> you could argue the same about dark matter/energy. Well, not really. The physical justification is, the multitude of observations that appear consistent with

> you could argue the same about dark matter/energy. Well, not really. The physical justification is, the multitude of observations that appear consistent with the theory that there is some form of matter out in space that does not interact with photons. It's not something someone just had a dream about one night - it's a real-world observation, with telescopes. If, tomorrow, a laboratory discovers a new or existing particle that is able to actually, or even just apparently, avoid interacting with photons and matter, then dark matter could be done and proven. By contrast, most dark matter competitors require us to rethink large swathes of what we know about physics and cosmology. That doesn't mean they're necessarily wrong, it just means the bar of skepticism is a bit higher.