A telescope is an instrument that makes distant objects appear closer and clearer by gathering and focusing light. When you look through a telescope at the night sky, stars that seemed like tiny pinpoints suddenly reveal themselves more clearly, and planets show their colors and moons.

Telescopes work by collecting much more light than your eye can capture on its own. Think of your pupil as a tiny window: a telescope lens acts like a huge window, gathering far more light and then concentrating it so you can see things much fainter than what your naked eye could detect. Some telescopes use curved mirrors instead of lenses, but they accomplish the same goal.

The invention of the telescope in the early 1600s revolutionized astronomy. Galileo used an early telescope to discover Jupiter's moons and see that our moon had mountains and craters. Today's telescopes are far more powerful. The Hubble Space Telescope orbits above Earth's atmosphere, sending back images of galaxies billions of light-years away. The James Webb Space Telescope can see very distant galaxies, peering back to a time not long after the beginning of the universe.

Beyond astronomy, people use the word telescope as a verb meaning to collapse or compress something into a smaller space, like how a telescoping ladder slides into itself for storage.