What people actually saw

Sleep paralysis

Waking while the body is still paralysed, with a felt presence and vivid figures at the bedside.

During REM sleep the brain switches off the body's muscles so that dreams are not acted out. Sometimes a person wakes before that switch releases. They are conscious, unable to move, and still partly dreaming. The result is a state that surveys find in roughly a quarter to a third of people at least once: pressure on the chest, dread, a sense of someone in the room, and often a figure that is seen, heard or felt.

The figure takes the shape the culture supplies. Medieval Europe saw incubi and the 'old hag'; Newfoundland still uses that phrase; Japan calls the state kanashibari and reports ghosts. Since the 1960s, and especially since Communion in 1987, people in the West report small grey beings with large eyes. The experience is the same; the costume changed.

Psychologists Susan Clancy and Richard McNally found that most people who recalled abductions had a history of sleep paralysis, and that their memories of examination aboard craft generally emerged later, in hypnosis or through reading. That does not mean the fear was not real. It was.

Accounts for

Bedroom visitations, paralysis, the felt presence, figures at the bedside, 'floating' sensations, and the peculiar detail that the beings arrive at night and leave no trace.

Where it runs out

It does not address daylight sightings, multiple-witness events, or cases with physical traces or radar tracks.

Hypnosis and false memory

Regression hypnosis produces confident, detailed memories that are often not memories at all.

Most abduction narratives were recovered under hypnosis: the Hills in 1964, the Allagash four in 1988, Zanfretta through the 1980s. Memory researchers, above all Elizabeth Loftus, have shown that hypnosis increases the confidence and vividness of recall without increasing its accuracy, and that a hypnotist's questions, even neutral ones, shape what is 'remembered'. Courts in most jurisdictions no longer admit hypnotically refreshed testimony for that reason.

The mechanism is ordinary. Under hypnosis a person fills gaps with imagination and cannot afterward tell which parts were which. If the hypnotist is a UFO researcher, and the subject has read abduction books, the gaps fill in a predictable direction. Dr Benjamin Simon, who hypnotised the Hills, concluded that their shared account was a fantasy built from Betty's dreams. Later researchers such as Budd Hopkins were open about having strong beliefs before the sessions began.

Accounts for

The consistency of abduction stories, the emergence of detail years after the event, and 'missing time' reconstructions.

Where it runs out

It says nothing about the original sighting that prompted the hypnosis, which in several cases was reported immediately and by more than one person.

Owls and other animals

Large eyes, silent flight, and a face that looks back: owls explain more creature reports than anything else.

A barn owl seen at night in a tree, wings half-spread and eyes catching a torch beam, is the leading explanation for the Flatwoods 'monster' of 1952. Great horned owls, which will defend a nest by swooping at people, are the standard explanation for the silver 'goblins' of Kelly-Hopkinsville, which the witnesses said floated, glowed and would not fall when shot. Sandhill cranes, with a seven-foot wingspan and red patches around the eyes, are the usual candidate for Point Pleasant's Mothman.

This is not a way of calling witnesses fools. People are bad at judging the size and distance of an unfamiliar animal at night, and a frightened brain fills in a face. Anyone who has been startled by an owl at close range knows how little it resembles a bird in that moment.

Accounts for

Single-night creature sightings in rural darkness, glowing eyes, silent movement, figures in trees and on rooflines.

Where it runs out

Owls do not stall car engines, leave landing marks or appear on radar.

Balloons, aircraft and things that fly

Most daylight objects are something built by people: balloons, flares, drones, satellites and secret aircraft.

The Roswell debris matched a Project Mogul balloon train, a classified array of balloons and radar reflectors flown from Alamogordo in June 1947. Captain Mantell died in 1948 chasing what was almost certainly a Skyhook research balloon that no one had told the Air Force about. The Phoenix Lights of March 1997 were, in their second and most photographed phase, flares dropped by A-10 aircraft over a bombing range; the earlier V-formation is still argued over. The 1980s black triangles arrived in the same years as the F-117 and B-2 stealth aircraft.

AARO's 2024 historical review found that a large share of the government's own UFO rumours could be traced to people glimpsing classified programmes they were not cleared to know about, and to the secrecy that followed. Since 2015 the fastest-growing category has been drones.

Accounts for

Daylight discs and triangles, formations of lights, objects moving in straight lines, sightings near military ranges.

Where it runs out

It does not explain reports of occupants, and struggles with objects reported to accelerate or turn in ways no known aircraft can.

