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I know that the earth's rotation causes day and night.
It seems/feels so natural to think that the earth's orbit around the sun causes the seasons, but no it's the tilt of the earth's axis that causes seasons.

So, what do planetary orbits cause?

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    $\begingroup$ I understand "Earth's revolution" to mean its revolution around the sun, that is its orbit. $\endgroup$
    – James K
    Oct 29, 2023 at 19:54
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    $\begingroup$ without Earth's revolution around the Sun, you wind up with one season, it lasts about 66 days, and there are no seasons after that, ever. $\endgroup$
    – notovny
    Oct 31, 2023 at 11:01
  • $\begingroup$ @PM2Ring ahh, the OP's choice of words is the confusion source. As per James K, they mean orbit. I'll delete my comment and edit the Question. $\endgroup$
    – Rory Alsop
    Oct 31, 2023 at 18:47

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The orbit of the Earth indirectly causes the seasons. If the Earth didn't orbit, then the seasons wouldn't change*.

The Earth's orbit is slightly elliptical, this means that the Earth moves closer and further from the sun as it orbits. It happens that the closest to the sun occurs on about Jan 4th, in the middle of the Southern summer, this makes summers slightly more extreme in the Southern hemisphere.**

It causes the position of the sun to move relative to the stars. This means that different stars are visible during winter nights from those visible on summer nights.

The motion of the Earth about the sun causes the motion of the other planets relative to the Earth to be a looping pattern. Greek astronomers thought that this was due to the planets moving in epicycles, this is actually due to the orbit of the Earth. Similarly the stars seem move in very small cycles (invisible to the naked eye) due to the orbit of the Earth.

Finally of course, it is the orbit of the Earth that prevents the Earth from falling into the sun.

(*) Unless some there was some other way for the direction of tilt to change relative to the sun.

(**) Again this is an indirect effect of the Earth's orbit. If there was some other way of changing the Sun-Earth distance (such as the sun orbiting the Earth) the effect would be the same

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  • $\begingroup$ It also causes the stars to shift position across the seasons... $\endgroup$ Oct 30, 2023 at 19:45
  • $\begingroup$ Perhaps better to say that the sun shifts relative to the stars. $\endgroup$
    – James K
    Oct 30, 2023 at 19:50
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    $\begingroup$ It's all relative. $\endgroup$ Oct 31, 2023 at 14:26
  • $\begingroup$ Is it believed that the The Milankovitch cycles within the orbit contribute to glaciation cycles? $\endgroup$
    – David S
    Nov 6, 2023 at 19:20
  • $\begingroup$ Yes. $\endgroup$
    – James K
    Nov 6, 2023 at 19:38

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