# What if the Earth suddenly stop revolving around its axis?

Discussion in 'Physics & Math' started by Saint, Sep 4, 2017.

1. ### SaintValued Senior Member

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What if the Earth suddenly stop revolving around its axis but continue to revolve around the Sun?
Will us still be pulled by the gravity and can stand firm on the ground?

3. ### originIn a democracy you deserve the leaders you elect.Valued Senior Member

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Earth's gravity would be the same. If you lived far enough North or South you might even survive the event.

5. ### superstring01Moderator

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The Earth roughly spins at 1037 miles per hour (1670 km/). Sudden means --well-- instantly. So a sudden stop of 1037 mph would mean near instant death for all life on the planet. Since the entire world would instantly stop, it would take some godlike force to do so. Presumably that godlike force could save all of our lives. If we suddenly stopped, you'd have to decide what that kind of stop means:
• Tidally locked with the sun (one side always facing the sun)
• No spin at all, such that an orbit of the sun results in our day being 365 previous days.

The net effect for the first would be that one side would be permanently warm. The heat from the sun impacting the oceans would mean greater hurricanes and such. Places like the Northern US and Canada would be decent places to live (if they were on the sunward side). The other size would freeze solid.

The consequences of the second option would be that the entire world would freeze. Six months wouldn't be enough time for the heat from the sun to melt the water that had frozen on the other side since ice reflects heat. Eventually the entire Earth would freeze over except the land covered areas which might become temperate once the sun comes out, but the oceans would freeze over.

7. ### originIn a democracy you deserve the leaders you elect.Valued Senior Member

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That's the speed at the equator, if you lived near the north pole the speed is much lower so you would survive the big stop, but any long term survival is highly doubtful.

8. ### hansdaValued Senior Member

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If the spin of the Earth is stopped but it continues to revolve the Sun; considering conservation of energy, the spin energy may be converted into increase of orbital speed. Orbit of our earth may change. It also may affect precession of our earth.

Gravity may not change. We still can stand firm on the ground. But angular momentum of atomic particles may change, considering conservation of angular momentum of our earth.

9. ### superstring01Moderator

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Yep yep. Very good point.

Yeah, but this is such a hypothetical scenario that I just allow for some godlike force that fixes those issues to allow further examination of what life would be like if we remained in the same orbit. That's a lot of supposition and artistic license on my part, I admit.

10. ### DaveC426913Valued Senior Member

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Note that, since the OP posits a God-like phenomenon that can stop Earth in its tracks, there's no reason to assume that phenom doesn't act equally on everything that is part of Earth - such as humans.

The OP is clearly struggling with what causes gravity, and confusing it with our motion around the Sun, so maybe we should not introduce real side-effects of magical processes, and should stick to the specific issue.

The gravity that holds us to the Earth comes from one source only: the matter that makes up the Earth itself. Every atom that makes up the Earth (including rocks, dirt, and you an me) exerts a tiny force pulling on us (and we on it). The cumulative effect of trillions of trillions of atoms pulling on us results in a force pulling us toward the centre of the mass, which is Earth.

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11. ### hansdaValued Senior Member

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Yaa, it is a hypothetical situation. Say our earth is hit by an asteroid in such a fashion that, spin of our earth gradually reduces to zero. Then what will happen?

12. ### DaveC426913Valued Senior Member

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Those of us not physically ejected into space by the impact event are vaporized by the firestorm.

Can we get back to the OP's question?

13. ### superstring01Moderator

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Man. If that asteroid is big enough to do that, just say goodbye to everybody!

Astronomers believe that a celestial impact is what flipped Uranus on its side.

14. ### Janus58Valued Senior Member

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A signal impact could not reduce the Earth's rotation gradually. The rotational energy of the Earth is something in the order of 2.14e29 Joules. A colliding asteroid would have to have at least that much KE to stop Earth's rotation. Even Ceres, the largest of the asteroids (technically a dwarf planet), would have to hit the Earth moving at over 21 km/sec at just the right angle for it to even have the possibility of stopping the Earth's rotation. But a body that size (473 km in radius) striking the Earth at a shallow angle at that speed would just punch through the Earth's crust. In addition, a lot of the energy would be lost as heat, so the actual energy of the asteroid would have to be much greater for enough to be left over to cancel Earth's rotation. This means even a faster asteroid. The faster the asteroid, the shorter the time over which the impact takes place, and the less time there would be for the asteroid to stop the Earth's rotation.

The only way to gradually slow the Earth would be through the force slowing it to act over a long time. A single impact is a short event.

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15. ### DaveC426913Valued Senior Member

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OMG stop. The event is immaterial to this thought experiment.

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16. ### originIn a democracy you deserve the leaders you elect.Valued Senior Member

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If the earth and everything on the earth stopped rotating and the Earth didn't change shape then pull of gravity would stay the same. You would stand firm on the ground.

17. ### Janus58Valued Senior Member

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I was replying strictly to Handsa's question regarding an asteroid impact's effect on the Earth's rotation.

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I know.

19. ### StrangerInAStrangeLandSubQuantum MechanicValued Senior Member

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^^^
If Earth stopped spinning, it would change shape.

<>

20. ### DaveC426913Valued Senior Member

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Which is why he mentioned it.

21. ### SaintValued Senior Member

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Will we be thrown out to the outer space?

22. ### Janus58Valued Senior Member

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No. Even at the equator you are traveling at ~464 meters/sec. To be thrown completely clear of the Earth, you would need to be moving at 11 km/sec. If you were moving between between 7.9 and 11 km per sec, you would be put into various elliptical orbits around the Earth. (these orbits would skim the surface of the Earth at their perigees). The stopping of the Earth's spin has no bearing on this. (If the earth were spinning fast enough that you were moving at 11 km/sec at the equator, you would be flung off into space whether the Earth stopped rotating or not.)

23. ### KristofferGiant HyraxValued Senior Member

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Sorry, couldn't resist.