Why are Sidereal Days and Solar Days different times and what is the purpose of the Sidereal day?

Question

I’ve researched it but it’s exact purpose eludes me.

In: 5

Answer 1

basically, they are different because of the earths orbit around the sun.

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a day is a complete rotation of the planet, yes? well, there are two reference points you can use to mark your progress against. there is the sun, and the stars of the galaxy.

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Because we are moving relative to the sun as we orbit it, their is a slight difference the two because we are in not quite the same position, hence the slightly different day lengths. basically, when we have completed a full day relative to the background stars (a sidereal day), the changes in our position relative to the sun mean were are not quite pointing at it, yet, but will do in a few more minutes (a solar day)