Susan Freed, age 11, of Oakland, Neb., for her question:

What causes the perseid meteor showers?

Meteors streak down upon the earth all the time, and if we watch only an hour or so we can spot a few of them during any countless night of the year. At certain times these so called shooting stars swoop down in great numbers. Their displays are called meteor swarms or meteor showers.

Once in a while a showy comet swoops in from the outer planets and makes a u turn close around the sun. Its golden head may be bright enough to rival the biggest stars, and its luminous trail may fan halfway across the sky. The comet soon leaves our skies and returns to its bleak realms far out in the solar system. But its glorious display is not forgotten, and sometimes it leaves us a reminder that lasts for many centuries. It may leave us with a yearly shower of meteors.

A close swing around the sun may be very upsetting to a passing comet. Powerful forces of the mighty star often jog loose and scatter its fragile particles. Streams of fine fragments and dusty debris are left behind along the orbit of the passing comet. In 1862 a certain bright comet left such a stream of meteor dust in its path. These particles still swarm in an oval orbit around the sun.

At one point the orbit of this meteor swarm intersects the orbit of the earth. Once each year our bulky planet crashes through the dusty debris, and we get a shower of meteors. The bright shower of sparks rains down upon us from a point in the constellation

Perseus in the northeastern sky. This showy meteor shower in called the perseids.  The earth reaches the path of the swarming meteors in late July or early August.

The glowing sparks from the direction of Perseus may shower down upon us for more than two weeks, but the peak displays occur on cloudless nights between August 9th  and 14th. We may see 50 or more so called falling stars in an hour the stream of debris left is 6 million miles wide, which is a very small slice of the enormous sky. The showering sparks come from a small central area and radiate in all directions. The central starting point of the meteor shower is called the radiant.

We are treated to several showy meteor displays during the year. Some have been arriving on yearly schedules for centuries, and several of them have been linked to passing comets. In June we get a daytime meteor shower also from the direction of Perseus, this one and the late October Taurids were left by the eneke comet. The famous Halley's comet may have left us meteor showers for early May and early October.