|This article or section may contain previously unpublished synthesis of published material that conveys ideas not attributable to the original sources. (March 2009)|
The interdimensional hypothesis (IDH or IH), also called the extradimensional hypothesis (EDH), is an advanced theory by Jacques Vallée that says unidentified flying objects (UFOs) and related events involve visitations from other "realities" or "dimensions" that coexist separately alongside our own. It is an alternative to the extraterrestrial hypothesis (ETH).
IDH also holds that UFOs are a modern manifestation of a phenomenon that has occurred throughout recorded human history, which in prior ages were ascribed to mythological or supernatural creatures.
A video manifestation recorded in the Denver CO metro area November 8, 2012 may prove evidence of the IDH hypothesis.
Directly quoting FOX 31 News KDVR Denver, Colorado:
"Mile High mystery: UFO sightings in sky over Denver
Posted on: 9:37 pm, November 8, 2012, by Heidi Hemmat, updated on: 02:58pm, January 30, 2012
"We wanted to verify the video we saw was legitimate and not doctored in anyway. So our photojournalist set up his camera in the same spot, and shot video from just before noon until just after 1:00 p.m. He also captured something unexplained on video."
What makes this a possible IDH event is that the UFO in question appears to fly directly into the Denver Metro area, either landing, or disappearing into the earth strata below the Denver Metro area, which would suggest that what is in fact taking place is an inter-dimensional shift of the UFO craft itself
Although ETH has remained the predominant explanation for UFOs by UFOlogists, some ufologists have abandoned it in favor of IDH. Paranormal researcher Brad Steiger wrote that "we are dealing with a multidimensional paraphysical phenomenon that is largely indigenous to planet Earth". Other UFOlogists, such as John Ankerberg and John Weldon, advocate IDH because it fits the explanation of UFOs as a spiritistic phenomenon. Commenting on the disparity between the ETH and the accounts that people have made of UFO encounters, Ankerberg and Weldon wrote "the UFO phenomenon simply does not behave like extraterrestrial visitors." In the book UFOs: Operation Trojan Horse published in 1970, John Keel linked UFOs to supernatural concepts such as ghosts and demons.
Also Jerome Clark was influenced by IDH but then he rejected this hypothesis and argued very cautiously in favor of the extraterrestrial hypothesis
The development of IDH as an alternative to ETH increased in the 1970s and 1980s with the publication of books by Vallée and J. Allen Hynek. In 1975, Vallée and Hynek advocated the hypothesis in The Edge of Reality: A Progress Report on Unidentified Flying Objects and further, in Vallée's 1979 book Messengers of Deception: UFO Contacts and Cults.
Some UFO proponents accepted IDH because the distance between stars makes interstellar travel impractical using conventional means and nobody had demonstrated an antigravity or faster-than-light travel hypothesis that could explain extraterrestrial machines. With IDH, it is unnecessary to explain any propulsion method because the IDH holds that UFOs are not spacecraft, but rather devices that travel between different realities.
One advantage of IDH proffered by Hilary Evans is its ability to explain the apparent ability of UFOs to appear and disappear from sight and radar; this is explained as the UFO entering and leaving our dimension ("materializing" and "dematerializing"). Moreover, Evans argues that if the other dimension is slightly more advanced than ours, or is our own future, this would explain the UFOs' tendency to represent near future technologies (airships in the 1890s, rockets and supersonic travel in the 1940s, etc.)
IDH is considered a belief system rather than a scientific hypothesis because it is not falsifiable through testing and experiment. Unlike ETH, it is not possible to verify IDH by experiment or by observation because there is no way to detect the alternative theories it postulates. IDH is evaluated by UFOlogists solely on the basis of how well it fits.
- Gary Bates (2005). Alien Intrusion. New Leaf Publishing Group. pp. 84–87,114–115,157–160,164. ISBN 0890514356. More than one of
- "History of UFOs". Funk & Wagnalls New Encyclopedia. World Almanac Education Group. 2006.
- Hugh Ross, Kenneth R. Samples, Mark Clark (June 1, 2002). Lights in the Sky & Little Green Men: A Rational Christian Look at Ufos and Extraterrestrials. NavPress Publishing Group. ISBN 1576832082. "While numerous mystical explanations have been proposed for UFOs, ufologists identify two distinct "otherworldly" hypotheses: the extradimensional hypothesis (ETH) and the interdimensional hypothesis (IDH)."
- "UFO Hunters - History of UFOs". the History Channel.
- Jacques Vallee (1980). Messengers of Deception: UFO Contacts and Cults. New York: Bantam Books.
- Steiger, Brad, Blue Book Files Released in Canadian UFO Report, Vol. 4, No. 4, 1977, p. 20
- John Ankerberg & John Weldon, The Facts on UFO's and Other Supernatural Phenomena, (Eugene, OR: Harvest House Publishers, 1992, pp10
- Steven J. Dick (1999). The Biological Universe. Cambridge University Press. pp. 313–320. ISBN 052166361X. More than one of
- David Hatcher Childress (1990). Anti-Gravity and the Unified Field. Adventures Unlimited Press. p. 134. ISBN 0932813100. More than one of
- Hilary Evans (1979). UFOs: The Greatest Mystery. Chartwell Books. p. 91.
Further reading 
- David Jacobs (December 1992). "J. Allen Hynek and the Problem of UFOs". History of Science Society Meeting, Washington D.C. p. 16.
- J. Allen Hynek and Jacques Vallée, ed. (1975). The Edge of Reality: A Progress Report on Unidentified Flying Objects. Chicago: Henry Regnery.
- Jacques Vallée (1980). Messengers of Deception: UFO Contacts and Cults. New York: Bantam Books.