Space debris orbiting the Earth has been a “thing” as far back as 1957, but today it poses an ever growing threat. That’s because there’s simply so much of it now, with the total fast approaching 20,000 pieces (if you only count the big stuff).So what exactly is space debris? It’s any object classed as junk or waste, typically left over from old satellites or rocket stages, or created when some man-made object already in orbit erodes and fragments break off. On Earth we classify debris by size, but only track objects larger than 5cm (2-inches). So while there are around 20,000 pieces of tracked debris circling the Earth, the actual total number of bits of debris up there is estimated to be close to 171 million, with 170 million of those smaller than 1cm (0.4-inches).It’s hard to picture what that looks like, but Dr. Stuart Grey from University College London and the Space Geodesy and Navigation Laboratory used the debris tracking data to produce a visualization:And remember, that’s just the big stuff.Add in all the tiny particles and you can see how busy and hostile it is up there. This is part of the reason why there has to be so much planning done before any new trip (manned or otherwise) is made into orbit. Coming into contact with this debris traveling at thousands of miles an hour could destroy expensive equipment or be fatal.There are a number of ways this debris can be dealt with, and in fact some of it deals with itself. An average of one piece of debris drops out of orbit each day. End of life satellites are required to move to a graveyard orbit, or if they can, an orbit that will eventually result in them de-orbiting (this can take hundreds of years, though). In the future, it seems likely debris will be targeted for capture and removal by remote-controlled craft, although we may end up blasting it out of the sky with lasers.