Who used telescopes for astronomy?

• A. Copernicus
• B. Tycho Brahe
• C. Kepler
• D. Galileo Galilei

Answer: (D)

Telescopes let us see details in the sky that our eyes alone can’t detect, which is why Galileo’s use of a telescope for astronomy is so significant. He built and refined telescopes, then for the first time carefully observed features we couldn’t see without one: the Moon’s craters and mountains, the four largest moons orbiting Jupiter, the changing phases of Venus, and hints of Saturn’s rings. These observations provided concrete evidence that not everything orbits the Earth and helped broaden our understanding of the solar system.

The other figures contributed greatly to astronomy in other ways. Copernicus proposed a sun-centered model based on reasoning and observations available at the time, but he never used a telescope to make his discoveries. Tycho Brahe relied on incredibly precise naked-eye measurements rather than telescope observations. Kepler used Brahe’s data to derive his laws of planetary motion and refine orbital models, using mathematics more than telescopic observations as his primary tool.