I read EM waves carry momentum and can exert pressure, if this is the case can ejecting them be used to generate thrust? Radiation pressure is cited as a real thing but I read about the EM drive and it was shown to not generate measurable thrust.
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1$\begingroup$ en.wikipedia.org/wiki/Photon_rocket $\endgroup$– GhosterCommented Apr 22, 2023 at 6:16
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1$\begingroup$ en.wikipedia.org/wiki/Radiation_pressure $\endgroup$– GhosterCommented Apr 22, 2023 at 6:18
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$\begingroup$ The reason the EM drive doesn't work is because it's a closed system photons neither enter nor leave, so momentum conservation implies it won't accelerate even though photons have momentum. $\endgroup$– J.G.Commented Apr 22, 2023 at 6:55
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The energy of EM waves can be demonstrated in the Compton effect when looking at electron scattering, hence the energy is given by $E= \frac{hc}{\lambda}$. So technically, yes, there is momentum and we know that momentum is conserved with interactions. However, given Plank's constant and the wavelength, the energy of the EM wave would not be enough to generate measureable thrust in terms of a traditional rocket taking off from earth. There are concepts of the energy being utilised in Solar Sails and Laser projection however this is still a developing concept.
If you would like more information I would recommend: (1) https://phys.libretexts.org/Bookshelves/University_Physics/Book%3A_Physics_(Boundless)/23%3A_Electromagnetic_Waves/23.2%3A_Electromagnetic_Waves_and_their_Properties
(2) https://scholar.harvard.edu/files/david-morin/files/waves_electromagnetic.pdf
