Why is it that the telescopes on earth are kept in such cold conditions? I've noticed that astronomers that enter the buildings wear winter jackets even when the observatories are located in very warm climates.

Although ground telescopes are in warm climates, they are also usually very high up and in places were it is very clear at night. These factors combine to make it get very cold at night and as the domes have to be open to the air (so that the telescopes can look out) it gets very cold inside them. The astronomers sit in the cold dome for long periods of time so need to wear lots of clothes to keep warm. The reason the domes are not heated is that then there would be lots of hot air flowing out of the top of the dome (hot air rises remember) which would add a lot to the movement of the atmosphere above the telescope and make the images worse.

This page was last updated July 18, 2015.