1. Sputnik 1 was about the size of a beach ball and took about 98 minutes to orbit the Earth.
2. Its launch is marked every year by International Space Week from October 4-10, a “celebration of science and technology, and their contribution to the betterment of the human condition”.
3. In the 16th century, the word “satellite” meant “an attendant on a person of importance” .
4. …In the 17th century it came to be used for a small planet revolving around a larger one.
5. In 2009 two communications satellites, from the US and Russia, collided. This is the only time two man-made satellites have collided by accident.
6. Geostationary satellites orbit the equator at the speed of the Earth’s rotation so seem not to move.
7. Polar satellites’ orbits pass over the poles so scan the whole Earth as it rotates beneath them.
8. More than 20 satellites make up the Global Positioning System, or GPS, enabling precise positions to be measured at any time.
9. There are now more than 2,500 artificial satellites in orbit around the Earth.
10. In 2012 satellite data showed that there were twice as many emperor penguins in Antarctica than was previously thought