Assuming it just spins at the same rate, the other way. Axial tilt is the same, year length is the same.

Perhaps winds and ocean currents? What would the effect be on geography? Would deserts or rainforests be in different places?

  • $\begingroup$ Questions asking how culture would change, are often closed as being too broad. $\endgroup$ – sphennings May 24 '17 at 16:35
  • $\begingroup$ But there might be something physical causing it? $\endgroup$ – Carlos May 24 '17 at 16:35
  • $\begingroup$ You're asking about weather, oceanic currents, other things, anything to do with culture, and life. This is extremely broad. As a general rule if someone would need to write a book to answer your question it is too broad. $\endgroup$ – sphennings May 24 '17 at 16:39
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    $\begingroup$ You really need to clarify. Some people have interpreted your question as to mean, what if the Earth suddenly started spinning the other way. But I think you mean, what would it be like if the Earth always spun the other way. If so, would the moon go the other way too? Would the Earth circle the sun the same direction? $\endgroup$ – ozone May 24 '17 at 17:18
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    $\begingroup$ I really love this question, but it's unfortunately too broad. Maybe break it down into smaller questions (I would start with weather). $\endgroup$ – Azuaron May 24 '17 at 17:19

A lot.

With weather patterns moving in the opposite direction, it's hard to predict what would happen. Weather is a chaotic system, after all.

For example, consider the El Niño effect. Normally, the trade winds blowing across the Pacific keep warm water bunched up to the wast, around Asia and Indonesia. With the trade winds reversed, that water would instead generally be pooled against the Americas, with unpredictable long-term effects.

The Gulf Stream is also driven in part by the trade winds in the Atlantic; with those winds reversed, again, it's hard to guess the consequences. Europe would likely be a frozen wasteland, while Canada and Greenland could become as warm as Europe - or perhaps not, especially when the permanent El Niño effect to the west.

Places that have formed deserts in the rain shadow of mountains could well become rainforests, and vice versa - perhaps. Again, it's too chaotic to know.

What I'm trying to get at is that this isn't as simple as "the sun rises on the other side" - everything would change.

  • $\begingroup$ Agreed. How humans spread across the planet and learned how to hunt may have been altered significantly if humans could have survived just fine from the treetops for instance. It likely would have changed distribution of humans on the planet and therefore all of history. This assuming human beings would evolve at all given the new climate and conditions. $\endgroup$ – Neil May 25 '17 at 14:02

Earth would be doomed (long term)

By doomed I mean : everything living on it at the moment of the impact will no longer be living. The Earth as a big ball of rocks and metal will be just fine apart from a big bruise. Which impact ? Well...

The Earth is currently spinning faster than the Moon, in the same direction. This causes the Moon to be accelerated (and the Earth decelerated), making it go further away a few centimeters per year.

Now, if you reverse the Earth rotation, you'll have the opposite effect, slowing down the Moon until it is pulled too close for comfort. Really, really to close.

Of course, this would take quite a bit of time. Phew...

  • $\begingroup$ Why doomed? Nice planetary ring is nice, some scientists start to wonder if "stabilizing effect" is as high as it was assumed so maybe no problem here, either. I like "doom scenario" all right, but why? $\endgroup$ – Mołot May 24 '17 at 17:04
  • $\begingroup$ The moon is tidally locked to earth, You can assume if earth's rotation is inverted the rotation of the moon might very well be too, or else it does not longer qualify as being tidally locked. $\endgroup$ – Hyfnae May 24 '17 at 17:16
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    $\begingroup$ @Hyfnae : Tidally locked means that the Moon always present the same face to Earth, which would remains the same if the Earth spun the other way around. Don't you mix it up with geosynchronous orbit ? $\endgroup$ – Keelhaul May 24 '17 at 17:48
  • $\begingroup$ @Molot : OK, due to the trespassing of the Roche limit, our Moon would probably disintegrate before hitting the Earth. Still, this ring would itself be slown down and crash. And I didn't talk about the huge volcanism due to the tremendous increase of tidal effects. $\endgroup$ – Keelhaul May 24 '17 at 17:52
  • $\begingroup$ I’m not so sure. $\endgroup$ – JDługosz May 24 '17 at 20:23

Physically all that would be different are the inversion of long term weather system and Coriolis effect, the sun would rise west and set east and that would be it. For example; tradewinds would blow in the opposite direction. A low pressure area on the northern hemisphere would turn clockwise instead of counterclockwise and that goes for all systems. Water would show the same thing when drained, spinning the other way around than it does now.

Oceanic currents would remain as usual as they are powered by convection caused by warm water having a lower density than cold water. They are not connected to the spinning of the earth as much as air currents are, it has more to do with the geography of the ocean floor.

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    $\begingroup$ "Oceanic currents would remain as usual": the best counterexamples are of course the Gulf Stream and Antarctic Circumpolar Current. Earth spins the other way means the trade winds blow the other way means no Gulf Stream. That would make Ireland and Great Britain two cold and desolate islands. Sad. $\endgroup$ – AlexP May 24 '17 at 17:12
  • $\begingroup$ Aren't they already cold desolate islands? I jest, I jest. But seriously... so much rain.... $\endgroup$ – amflare May 25 '17 at 18:14

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