Scientists have estimated the age of the Universe to be 13.73 billion years old (with an uncertainty of about 120 million …
This animated video illustrates how far a light second, minute and year are. NASA-JPL-Caltech. For much greater distances …
You know what a kilometre is – you can walk that distance easily. You know what 100 km is – that’s how far a car could travel in an …
更多内容请点击：How do we measure the distances to things in space? - NASA