Want to believe? Good. Now rule out everything else first. Checklists, famous cases, a quiz and the best books and films from both sides.
Saw something? Go through each question. Mark it "Ruled out" if you have checked and it was not that, or "Could be" if it might explain what you saw.
Check the sky first
0 / 5
Most sightings are ordinary things in the sky seen in unusual conditions.
Was Venus, Jupiter or a bright star low in that direction?Why it matters
Low bright planets twinkle, change colour and seem to "follow" a moving car. Use a free sky map app for the time and place.
Could it have been a Starlink "train" or the ISS?Why it matters
Fresh Starlink launches look like a string of pearls crossing the sky. Pass predictions are on Heavens-Above.
Did a flight tracker show an aircraft there?Why it matters
Landing lights pointed at you look like a hovering, silent ball of light for minutes.
Any drones, balloons or sky lanterns nearby?Why it matters
Lanterns drift in groups, glow orange and fade out one by one. Weather balloons can reflect sunlight long after sunset.
Was there a launch, flare drop or military exercise?Why it matters
Rocket launches make spectacular glowing "jellyfish" at twilight. Flares hang and drift in a line.
Check the camera
0 / 6
Phones are brilliant at people and terrible at tiny lights in a dark sky.
Is the object exactly opposite a bright light in the frame?Why it matters
Lens flares sit on a line through the centre of the image, mirrored from the light source.
Could it be a reflection in a window or windshield?Why it matters
Shoot again with the lens pressed against the glass. If it vanishes, it was the glass.
Is it a soft, see-through disc?Why it matters
Out-of-focus dust, rain, insects or birds close to the lens become glowing orbs (bokeh).
Was digital zoom or heavy night mode used?Why it matters
Digital zoom and stacking invent detail. Shapes and "structure" can be processing, not the object.
Does a fast object look bent, stretched or wobbly?Why it matters
Rolling shutter distorts fast motion and spinning things, like propellers.
Is the original file, with its EXIF, still available?Why it matters
Screenshots and re-uploads strip metadata and recompress the image. The Capture app keeps the original sealed with a hash.
Check the story
0 / 4
Memory is a reconstruction, not a recording.
Was it written down within the hour?Why it matters
Accounts grow more detailed and dramatic with retelling. Early notes are worth more.
Are there independent witnesses who did not talk first?Why it matters
Witnesses who compare notes converge on one story without meaning to.
Are the size, distance and speed actually measurable?Why it matters
A light in the sky has no scale. "Huge" and "fast" are guesses unless something gives a reference.
Were you expecting or hoping to see something?Why it matters
Expectation shapes perception. That applies to sceptics too.
Check the evidence
0 / 3
Extraordinary claims need evidence that would convince someone who was not there.
Is there more than one camera angle or sensor?Why it matters
Two locations allow triangulation. That turns "a light" into a real distance and speed.
Has someone tried to explain it in an ordinary way?Why it matters
Ask for an explanation before calling it unexplained. "I can't identify it" is not "it can't be identified".
Would the evidence still look strange to a pilot or astronomer?Why it matters
Specialists recognise things the rest of us never see.
Guess each verdict before you reveal it.
1942 · Los Angeles, California, USA
Battle of Los Angeles
The claim
Weeks after Pearl Harbor, air-raid sirens sounded and anti-aircraft guns fired more than 1,400 shells at unseen targets over the city. A newspaper photo appeared to show an object caught in searchlights.
Your guess:
Probably explained
The sceptic's take
No aircraft was found and no bombs fell. The Navy called it a false alarm caused by war nerves, and a weather balloon may have started it. The famous photo was heavily retouched for publication, which made the searchlight beams appear to meet on a solid shape.
1944 · Skies over Europe and the Pacific
Foo fighters
The claim
Allied aircrews in the Second World War reported glowing balls of light that paced their planes at night.
