Extraterrestrial hypothesis (Ufology)

The extraterrestrial hypothesis (ETH) is a position in ufology that proposes UFOs constitute contact with beings that exist in the same physical dimension as human beings, and come to Earth from other planets and distant galaxies in spacecraft. This "nuts and bolts" ufology is distinguished from the interdimensional hypothesis, which holds that such beings are from alternate dimensions that coexist separately from but alongside our own (similar to ghosts), sometimes denigrated as "new age" ufology.