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The Question

(Submitted April 11, 1998)

How many asteroids and meteoroids enter our atmosphere a day.

The Answer

The nominal flux of meteoroids with diameter 1 cm or larger is 10^-6 per square meter per year.

Using 6500 km as the radius of the earth + atmosphere, the area is about 5 x 10^14 m^2.

This means that, averaged over the earth's surface, there are about 1,400,000 meteoroids with diameter 1 cm or larger hitting each day.

Needless to say, the vast majority of these burn up in the top parts of the atmosphere, and the number of meteoroids drops rapidly with increasing size.

Dave Thompson and Damian Audley
for Ask an Astrophysicist

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