Your guess:
Probably explained
The sceptic's take
Both sides suspected the other of secret weapons. Postwar reviews found no such weapons. The likely causes were St. Elmo's fire, reflections, flares and the stress of night combat. Each side also reported them over its own territory.
1947 · Mount Rainier, Washington, USA
Kenneth Arnold
The claim
A private pilot reported nine bright objects flying in formation at incredible speed. His description of them moving "like a saucer skipped across water" gave the world the phrase "flying saucer".
Your guess:
Still open
The sceptic's take
Arnold described the motion, not the shape, but the press ran with "saucers". Proposed explanations include a meteor fireball breaking up, a mirage of distant peaks, or a flock of birds such as pelicans. None is proven.
1947 · New Mexico, USA
Roswell
The claim
The Army announced it had recovered a "flying disc", then retracted it a day later. Decades later, stories of alien bodies and a cover-up emerged.
Your guess:
Explained
The sceptic's take
USAF reports in 1994 and 1997 concluded the debris came from Project Mogul, a classified string of balloons built to detect Soviet nuclear tests. The "alien bodies" accounts appear to blend memories of later crash-test dummy drops and other events.
1948 · Kentucky, USA
Mantell incident
The claim
Air National Guard pilot Thomas Mantell died chasing a huge, metallic object high above Godman Field.
Your guess:
Explained
The sceptic's take
Mantell climbed too high without oxygen and blacked out. The object is generally identified as a then-secret Navy Skyhook balloon, a giant high-altitude research balloon that looks metallic in sunlight.
1951 · Texas, USA
Lubbock Lights
The claim
Professors and residents saw arcs of glowing lights cross the night sky on several evenings, and a student photographed a V-shaped formation.
Your guess:
Probably explained
The sceptic's take
The Air Force concluded the lights were night-flying birds (plovers) reflecting new mercury-vapour streetlights. The photographs remain debated.
1952 · Washington, D.C., USA
Washington, D.C. flap
The claim
Radar at two airports tracked unknown targets over the capital on consecutive weekends, and jets were scrambled.
Your guess:
Probably explained
The sceptic's take
The Air Force attributed the returns to temperature inversions bending radar beams during a heatwave, combined with visual sightings of stars and meteors. Some radar specialists disputed this at the time.
1952 · West Virginia, USA
Flatwoods monster
The claim
After a fireball crossed the sky, a group of locals said they met a ten-foot creature with a glowing face and a spade-shaped hood.
Your guess:
Probably explained
The sceptic's take
The fireball was a meteor seen across three states that night. Investigators have argued that the "creature" matches a startled barn owl on a branch, with its heart-shaped face and talons, seen by flashlight by frightened witnesses.
1961 · New Hampshire, USA
Betty and Barney Hill
The claim
A couple reported a light following their car, and later, under hypnosis, recalled being taken aboard a craft and examined. It became the template for abduction stories.
Your guess:
Probably explained
The sceptic's take
The detailed abduction story only emerged through hypnosis, which is known to produce confident false memories. Their therapist did not believe it was a literal event. Sceptics suggest the original light was Jupiter or a nearby beacon.
1964 · New Mexico, USA
Socorro landing
The claim
Police officer Lonnie Zamora said he saw an egg-shaped craft with two small figures beside it, which then took off with a roar, leaving burn marks.
Your guess:
Still open
The sceptic's take
Zamora was considered a credible witness, and Project Blue Book left the case unidentified. Proposed explanations include a hoax by students and a test vehicle, but none has been confirmed.
1965 · Pennsylvania, USA
Kecksburg
The claim
A fireball came down in the woods, and witnesses later described soldiers recovering an acorn-shaped object.
Your guess:
Probably explained
The sceptic's take
The fireball was seen across several states and Canada, and its path fits a meteor that broke up well away from Kecksburg. A Soviet probe was ruled out by its orbit. Accounts of the acorn grew over decades of retelling.
1966 · Melbourne, Australia
Westall
The claim
Hundreds of students and teachers watched a silvery object descend near a school playing field, then fly away.
