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 ...

How is astronomical distance determined? Just cannot get my head around cepheid variables, parallax, etc. How is it possible to tell how far away something is when you cannot bounce a radar beam off ...

“Space is big,” wrote Douglas Adams, and he wasn’t kidding. Familiar units of distance, like miles and kilometers, quickly become too unwieldy to use in cosmic discussions. After all, we don’t say the ...