I'm always pleased to see the ISS as it passes and I'm lucky enough to live in Blackheath so, in Summer, I can often time it so that when there's a really good pass (travelling directly overhead and so taking a long time to cross the sky) I can be on the heath which has a lovely big sky feel to it.
|From NASA and Flickr user Tim Hamilton|
This is my handy guide for the next time I find myself out and about and watching the skies and in want of snappy facts to tell the nearest passerby.
What is it?
It's basically a small spaceship which is circling the Earth several times a day (I think it whizzes round once every 80 minutes or so).
Where is it?
It's about 250 miles away, directly up, and orbiting our planet. It varies in height but is in Low Earth Orbit (so it's not a spaceship in the Star Trek sense).
Are there people on it?
Yes, at the moment there are six astronauts / cosmonauts from the US, Japan and Russia. At the time of writing they're on Mission 33 which runs until 12 November and is staffed by Sunita Williams (US - she's the Commander for this mission), Yuri Malenchenko (Russia), Akihiko Hoshide (Japan), Evgeny Tarelkin (Russia), Oleg Novitskiy (Russia) and Kevin Ford (US).
Edit: 29 March 2013 - they're on Mission 35 and Canadian Commander Chris Hadfield's in charge.
What are they, and the ISS, doing up there?
Science! They're doing stuff on muscle and spinal weakness and how a space environment affects people, also looking at ways of tweaking communications satellites and having a jolly good nosey at the Earth and taking lots of photos.
More info here http://www.nasa.gov/pdf/688643main_Exp33_summary.pdf
If you're looking at this post after Nov 12 then look here for info on the most current mission.
How fast is it going?
It's going at a fair old pace, about 17,000 miles per hour (to be fair it's got quite a way to travel), more info about it on the wikipedia page.
How big is it?
Apparently about as big as a five bedroom house. More factoids here.
How do I see it?
If you're on Twitter just follow @twisst - it will start sending you automatic messages whenever the ISS passes overhead with a visible pass. You'll need to have your city in your Twitter bio (eg London, UK) otherwise it won't work.
Other helpful pages on visible sightings are NASA's own page and Heaven's Above
It's cool, it's up in space, there are people on it, doing science and taking awesome photos.