Your guess:
Probably explained
The sceptic's take
Researchers have linked it to the HIBAL programme, which was launching high-altitude research balloons from nearby that year. A fallen balloon followed by a search aircraft fits many accounts.
1975 · Arizona, USA
Travis Walton
The claim
A forestry worker vanished for five days after his crew saw him struck by a beam from a hovering craft.
Your guess:
Still open
The sceptic's take
There is no physical evidence. Sceptics such as Philip Klass argued it was a hoax, pointing to disputed polygraph results and a contract the crew was behind on. Walton and his crew still stand by the story.
1980 · Suffolk, England
Rendlesham Forest
The claim
US airmen reported a glowing craft in the woods near RAF Woodbridge, and later, landing marks and raised radiation.
Your guess:
Probably explained
The sceptic's take
Investigators including astronomer Ian Ridpath showed the flashing light lined up with the Orford Ness lighthouse, and the first sighting matched a bright fireball. The "landing marks" were rabbit diggings, and the radiation readings were background level.
1981 · Hessdalen valley, Norway
Hessdalen lights
The claim
Balls of light have been seen floating over a remote valley for decades, sometimes daily.
Your guess:
Still open
The sceptic's take
This is a real, recurring phenomenon and is under scientific study with automated cameras. Leading ideas are natural, such as plasma or dust ignited by the valley's minerals. It is an unexplained light, not a spacecraft.
1983 · New York, USA
Hudson Valley boomerang
The claim
Thousands of people reported a huge, silent, boomerang-shaped set of lights hovering over the Hudson Valley over several years.
Your guess:
Probably explained
The sceptic's take
Investigators traced many sightings to a group of pilots flying light aircraft in tight formation at night as a stunt, switching their lights on and off. Witnesses joined the lights into one giant craft.
1986 · Alaska, USA
Japan Air Lines 1628
The claim
A cargo jet's captain reported huge lights pacing his aircraft for almost an hour, including a walnut-shaped mothership.
Your guess:
Still open
The sceptic's take
The FAA investigated and found no corroborating radar. Sceptics such as Philip Klass argued the captain saw Jupiter and Mars, both bright and low that night. The crew's accounts differed in detail, and it remains debated.
1990 · Petit-Rechain, Belgium
Belgian UFO wave photo
The claim
During a wave of triangle sightings, a striking photo of a dark triangle with three lights became one of the most famous UFO images ever.
Your guess:
Explained
The sceptic's take
In 2011 the photographer admitted he made it from painted polystyrene and lights. Many other sightings in the wave were never resolved, though some radar contacts were attributed to weather effects.
1994 · Ruwa, Zimbabwe
Ariel School
The claim
About 60 schoolchildren said a craft landed near their playground at break time and small beings with large eyes communicated with them.
Your guess:
Still open
The sceptic's take
There is no physical evidence. Sceptics point to excitement after a bright meteor seen days earlier, the children's shared retelling and leading interviews. The children's sincerity is not in doubt, and many still describe it the same way today.
1995 · London, England
Alien Autopsy film
The claim
Grainy black-and-white footage, said to be from 1947, showed doctors dissecting an alien body from Roswell. It aired around the world.
Your guess:
Explained
The sceptic's take
In 2006 the man behind it admitted it was a staged "reconstruction". The body was a dummy filled with sheep brains, chicken guts and jelly, made in a London flat.
1997 · Arizona, USA
Phoenix Lights
The claim
Thousands saw a huge V of lights glide silently over the city, and later a row of hovering orbs.
Your guess:
Explained
The sceptic's take
The later, famously filmed orbs were illumination flares dropped by A-10 aircraft on the Barry Goldwater range during an exercise. The earlier V is best explained by aircraft flying in formation. Witnesses joined the separate lights into one giant craft.
2004 · Pacific, off California
Nimitz "Tic Tac"
The claim
Navy pilots reported a white, wingless object that moved abruptly near the USS Nimitz, and an infrared video was later released.
