# If earth's rotation slowed down...

If earth’s rotation gradually slowed down from 1000 MPH to 30 MPH over a couple hundred years, what would that do to the planet’s atmosphere, biosphere, climate, tectonics, or any other relevant factor?

Also, how long would the new “day” be?

The day would be (1000/30)*24 hours= 800 hours. Or, more reasonably expressed, 33 1/3 days (as currently measured). This doesn’t take into account the fact that the earth is also revolving around the sun (which would slightly affect the length of the day).

All of that other stuff? Plate tectonics are heavily influenced by the earth’s molten layer, which appears to stay molten because of friction during the earth’s rotation (which would be much less). So, I guess plate movement would slow and some of the molten layer would harden. Seems to me, plants would have to evolve (you didn’t say how gradually the earth’s rotation would change, hypothetically) to store energy for when it was “night” for 2 weeks. Strictly diurnal and nocturnal animals would have a rough time; I think most animals would have to adapt to both a day and night existence, like humans can do. I think the moon would also slow it’s revolution around the earth (which would wreak havoc with the tides), although it would stay locked to the earth such that we would still not see the far side of the moon (in time, all moons eventually do this to their planets).

Quite a can of worms you’ve opened up. Frankly, I think the planet would be screwed under those conditions regardless of how gradual the process was. Know something?

The primary effects would be on the atmosphere and climate, not so much because of the reduction of speed (although that would reduce the pressure gradient due to the much reduced Coriolis effect from slower rotation) but because the slower rotation (which would increase the length of the day to about 800 hours) would result in the atmosphere seeing more extreme heating rates. The solar-facing side will become hotter as it isn’t able to radiate away heat, and the far face will get colder. This will cause a larger temperature differential that will drive equatorial winds. This would obviously have significant (and hard to predict) effects on the biosphere, especially due to radical alterations in jet stream and ocean current dynamics. I doubt there would be much if any effect on plate tectonics, provided that the rotation of the Earth’s core slowed down proportional to the equatorial rotation, though it is possible that the lower overall rate of rotation might disrupt convection currents in the mantle.

Stranger

I stopped in to say that I just saw this on the science channel a few days ago. Then I thought that saying so would be rude to the OP and all who didn’t see it.

Very interesting stuff. Carry on.

Looks like I’m gonna need a new watch.

And calendar.

And this time, you really did pick the wrong day to quit smoking.

Since we make a software product the displays a composite rendered view of the world as your desktop picture, and updates in real time (showing day/night areas), we’d have to release a new version. If the rate of slowing was not predictable, we’d have to probably switch to a subscription system.

Thanks all! Got some laughs too… bonus!

Hey Desert Nomad, you wouldn’t happen to be EarthDesk guy, would ya?!

I’m researching as much hard science as I can get to see if it’s worthy of a screenplay idea I have. I’m curious, since Stranger On A Train’s comments were very close to what I had figured, so that’s good news. Yet, it only spawns more questions:

If the day side was inhospitably hot, and the night side likewise cold, might the Terminator (I can feel the Arnold jokes coming already), the penumbra zone between night and day, be a constantly moving safe haven, if you could keep up with the 30 mph rotation?

Or might this zone be a roiling torrent of weather phenomenon, the likes never been seen.

One more: The oceans. Would the increased 2 weeks of direct sunlight, and say 220°F atmosphere boil away most of the water? If so, would this render our atmosphere unbreathable?

Claude Remains: what show was that called? I’d love to try and track it down!

Sorry, not the science channel. National Geographic. Aftermath -When the earth stops spinning.

The oceans would distribute due to the lower centrifugal force. Here’s a mapshowing our new oceanic layout if the earth were to stop rotating altogether. It shows the oceans at the poles and an equatorial continent. Such a dramatic slowdown might create a situation almost as bad as this.

Ohhh, that’s good stuff. Very interesting to look at the planet we’re so familiar with in a new but scientific light, no matter how unlikely. Also, according to this, my house is now at the bottom of an ocean. I never get to live to see the apocalypse!

Also, thanks Claude R!

One thing I wonder about that map is where the new rivers would be. Would the equatorial continent be desert or would the new weather patterns still result in rainfall in the lower latitudes? I think that the increased land area would generate higher temps from solar heating that would generate low pressure zones straddling the equator. This would suck in winds from the polar regions maybe carrying water. I don’t know how wet the winds would be coming from the colder regions, though.

Snipers would have to modify their techniques: http://boards.straightdope.com/sdmb/showthread.php?t=568406&highlight=sniper