A little interesting physical phenomenon was brought to my attention by a slashdot post — this article on salvaging the Hubble Space Telescope. It turns out the replacement for the HST will not orbit the earth rather it will orbit the sun at an Earth Sun Lagrangian Point known as L2. Lagrangian points are points on a line between and extended beyond two bodies of significant mass, such as the earth and the sun, where a body of insignificant mass will orbit the larger significant mass at the same speed as that of the Smaller significant mass. What this means for the Hubble replacement James Webb Space Telescope will orbit at this point ensuring that it’s always on the dark side of the earth. It will still need thrusters to counteract the destabilising effects of other masses in the universe. Far better explanations from the Wikipedia.