It could be an aircraft, atmospheric phenomenon, ball lightning, bird, flare, meteor, reflected artificial light, rocket, satellite, weather balloon, or something else. However, the term usually refers to a belief that it is an alien aircraft.
Almost no UFO reports are logged by professional astronomers who watch the sky and space for anomalies. They see lots of images, but recognize them as natural or manmade objects.
While there is no evidence for alien life, it certainly may exist. With trillions of stars and their orbiting planets, the odds would seem good that life has developed elsewhere. However, the vast numbers also make alien visitation supremely unlikely. It would take 100,000 light years to cross the Milky Way and in the observable universe, our galaxy is an imperceptible speck.
Closer to home, Alpha Centauri is four light years away, or about 25 trillion miles. Let’s make the extremely gracious allowance that one of the star’s planets is home to beings that have mastered inter-solar system travel. Even then, the numbers don’t support them stopping by for coffee. To reach Earth, the aliens would need either extremely fast spacecraft or astronomical life spans and an inexhaustible fuel supply. At one million miles an hour, it would take 2,500 years to get here. Reaching us in 25 years would necessitate an average speed of 100 million miles per hour, done safely and with provisions for repairs managed in deep space.
Coming from even farther away, space travelers would need to keep a population alive for millions of years. There are alternate theories, such as wormholes or other dimensions. But it requires the most desperate desire to believe to take an unproven notion, tie it to flashes in Earth’s sky, and deduct that aliens are overhead.
Descriptions and accounts of UFOs are a relatively modern phenomenon. It wasn’t until the airplane began being seriously contemplated in the 1890s that sightings began. And these described not saucers or flashing lights, but long cylinders and objects resembling advanced hot air balloons.
In 1947, pilot Kenneth Arnold saw nine brightly glowing meteors speed past his plane. Since they were pieces of an exploding fireball breaking up, they seemed to be flying in formation. He assumed their brightness was reflected sunlight. Arnold told reporters they flew “like a saucer skipping over water.” Arnold’s description of the meteors’ actions (skipping like saucers) was mistranslated into that being their shape, and the flying saucer fixation began that day and continues unabated.
The best evidence for alien visitation would be an alien landing and showing us the aircraft. This could be bolstered with photos from its planet and journey, its DNA, extraterrestrial objects, and demonstrations of science or technology we have yet to manage. Instead, for evidence we have blurry photos, shaky videos, and anecdotes.
The most intense stories involve alien abductions. Fairy, elf, and goblin abduction tales go back for millennium in Europe. These tiny humanoids were fused with supernatural powers and scurried about the countryside nocturnally, snatching victims. Other Medieval delusions centered on demons raping nuns, or on gods incarnating as swans to seduce women. These have vanished today because we have our own fairy tales. These ideas seem silly to us, just as spaceships and alien abductions would have been scoffed at in Elizabethan England. Our culture heavily influences the belief in UFOs and aliens. Author and investigator Robert Scheaffer has said, “We find all the major elements of contemporary UFO abductions in the 1930s comic, ‘Buck Rogers in the 25th Century.’”
Most alien abductions are explicable through sleep paralysis, which is the opposite of sleepwalking. Instead of being unconscious and mobile, a person is awake and paralyzed. Abductees report being unable to move or speak and they sense a presence. This mirrors the experience of sleep paralysis. Most tales involve a probe and implant of some kind. Yet when NOVA asked to abductees to submit implants for scientific scrutiny, no one took the offer.
If mankind ever manages intergalactic travel, I hope the impression we leave on exoplanet inhabitants is better than crop circles, painful injections, and repeated nighttime desert visits.