# Oh no, the earth is rotating "backwards".

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Say we wake up one day to find the earth rotating in the opposite direction. What would be different besides the sun rising in the west?

Ignore the physics of accomplishing such a feat and let's assume everything has stabilized (tides, winds, etc). Just wondering about the effects - especially on the living things.

In a similar fashion, what would be different if our path around the sun changed direction?

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The Moon would have decelerated and crashed into the Earth by now if the Earth was turning in the opposite direction. Without the Moon life on Earth would be different.

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The Moon would have decelerated and crashed into the Earth by now if the Earth was turning in the opposite direction. Without the Moon life on Earth would be different.

Why?

There are about 29.53... days in a lunar month so it's not as if the orbit of the moon is related to the rotation of the earth. if it rotated the other way why would it make much odds?

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Say we wake up one day to find the earth rotating in the opposite direction. What would be different besides the sun rising in the west?

Ignore the physics of accomplishing such a feat and let's assume everything has stabilized (tides, winds, etc). Just wondering about the effects - especially on the living things.

In a similar fashion, what would be different if our path around the sun changed direction?

If we ignore the physics then nothing, otherwise we'd all be floating in space.

Edited by dimreepr
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Why?

There are about 29.53... days in a lunar month so it's not as if the orbit of the moon is related to the rotation of the earth. if it rotated the other way why would it make much odds?

Tidal deceleration. Right now the Earth rotates in the same direction as the Moon orbits and in a shorter period. Because of this, tidal interaction between the two bodies transfers angular momentum from the Earth to the Moon, causing the Moon to drift into a higher orbit. If the Moon orbited in the opposite direction than the Earth ( or the orbited faster than the Earth rotated), the opposite would occur, and the Moon would move into a lower and lower orbit.

This however does not mean that The Moon would crash into the Earth. Once it got close enough, tidal forces would tear it apart and it and the Earth would have a ring.

That being said, this does not apply to the original question, which was not about the Earth rotating in the opposite direction since sometime long in the past, but instead started rotating backwards from this point onward. Yes, the Moon would start moving inward, but it would take billions of years to move in by a large amount.

One thing that would change for such a counter-rotating Earth is that the world-wide climate would be disrupted. Trade winds and ocean current would change. Some deserts may bloom while some fertile regions will become deserts. Plants that are adapted to a given local climate will fail as will any animals that rely on those plants.

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If the interaction was large then the earth and moon would be tidally locked, They are not: it is not.

As you say " but it would take billions of years to move in by a large amount."

Well the sun will go red giant before then so...

Manchester would lose its reputation for rainy weather.

Edited by John Cuthber
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Equal but opposite rotation there would be 2 more, but shorter, days in the year. Same if the revolution was opposite, with the same current rotation.

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What about birds and insects? Would their navigation be screwed up, possibly leading to chaos and mass extinction?

Would the GPS system still work?

If the ocean currents and prevailing winds change I can see huge ecological disaster happening.

I wonder if it will affect crops in any way.

Plus, all our sundials will be out of whack!

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• 2 months later...

Tidal deceleration. Right now the Earth rotates in the same direction as the Moon orbits and in a shorter period. Because of this, tidal interaction between the two bodies transfers angular momentum from the Earth to the Moon, causing the Moon to drift into a higher orbit. If the Moon orbited in the opposite direction than the Earth ( or the orbited faster than the Earth rotated), the opposite would occur, and the Moon would move into a lower and lower orbit.

This however does not mean that The Moon would crash into the Earth. Once it got close enough, tidal forces would tear it apart and it and the Earth would have a ring.

Very true, trouble is that's assuming the Moon starts where it is. But of course long ago, I understand, the Moon was a lot closer and correspondingly an Earth day was something like 6 hours. And if the earth was also rotating in the opposite direction at that time long ago, the Moon would then move even closer than the close point it already was and the Earth day would get even shorter. The consequence being the current Earth Moon situation today would not exist with the profound certainty we wouldn't be here asking the question either.

In other words, it's pointless question about something that would never unfold.

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Very true, trouble is that's assuming the Moon starts where it is. But of course long ago, I understand, the Moon was a lot closer and correspondingly an Earth day was something like 6 hours. And if the earth was also rotating in the opposite direction at that time long ago, the Moon would then move even closer than the close point it already was and the Earth day would get even shorter. The consequence being the current Earth Moon situation today would not exist with the profound certainty we wouldn't be here asking the question either.

In other words, it's pointless question about something that would never unfold.

Where did you get this info from? When was that?

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Where did you get this info from? When was that?

Presumably you're referring to the Moon currently moving away therefore it must have been closer long ago and the Earth rotating faster?

