slow earth

What would happen if the earth’s rotation slowed noticably?
Earthquakes?
Warming?

Days and nights would be a lot longer, for one…

The Earth isn’t a solid object, in fact the crust is in many ways bit like the skin on custard; unless the slowing force was applied evenly (somehow) to everything - solid and liquid components, including the oceans, I suppose), there would be a tendency for the unslowed bits to keep moving, which would be really nasty; oceans would slop out of their basins forming huse Tsunamis, mountain ranges would buckle, deform, split and topple, huge rifts would be torn in the crust, waves of magma would slop out of cracks in the Earth.

If a way was found to slow just the planet evenly and fairly quickly, anything not bolted down and anything tall and not designed to cope with shear forces would fall over, but this would be a one-time event - when the planet was again turning at a constant speed, there would be no noticeable lateral forces.

Once the Earth had been slowed down, days and nights would be longer (although seasons and years would be the same length) - extended daytime would mean that things got a chance to really heat up and possibly boil, extended nighttime would allow things to really cool down and possibly freeze, but this would likely have a very significant effect on the weather in general; the water cycle and atmospheric currents would be affected in ways I couldn’t begin to predict.

It would be a very serious event indeed and would result in extinction for a great many species, possibly including humans.

Oh, and your shopping would feel a little heavier (as indeed would you) - at the moment, the rotation results in centrifugal (or is it centripetal, I can never remember) force that tends to fling you away from the Earth just a little bit - with the rotation decreased, this force would be smaller and you would feel more of the Earth’s gravity.

:smack: Oh, no. Please don’t tell me you’ve been listening to Nancy! :smack:

It would seriously mess up all your installment loan contracts. You’d have to wait a long time for tomorrow’s paper. If you keep feeding your dog once a day, he won’t take it very well. Those plants that regulate their blooming and fruiting by the length of day would have to change something. Either they’d adapt to the new time, or there would be several growing seasons in a year. Couch potatoes would get a huge increase in the number of times they could watch MASH every day. :stuck_out_tongue:

In addition to weather changes mentioned by Mangetout, there would be the Earthquakes you suspected. The Earth is oblate (fatter at the equator than across the poles) due to it’s rotation. The “natural” oblateness would be less for a more slowly spinning Earth, and it would slump back towards a smaller oblateness, leading to Earthquakes.

Actually, it wouldn’t just shift back into a less oblate form, but it would overshoot that form and oscillate back and forth a bit, which would be worse for the inhabitants.

For the record, Earth has been slowing down through geologic time, thanks to friction from the tidal forces that the Moon exterts on the Earth. The Moon’s gravitational attraction produces tidal bulges in the Earth, both in the oceans and in solid rock, on the sides of Earth closest and furthest away from the Moon. (See the link for an illustration of the effect.) But since the Earth is rotating around its axis (24 hours) faster than the Moon is revolving around the Earth (1 lunar month, about 28 days), the Moon creates a drag that slows down the Earth’s rotation rate. That loss of spin (angular momentum) from the Earth has to be transferred somewhere (a law of physics!), so the Earth’s loss is the Moon’s gain - and the increase in angular momentum for the Moon is accommodated by an increase in the size of the Moon’s orbit. For an everyday example of this, think of a spinning ice skater - as long as her arms are held close to her body (= Moon orbiting close to Earth) she can spin quite fast, but if she extends her arms (=Moon orbiting further from Earth) she will end up spinning more slowly.

So, in a nutshell - Earth’s rotation speed slows down as the Moon’s distance from Earth increases.

Now, normally this process is very slow; Earth’s day has lengthened only 2 hours (to the current 24) over the last 400 million years. The sort of catastrophe vanilla seems to be thinking about would probably be most “easily” accomplished by increasing the Moon’s orbit drastically - maybe through collision with an asteroid, or perhaps gross negligence on the part of humans (cue music). :wink:

It’s not terribly likely to happen, but the short-term effects would be pretty unpleasant along the coastlines as the oceans sloshed about before finding their new equilibrium state. Since the solid earth tide involves deformation measurable at the scale of centimeters, I would expect earthquakes, but nothing quite so dramatic as mountain ranges buckling, toppling, etc. After the initial trauma of large-scale momentum transfer to the Moon, the daily tidal ranges on Earth would diminish considerably.

