In A Nutshell
While both of these words are etymologically similar in terms of meaning “from beyond Earth,” they are used by conspiracy theorists and UFOlogists in markedly different ways. An extraterrestrial is generally considered to be an entity from beyond Earth but within the universe as we know it, such as from another planet or star system. Ultraterrestrials are beings who come from beyond the realm of human experience altogether, whether from a parallel universe, alternate dimension, or another plane of reality intersecting with our own. This theory is used to explain other strange phenomena that often accompany UFO sightings, such as time discrepancies, mysterious flying creatures, poltergeist activity, and mysterious Men in Black.
The Whole Bushel
Other than the null hypothesis that UFOs are based on the misidentification of mundane artificial and natural aerial phenomena, the most popular alternative explanation for UFOs is the extraterrestrial hypothesis (ETH). Indeed, when you say the word “UFO,” the image that pops into most people’s heads is that of a flying saucer piloted by strange, large-headed humanoids.
While often dismissed out of hand, ETH is bolstered by the fact many prominent scientists since the 1960s seriously considered that extraterrestrial life could be quite common throughout the universe.
Francis Drake developed the Drake equation, a mathematical model on the prevalence of extraterrestrial life, which takes into account variables such as the rate of galactic star formation, the fraction of stars with planets, the number of Earth-like planets per system, the fraction of such planets which will form life, the fraction of ecologies evolving intelligences, the fraction of ETI developing civilization, and the mean lifetime of an advanced civilization.
Some scientists investigating this problem assume ETIs are either rare, nonexistent, paranoid and isolationist, or simply disinterested in space exploration. However, others look at the Drake equation and the enormous number of star systems in our galaxies, as well as the time frames involved, and say that even by low-balling the variables, it is likely there are a staggering number of past and present extraterrestrial civilizations in the Milky Way. Assuming you dismiss the null hypothesis, as well as the hypothesis that UFOs are evidence of covert government or military technology, the ETI hypothesis could seem plausible.
There are, however, several serious objections to this idea, not least due to the vast distances involved and the fact that under our current understanding of the laws of physics, travel between solar systems would be highly difficult and impractical, if not completely impossible. The constraints of the speed of light would raise questions about why exactly aliens would spend centuries or millennia traveling to Earth to crash in deserts or mutilate cows.
If they had such technology, why wouldn’t they simply observe us from afar?
Another objection raised is that the stunning variety of different kinds of craft and beings which are reported are in UFOs. If ETI was true, this would seem to indicate that Earth is something of an interstellar tourism hub. There is also the objection that many UFOs are reported to engage in behavior or possess abilities that would be seemingly impossible for a physical object, like changing shape, splitting, merging, and dematerializing. Or take the fact the alleged behavior of UFO inhabitants often seems to resemble the behavior of beings of folklore such as fairies, jinn, and demons. This suggests a modern reinterpretation of ancient myths.
One of the other most prominent alternatives to ETH and the null hypothesis is the ultraterrestrial hypothesis. This hypothesis suggests that rather than originating from other star systems within our universe, UFOs are craft or phenomena originating from some form of “elsewhere,” such as another dimension, universe, or reality. This theory would allow the UFO phenomenon and its various incarnations and seeming contradictions to be addressed in a holistic manner.
It also suggests that UFOs are so difficult for us to get a grip on simply because they come from somewhere beyond the realms of modern human understanding. The theory also helps explain other related aspects of UFO lore, such as the supposed Men in Black, who are linked to mysterious demonic or devilish figures in black reported in legend and folklore.
While the model for ETH intelligences seems to assume that they are explorers or invaders of some kind, the ultraterrestrial hypothesis lends itself to different speculations. UFO researchers John Keel and Jacques Vallee suggested there was a “control system” created by ultraterrestrial beings which has power over our three-dimensional reality and the human perception of it, a role some have called a “custodian” role. Others see extradimensional “rats” which are able to hide from us due to the relatively narrow range of perception of the electromagnetic spectrum. Or they could be cosmic tricksters, creatures from different realities that our ancestors once perceived as magical little people lurking in the forest, or burning chariots, or winged angels in the sky.
Of course, the problem with this hypothesis is that it purports that UFOs are simply beyond our ability to understand, comprehend, or even perceive, making it simply impossible to verify or test the theory. This in and of itself doesn’t make the hypothesis wrong, but it does put it in the same category as magic and ghosts.
Show Me The Proof
Thieme Works: Michael Swords on the Extraterrestrial Hypothesis
UFO Research: The Extraterrestrial Hypothesis—Objections and Counter-Arguments
The UFO Phenomenon, by John Michael Greer
The Skeptic’s Guide to Conspiracies: From the Knights Templar to the JFK, by Monte Cook
Mysteries Explored: The Search for Human Origins, UFOs and Religious Beginnings, by Jack Barranger and Paul Tice