Part of the show Naked Science Questions and Answers
Tony in Minneapolis asked:
How many satellites are currently circling the Earth?
We've obviously got one natural satellite, our Moon. But we've actually launched around 8000 artificial satellites up into orbit around the Earth. However, that's not all there is orbiting around the Earth. As well as these 8000 solid lumps of whole satellite that are up there, we've got lots and lots of little bits of junk swirling around. Now that can be anything from a nut and a bolt that's been lost to astronaut gloves that have been lost during space missions. This stuff can actually be quite a problem, because as it's up there whizzing around at kilometres per second, if it hits another satellite it can seriously damage it and blow some more bits off. So all the time this stuff is accumulating, but there's no easy way to go up and remove it. Eventually all of it will slow down and fall into the Earth but it's up there for a long period of time.