Fortean Picture Library
In a 1950 monograph California occultist N. Meade Layne proposed that UFOs and their occupants come here not from other planets but from another order of reality. Layne called this place Etheria and declared that it surrounds us yet is usually invisible.
Psychically inclined individuals are most attuned to it, but some of its manifestations, such as flying saucers, can be seen by anyone. The saucers can materialize and dematerialize; at certain stages they are "jelly-like," enabling them to "change in shape and apparent size." Layne's theory, at least in general, would survive to be championed by ufologists (most notably John Keel and Jacques Vallée).