Looking up at the night sky recently, I spotted a satellite.. then another.. then another; all within a very short space of time. When I was a kid, I remember my record for an entire evening was 13.

There's certainly far more satellites up there than 30 years ago, but not everything we're seeing traversing the skies are satellites, nor are the streaks of light always meteors - some of it's other junk from man; everything to bits of satellites, to tools to underwear.

Yes, underwear.

Astronauts have to change clothes and there's no washing machine on board craft such as the International Space Station, they just put their dirty laundry into Russian cargo modules and push them towards the Earth where they burn up when re-entering our atmosphere. 

Bearing in mind that most meteoroids that cause meteors are about the size of a pebble, the next shooting star you see may not be of extra-terrestrial origins, but just a pile of flaming boxers :).

While space junk isn't high up on the scale in terms of environmental issues, it is a reminder of just how much we leave our mark on this planet - and beyond.. and space junk does pose somewhat of a threat.

In 2008, the US Navy fired a missile to take out a spy satellite that had spun out of control to prevent its toxic fuel tank from crashing to Earth. The fuel, hydrazine, would have posed a potential health hazard if it had crashed in a populated area.

There are more than 600,000 objects larger than 1 cm  in our orbit already - that's accumulated in just 50 or so years. There's over 2,000 satellites out there, with many more to come; particularly now that a company is offering to launch mini-satellites for under ten thousand bucks a pop.

According to Space.com, a 1999 study estimated there are some 4 million pounds of space junk in low-Earth orbit - and some of this rubbish is travelling at over 17,000 miles per hour. At that speed, even small objects can pose a threat to satellites and astronauts. For example, a speck of paint from a satellite gouged a quarter-inch pit in a space shuttle window.

Probably the biggest threat to those of us on earth relatively recently was a new form of space junk - advertising. In the early 90's an American company had its sights set on creating a 1 square kilometer illuminated billboard that would have been visible from Earth - around the same size and light intensity as the full moon. Thankfully, a bill was introduced that banned all U.S. advertising in space.

So, while we no longer have an unsullied view of space due to space junk and increasingly, light pollution, it could have been much worse. Imagine looking up at the night sky and seeing an ad.

While the space advertising ban is only applicable to companies in the USA, I think much of humanity would vigorously object to such a monstrosity.

I hope..