# Physics Reduced to Probability

Philosophers have said that if the same circumstances don't always produce the same results, predictions are impossible and science will collapse. Here is a circumstance—identical photons are always coming down in the same direction to the piece of glass—that produces different results. We cannot predict whether a given photon will arrive at A or B. All we can predict is that out of 100 photons that come down, an average of 4 will be reflected by the front surface. Does this mean that physics, a science of great exactitude, has been reduced to calculating only the probability of an event, and not predicting exactly what will happen? Yes. That's a retreat, but that's the way it is: Nature permits us to calculate only probabilities. Yet science has not collapsed.

## Notes:

Feynman explains that probabilities are the best we can hope for in complex systems.

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QED: The Strange Theory Of Light And Matter
Books, Brochures, and Chapters>Book:  Feynman, Richard (1985), QED: The Strange Theory Of Light And Matter, Universities Press, Retrieved on 2012-05-16