What is an astronomical unit? Distances in our solar system are vast. So astronomers often don’t speak of the distances to planets, asteroids, comets or spacecraft in terms of miles or kilometers.

If you want to find the size of a basketball, you can use a normal meter stick to measure the diameter. You should get a value of around 0.24 meters. Please don't use inches—they are just harder to ...

Click anywhere on this site, and you’ll likely run into a measurement in terms of light-years, solar masses, astronomical units, or arcminutes. These units are unique to astronomy, and all can be ...