substantial object. But it is made of the rarest of gases in which molecules and assorted sub microscopic particles are separated by plenty of space. These fine fragments catch and reflect light from the sun, and the streaming tail of the comet becomes a radiant object.
When the earth moves through a comet's tail, the rare gases mingle with the upper atmosphere. But the fragments are so fine and so sparce that they cause little or nothing to happen to the air or to the earth.
A visit from a large comet is quite rare. On a few of these rare occasions, the earth is surf to tangle with a comet's tail. In still rarer occasions, the earth must collide with the lumpy head of a comet. A comet then strikes our globe as a giant meteorite and most likely falls into the sea. Experts estimate that we could collide with a comet once in about i5 million years.