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Question
Happy Holidays,

If an exterior force moved the earth into a smaller orbit without affecting any other thing at all regarding the earth, and then that force disappeared, what would the earth do ?  

Bounce back to its original orbit size due to gravity equilibreum ?  Remain in the smaller orbit but moving faster due to a shorter orbit length ?

Thanks,
Dave

Answer
Neither, it would go into a very elliptical orbit.  If a force acted on it to move it in, it would speed up, so that would be as close as it got and its maximum orbit would be further out than the current orbit.  See Kepler's laws.  But if your magically (and that would violate the laws of physics) teleported the Earth to a smaller orbit at its current velocity then it wouldn't be going fast enough and that would be its maximum orbial distance (where it ended up at the smaller orbit) and it would orbit with a minimum distance closer to the Sun.  Again, refer to Kepler's laws.  The orbits of the planets are elliptical, with the Sun at the center of one focus for that ellipsis (because it's much heavier).  You'd just be adjusting us from a very nearly circular orbit to a very squished elliptical one.  Maybe not as elliptical as a comet, but that kind of orbit.

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Dr. Stephen O. Nelson

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I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

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I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

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Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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