How can you spot the International Space Station with your own eyes?

You can see the International Space Station because it reflects sunlight while the sky around you is dark. It is visible to the naked eye as a bright white moving dot, during twilight, the hours after sunset and before sunrise, when the station is still in sunlight but the ground and sky are dark. In the middle of the night it is often in Earth's shadow, and in the middle of the day the sky is too bright, so twilight is the window.

It is easy to recognise. The ISS is the brightest artificial object in the sky, with a maximum magnitude of about minus 4, similar to Venus, and it moves steadily across the sky in a few minutes: a pass may last up to 10 minutes, though it is likely visible for only part of that time, because it moves into or out of Earth's shadow. Satellites are distinguished from aircraft because they leave no contrails and have no red and green navigation lights. They shine only by reflecting sunlight.

The station is big and fast. It is about 400 kilometres up, travelling at 27,600 kilometres an hour, so it circles Earth roughly every 93 minutes, about 15.5 times a day. It is as large as a football field. Because the time of day of its passes shifts over some weeks, you will see it on a run of evenings or mornings, then not for a while.

You do not have to guess when. NASA's Spot the Station service sends alerts when the station is due to fly above your town, and the station can be seen from 95% of the inhabited land on Earth. Go outside a few minutes early, and look for a bright, steady, silent dot, and remember that people have been living up there continuously since November 2000.