Why is the outcome of a coin toss random? That is, why is the probability of heads 1/2 for a fair coin? Since the coin toss is a physical phenomenon governed by Newtonian mechanics, the question requires one to link probability and physics via a mathematical and statistical description of the coin’s motion. However, that is not typically how one approaches the question. An empirical approach based on repeated experiments might suggest that the result is approximately correct. Another route is based on symmetry; since a coin of zero thickness can land on either of two equivalent faces, the probabilities for each must be the same. But such is clearly not always true. For example, a coin that does not flip even once will end up the same way it started. And even if it flips, it might not do so frequently; instead, it could wobble like a Frisbee and...

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