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Many of us will be familiar with XKCD 162: Angular Momentum, in which someone spins counterclockwise to slow down the rotation of the earth and make the night longer.

The mass of an individual human is not all that much compared to the earth, so the gesture is poetic but futile. On the other hand, the mass of forty 3,300 pound cars driving counterclockwise is quite a lot more considerable.

How much does an individual NASCAR race affect the rotation of the earth? How much time does an individual NASCAR race remove from (or add to) the length of a day on our planet?

Let's assume we're operating on the Daytona International Speedway's not-quite-oval outer track which is oriented thus, with 200 laps of a 2.5 mile track made by forty cars weighing exactly 3,300 pounds each. The race lasts approximately three hours.

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I don't think it would. The main reason is that a car gains momentum (including, possibly angular) as it speeds up, but it must also relinquish that momentum again, when it slows down and stops.

So, I think it is, in theory, possible that the angular momentum of the Earth may be reduced very slightly when a NASCAR race starts; however, that momentum will be given back to the Earth again when it stops. Some momentum will be transferred to the surrounding air by frictional losses; however, I would also expect that to be eventually transferred back to the Earth, through the effects of friction between the air the Earth.

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