Your guess:
Still open
The sceptic's take
The released footage is low resolution and has been argued to show a distant aircraft. The pilots' visual accounts have not been explained, and the Pentagon still lists it as unidentified. It is the strongest open case and worth studying carefully.
2006 · Chicago, Illinois, USA
O'Hare Airport disc
The claim
Airline staff reported a dark, disc-shaped object hovering over a gate, which then shot up through the clouds and left a hole.
Your guess:
Probably explained
The sceptic's take
There was no radar contact and no photos. The FAA attributed it to a weather phenomenon. Meteorologists note that low, ragged cloud and hole-punch clouds can produce exactly this impression.
2014 · Chile
Chilean Navy video
The claim
A Navy helicopter filmed an object leaving a strange trail over the sea in infrared. Officials could not identify it.
Your guess:
Explained
The sceptic's take
Independent analysts matched it to a commercial airliner leaving Santiago, seen from far away, with its engines venting a contrail.
2015 · Atlantic, off Florida
Gimbal
The claim
A Navy targeting pod filmed a glowing object that appears to stop and rotate in mid-air.
Your guess:
Probably explained
The sceptic's take
Analysts such as Mick West argue the shape is infrared glare from a distant jet, and the "rotation" is the camera's gimbal mechanism turning. The Navy has not offered an explanation.
2015 · Atlantic, off Florida
GoFast
The claim
A Navy video seems to show a small object skimming the ocean at very high speed.
Your guess:
Explained
The sceptic's take
NASA's 2023 UAP study team calculated from the on-screen data that it was about 13,000 feet up and moving at roughly wind speed. The apparent speed is parallax from the fast jet.
2023 · USA and Canada
The 2023 shootdowns
The claim
After downing a Chinese surveillance balloon, US jets shot down three more unidentified objects in a week, prompting headlines about UFOs.
Your guess:
Probably explained
The sceptic's take
Officials later said the three smaller objects were most likely benign balloons. A hobby club reported losing a small, cheap research balloon over Alaska at the same time. Radar had been retuned to catch slow objects, so it suddenly saw many more balloons.
2023 · Mexico City, Mexico
Mexican "alien" mummies
The claim
Two small, three-fingered bodies were presented to Mexico's Congress as non-human beings.
Your guess:
Explained
The sceptic's take
Scientists who examined similar bodies from Peru found they were assembled from human and animal bones and modern glue. The presenter had previously promoted other claims that were shown to be false.
1947
The "flying saucer" is born
Kenneth Arnold's sighting and the Roswell announcement start a wave of reports across the US within weeks.
1948
Project Sign
The US Air Force begins studying reports. It is followed by Project Grudge in 1949.
1952
Project Blue Book
The Air Force's long-running study begins, the same year as the Washington, D.C. radar sightings.
1953
Robertson Panel
CIA-convened scientists conclude reports pose no direct threat but could clog defence channels. They recommend public education, and critics later call it debunking.
1968
Condon Report
A University of Colorado study finds nothing to justify further scientific study, though some of its own cases remain unexplained.
1969
Blue Book closes
Final tally: 12,618 reports, of which 701 remain unidentified.
1977
France's GEPAN
The French space agency CNES sets up a unit to study reports. Now called GEIPAN, it publishes case files online.
1997
"Case Closed"
The Air Force publishes its second Roswell report, explaining "alien body" accounts as later crash-test dummy drops and other events.
2007
AATIP
A small, little-known Pentagon programme begins studying unidentified aerial threats, funded until 2012.
2009
UK closes its UFO desk
The Ministry of Defence ends its reporting line after decades of finding no defence threat, and releases its files to the National Archives.
2017
The New York Times story
AATIP is revealed and the Navy's FLIR "Tic Tac" video goes public, reviving mainstream interest.
2020
Pentagon releases the videos
The Defense Department officially publishes the Tic Tac, Gimbal and GoFast videos.