Now, weather and climate would be profoundly changed, since the Earth’s angular momentum plays a major role in driving the circulation of the atmosphere (i.e., wind patterns), especially with regard to moving heat from the tropics toward the poles, and the movement of energy along bands of latitude. Zonal winds, like the trade winds and jet streams, would weaken. The longer days would mean greater extremes of day and nighttime temperatures, especially over land, since land doesn’t absorb and retain heat the way the oceans do. There would also likely be changes in storm tracks (the typical paths storms would take), and possibly heavy-duty storms as a matter of course along the day-night divide (a result of sharply contrasting temperatures in air masses from either side of the divide). Not a lot of fun. Plus, the changes in weather and climate would have a major impact on agriculture, and not for the better.

And as AskNott and others have pointed out, there are some more immediate logistical issues involved in having a longer day. What do we call the fourth meal of the day? Remember, the length of the year hasn’t changed (presumably), so what days would you like to axe out of the calendar? How long a workday do you want to have, assuming that you’re not working some sort of progressive shift? Sure, you could sleep longer too, but still… On the plus side, though, if you wanted to party all night, you would have more time to do that. :smiley:

Just to clarify (I’m certain you understood me anyway), my comment in this direction was in the context of applying some sort of braking force to, say, the Earth’s crust, *but not the mantle etc) - attempting that (if it were possible) would pretty much peel the crust off the face of the planet.

[Quick hijack] How fast would the Earth have to rotate for the centrifugal force to overcome gravity and send us all flying off into space?

Since the escape velocity at the earth’s surface is 25,000 mph, and the equator rotates at about 1000 mph, the earth would have to be sped up about 25 times for people to fly off. It would have to spin faster for people to be thrown off from higher latitudes.

Note that the crust and oceans would also fly off into space.

For the record, there’s no such thing as a centrifugal force, meaning that it isn’t a real force. It’s actually an inertial effect, but the imaginary “centrifugal” force is usually introduced when analyzing the system in a rotating reference frame, and it offsets the centripetal force (in this case, gravity). In fact, there is no centrifugal force at the poles of the earth (in specific, the poles of the rotational axis, not magnetic north), as it’s always perpendicular to the axis of rotation. So if you want to know what it would feel like if the earth slowed down, go visit Antarctica.

There’s a good explanation of this here.

I understand, and I was just thinking of ways one might brake the Earth more “gently.” If we ever encountered anything that would slow the Earth in the manner you described, I think watching the crust rumple up like a rug might be the least of our worries. :smiley:

You probably don’t refer to a certain dinosaur as a brontosaurus, either, do you?

Since people are talking about Earth’s rotation, a small question for anyone knowing this: If you are standing directly on the top of the planet(rotation axis), would you notice any difference compared to standing on the equator. This icnluded movement of stars, weight, anything difference between the two places besides temperature.

I admit right now that this is badly worded so feel free to ask for clarification or slap me.

I’m not the kind of guy who would slap a road for clarification. It’s not sporting. And it’s just…not right. I’m not running for office, even. I’m a catch-and-release guy when it comes to roads, even on Highway Sixty-One.

You seem to be saying here that moving the Moon to a higher orbit by hitting it with an asteroid would cause the Earth’s rotation to slow, but that’s not correct. The interaction between the Moon and Earth that’s slowing down the Earth isn’t going to somehow be sped up by hitting the Moon with an asteroid.

All of you have forgotten the most interesting side effect would be the slowing of time. Relative to someone standing still in space, time for those on the surface of the Earth would slow to a rate directly proportional to the slowing of the Earths rotation. If you somehow managed to actually reverse the rotation of the Earth, you would reverse time itself. Of course all of us on Earth would be oblivious, but it is still interesting to consider.

I’m admittedly reaching here for some means of dramatically changing the distance between the Earth and Moon in a short time. AFAIK, though, displacing the Moon to a higher orbit by any means - asteroid impact, the hand of Q, the Asgard getting a sense of humor, whatever :slight_smile: - would increase the tidal drag on the Earth and force a slowing of its rotation rate.

Now, if an asteroid impact were to push the Moon into a higher orbit, granted it would have to be an awfully big one. (You’re right in saying that a “normal” impact wouldn’t have any effect.) In that case we are back to worrying about all sorts of fallout apart from a simple lengthening of the day. That kind of fallout would be a by-product of the impact, though, not the lengthening of the day in and of itself.

Muad’Dib - you’re kidding, right?