4 ms·

Another theory is that we're being visited be entities from a parallel dimension.

• api 9y ago
  The ET speculation is the most popular because we know for a fact that other stars and other planets around those stars exist and we know for a fact that it's (theoretically) possible to travel between at least nearby stars with sufficient technology. We do not know for a fact that time travel is possible and there are good physics-based reasons to think it isn't. We definitely don't know that there are parallel dimensions or universes that are actually inhabitable. Dimensions and parallel universes may be mathematical artifacts. In math a dimension is just a degree of freedom. A penny is five-dimensional if you count temperature and electrical charge as dimensions. Another speculation you run into is the "ultra-terrestrial" idea-- that they might be from Earth itself. Maybe they live deep underground or under the ocean, etc. This one is pretty implausible too. I could believe that there are unknown species, sure, but not an unknown species with an industrial infrastructure capable of producing flying machines. No way. Even deep underground we'd detect its vibration and EM emissions. So yeah, space aliens are the most reasonable hypothesis if these things were to actually be artificial and not made by humans. That's the big "if" of course. Like I said elsewhere there's some intriguing evidence out there but nowhere near enough to draw such a conclusion.