How do humans measure distances in space?
The Cosmic Ladder
How do humans measure distances in space?
Space is far away. Really far away. So far that if you tried to measure it with a tape measure, you'd be unrolling it until the sun burned out, and you'd still only have made it to the moon. So astronomers got creative. They invented a whole toolbox of tricks, each one designed to reach a little farther into the dark.
The closest trick is radar — bounce a radio wave off something and time how long it takes to come back. Light travels at a fixed speed, so if the echo takes six seconds, you know the object is three light-seconds away. This works beautifully for the moon and nearby planets, but radio waves get too faint to bounce back from anything farther than Saturn.
