4 ms·
Exactly a 360 degree rotation about it's axis. Edit: Which 1 minute after posting I realize is the same thing, so forget that half-baked response and instead l
by jonesetc 13y ago
Exactly a 360 degree rotation about it's axis.
Edit: Which 1 minute after posting I realize is the same thing, so forget that half-baked response and instead look at these different ideas of the measure of a day:
http://en.wikipedia.org/wiki/Day#Astronomy http://en.wikipedia.org/wiki/Day#Astronomy
- sixbrx 13y agoYour first answer wasn't wrong, it just defines a "siderial day", using other stars as a reference point instead of the sun. After rotating 360 deg with respect to the background stars (which we assumed fixed for our purposes), the earth then has to rotate a few minutes more to get the sun back in the same position.
- Roboprog 13y agoAnd thus "right ascension" is measured in minutes (and hours). Astronomers don't use degrees to measure "longitude" (right ascension) on the celestial sphere. Face North (at night) and look right. Everything on that side ascends. In astronomy, East-West distances are measured by how long it takes things to rotate past a fixed observational direction. Every night, a slightly different chunk of sky will also be directly overhead at midnight, due to the difference observed earlier between solar (sun-relative) day length and sidereal (star-relative) day length.