Space
How Do Telescopes Work? From Galileo to the 39-Meter ELT
A telescope gathers more light than the eye and resolves finer detail. Galileo's 1609 refractor showed him moons around Jupiter. ESO's 39.3-meter Extremely Large Telescope collects nearly a million times more light than Galileo's lens, once adaptive optics cancels the blur of Earth's atmosphere.