Physics question. (I think)

[Traab]

If the earth were to suddenly stop spinning, then spin the other way, what effect would that have on the planet itself? Would it tear apart the world? Would it cause massive climate shift? Would it do nothing but makes us all have to reset our clocks?

[kamikasei]

The effects of the actual transition would depend on the mechanism. What's causing the Earth to stop spinning and then reverse? No useful answer is possible without more detail.

If you just take the scenario "if the Earth spun in the opposite direction, what would be different?", the answer is that the Coriolis effect would change. Large-scale air and ocean currents would switch direction. That'd have a big impact on climate, sure.

[Borgh]

also, if it is just the core that stopped, we woudn't notice for a bit as inertia would continue to keep the crust spining in the direction it was used to.

[thubby]

the stop would catapult us all at several thousand mph into nearby objects.

moving in the opposite direction would effect wind and tidal currents. in what way im not entirely sure, but screwing with those is more than a bit disastrous.

[Gravitron5000]

Another thing that would be important is how rapidly this change in rotation occurs. Too rapidly would cause the world to effectively tear itself apart (although the earth would still be in one mashed up mass). The world would likely deform somewhat, even at a slower rate of rotational change due to density differences resulting in differences in localized angular acceleration. Considering the amount of angular momentum that the earth has, the rotational reversal would have to be quite slow (probably in the tens of thousands of years, although I am pulling this number out of the ether) in order for there to be a negligible effect on the earth's topography. Equatorial regions would be most effected, as they have the most angular momentum.

[Abies]

If the Earth were "to suddenly stop spinning" all life would be destroyed, as would most land features. That much mass can not be accelerated that quickly without some very serious consequences. The degree of the damage depends a lot on what is or is not effected by the magical "stopping". If the water in the oceans is not stopped, it would all suddenly reach escape velocity and vaporize. I'm not entirely sure what the consequences of having all water on the planet become gaseous, but I'm sure it would not be a good thing.

Another thing to consider, once the Earth starts spinning the opposite way the Moon will be in a retrograde orbit. If the oceans and tectonic plates survived the stopping, the effect of the Moon in a retrograde orbit would result in tides being twice as frequent.

[golentan]

Yeah. This depends on a whole mess of things. The speed of the change, the mechanism that caused it, etc. etc. This is too vague to give you a better answer than the others have already.

[Traab]

I figured as much. I was thinking about the classic superman film where he flies so fast around the planet that he turns back time after lois dies. ignore the time travel aspect of it (http://www.youtube.com/watch?v=CCsHTNP2MaU) I figured it would basically tear apart the planet. Didnt even occur to me that it would effect US as if we got into a 12000 mile an hour car crash and basically make everything on earth explode from the sudden deceleration but it makes sense. So basically, all life would end if the planet stopped spinning that quickly and started going in the opposite direction?

[kamikasei]

So basically, all life would end if the planet stopped spinning that quickly and started going in the opposite direction?
If it's caused by a force directly applied, rather than some kind of technobabble-inertia-magic? Hell, I'd expect the planet to liquefy given the amount of energy that'd have to be dumped in to / liberated from it.

[Zejety]

The sun will rise in the west and set in the east.
:cool:

[Manga Shoggoth]

I figured as much. I was thinking about the classic superman film where he flies so fast around the planet that he turns back time after lois dies. ignore the time travel aspect of it (http://www.youtube.com/watch?v=CCsHTNP2MaU) I figured it would basically tear apart the planet. Didnt even occur to me that it would effect US as if we got into a 12000 mile an hour car crash and basically make everything on earth explode from the sudden deceleration but it makes sense. So basically, all life would end if the planet stopped spinning that quickly and started going in the opposite direction?

Actually, he is supposed to be travelling faster than light and pushing himself back through time. The Earth isn't revolving backwards - it is just supposed imply the time travel.

The trouble is that he is only going back about an hour tops, so the earth should only appear to move by a maximum of 15 degrees.