2021
First intelligence report
The US intelligence community reviews 144 military reports from 2004 to 2021 and explains one, a deflating balloon. The rest lack enough data.
2022
AARO and hearings
The Pentagon creates AARO to investigate UAP, and Congress holds its first open hearing on the subject in more than 50 years.
2023
Whistleblower and NASA
A former intelligence officer testifies about alleged crash retrievals without showing evidence publicly. NASA's independent study calls for better data and less stigma.
2024
AARO's historical review
The Pentagon reports finding no evidence that any US government investigation has confirmed extraterrestrial technology.
1 / 12Score 0
Just after sunset, a brilliant white light hangs low in the west for an hour, flickering red and green. It seems to follow your car.
Venus is low in the west after sunset for months at a time. Turbulent air makes it flash colours, and distant objects appear to keep pace with a moving car.
A perfectly straight line of 30 evenly spaced lights glides silently across the sky, all at the same speed.
Newly launched Starlink satellites travel in a line before spreading out. They are visible for a few days after each launch.
Your photo of a streetlit road shows a translucent green disc that you did not see at the time. It sits exactly opposite the brightest lamp.
Flares from internal reflections appear opposite the light source, mirrored through the centre of the frame, and you never see them by eye.
At a summer wedding, a loose cluster of orange lights rises slowly, drifts with the wind and blinks out one by one.
Sky lanterns are released in groups at celebrations, drift with the wind and go out as their fuel burns away.
Near a coast at twilight, a glowing, expanding jellyfish shape with a bright point at its tip rises across the sky.
At twilight, a rocket's exhaust plume high in the atmosphere is lit by the sun while the ground is dark, making a dramatic glowing cloud.
Night-time video shows a soft, see-through ball of light zipping past the camera. Nobody saw it at the time.
Out-of-focus insects, dust or rain near the lens, lit by the camera's infrared or flash, look like large glowing orbs.
A bright light hangs motionless for five minutes near an airport, then slowly turns into red and green blinking lights and a faint engine sound.
An aircraft flying straight at you barely seems to move, and its landing lights hide the navigation lights until it turns.
Dozens of people report a slow, glowing fireball breaking into pieces with long trails, crossing the whole sky in under a minute.
Bright meteors (fireballs) and re-entering rocket stages break apart in long glowing trains and are seen over huge areas at once.
A dark disc appears in one photo of a landscape. Nobody saw it, and it is in focus while everything around it is sharp too.
Fast-moving birds and insects cross the frame in a split second and get frozen as odd shapes. That is why "I only noticed it later" is a red flag.
Three bright lights in a perfect triangle hover silently in the evening, then drift apart slowly over ten minutes.
The brain links separate lights into a single shape. If they drift apart, they were never one object.
A bright point of light moves steadily across the sky, never blinks, then fades to nothing in the middle of the sky.
Satellites shine by reflected sunlight. When they pass into Earth's shadow they fade out mid-sky, often just after dusk.
Infrared footage from a fighter jet shows a dark blob that seems to skim the ocean at incredible speed.
This is the GoFast video. NASA calculated the object was about 13,000 feet up, moving at wind speed. The jet's motion made it look fast.
Debrief
A light in the sky has no scale. Hold your arm out straight and measure the object with your hand, then see how big and fast it would be at different distances.
If it was
Size
Speed
About as big as
Same light, wildly different answers. Without a real distance, from a second camera, radar or a landmark, any claim about size or speed is a guess.
Basics · 3 min readUnidentified is not the same as alien
"UFO" means one thing: someone saw something in the sky and could not say what it was. That is a statement about the witness's information, not about the object. Governments have started using "UAP" (unidentified anomalous phenomena) partly to shed the flying-saucer baggage.
Every large investigation has found the same pattern. The US Air Force's Project Blue Book logged 12,618 reports between 1952 and 1969 and left 701 as unidentified. The UK Ministry of Defence, France's GEIPAN and, more recently, the Pentagon's AARO report similar shapes: most cases are solved, and a stubborn minority stay open because the data is too thin, not because it points somewhere exotic.
