How have we come to know about space?
Powerful telescopes are used to observe the space. Presence of stars, not visible even through powerful optical telescopes, is determined by even more sophisticated telescopes like radio telescopes etc. These telescopes can detect radio waves, U.V. rays and X-ray signals which are emitted by distant stars and other celestial bodies. These days probes or unmanned satellites, remote sensing satellites etc. can record the photographic images of these celestial bodies.
