# Can probability be relative?

Is it possible for the probability of an event to be relative, i. e. valued differently for different objective observers? Does this say anything pertinent about the feasibility of unifying quantum mechanics and relativity?

quasar987
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Just doing the calculations informally in my head, it seems to me, that for two inertial observers, of a same quantum phenomenon, the probability distribution is modified just so that an event happens at (x,t) in S with probability P, then it happens in at (x',t') in S' with the same probability, where (x',t') is related to (x,t) by a Lorentz transformation.

But what I don't understand is why you posted the question in the math forum. It is not the task of math to say what is and what is not physically possible. A mathematician just has to say "Let P1 be the probability of the event according to S and let P' be the probability of the event according to S'" and it's done.

quasar987,

On second thought, I should have posted this in the General Physics forum. Maybe a moderator will transfer it there.

quasar987
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Gold Member
You can always report your own post. Hit the Report button under your little medal name and say this post belongs in the GR forum. I do it all the time.

Probabilities can be different for two different observers if they have access to different prior information.

Look at Bayesian statistics and conditional probabilities.

Is it possible for the probability of an event to be relative, i. e. valued differently for different objective observers?

Please have a look at Bertrand's Paradox. Depending on the notion of randomness of the observer, the problem has three different answers.

My SWAG on Bertrand? Something to do with Aleph1 probabilities expressed as those of Aleph0.

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