An honest sceptic keeps that minority open. "We don't know" is a perfectly good answer, and it is the only one the evidence supports until something better arrives.
Sky · 4 min readThe usual suspects: what people really see
Venus is the all-time champion. It is the brightest thing in the night sky after the Moon, it hangs low near dusk or dawn where the atmosphere makes it flicker red and green, and it appears to pace a moving car. Police officers have chased it.
Since 2019, Starlink satellites have generated a new wave of reports: a straight line of evenly spaced lights gliding silently overhead shortly after a launch. Aircraft landing lights pointed straight at you make a bright, stationary ball for minutes. Sky lanterns drift in loose formation and blink out one at a time. Balloons, from party Mylar to high-altitude research flights, catch sunlight after the ground is dark.
Rocket launches seen at twilight create glowing, expanding plumes that look like nothing else on Earth, and they often trigger hundreds of reports in a single evening.
Camera · 4 min readYour phone is lying to you (a little)
Phone cameras are computers that guess. At night they stack multiple frames, sharpen edges and smooth noise. Pointed at a single bright point, they can invent shapes, halos and "structure" that are simply processing.
Lens flares appear opposite a bright light, mirrored through the centre of the frame. Raindrops, dust, insects and birds close to the lens become glowing translucent discs. Rolling shutters, which read the sensor line by line, bend fast-moving objects and turn propellers into impossible curves.
The fix is boring and effective: keep the original file, note the time and direction, take a wide shot that includes the horizon or a landmark, and avoid digital zoom. This is exactly why Hello Mr. Alien seals every original with a SHA-256 hash.
Mind · 3 min readWhy smart people see saucers
Seeing something odd is not a sign of gullibility. Human vision evolved to find patterns fast and fill gaps, which is why we see faces in clouds (pareidolia) and assume a cluster of lights is one connected object.
A single light in a dark sky has no reference for size or distance. The brain picks one, and from that guess follow wrong conclusions about speed and manoeuvres. The autokinetic effect makes a fixed point of light in darkness appear to drift.
After the event, memory keeps editing. Talking to other witnesses, seeing news coverage or being hypnotised can add vivid, confident detail that was never seen. Psychologist Susan Clancy's research on people who report abductions found them sincere, not liars, which is exactly why first-hand testimony alone is not enough.
Method · 3 min readA baloney detection kit for UFO claims
Carl Sagan proposed a "baloney detection kit" in The Demon-Haunted World. Applied to UFOs, it looks something like this.
Seek independent confirmation of the facts. Encourage debate from people who know the field, such as pilots, astronomers and radar operators. Don't trust authority alone, whether it is a general or a famous researcher. Consider more than one hypothesis, and try to knock down your favourite. Quantify: how far, how fast, how big, and how do you know? Ask whether the claim could ever be shown wrong; if not, it is not really a claim.
Finally, Occam's razor: when two explanations fit the data, prefer the one that needs fewer new assumptions. A misidentified balloon needs none. Interstellar visitors need quite a few.
Balance · 3 min readSteelman the believers
A good sceptic understands the strongest version of the other side. Believers point to trained military pilots, multiple sensors and governments that have been secretive about real programmes. Those are fair points.
The US Congress has held public hearings on UAP since 2022, the Navy has confirmed its videos are genuine, and NASA ran an independent study in 2023. None of them found evidence of extraterrestrial technology, but all of them called for better data, less stigma and more reporting. That is a position both sides can sign.
Use this site the same way: capture originals, record the facts, and let the evidence lead. If something truly anomalous turns up, the best people to recognise it will be the ones who ruled out everything else first.
Method · 4 min readHow to report a sighting like a pro
Write it down immediately: date, exact time, where you stood, which direction you faced, and how high above the horizon the object was. Use your hand at arm's length: a fist is about 10 degrees, a finger about 1 degree. That is far more useful than "huge" or "fast".