Planets, stars and lighthouses

A bright light that follows the car, hangs over the trees and changes colour is usually Venus, Jupiter or Sirius.

Venus at its brightest is the most reported UFO in history. Low on the horizon it twinkles through colour, appears to move as the observer moves, and seems to keep pace with a car. Jupiter played a part in the 1976 Tehran case; the star Sirius and a rotating lighthouse beam at Orford Ness are the sceptical account of the lights the Rendlesham airmen followed through the forest. The Hills' light in 1961 began, by their own first account, as a bright star-like object that Betty took to be a planet.

Add atmospheric refraction, a moving observer, and the absence of any reference point in a dark sky, and a fixed light becomes a craft that 'paced' the witness for miles.

Accounts for

Single lights at night, lights that 'follow', colour changes, objects that vanish at dawn.

Where it runs out

It cannot account for structured craft seen at close range or objects that pass in front of terrain.

Meteors and satellite re-entries

A fireball crossing the sky, followed by a search of the ground, opens many creature and landing stories.

The Flatwoods encounter began with a bright object crossing the evening sky, which the boys took for a crashed craft on the hill. It was almost certainly a meteor seen that night across three states. A Soviet rocket stage re-entered over southern England in the early hours of 26 December 1980, the first night of the Rendlesham events, and was widely reported. A fireball puts people in an expectant state and sends them out into the dark to look; whatever they find next is read as related.

Accounts for

The 'craft coming down' that starts a story, glowing objects in fields, and the timing of many landing reports.

Where it runs out

A meteor lasts seconds; it does not explain what witnesses report over the following hour.

Misperception and expectation

People see what they are primed to see, and estimate size, speed and distance poorly in the dark.

Perception is reconstruction. The brain builds a scene from fragments and expectation, and at night, with no depth cues, it guesses. A light of unknown size at unknown distance can be a lantern at a hundred metres or a craft at ten kilometres; the eye cannot tell. Once a witness has decided what they are looking at, later details are recruited to fit.

Expectation is set by culture. Airship 'sightings' swept America in 1896, when airships were in the newspapers. Flying saucers followed Kenneth Arnold's 1947 report within weeks. Greys spread after the 1975 television film about the Hills and the 1987 Communion cover. The psychosocial hypothesis holds that this pattern is the phenomenon: the reports track the imagery of the moment.

Accounts for

Why aliens look like the aliens in last year's films, why waves follow media coverage, and why honest witnesses disagree about basic details.

Where it runs out

It explains the shape of reports better than it explains any single strong case, and it can be stretched to dismiss anything.

Hoaxes

A minority of cases, but a loud one; the fakes shape what everyone else reports.

George Adamski's photographs of a Venusian scout craft were shown to match a lantern and other household objects. The famous Belgian triangle photograph of 1990 was admitted to be a model in 2011. The Ummo letters were claimed by a Spanish psychologist as an experiment. The Majestic 12 papers were judged forgeries by the FBI. The 'alien autopsy' film of 1995 was confessed to in 2006. Crop circles were demonstrated by their makers in 1991.

Hoaxes matter beyond themselves. They supply the images that later sincere witnesses reproduce, and they poison the record for cases that were reported in good faith.

Accounts for

Photographs, documents, artefacts and the small number of cases with a clear motive.

Where it runs out

Most witnesses gain nothing and lose a great deal by reporting; the hoax explanation fits few of the cases in this archive.

What remains unexplained

Honest accounting: a residue of cases resists every conventional reading, which is not the same as proving anything.

Project Blue Book left 701 of 12,618 reports unidentified. The Condon Committee, set up to close the subject, left around a third of its own sample unexplained. The 2021 ODNI report could account for one of 144 military incidents. Socorro in 1964, with its burned ground, two witnesses to the departing object and a police officer of unblemished record, has never been convincingly resolved. Nor has the Nimitz encounter of 2004, tracked by radar and seen by four aviators.

'Unexplained' means the available evidence is insufficient. It is not a synonym for extraterrestrial. The honest position, which the Atlas tries to hold, is that the archive contains a great deal of misperception, some fraud, a large body of sincere experience with ordinary causes, and a small residue about which the only accurate statement is that we do not know.

Accounts for

The strongest cases, and the reason the subject has not gone away.

Where it runs out

Absence of an explanation is a gap in knowledge, not evidence for any particular filling of it.