Sidereal time

[AtomSplitter]

What is sidereal time, how does it differ from solar time?

[Klaynos]

wikipedia is your friend...

 

http://en.wikipedia.org/wiki/Sidereal_day

[AtomSplitter]

wikipedia makes frequent mistakes, i do not like to rely on it, it is my last resort.

[iNow]

Wrong approach. Use it as a first resort, then follow-up for detailed information to make sure it's accurate.

[AtomSplitter]

by that i just meant that i would prefer to ask people because you cannot really ask wikipedia questions and get the exact information that was wanted...

[Klaynos]

wikipedia is less likely to make mistakes than people

 

Better to read wikipedia then ask specific questions about difficulties or clarifications.

[AtomSplitter]

yep, i do use it for general overview of a subject but if i cant find what im after i usually ask someone. sometimes i get a good answer sometimes a bad one, luck of the draw really. can anyone sum sidereal time up in one sentece so that the average peon could understand?

[swansont]

yep, i do use it for general overview of a subject but if i cant find what im after i usually ask someone. sometimes i get a good answer sometimes a bad one, luck of the draw really. can anyone sum sidereal time up in one sentece so that the average peon could understand?

 

Time measured in reference to the location of distant stellar objects, i.e. a star returns to the same overhead position in one sidereal day.

[AtomSplitter]

thankyou very much, this has helped me to no end thankz guys!

[npts2020]

An easy way to remember it is that a siderial day is how long it takes for the earth to complete 1 rotation on its axis (on average). A solar day is how long it takes for the sun to reach its highest point in the sky from one day to the next (on average). About 3 minutes and 56 seconds difference due to earths orbiting the sun.

[D H]

wikipedia makes frequent mistakes, i do not like to rely on it, it is my last resort.

Wrong approach. Use it as a first resort, then follow-up for detailed information to make sure it's accurate.

I agree with iNow. Wikipedia is, in general, quite accurate. One just has take what it says with a grain of salt.

 

by that i just meant that i would prefer to ask people because you cannot really ask wikipedia questions and get the exact information that was wanted...

Ahhh. You are lazy. Nothing wrong with that per se, but when you get to more advanced topics you will not so readily find someone around to pester. Learning how to understand what you are reading is an important skill, and it won't magically pop into existence.

 

wikipedia is less likely to make mistakes than people

Time measured in reference to the location of distant stellar objects, i.e. a star returns to the same overhead position in one sidereal day.

Better to read wikipedia then ask specific questions about difficulties or clarifications.

Klaynos was prescient. Read the first paragraph of the Wikipedia article on sidereal time to see why.

[swansont]

Klaynos was prescient. Read the first paragraph of the Wikipedia article on sidereal time to see why.

 

If one were not schooled in the jargon, though, that paragraph would not make a lot of sense.

[D H]

If one were not schooled in the jargon, though, that paragraph would not make a lot of sense.

The problem is that this is not technically correct:

Time measured in reference to the location of distant stellar objects, i.e. a star returns to the same overhead position in one sidereal day.

The opening paragraph of the Wikipedia article:

Sidereal time is a measure of the position of the Earth in its rotation around its axis, or time measured by the apparent diurnal motion of the vernal equinox, which is very close to, but not identical to, the motion of stars. They differ by the precession of the vernal equinox in right ascension relative to the stars.

Technically correct, poorly written. The problem is that the reference system for sidereal time is not quite inertial. How to communicate this without jargon?

 

A star will return to nearly the same overhead position in one sidereal day. The reason the star doesn't return to exactly the same position is because the Earth's rotation has a little wobble to it, and sidereal time is measured with respect to this wobbling reference. It takes about 26,000 years for the Earth's rotation axis to trace out a cone with about a 23 degree half angle, making this wobble very small.

Edited October 21, 2008 by D H