|Why is the Hubble telescope in space rather than on earth? — L
The earth's atmosphere has poor optical properties that seriously diminish the resolving powers of even the finest earth-based telescopes. You can see these optical problems by watching the warm air rise above a radiator or hot pavement on a summer day. The little swirls and eddies of heated air distort the scenery beyond them. Earth-based telescopes have to look at the stars through several miles of swirling, inhomogeneous atmosphere and they struggle to compensate for the imaging problems this air causes. Most world-class telescopes are located on mountaintops, far from lighted urban centers and away from humidity and clouds. But even the sky above these mountaintop observatories causes problems. By putting Hubble in space, they got rid of all atmospheric problems—air turbulence, clouds, and nearby lighting. They also made it possible for Hubble to operate around the clock by eliminating the blue sky that blinds telescopes during the day.