The earth is approximately a sphere (actually it is sphere slightly flattened at the poles). Its volume can be calculated if you know its radius. Use the equation for the volume of a sphere which is V = 4/3 x Radius^{3}

The mean radius of the earth is approximately 6.4 million meters (exact = 6.37 x 10^{6} m). Its volume is then:

(4/3) x 3.14 x 6400000^{3} m^{3}

This comes to 1,097,509,500,000,000,000,000 cubic meters. Needless to say, this is very large! Inside of one cubic meter you could fit seven or eight high school students. I know, I teach high school and I have fit eight students in a cubic meter! So, this would be
137,188,690,000,000,000,000 students. Is your high school this big?

This number of students is so large that if you could count one number per second
it would take you more than 4 trillion years to count this high. If you counted by
millions it would still take you over a million years to get to this number! It
would take you over eight million years to count to the number of cubic meters the
earth is. So, the earth is very large indeed!
Answered by:
Tom Young, B.A., Science Teacher, Whitehouse High School

'Our job in physics is to see things simply, to understand a great many complicated phenomena, in terms of a few simple principles.'