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Do photons expand spherically as they travel?  That is, do they project outward as a sort of bubble?  If so, when do they burst?

> Do photons expand spherically as they travel?
Thus, your next two questions are moot.

The best way to view a photon -- indeed, to view any fundamental particle -- is as a point-size entity.

The photons, that are part of the cosmic microwave background radiation, arrive at our Earth after having traveled for about 13 billion years without much with matter. When they arrive at our planet, they are no larger than when they broke "free" from the nucleon electron soup about 377,000 years after the Big Bang.


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Have been fascinated by physical laws ever since I learned, at age seven, that magnets work under water. My study continued through college and has not ceased even after I retired.

B.A. in Physics (with honors) from University of California at Berkeley.M.A. in Physics (with honors) from University of Texas Austin.

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