If so, I think you will find that according to measurements taken over the years from the reflectors placed on the Moon from the Apollo missions, the Moon is moving away. All this is occasioned by gravitational drag. The Earth rotating 28 (approx) times faster is effectively pulling on the Moon and speeding it up. It thus moves away - conservation of momentum and all that. Clearly, going back in the past it must have been closer, with the Earth rotating faster (shorter days).

Although I think part of my description might be wrong when I said the Earth would speed up when it's rotating backwards - I think it will still slow down.

I understand the Moon is moving 3.78 cm a year away from Earth, and the day is getting longer by 1.7 milliseconds a century.

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Presumably you're referring to the Moon currently moving away therefore it must have been closer long ago and the Earth rotating faster?

If so, I think you will find that according to measurements taken over the years from the reflectors placed on the Moon from the Apollo missions, the Moon is moving away. All this is occasioned by gravitational drag. The Earth rotating 28 (approx) times faster is effectively pulling on the Moon and speeding it up. It thus moves away - conservation of momentum and all that. Clearly, going back in the past it must have been closer, with the Earth rotating faster (shorter days).

Although I think part of my description might be wrong when I said the Earth would speed up when it's rotating backwards - I think it will still slow down.

I understand the Moon is moving 3.78 cm a year away from Earth, and the day is getting longer by 1.7 milliseconds a century.

I believe you were referring to Gravitational Frame-Dragging, rather than Gravitational Drag, but either way it's not the effect that causes Moon to drift away. I think the main culprit is the Tidal Acceleration.

Coming back to the original question, I believe that all animals that use some sort of navigation, be it Sun, Moon or stars will have a hard time adapting to new conditions. Plants should be fine, though. You can grow plants under artificial lighting with highly variable "day/night" cycles and it doesn't kill them, so reversing the rotation should be fine too.

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I believe you were referring to Gravitational Frame-Dragging, rather than Gravitational Drag, but either way it's not the effect that causes Moon to drift away. I think the main culprit is the Tidal Acceleration.

Whichever,, it appears to be gravitational forces.

Coming back to the original question, I believe that all animals that use some sort of navigation, be it Sun, Moon or stars will have a hard time adapting to new conditions. Plants should be fine, though. You can grow plants under artificial lighting with highly variable "day/night" cycles and it doesn't kill them, so reversing the rotation should be fine too.

But as said, if the Moon orbited contrary to what it does today we almost certainly wouldn't be here asking the question - along with probably every other creature; for the reason previously said. That reason being that long ago the Moon being closer and at the same time orbiting in the opposite direction the Moon would've been slowed by gravitation drag (or tides) and probably end up orbiting even closer - with all the consequences.

There's also the origin of the Moon to consider. I understand the current thinking is that Moon was the result of a celestial collision, with resultant the debris condensing to form the Moon. With the debris to be moving opposite I think would require a completely different, if not impossible, scenario. Indeed, the only way the Moon could've ended up in such a retrograde orbit is if it were captured. But again, living in the form of walking and crawling limbed creatures would've endured a totally different environment to the point that they would never have evolved.

The upshot is that idea of the Moon orbiting in the opposite directing in the same orbit it is today would've never occurred - it's a pointless question, if not unscientific.

It seems to me the question should be consigned to the Lounge or Speculations.

Edited by Delbert
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Estate agents would have to change their property descriptions from "The breakfast room has magnificent views of the Malvern Hills at sunrise" to "The supper room has magnificent views of the Malvern Hills at sunset".

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There's also the origin of the Moon to consider. I understand the current thinking is that Moon was the result of a celestial collision, with resultant the debris condensing to form the Moon. With the debris to be moving opposite I think would require a completely different, if not impossible, scenario. Indeed, the only way the Moon could've ended up in such a retrograde orbit is if it were captured. But again, living in the form of walking and crawling limbed creatures would've endured a totally different environment to the point that they would never have evolved.

The upshot is that idea of the Moon orbiting in the opposite directing in the same orbit it is today would've never occurred - it's a pointless question, if not unscientific.

I'm not quite sure what your point is. The question was about Earth rotating in the opposite direction, not the Moon. On a side note: depending on the direction of the impact I do believe it's quite possible for the resulting debris to end up on a retrograde orbit.

It seems to me the question should be consigned to the Lounge or Speculations.

If the OP said that the Earth actually does rotate backwards, then yes, but now we're discussing a pure thought experiment of what would happen if that were the case.

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I'm not quite sure what your point is. The question was about Earth rotating in the opposite direction, not the Moon. On a side note: depending on the direction of the impact I do believe it's quite possible for the resulting debris to end up on a retrograde orbit.

