How can a particle that has no mass like a photon have an effect on another object?
Like in radiotherapy, where you shoot at cancer cells with photons using an accelerator.
Why does the photon destroy the cancer cell? If the photons mass is zero, shouldn't it be irrelevant how fast you get it to move, since the mass is zero?
Imagine something hits you that weighs absolutely nothing. How can something that weighs nothing transfer energy to you?