A few days ago I posted a video by José Francisco Salgado showing the sky over telescopes in Chile.
He's just put up another one, this time showing the motion of the sky over several observatories: "Sidereal Motion".
Sidereal motion is literally the movement of the stars; the apparent rising and setting caused by the rotation of the Earth. You don't notice it second-by-second as you watch the sky, but over minutes and hours the inevitability of our planet's angular momentum makes itself known.
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