[grimbold]

I figured as much. I was thinking about the classic superman film where he flies so fast around the planet that he turns back time after lois dies. ignore the time travel aspect of it (http://www.youtube.com/watch?v=CCsHTNP2MaU) I figured it would basically tear apart the planet. Didnt even occur to me that it would effect US as if we got into a 12000 mile an hour car crash and basically make everything on earth explode from the sudden deceleration but it makes sense. So basically, all life would end if the planet stopped spinning that quickly and started going in the opposite direction?

the other problem there is that if he crashed into the earth that fast he would probably break through the earth's crust

[Gravitron5000]

If the water in the oceans is not stopped, it would all suddenly reach escape velocity and vaporize.

... escape velocity of the earth is 11.2 km/s

The circumference of the earth is about 40,000 km, which rotates once in 24 hours. That comes out to around 0.46 km/s, which means that that is about as fast at anything is moving due to the earths angular velocity. It would actually be marginally faster as there are differences in distance from the center of the earth, but you can double it without getting close to escape velocity. Since the mass of the earth is not changing I doubt that anything much would get thrown from the earth. The oceans (along with everything else) would end up sloshing around quite dramatically though.

[Traab]

the other problem there is that if he crashed into the earth that fast he would probably break through the earth's crust

But he didnt crash into the earth, he went out of the atmosphere, and flew so fast it countered and reversed the rotation of the earth. (Which has to violate about 50 different laws of nature all by itself. lol) And honestly, I think that interview where they tried to explain the whole time travel aspect was a bit of an asspull after the fact. They had to try and justify a scene that violated so many natural laws that not even suspension of disbelief was enough to excuse it. Being able to fly so fast he travels in time? I could let that slide, especially with the whole, "It is forbidden" stuff that explains why he never did it before or since. But flying so fast he stops the rotation of the world and reverses it, and this somehow turns back time? Uhhhhhh, no.


The oceans (along with everything else) would end up sloshing around quite dramatically though.

If by sloshing you mean likely creating a new beachfront in kansas. Seriously, the sudden change in momentum would almost HAVE to cause some sort of massive worldwide tsunami effect.

[Gravitron5000]

If by sloshing you mean likely creating a new beachfront in kansas. Seriously, the sudden change in momentum would almost HAVE to cause some sort of massive worldwide tsunami effect.

It was a deliberate understatement. Since the continents/landmasses/mountain ranges/tectonic plates/etc. would also be sloshing about, I'm not sure that the location of Kansas would be readily locatable/identifiable (I don't think we're in Kansas any more, toto :smalltongue:).

[Mina Kobold]

I figured as much. I was thinking about the classic superman film where he flies so fast around the planet that he turns back time after lois dies. ignore the time travel aspect of it (http://www.youtube.com/watch?v=CCsHTNP2MaU) I figured it would basically tear apart the planet. Didnt even occur to me that it would effect US as if we got into a 12000 mile an hour car crash and basically make everything on earth explode from the sudden deceleration but it makes sense. So basically, all life would end if the planet stopped spinning that quickly and started going in the opposite direction?

The weirdest part about that, as the Nostalgia Critic and Linkara have pointed out, is that he couldn't catch up to a missile just seconds before doing that.

He can somehow go around the world in a second but catching up to a slow-moving weapon that he would have passed in a microsecond? That's just impossible!

[Traab]

The weirdest part about that, as the Nostalgia Critic and Linkara have pointed out, is that he couldn't catch up to a missile just seconds before doing that.

He can somehow go around the world in a second but catching up to a slow-moving weapon that he would have passed in a microsecond? That's just impossible!

Well going by all the ghostly forbidden talk, id assume he was working within certain limits. I also remember an episode of justice league unlimited when he fought darkseid, and he mentioned something about how he has never been able to fight at his full strength because he was afraid of how much damage he would do, but now he would. And from then on the shock waves of his punches were shattering buildings and creating massive craters.

