For centuries, humans have gazed at the night sky in wonder, trying to make sense of the stars and planets shining overhead. In 1609, that all changed when Galileo Galilei pointed a telescope at the heavens and discovered that there was much more to see than the naked eye could ever reveal. In the 400 years since then, the telescope has evolved into one of the most important scientific tools we have, helping us to unlock the mysteries of the universe.
The First Telescope
Galileo was not the first person to build a telescope—in fact, he was not even the first person to point one at the night sky—but he was the first to realize its potential for observing and understanding our place in the cosmos. Up until that point, telescopes had been used mainly for terrestrial applications like navigation at sea. Galileo recognized that if a telescope could make things appear closer on Earth, perhaps it could also be used to see distant objects in space.
He set about building his own telescope, using a convex lens for the eyepiece and a concave lens for the objective. Galileo’s modest instrument magnified objects 20 times, but it was enough to allow him to make some groundbreaking discoveries. He observed sunspots on our nearest star, discovered that Venus goes through phases like our own Moon, and found four moons orbiting Jupiter—the first planets beyond Earth ever discovered. In doing so, he forever changed our perception of our place in the universe.
The telescopes of today are vastly more powerful than anything Galileo could have dreamed of. Thanks to advances in optics and technology, we now have telescopes that can detect objects billions of light-years away and capture images with an incredible level of detail. Our biggest telescopes have resolutions measured in milliarcseconds—that’s thousandths of an arcsecond! To put that into perspective, if you were looking at someone standing on Mars through one of these telescopes, you would be able to resolve features as small as a dinner plate from billions of kilometers away.
From its humble beginnings 400 years ago, the telescope has evolved into one of humankind’s most important tools for understanding our place in the universe. From Galileo’s crude early instrument to today’s massive ground-based observatories andspace-based satellites, this simple device has allowed us to unlock countless secrets about our solar system, our galaxy, and even the distant reaches of space and time. Who knows what new discoveries await us in the centuries to come?