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I was always wondering if this sudden change would cause some sort of apocalypse on earth because of the changes from the now non existant moon gravity. Would the earths rotation be affected and it would drift into the sun or something else crazy?

Or for a more reasonable scenario if a big meteor would hit athe moon trowing it out of earths orbit what would happen then (lets say almost no debris hit earth)

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  • $\begingroup$ First idea (not calculated, thus not an answer): Earth's orbit would change, the rotation speed of earth would not change at the current rate anymore (because of moon slowing us down). Fewer tide hub, too. Going to calculate that, it seems interesting... For further research, look at f.ex. news.discovery.com/earth/weather-extreme-events/… $\endgroup$ – arc_lupus Dec 2 '14 at 11:19
  • $\begingroup$ The moon's gravity is an illusion. $\endgroup$ – TheDoctor Oct 25 '17 at 22:15
  • $\begingroup$ @TheDoctor If by your comment you mean that General Relativity thinks of gravity as geometry rather than as a force, then maybe there is something to your statement. But the Moon's presence most assuredly influences the Riemann tensor and geometry, so from a theoretician's (which I am) standpoint it's a highly misleading statement. From a surfer's or scuba diver's (which I also am) standpoint (or that of a similar person very used to tracking the Moon's influence on the seatides pretty much every day), one would say it's downright wrong! $\endgroup$ – WetSavannaAnimal Oct 26 '17 at 0:20
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Edit from future:

Sudden removal of sun causes space-time distortion with infinite amplitude of gravitational shock-wave. This wave would evaporate all celestial objects in the universe. Technically it's not possible. It violates "General Theory of Relativity" Following post is belong to my ignorant past. I will not delete.

...

The common mass center of Earth-Moon couple is about 4600km away from Earth's center. Earth's orbit around the sun is not a perfect ellipse. Earth is also moving around the earth-moon couple's center of mass like moon. Imagine an ellipse superposed with a little wave.

Vs: Earth's linear speed around sun (about 30 km/s)

Vm: Earth's linear speed around the earth-moon common mass center. (about 0.0111km/s)

Sudden removal of moon changes the orbit of earth around the sun because of Vm, not for mass removal. The distance of earth from sun is free from Earth's mass, but related with Earth's speed.

Moon-Earth orbital plane is tilting about 5 degree to Earth-Sun orbital plane. If my instincts does not fault me, the orbit of earth around the sun is forced to be a little parabolic and orbital plane changes.

On the other side the rotation speed of earth around itself does not change.

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