David Decks, age 10, of Victoria, B.C. for his question:

What is the circumference of the earth's orbit?

We cannot figure this down to the last inch because the distances of space are so vast and there are always slight variations in the movements of heavenly bodies. But we can get a good approximate idea of the size of the earth's orbit.

The radius of the earth's orbit is about 93 million miles, which is its average distance from the sun. The diameter, a line from side to side straight through the middle, is twice the radius or about 186 million miles. If you know your math, you should be able to use this information to discover the circumference of the earth's orbit. For the circumference of any circle is equal to the diameter times Pi. Pi is a math symbol with value to the seventh place of 3.14159265.

The answer to this fascinating math puzzle comes to about 600 million miles. This is the circumference of the earth’s orbit, its journey around the sun. And the earth travels around this orbit at about 18 miles a second, completing journey is about 365 days, or one year.