Wikipedia says it uses 16.56 megawatts. Would that really be trivial to add? I assume it could be done with enough modifications but it doesn’t sounds trivial or like it could go very far without running out of diesel.
That’s equivalent to about 5 freight locomotives. Shouldn’t be difficult to add to a machine of that size.
Come to think of it, I think qpw3141 really meant to say permanently attached, not rigidly.
In looking for the upper limit, can anyone calculate the mass and force produced in the wheels necessary to begin altering the rotation of the earth? I would think at some point the earth would turn into a tread mill. (avoiding follow-up question if that could happen).
A little inch-long battery-powered toy will do that. You’re going to need to specify how much of an effect on the rotation you want.
Did anyone else think instantly The Inverted World by Priest… you know, moving city and all that?
I’m guessing the upper limit comes when a significant portion of the planet is moving… but I can’t imagine why would you ever need to build a vehicle that masses even a single percentage of the planet’s mass.
Let’s say a vehicle on the equator heading due east, that would stop the earth’s rotation in less than 1 year. Let’s assume that such a landcraft could run underwater so the oceans are a constraint. Maybe something that big would stick out of the water anyway.
Another approach might be to head towards a pole, and induce longitudal rotation in less than 1 year.
Pick any time frame thats convenient to use. And forget about the giant ruts left over, we can assume there’s enough wheels of sufficient width to keep it from digging through the earth. Also assume everyone in China is not running in the opposite direction:)
The limiting factor in the design of wheeled vehicles is the tires. They must be shipped from the factory as one unit. So they have to get on trucks, under bridges and through tunnels. If you go with a treaded tank or bulldozer, you would need a lot more power, but could build bigger.
What’s the year for? How long the vehicle continues moving is irrelevant. Angular momentum is conserved, so while the vehicle is moving east, the Earth’s rotation is slowed (by an amount depending both on the vehicle’s mass and on its speed), and when the vehicle stops, the Earth’s rotation speeds back up again.
Actually, I should include more information: If the vehicle is moving at the same speed as the rotation at the equator (a little more than a thousand MPH), and you want to stop the Earth’s rotation (transferring all of the angular momentum to the vehicle), it needs to be 2/5 the mass of the Earth. You can decrease the needed mass by increasing the speed by the same proportion, or vice-versa (so, for instance, at 500 MPH it would take 4/5 the mass of the Earth).
Good heavens, Holmes! :eek:
True for pneumatic tires. You could fabricate steel wheels from components. (I’m thinking of one of those old steam-powered tractors.)
Okay, so that’s where the earth would stop rotating, relative to something in a concentric orbit around the sun? And then the ‘truck’ moving any faster would cause the earth to rotate in the opposite direction of the trucks travel, at the speed of the increase in the speed of the truck? i.e, the 4/5 earth mass truck at 600mph would have the earth rotating ‘backward’ at, hmm, was going to go with 100mph, but it seems like it would be 50mph. There really is no treadmill where the truck would seem stationary relative to the thing in concentric orbit is there?
All those of you thinking about stopping the Earth over a significant period of time are missing a very important point:
You only change the rotation of the Earth whilst accelerating.
Once you are up to your maximum speed all the energy input from your engines goes to overcoming friction and air resistance. The friction component will simply result in extra heat whilst the air resistance element will result in further turning motion. But, because drag is non linear wrt speed, you’ll need quite a lot of speed to make any difference in anything other than geological time.
Longest train in the world. An iron-ore train in Australia with eight locomotives and 682 loaded cars massing almost 100 000 tonnes total, all controlled by one person.
In geological time there will be no change to the Earth’s rotation unless moving material is either received from or ejected to outer space. For as long as something is in motion there can be a temporary change, but that motion pretty much has to cease eventually.
That’s just hilariously long.
“Must be nearly finished now”
“No, no there’s still another five minutes on the video.”
Wrong!
For example, See here. This doesn’t deal with the case in point but does indicate one way in which the Earth slows down without gain or loss of material.
If you consider a perfectly spherical planet with an atmosphere but nothing else except one car continually moving in the same direction around the equator, the car will necessarily be causing a reaction in the planet as it uses power to overcome air resistance. The ‘lost’ power will be converted into heat which will either make the atmosphere hotter or be radiated away, but the result of the force applied to the planet is cumulative.
No. Even in the case you describe, angular momentum is still conserved. In the case of the earth’s rotation slowing from the moon’s tidal drag, the drag from the earth’s rotation is causing the moon to be slowly pushed into a higher orbit. The total angular momentum of the earth-moon system is staying the same even though the earth is slowing down. In the case of a train driving around the equator forever the force from the train pushing against the rails to overcome air resistance is balanced by drag forces from the air accelerated by the train pushing against the planet.
Look at the preceding posts more carefully.
I said that the rate of the earths rotation can change without matter being gained or lost, not that angular momentum is not conserved.
That I would agree with. Although any heating of the air by the train as it move through it will result in fairly random changes of molecular motion they must at some point all resolve to exactly balance.