Film wide before you zoom. A shot that includes the horizon, a roofline or a tree gives investigators a reference to measure against. Keep the camera as still as you can, ideally braced against something, and keep recording for longer than feels necessary.
Keep the original file. Do not crop, filter, screenshot or re-upload it before filing. Upload it through the Capture page, which hashes the file on your phone and again on the server so anyone can confirm it was not altered.
Finally, note anything nearby that could explain it: an airport, a launch site, a festival, a bright planet. Ruling things out is part of the report, not a sign of disbelief.
History · 4 min readFamous hoaxes and how they were caught
In the 1950s, George Adamski photographed "scout ships" that critics identified as a chicken brooder or a lamp shade. In the 1970s and 80s, Swiss farmer Billy Meier produced beautiful saucer photos, and analysts found models hung on strings and, later, pictures copied from TV and magazines.
The Belgian triangle photo of 1990 was polystyrene and lights, as its maker admitted 21 years later. The 1995 "Alien Autopsy" was a dummy filled with animal parts. In the UK, Doug Bower and Dave Chorley revealed in 1991 that they had been making crop circles since the 1970s with planks and rope.
The pattern is useful. Hoaxes tend to come from one person with no independent witnesses, have only a single photo or a short clip, never get better with follow-up, and grow more elaborate over time. Real phenomena get easier to study, not harder.
Sensors · 3 min readGhosts in the machine: radar and infrared
"It was on radar" sounds decisive, but radar has its own illusions. Temperature inversions bend beams back to the ground and produce phantom targets. Flocks of birds, insect swarms and chaff can all appear as solid contacts, and software can join separate returns into one impossible track.
Infrared cameras see heat, not shape. A distant jet engine can bloom into a glowing blob that hides the aircraft entirely, and the camera's own optics can add glare that rotates as the mount turns. That is the leading explanation of the Gimbal video.
Multiple sensors agreeing is genuinely strong evidence, which is why the best cases are taken seriously. But "multiple sensors" claims often rest on testimony about data that has never been released. Ask to see the data.
AARO
The All-domain Anomaly Resolution Office, the Pentagon office that investigates UAP reports.
Autokinetic effect
A fixed point of light in a dark sky appears to drift or move because the eye has no reference.
Bokeh
The blurred look of out-of-focus points. Dust and insects near the lens become glowing orbs.
Chain of custody
A record of who handled a piece of evidence and when. Hello Mr. Alien uses a SHA-256 hash to show a photo is unchanged.
Close encounter
J. Allen Hynek's scale: first kind is a close sighting, second kind leaves physical traces, third kind includes beings.
Confabulation
Sincerely remembering things that did not happen, often filling gaps in memory. Hypnosis can encourage it.
EXIF
Data a camera stores inside a photo: time, settings, device and often GPS location.
Falsifiable
A claim that could, in principle, be shown wrong by evidence. Claims that cannot are not testable.
FLIR
Forward-looking infrared, the heat cameras in military targeting pods that recorded the Navy videos.
GEIPAN
France's official UFO study unit, part of the space agency CNES. It publishes its cases online.
Lens flare
Light scattered inside a lens, appearing as discs or rings opposite a bright light in the frame.
Misidentification
Mistaking an ordinary thing, such as a planet, aircraft or balloon, for something unknown. The cause of most reports.
Occam's razor
When two explanations fit, prefer the one that needs fewer new assumptions.
Parallax
Apparent movement of a distant object caused by the observer's own motion. It makes slow objects look fast from a moving jet.
Pareidolia
Seeing meaningful shapes, such as faces or craft, in random patterns.
Project Blue Book
The US Air Force study of UFO reports from 1952 to 1969.
Rolling shutter
A camera reads the sensor line by line, so fast motion is bent or stretched.
SHA-256
A digital fingerprint of a file. Change a single pixel and the fingerprint changes completely.
Starlink train
A line of newly launched satellites travelling together before they spread out. A big source of modern reports.
