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General Science / Re: A Question About Solar Time.
« on: Yesterday at 19:44:40 »Is it because the earth spins faster when it is closer to the Sun?The sidereal spin rate (23:56:04) is fixed* to an awful lot of digits, but it is indeed due to Earth distance from sun.
The effect is so great on planets with high eccentricity like Mercury that the sun actually stops in the sky and goes backwards for quite a while every 'day'. Where it does this in the sky depends on where you are on the planet, but it's the same place each time.
When the sun is close, the Earth needs to rotate more degrees to get the sun back beyond the horizon, and that lengthens the day. The sun also moves faster relative to Earth, and that shortens the day, but not as much as the former effect lengthens it.
* The sidereal spin rate slows over very long times, due to tidal drag. The day used to be 10 hours or less, and will be again if the sun doesn't swallow Earth first, but it will.