On a clear night, you can see thousands of stars twinkling above Earth. Hundreds of years ago, people thought they knew all there was to know about the sky.
Then, in 1608, a Dutch lens maker put two glass lenses into a metal tube. The device, which was later named a telescope, made distant objects seem close. Scientists aimed the new device upward. There, they found new stars, new planets, and new moons. They also found evidence that the Sun does not go around Earth, as most people then believed. Instead, Earth orbits the Sun, spinning like a top as it goes.
Telescopes have gotten stronger since then. We now know that, cosmically speaking, Earth is tiny. Our home is a mere speck in the Milky Way galaxy, which is only one of billions of galaxies.
Astronomers can peer far out into the universe. However, humans haven’t yet learned how to travel into deep space. Until we do, telescopes will be our guides to the wonders of the cosmos.
