Metaphysics means ‘greater physics’. Many cosmology speculations are metaphysical by default; there are no certain answers yet (such as a complete explanation of how gravity works). Some theories are taken as fact and are just physics. If one wants to consider metaphysical questions it should be possible to have some solid ground for cosmological physics to work from. What about something as well gone over as general and special relativity?
When people explain special relativity they tend to say that the effects are mostly illusory. That is, neither individual in the twins paradox experiences change subjectively, though comparatively one ages slower than the other as he travels near light speed.
Yet when the special theory is given flesh and blood in the general theory, an individual should experience mass as virtually increasing towards infinite as he approaches the speed of light. It should be comparable to the way a bicycle rider experiences increased resistance when he rides into a headwind as he pedals harder.
I may be way off about this. It may be that I have too much general theory and quantum cosmology stuff in mind. I should say that occasionally I write science fiction, so I am trying to be correct about that. I cannot find anything about it.
For some reason I got the idea that traveling faster through the fields of the Universe- including gravity and electromagnetism- made one experience those fields faster with increasingly shorter intervals-My understanding-that may well be incorrect, is that if a Lorentz invariant is “a temporal separation between two events”, then a traveler crossing through different elements/spaces of a field such as may exist in the Universe containing all other fields the Higgs perhaps) would encounter the strength of those field elements closer together with increased speed, temporally, and approaching the speed of light, the virtual addition to the traveler’s mass would be infinite.
That is why photons need be massless to travel at light speed. Gravity waves travel at light speed too. Steady state, decohered quanta approaching light speed have a ‘virtual’ mass increase that is added to them by virtue of traveling so quickly through the field. I thought the general theory added empirical content to the special theory among other things.