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

'The strength and weakness of physicists is that we believe in what we can measure. And if we can't measure it, then we say it probably doesn't exist. And that closes us off to an enormous amount of phenomena that we may not be able to measure because they only happened once. For example, the Big Bang. ... That's one reason why they scoffed at higher dimensions for so many years. Now we realize that there's no alternative... '