As far as I can see, the exchange particle involved in gravitational forces is the graviton. However, in the markscheme for both the original and revised EDEXCEL A-Level Physics PHY3 Topics Paper (topic C) it states that it is the photon. Which is correct, or are both correct? Why is there this difference? The question states: "List the other fundamental interactions. Circle the one for which the photon is the exchange particle." The markscheme says Weak, Electromagnetic, Gravitational, Gravitational Circled. I thought the photon was exchanged between two electrons interacting, which is what the Letts revision textbook says. Is this in fact a gravitational interaction? Surely its electrostatic! Im guessing I should learn it to be the photon, but this seems strange as most other sources I've found say its the graviton - including the revision textbook which covers the EDEXCEL syllabus. Can anyone help? Thanks!