Scale: 109 meters = 1 Gm = 1 gigameter: Light requires 3 seconds to cross this picture.

Earth and Moon

In this image, Earth is shown actual size. The Earth at this scale is about 1 mm across. The Moon is about 1 pixel in diameter, located somewhere on the ellipse representing its orbit. Earth and the Moon together speed across this image from right to left in less than 10 hours. In that 10 hours the Moon will traverse about 5 degrees of its orbit -- the distance indicated by the red line to the upper right. From the point of view of the Sun, the Earth and Moon both orbit the Sun in a nearly circular orbit, with the Moon wobbling in and out slightly. Light, and thus radio communication, requires about 2 1/2 seconds for the round trip between the Earth and the Moon. The Sun is about 8 minutes and 20 seconds from the Earth at the speed of light.

Copyright © 2016 by Bruce Bryson