Astronomy
The Moon
Planet Earth

Is it possible to stop Earth's rotation and if so how?

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Answer

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Wiki User
01/19/2007

It would be extremely difficult. You would have to somehow put an unbalanced force opposite the initial direction of rotation. I can think of two ways to do that: 1: direct an external body into a location on the surface so that the combined system would have zero angular momentum 2: Use a mass driver to throw mass away from the earth at high speed. For option 1, you might be able to run an asteroid . The second moment of the earth is something like 10^38 kg

User Avatar
Wiki User
01/19/2007

It would be extremely difficult. You would have to somehow put an unbalanced force opposite the initial direction of rotation. I can think of two ways to do that: 1: direct an external body into a location on the surface so that the combined system would have zero angular momentum 2: Use a mass driver to throw mass away from the earth at high speed. For option 1, you might be able to run an asteroid . The second moment of the earth is something like 10^38 kg·m2, and its angular velocity is 2*pi/86400 radians/sec. An "asteroid" with a mass of, say 10% of the earth would have to impart an opposite angular momentum, so it could have a velocity rmv = I*omega v= 10^38 kg·m2 * 2*pi/86400 rad/sec / (6.4 e6 m * 0.1 * 6x10^24 kg) which is a mere 1.9 km/s, if my calculations are correct. So you could probably get better results with an asteroid that is 1% of the mass of the earth, but had velocity of 19 km/s, about how fast the earth moves around the sun. Ceres has a mass much less than this(1x10^21 kg vs 5x10^24 kg), so it would have to be tossed in appropriately faster. This is all vector stuff, so you would have to get it in just the right direction, too. For example, it could fly fly in from due east and crash into Venezuela, thereby stopping the rotation of the earth and ending the regime of of Hugo Chavez. The benefits of either of these effects are left as an exercise to the student. It would seem that this probably happened to Venus at some time in the past, since it has basically no rotational angular momentum now. Very strange. The other alternative could be enacted by building a string of nuclear generating stations along the equator, then using them to toss mass eastward into space. Suppose you tossed mass out in 1 kg pills at somewhat above escape velocity, say 10 km/s for the sake of argument. Since the station is 6400 km from the axis of the earth, then each would take away rmv=6400 km * 1 kg * 10 km/s = 64x10^9 kg m2 of angular momentum. You would need to toss off N = I*omega/h = 1.14e23 of these things to stop the earth. The energy required to accelerate them would be 1/2 mv2 = 50 MJ. Since a decent nuke plant can generate about 1 GJ/s, one reactor could generate enough to fire off 20 projectiles a second. Tossing off 1.14e23 of them would take about 180 quadrillion years, or about 10000 times as long as the universe has been around. The value of this exercise has also not been demonstrated.