Notes from Under Sky

Some Power The Giftie Gie Us

A simulated view of the Earth from other planets

We've all seen, I think, pictures of the Earth from its orbiting artificial satellites, with the blue-white orb nearly filling the field of view, or perhaps we've seen Carl Sagan's Pale Blue Dot, a lonely cerulean pixel in a sea of black. But this picture is from somewhere in between. What would the Earth and Moon look like, if we were to view them through an amateur's telescope from, say, Mars? Under stable conditions, the seeing would be terrific, since the atmospheric pressure there is but a smidgen of Earth's, but the physical limitations imposed by the wave nature of light are still relevant.

What I've done here is taken a fairly natural image (I think) of our planet and its satellite, recorded by the Galileo satellite on its way to Jupiter and its satellites, and blurred it by an amount that represents the effect of diffraction in, say, an 8-inch (203 mm) telescope. What's most evident here is the intense blueness of our world (by far the bluest in the solar system), and the dimness of our Moon, when compared to the Earth. Imagine the glare presented by the Earth in the Moon's nighttime sky at new Moon!

Copyright (c) 2001 Brian Tung