[Durmegil Guldur]

The damage done would very much depend on the angular deceleration/acceleration of the earth in this motion. The more time the energy transfer is spread over, the less damage things would suffer in general.

[Traab]

The damage done would very much depend on the angular deceleration/acceleration of the earth in this motion. The more time the energy transfer is spread over, the less damage things would suffer in general.

But thats just damage done by inertia, is there anything intrinsically bad about the earth not rotating? Or rotating backwards? Would that effect gravity in any way? Tides? Weather? (aside from 24 hour long days and nights etc)

[factotum]

Depends what you mean by "not rotating". If the Earth's rotational period became the same as its orbital period then it would always present the same face to the Sun (same as the Moon does to us) and that would cause all sorts of havoc--it would be very cold on the night side and eternally hot on the day side; no idea if life could even continue under conditions like that. If it was somehow not rotating at all then you'd effectively have the length of the day being the same as the length of the year, which would certainly mess around with the biological clocks of everything that's become used to a 24-hour day!

Rotating in the opposite direction at the same speed as it does now? It wouldn't actually make much difference. It wouldn't even make much difference to the tides, contrary to Abies' statement--almost all of the delay between one tide and the next is due to the rotation of the Earth; I think the time between two tides would drop from its current twelve and a half hours to maybe eleven and a half.

[grimbold]

The damage done would very much depend on the angular deceleration/acceleration of the earth in this motion. The more time the energy transfer is spread over, the less damage things would suffer in general.

this is a very good summary of all the points

in even shorter terms
we would be screwed

[Mina Kobold]

But thats just damage done by inertia, is there anything intrinsically bad about the earth not rotating? Or rotating backwards? Would that effect gravity in any way? Tides? Weather? (aside from 24 hour long days and nights etc)

Well, the evening out of the temperature, pressure and other meteorological phenomena are very dependant on the Earth's movement in comparison to the Sun so they would be slowed immensely. It's possible that life would face a challenge if that happened, but I am not entirely sure how severe.

But a night that lasts 180 times 24 hours is ostensibly not a very good thing. Would probably slow tides and wind down too.

Gravity is primarily dependant on mass, though, so I'm not sure if loss of rotation will affect that. ^_^'

[Flame of Anor]

Well, just watch that Futurama episode for an entirely reasonable and scientifically accurate method of doing this and its effects.

[Dr.Epic]

Well, the way momentum works, we'd all be flung at very fast speeds.

[ben-zayb]

If the earth were to suddenly stop spinning, then spin the other way
The earth suddenly stopping its rotation is hardly likely to happen in the first place.
Afterall, the torque required to keep it from rotating should logically at least be equal to the amount of needed to rotate it in the first place. Basically you need at least twice the original torque to make the earth rotate the other way around.

Factor in the angular momentum of the mantle that could (probably?) prevent the core from instantly stopping.

I do not claim to be an expert on this field though, my rusty vector-mechanics knowledge may in fact be totally wrong.

[Nameless]

We'd all go back in time. Duh.

[Ted_Stryker]

The type of physics you're asking about is basically, "Jeannie folds her arms and blinks." Any sort of event conforming to physics as we understand it that would cause such a drastic shift in the earth's overall angular momentum on timescales that humans would describe as "suddenly" would make a description like "catastrophic" into an exercise of wretched understatement.

[Jubal_Barca]

The interesting one is if the world stopped spinning and reversed over, say, 60 years.

All the water would flow to the poles, since the centripetal force shoves it 3km up at the equator. We'd just be one big continent with seas at the top and bottom.

[Traab]

The interesting one is if the world stopped spinning and reversed over, say, 60 years.

All the water would flow to the poles, since the centripetal force shoves it 3km up at the equator. We'd just be one big continent with seas at the top and bottom.

Yeah, but how much of our current landmasses would be underwater by that point?