# Reversing the direction of the Earth's spin...

I know that we’ve already had two threads closed on a similar subject, but I actually would like to reverse the spin of the Earth for purely aesthetic reasons (my bedroom window faces West, and I’d prefer to see the sunrise there in the morning).

How much energy will I have to expend to reverse the rotation of the Earth? Assuming that I do this over a period of 1 week, How much trouble can I expect with things like plate tectonics, tides, weather etc?

Are there any other problems that I should be aware of before embarking on this?

[sub]NB: please do not hijack this thread in the direction that caused the last two to get closed.[/sub]

The rotational kinetic energy is E = ½ I [symbol]w[/symbol][sup]2[/sup] where I is the moment of inertia (rotational inertia) and omega is the angular speed. In the case of the earth that works out to about 2 × 10[sup]29[/sup] joule, unless I did something wrong. (I got the figures for I and omega from the CRC Handbook.) That’s how much work you would have to do to stop the rotation of the earth. You need to do that much again to reverse the spin, for a total of about 4 × 10[sup]29[/sup] joule.

Thanks **bibliophage[/] - I think I’m right in saying that this equates to roughly 1.1112 x 10[sup]22[/sup] Kilowatt-hours, or, over the course of the project (1 week), I’ll need a power source capable of supplying 6.7 x 10[sup]22[/sup] watts - that’s going to be quite a thick wire.

Plus, that’s the net energy you’ll need, not counting heat loss, inefficiency of your motor or whatever method you’ll be using.

I think, for the sake of economy, I may how to consider storing some of the energy of the current spin direction so that it can be used for spinning it up the other way.

I think, for the sake of economy, I may have to consider storing some of the energy of the current spin direction so that it can be used for spinning it up the other way.

Like a giant rubber band? Assuming you had a stable anchor in space, what would you attach the other end to? You would need to loop it around some kind of large geological feature like a mountain with a really wide base, near the equator, that wouldn’t snap off.

I don’t have anything real to add, but in case you were wondering how to compute the value for, say, some other planetoid, here’s how you do it.

The moment of inertia I = A M R[sup]2[/sup], where M is the mass of the body, R is the radius, and A is some constant that depends on the mass distribution, or shape of the object. For instance, a cube will have a different value of A than a sphere will. For a sphere of uniform density, A = 2/5 = 0.4. For something like the Earth, where the mass is more centrally located (because of the dense core), it will be less. Not a whole lot less; around 0.33.

Omega in metric is easy to compute. It’s 2 pi / T, where T is the period of revolution, or one day = 86400 s.

I’m guessing it’s more energy than you’d need to expend to rotate your house 180 degrees…

Yes, but then the front door would open into the back garden, so I figure it’s easier to leave the house where it is.

That will be a challenge without a fixed structure to work from. Bathtub genius Archimedes said he could move the earth with a long enough lever and a place to stand. The lever isn’t so hard but the bitch if finding a place to stand. I can put a coil spring on the floor and drop a rock on it and the rock will bounce up nicely on the returned energy from the spring. With the same spring suspended in space it’s a different matter. You’ll have to expend a significant amount of energy to keep the energy return device, be it spring, rubber band or hamster wheel, in place against the opposing force. That may come from rocket motors or Superman’s morning bowl of wheaties but it’s a significant hurdle.

The one week time period is a problem. If you could wait a little longer, you might be able to begin diverting the paths of large asteroids, causing them to impact the equator in the opposite direction of the current spin of the earth. You get a lot of free energy, because the asteroids already have massive potential energy, and you need only expend enough energy to divert them to the proper path to impact the earth in the right direction. It will probably take a while to find enough asteriods to do the job, and the effects on the planet might be contrary to some of your goals (i.e., the sunrise might not be visible, due to the extended pall of darkness caused by the dust and debris in the atmosphere after the impacts; also, if you don’t aim right, you might destroy your home state). But hey, no pain, no gain.

Shelbo: Why not just use the moon? That might be big enough to do it…

Oh, and Mangetout, since you asked about other things you’d have to watch out for: This would seriously mess up all sorts of migratory patterns, which would get all the environmentalists in a downright tizzy.

Wouldn’t it be alot easier to just flip the planet over? Why do you kids always have to do things the hard way?

Redo the interior of your house. I don’t want the sun in my window in the morning.

I wonder if using the moon is a good idea. How much rotational energy could we harvest from the moon if we had a big rubber band attaching the earth to the moon? And which way would the moon be rotating when the effort was complete?

And as a follow-up to Beelzebubba’s question, would the energy required overcome the gyroscopic force of the spinning earth in flipping it pole to pole be the same as that required to just make it spin the other way?

Hijack, but not the one you are thinking of.

If someone really wanted to try this, would they be breaking any laws, including international law?

410[sup]29[/sup] joules of energy correspond to an energy equivalent of (very roughly) four billion metric tons, correspodning to four billion cubic metres of water. Given the total surface of the world’s oceans, about 360 million square kilometres or 36010[sup]12[/sup] square metres, this would (if we had a 100 per cent efficient mass-energy converter and decided to sacrifice some H[sub]2[/sub]O for this noble goal) reduce the global sea level by about 0.01 millimetres, which we could easily afford.

Dunno, but James Bond and his 18 year old geologist chick Gravity McSlutrock would show up. I suggest hiring Oddjob and Jaws.

The major problem isn’t the energy scales but what to do about the angular momentum. That’s what’s really hard about this project. You need to get something that will essentially delete the angular momentum of Earth. The lever idea would work in principle, but you’d have to get it spinning at quite a tangential velocity to actually get enough torque to change the planet’s momentum. I’m not sure I can think of an easy way to approach this problem. Nature certainly hasn’t thought of one since we’ve been happily spinning at a rather appreciable rate for nearly 5 billion years. And before anybody says it: I know that the Earth is slowly spinning down… but if the timescale that Mama Nature does things on are billions of years how are we going to ever hope to accomplish this task in a whimpy human lifetime? Or even a whimpy human-species lifetime?