Well, the consequence of the Moon orbiting in the opposite direction is exactly what would happen with the Earth rotation in the opposite direction. Orbiting in the opposite direction with all the consequences. Like as I've said, the Moon wouldn't be in the position where it is now, as I understand it is currently moving away due to gravitational drag (because the Earth is tending to pull or drag the Moon faster and thus a higher orbit) the Earth rotating in the opposite direction the Moon would presumably then be slowed or dragged slower such that it would be even closer how than how close it was countless millions of years ago. Possibly to the effect that the Moon would've collided with the Earth some time ago. In other words the situation you propose wouldn't exist and the question is pointless.

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Well, the consequence of the Moon orbiting in the opposite direction is exactly what would happen with the Earth rotation in the opposite direction. Orbiting in the opposite direction with all the consequences. Like as I've said, the Moon wouldn't be in the position where it is now, as I understand it is currently moving away due to gravitational drag (because the Earth is tending to pull or drag the Moon faster and thus a higher orbit) the Earth rotating in the opposite direction the Moon would presumably then be slowed or dragged slower such that it would be even closer how than how close it was countless millions of years ago. Possibly to the effect that the Moon would've collided with the Earth some time ago. In other words the situation you propose wouldn't exist and the question is pointless.

This still doesn't make sense. The question was about how Earth rotating backwards would affect living things here, not how it will affect the orbit of the Moon, which, even though it will drop lover and eventually be ripped apart by tidal forces, will not happen for hundreds of millions of years.

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This still doesn't make sense. The question was about how Earth rotating backwards would affect living things here, not how it will affect the orbit of the Moon, which, even though it will drop lover and eventually be ripped apart by tidal forces, will not happen for hundreds of millions of years.

I'm sorry, but it's still a pointless question. The situation today would never be for you to pose the question. It's not much different than asking what would happen if snow on mountains were made of ice cream. Or the Moon was Swiss cheese.

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I'm sorry, but it's still a pointless question. The situation today would never be for you to pose the question. It's not much different than asking what would happen if snow on mountains were made of ice cream. Or the Moon was Swiss cheese.

The point of the question - and it most assuredly has a point - is to explore the biological implications of a contra-rotating Earth. It is the kind of hypothetical question that, by generating a significantly different perspective, can lead to valuable and interesting insights.

The astronomical consequences are irrelevant; the plausibility of the scenario is irrelevant. What is relevant is the change in perception the question induces.

And it is just as pointed and valuable as asking what if the snow on mountains were made of ice cream. Any glaciologist, geographer, materials scientist, or geomorphologist would have some refreshing ideas when confronted with that question. It focuses ones mind on the characteristics of snow that have definite, measurable, significant consequences for its behaviour on mountains. (And it has already given me some embryonic ideas for avalanche mitigation.)

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• 3 months later...

Good question and definitely not a pointless one.

If the earth began spinning in the opposite direction then this would have a profound effect on the earths climate, biology and biogeography.

Because of the coriolis force generated by earth's rotation, low pressure systems spin anti-clockwise in the northen hemisphere and clockwise in the the southern hemisphere. The opposite is true for areas of high pressure and these forces combine to create the west to east movement of weather in the earths temperate zones, which in turn creates the pattern of currents seen in the earths oceans.

If we reverse the rotation, the weather patterns and prevailing winds will now reverse, which will in turn completely alter the pattern of ocean currents and the distribution of heat in the oceans.

Whole continents would have permanent and dramatic changes to climate, with areas which were once wet becoming deserts and areas which were once dry becoming moist. Many rivers would run dry and new rivers would cut their path to the ocean.The dramatic changes to local climates would likey lead to extinctions and dislocations of flora and fauna on a massive scale.

Edited by mals64
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There would be an impact on how humans schedule activities. Airline schedules would change, locations of call centers could be impacted, The time stockbrokers awaken would change to be available for Wall Street hours, the number of people watching Monday Night Football would increase on the West Coast of the United States and decrease on the East Coast, etc.

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• 4 months later...

Say we wake up one day to find the earth rotating in the opposite direction. What would be different besides the sun rising in the west?

Ignore the physics of accomplishing such a feat and let's assume everything has stabilized (tides, winds, etc). Just wondering about the effects - especially on the living things.

In a similar fashion, what would be different if our path around the sun changed direction?

Assuming that there not need be a reversal of the existing directions of our orbit and rotation, and that, say, even from the Gitgo--the initial cosmological machinations that spawned the Earth some 4.6 BYA--the Earth began to acrete matter and orbit and rotate around the same star we now have and call the Sun, no: there is no reason why we could not spin and orbit around the sun in the opposite direction. So long as our moon of course was orbiting in sync with our rotation as it does now, and that the innermost two planets, Mercury and Venus, were also orbiting in the same direction as we were.

In other words: sure! The sun could just as easily and effectively rise in the west and set in the East. If I may be allowed to use that popular misnomer for alliterative purposes.

Thanks, BTW: this is a great question!

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