“I’m here for several reason, Mr. Pepin, first of all for aid. When something tragic happens in our skies, we do our utmost to extend sympathy. But sympathy without action,that’s an empty emotion. Mainly I’m here for the purposes of reentry.”
“I don’t understand.”
“Adjustment,” Harold said, “to earth. I’m here to make sure you didn’t leave your whole life in the sky.” -Adam Ross
When we launch a satellite into orbit around the Earth, we expend a tremendous amount of fuel and energy to make it happen. From hundreds of miles up — well above the definition of space — these satellites zip around the Earth many times per day, at more than 70% the escape velocity at their position in low-Earth orbit.
Yet these satellites aren’t stable at all, and will tumble back to Earth in a matter of decades if left unattended. The Moon, on the other hand, has stably orbited Earth for billions of years, and will continue to do so long into the future. The science of why satellites decay is due to five different components, all of which contribute. While atmospheric drag is the strongest for low-Earth orbit satellites, everything will eventually decay.