Experts believe there are more than 200,000 objects floating around up there forming an orbiting garbage dump around Earth. A hazard to spacecraft, some of those bits and pieces scream along at 28,000 kilometres per hour – that's 10 times the speed of a bullet!

Objects from one to 10 cm in size cause the real worry, writes Dave Reneke from Australasian Science Magazine. These are too small and numerous to be individually tracked but could cripple or kill an astronaut in orbit.

As an example of the hazard, in 1983 a tiny speck gouged a pea-sized pit in the window of a space shuttle in orbit.  A paint fleck might sound trivial but a mere speck carries a lethal punch when it's flying at several km per second.

Most bits burn up in the atmosphere but if they're big enough they can come down with a mighty thud – remember the orbiting US space station Skylab?  Launched in 1973, it crashed to Earth six years later with the biggest part ending up in Australia. That's space junk.

Private enterprise is adding to the congestion. Believe it or not, you can even be buried in space now in lipstick-sized containers. An American company, Celestis, conducted its first “space funeral flight” in 1997 with the ashes of Star Trek creator Gene Roddenberry and 23 other people from all walks of life.

Another US company, Masten Space Systems is offering to send any of your mementos into orbit in a soft drink sized container for a mere $9.95… err, as long as you use your credit card. More space junk.

But, wait a minute, why should I worry, if it's in space it can't fall on me, right? Wrong! It can fall and it has before, in fact pieces of space junk enter the atmosphere almost every week. We accumulate on average 40 tons of it per day! In a year, it’s enough cosmic junk to fill a six-storey office building. Sleep well tonight.

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