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Q & A: conserved angular momentum

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Most recent answer: 03/10/2009
Q:
Is it true that the total momentum of the universe is conserved? If yes, would this mean that if I start rotating about an axis, there would be some movement to conserve this momentum due to my rotation? Could this validate the fact that there is an exact " reverse copy" of our universe made up of antimatter? (I know it sounds wierd but please answer this) Thanks
- Nimish (age 17)
Mumbai, India
A:
I think you're asking about angular momentum, not momentum, since you want to know what happens when you rotate. It certainly seems, both on the basis of theory and experiment, that it's conserved. So if you start rotating, something else nearby picks up the opposite angular momentum. In a typical case, you might be on a spinning stool and push the walls to rotate it. In the process you give the whole Earth a little spin the opposite way.

 As for whether there are any exact antimatter copy universes, I don't know. I don't think it depends much on whether angular momentum is conserved, but rather on whether there are multiple universes at all, and on the role of time-irreversible processes in setting up particular matter configurations.

Mike W.

(published on 03/10/2009)

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