Dark energy; are there now believed to be 5 fundamental forces?
Good question. As far as I now no one considers dark energy as a 5th fundamental force. I think the reason being is that dark energy is more of an observation. That is the universe is expanding at ever increasing rate and so where does this extra energy come from?? We don’t know, which is why it’s called dark energy. So there aren’t any theories out (that I know of) to explain how dark energy works, rather it’s just there and we don’t really have an explanation for it. So without a theory it’s hard to call it a fundamental force. Edit: The problem with saying that dark energy is a 5th fundamental force, as I have stated, is that it’s not well understood. For instance, as has been stated, it’s possible that gravity could account for this. All masses that we experience all have “positive” mass and thus all attract to each other. If negative mass exists (which is HIGHLY hypothetical) then gravity might be able to explain the expansion of the universe because perhaps there are clumps of ne