Temperature inversion
Warm air above cool air bends light and radar, creating mirages and false radar returns.
UAP
Unidentified anomalous phenomena. The official US term since 2022, replacing UFO to include objects in the sea and in space.
UFO
Unidentified flying object. Coined by the US Air Force in the early 1950s to replace "flying saucer".
No matching terms.
Sceptical
The Demon-Haunted World
Carl Sagan · 1995
The classic on scientific thinking, with the "baloney detection kit" and chapters on abductions.
Sceptical
Abducted: How People Come to Believe They Were Kidnapped by Aliens
Susan A. Clancy · 2005
A Harvard psychologist interviews abductees and explains false memory without mocking anyone.
Sceptical
Escaping the Rabbit Hole
Mick West · 2018
How to talk to friends who believe conspiracy theories, from the man who analysed the Navy videos.
Sceptical
Bad UFOs
Robert Sheaffer · 2016
A long-time investigator goes case by case through famous sightings.
Sceptical
UFOs Explained
Philip J. Klass · 1974
The original hard-nosed sceptic, an aviation journalist who dissected classic cases.
Sceptical
Watch the Skies!
Curtis Peebles · 1994
A cultural history of how the flying-saucer myth formed and spread.
Sceptical
Why People Believe Weird Things
Michael Shermer · 1997
The psychology of belief, from the founder of Skeptic magazine.
Believer (steelman)
The UFO Experience
J. Allen Hynek · 1972
Blue Book's scientific adviser, who started a sceptic and came to think some cases deserved study. He coined "close encounters".
Believer (steelman)
UFOs: Generals, Pilots, and Government Officials Go on the Record
Leslie Kean · 2010
The strongest testimony-based case, from the journalist who later broke the 2017 Pentagon story.
Sceptical
The UFO Handbook
Allan Hendry · 1979
An investigator for a pro-UFO research centre shows how nearly all of 1,300 reports he chased had ordinary causes. A practical field manual.
Sceptical
The UFO Invasion
Kendrick Frazier, Barry Karr and Joe Nickell (eds.) · 1997
Essays from Skeptical Inquirer covering Roswell, abductions and crop circles.
Believer (steelman)
Passport to Magonia
Jacques Vallée · 1969
A scientist argues UFO stories echo older folklore about fairies and visitors. Fascinating whichever side you take.
Primary source
Project Blue Book records
US Air Force · 1969
12,618 reports, now in the US National Archives. Read the originals, not the retellings.
Primary source
Report on the Historical Record, Vol. 1
AARO, US Department of Defense · 2024
The Pentagon's review of US government UAP investigations since 1945.
Primary source
UAP Independent Study Team Report
NASA · 2023
Short, readable, and focused on what better data would look like.
Sceptical
Mirage Men
2013
How intelligence agencies seeded UFO stories to cover secret aircraft and test disinformation.
Sceptical
NOVA: Kidnapped by UFOs?
1996
PBS looks at abduction claims, hypnosis and memory.
Sceptical
Behind the Curve
2018
About flat-earthers, not UFOs, but it is the best film on how communities protect a belief.
Primary source
NASA UAP Public Meeting
2023
Four hours of scientists working through real cases, including GoFast. Free online.
Primary source
US House Oversight UAP Hearing
2023
Pilots and a former intelligence officer testify under oath. Watch it, then ask what evidence was shown.
Sceptical
Carl Sagan's Cosmos: "Encyclopaedia Galactica"
1980
The episode where Sagan explains why he takes the search for life seriously and UFO claims less so.
Believer (steelman)
Out of the Blue
2003
A well-made believer documentary with many famous witnesses.
Believer (steelman)
The Phenomenon
2020
James Fox's survey of cases and officials, including Westall.
Believer (steelman)
Unidentified: Inside America's UFO Investigation
2019
The History series around the Navy videos and AATIP.
Believer (steelman)
Encounters
2023
Netflix series on witness stories around the world, including Ariel School in Zimbabwe.