If we were to take a cross-section of our planet on the equator, we would get a circle. So, the circumference of this circle is the distance one would have to travel to go around the earth. The formula for the circumference of the circle is 2 x r x pi. The radius of the Earth is r, and pi is approximately 3.1415. So, the circumference is 2 x 6370 x 3.1415, which equals 40 029 km, or approximately 40 thousand kilometers.
