I understand that it’s impossible to bring a photon to a state of rest, therefore impossible to collect them into a cup to weigh them and calculate their mass. A guy in a pub explained to me, quite smugly, that photons are just expressions of energy and that’s that. From my understanding solar sails would be just large surface areas being hit by photons, pushing the spacecraft in a desired direction, just like normal ship sails are being pushed by wind. But air particles do have mass. How could photons push the spacecraft if they don’t weigh anything?
In: Physics
Photons are massless, they have no weight. They do however have momentum, so solar sails are not sci-fi, they are very much real. An actual solar sail satellite that has flown [https://en.wikipedia.org/wiki/IKAROS](https://en.wikipedia.org/wiki/IKAROS)
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