| From one of the comments: "As soon as you start adding extra fields that couple to the gravitational field, you're no longer modifying gravity. You're doing something that is much closer to what dark matter is doing, with the only difference being that you're invoking an additional particle-free field rather than a field that does have particles. Which is frankly just weird because any field should be quantizable and thus any field should have something that looks like a particle, in principle. Your proposal would basically be to throw quantum mechanics out in order to explain the bullet cluster, which is frankly a lot more problematic than simply adding an extra field to the already existing ones." If I understand the gist of that, the whole argument for modified gravity being somehow simpler seems to go out the window. The author responded: "That's how it's called. Don't blame me for the terminology. Sure, the field should have particles if you quantize it, but at low energies the classical mean-field approximation should be good." It sounds like the Occam's Razor argument about modified gravity being better because it's just a revision of universal laws was conceded somewhere along the line, so why even bother? Edit:
From my lay perspective, I imagine it like this: we see dinosaur footprints appearing for no apparent reason. Dark matter theorists say it's invisible dinosaurs. Modified gravity theorists say (I thought) that the laws of gravity can be adjusted to explain it as a "natural" phenomenon. But now it sounds like they are saying there is a continuous field that happens to have significant amplitudes in the places that we would otherwise appear to have quantized invisible dinosaurs. But how does that explain at all the reason for the field having an amplitude here and not there? Why is it more pleasing or likely than distinct individual dinosaurs? It all seems like a bait and switch so ridiculous I feel like I must be misunderstanding grossly. |