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"it is about the time it takes for the sun to be in the same position from one day to another." How else would you define a day?
by asmithmd1 13y ago
"it is about the time it takes for the sun to be in the same position from one day to another."
How else would you define a day?
- jonesetc 13y agoExactly 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.
- FkZ 13y ago86400 seconds.
- huherto 13y ago1.- As a string of length 3. :P 2.- When we talk about the longest day, we are talking about daylight. That changes according to time of the year because of the inclination of the earth. This is what I originally thought they were talking about. 3.- The usual way to define a day is exactly 24 hours. But this is a little bit different. It is not even exactly a turn of the earth of 360 degrees.
- Strilanc 13y agoSynodic day ( https://en.wikipedia.org/wiki/Synodic_day https://en.wikipedia.org/wiki/Synodic_day ) Sidereal day ( https://en.wikipedia.org/wiki/Sidereal_time https://en.wikipedia.org/wiki/Sidereal_time )