If Earth had spun in the opposite direction right from the get-go, animals might have evolved a bit differently. But if it suddenly went the other way tomorrow, I wonder how animals and plants that are adapted for life in the intertidal zone would do with the tides rolling in/out on a faster schedule.
Larry Niven would not need to correct the first paperback printing of Ringworld.
Stranger
I do not know enough about this, at least definitely not off the top of my head. The obvious example of a planet spinning backwards is Venus. But, how did Venus end up that way? Wiktionary suggests atmospheric tides.
Now, we know that the Moon’s tides are slowing down the rotation of the Earth, not that it can stop or reverse it. However, we can imagine the Earth already spinning retrograde when whatever event created the Moon happened. What happens then?? Perhaps something to throw into a rough simulation…
I had never considered the coriolis force to have affected plate tectonics, but thinking about how we all float around on liquid magna it makes sense. I mean, in addition to various other forces and inertia.
Thanks for the insight.
ETA, seems I was presumptive. Dankie, @MrDibble
Well, we’re still not absolutely sure what created the Moon, but:
- The giant-impact theory is most widely accepted today. This proposes that the Moon formed during a collision between the Earth and another small planet, about the size of the planet Mars. The debris from this impact collected in an orbit around Earth to form the Moon.
If this is how the Moon was formed, then its direction of orbit would most likely match the direction of spin of the Earth, so things would be the same, just mirror-imaged to what we have now.
If one of the other theories is what really happened, then it’s probably a coin flip as to whether the orbit matches the spin, or not.
Just wanted to note the OP’s handle/thread topic synchrony.
The North American and South American continents drifted away from Africa and are creating the mountain ranges on the west side of each continent as they collide and override the Pacific plates (simplified version). Presumably their drift direction is somehow tied to earth’s rotation?
OTOH India is drifting north-eastward and Australia below the equator north-westaward?
I read someone, Stephen Jay Gould maybe, who said Venus doesn’t spin backwards, but rather it’s upside-down. (As a paleontologist, he was repeating from another source but I don’t remember who.)
There’s not really any difference between those two positions.
Venus would normally be tidally locked to the Sun, but there’s some tidal effect on its dense atmosphere that caused it to overshoot tidal locking by a small amount. Hence it rotates slowly backwards.
Nope. For instance, you’re looking at the Eastern edge of the Pacific plate (for North America) and thinking it’s significant, but the plate is subducting under the Aleutians (E-W axis) too.
Yeah, when I mentioned it, I had sort of misunderstood the OP to be asking what if the Earth had always spun that way. I think the coriolis forces would have some effect on the way continental plates form and change, if those forces were applied over geological spans of time.
But it’s kind of a moot point because if you started with two identical proto-earths, both spinning in the same direction and left them for billions of years, you’d end up with two different continental maps anyway, just because there’s bound to be some chaos in the process.
One thing I should clarify - I didn’t say the Earth’s rotation has no effect on tectonics, I said the Coriolis force has no effect. The equatorial bulge might have a slight impact on preferred direction for things and that’s also a result of rotation, but that’s centrifugal force at play, not Coriolis force, and a mere change in direction would make no difference there, as the magnitude would stay the same and we should expect the same equatorial bulge.
The difference, which is significant, would be that either (a) Venus used to spin the same way as does Earth when viewed from above, slowed down to a stop, and then began spinning the other way; or (b) Venus used to spin the same way as does Earth when viewed from above, and then flipped over, maintaining its direction of spin all the while.
Seems unlikely to me. Any north-south continental drift is so slow - a few inches per year at best - that any east-west velocity component a tectonic plate might exhibit has millions of years over which to adjust.
That is what I was thinking about, what if the Earth had always spun that way,
Why am I awake at 4:00 a.m.?
Thank you for the clarification; it’s kind of hard to formulate a thought experiment in which the spin is the only thing that would be different - if you started with any identical proto-earth and ran the thing for billions of years, you would end up with some earth-like planet, but with a very different map, just because of the chaotic nature of the formative processes.
Or (c): Venus formed spinning the way it does now. IOW opposite most of the rest of the solar system.
I guess we would have to sort of ignore the chaos to get anywhere with this thought experiment.
As covered in some of the earlier threads, it really depends on what you assume is different and what you assume is the same.
Heck, if we started with the exact same molten proto-Earth / Moon system from ~4B years ago spinning the way it does now and re-ran the experiment up to today it’s a statistical certainty the continents, climate, life, etc., would be vastly different than what we see outside. The movie we call “planetary history” could have unfolded lots of different ways and we only get to see this one version.
To that mix, adding opposite spin would IMO be like adding a pinch of salt to a giant industrial batch of spaghetti sauce.
One thing that would be different is that a sidereal day would be 4 minutes longer than a solar day, instead of shorter. Astronomers would care about this.