# What if earth's rotation stopped

1. Jul 1, 2013

### Bandarigoda

If that happened,
Will it affect to the gravity?

2. Jul 1, 2013

### beamthegreat

Every building and object would be instantly be crushed near the equator and gradually reduce in damage as it was nearer to the north or south pole. Objects in the equator are moving at around 1674 kilometers per hour so if the earth immediately stopped it would be like crashing a jet plane into the ground. As for the centrifugal force, it wouldn't really be noticeable. From the link below, people on the equator weighs about 0.3% less due to the centrifugal force exterted on them. You can read more about it on the link I provided below about the earth rotation and the effect on gravity.

http://curious.astro.cornell.edu/question.php?number=310 [Broken]

Last edited by a moderator: May 6, 2017
3. Jul 1, 2013

### wotanub

For one, we'd die because one side would freeze without sunlight, and the other would be too hot.

I don't think so. How would you get a crushing force (towards the center of the earth) from stopping rotation?

Also, a jet plane into the ground? Energy? Force? What?

4. Jul 1, 2013

### beamthegreat

No, the force will be exerted sideways when the earth stopped moving. So, buildings would be crushed upon itself and objects would be hurled great distances relative to the ground. I am assuming that the earth stopped almost instantaneously so you can imagine how devastating the impact would be.

The acceleration of all things on the surface would be:
(400 m/s - 0 m/s) / infinitesimally small time

This acceleration we perceive in this scenario could be comparable to driving a jet plane (at 1600 km/h) and then crashing in into the ground.

As for the second part, the earth rotation plays a role in determining the gravity on the surface of the earth (due to centrifugal force) so if the earth stopped moving, objects near the equator would weigh more than it would now by around 0.3%.

5. Jul 1, 2013

### wotanub

Maybe some things would "fly" but it wouldn't crush and buildings since the buildings are "bolted" to the earth and the entire thing would be a rigid body. Even if we don't consider them absolutely bolted, there are frictional forces to consider, as well as the strength of their fondation.

I still don't buy the jet plane angle. You need to consider things like the time it takes the plane to crash and how massive it is... A jet crash would actually deliver a much smaller impluse.

6. Jul 1, 2013

### beamthegreat

Ok ill admit the jet plane part was a bit too simplified. My point is that if the earth were to stop instantly it would certainly be devastating to everything on earth. Also, I believe the structural strength of the building is enough to cause it to collapse upon itself but I could be wrong.

7. Jul 2, 2013

### Bandarigoda

Then also tsunamis will be happen?
Will it affect to moon? What about the air? A fastest air should be start, then might affects to air planes, and other objects on the land. Am I correct?

8. Jul 2, 2013

### CWatters

Gravity wouldn't be affected.

There is a big question mark over how the earth could be stopped without destroying it. You mention tsunamis, which presumably you think would occur due to the inertia of the water, but that's the least of your problems. If you tried to stop the planet rotating by applying a force to the surface of the earth there is the inertia of the rest of the planet to worry about. The inside would try to keep spinning. Is the earth strong enough to take the braking forces? If you can figure out a way to stop the whole planet spinning at once then stopping the little bit of water on the outside and the atmosphere spinning should be easy by comparison.

9. Jul 2, 2013

### D H

Staff Emeritus
Some unknown physics are needed to make the Earth stop rotating. You apparently are assuming that this unknown physics pertains to rocks only. Why? Certainly you could also assume that the same magic that works on rocks also works on water, buildings, people, etc.

This is one of those "what do the laws of physics say would happen if the laws of physics are wrong" kinds of questions.

10. Jul 3, 2013

### CWatters

Well said.

11. Jul 3, 2013

### Staff: Mentor

Yes, the ocean would still be moving and would flood most of Earth's landmass.

Nothing would happen immediately, but the long term effects would be that the Moon stops receding from Earth. This happens because, without rotation, the Earth cannot transfer its angular momentum to the moon through the tides.

Lots of wind. LOTS of wind.

I don't understand what you said. "A fastest air should be start" doesn't make any sense.

Luckily for us, none of this will ever happen, as it is impossible, so we don't have to worry about any of it.

12. Jul 3, 2013

### D H

Staff Emeritus
Why?

Once again, why do you say this?

It would require magic to suddenly make the Earth stop rotating. Why are you assuming the magic only works on rocks? It's magic. It can do anything it wants.

13. Jul 3, 2013

### Staff: Mentor

The moon is still orbiting the earth so we'd still have tides. They'd just rise and fall twice a month instead of twice a day.

14. Jul 3, 2013

### Baluncore

The original post did not say that that Earth rotation must stop suddenly, that is clearly physically impossible as all rotational energy would have to be removed through the very thin crust.

In short, gravity will not change.

The Earth's figure, an oblate spheroid, will without rotation become spherical. At an astronomical distance gravity should not change as the mass of a spherical Earth is identical to the entire Earth's mass being located at the centre of the Earth's sphere. If there is still local density variation within the Earth then there will still be minor local variations in gravity on the Earth's surface.

The Earth's rotation is slowing down now due to the presence of the Moon releasing the tidal energy we see twice each day. The Moon has already ceased to rotate and has locked one face to the Earth. With time the Earth will lock a fixed face to the Moon. The Earth now has a rotational period of 24 hours, that will become a period of one month when the Earth's face finally locks to the Moon. So the Earth cannot completely stop rotating, except relative to the Moon.

Most atmospheric winds are caused by Earth rotation so they will cease as rotation stops. Only katabatic winds would remain as they are caused by local variation in density of the atmosphere as sunlight heats one side and the other side cools.

15. Jul 3, 2013

### cjl

Which, interestingly, would start to accelerate the earth's rotation, since the energy transfer would now be from the moon's orbit to the earth's rotation (rather than the other way, as it is currently). It would also cause the moon's orbit to spiral inwards.

16. Jul 3, 2013

### Staff: Mentor

Okay. Let's assume it works on everything. Then nothing interesting will happen and we won't have any discussion and no one will learn anything about things like conservation of momentum and energy.

Of course, I never meant to imply we wouldn't, only that the Moon would stop receding from the Earth.

17. Jul 3, 2013

### Staff: Mentor

And because we still have tides, the angular momentum transfer processes will still be at work, just operating at more slowly. The moon's recession continues.

18. Jul 3, 2013

### D H

Staff Emeritus
It would work the other way around, though. Angular momentum transfer would be from the Moon's orbit to the Earth's rotation if the Earth wasn't rotating or if its rotation rate was longer than a lunar orbit. The Moon would slowly spiral in rather than out.

19. Jul 3, 2013

### Staff: Mentor

D'oh. Thanks.

20. Jul 3, 2013

### BruceW

I'm not sure what answer the OP was looking for. But I guess it is something like "would we all feel a lot stronger gravity". And the answer is no, not really. We would feel slightly more gravity, but it would only be a small amount. This is because the Earth is not really rotating fast enough to be on the same order of magnitude as gravity.