Research student Jocelyn Bell Burnell was working with a radio telescope in 1967 when she noticed a peculiar signal. Using sidereal time, it was a series of 1.3-second pulses that occurred every day at the same moment (a timekeeping system based on the rotation of the Earth relative to the stars rather than the Sun). Signals from outer space can be detected by looking at this pattern. In contrast to other known pulsating sources, however, the 1.3-second gap between pulses was far shorter and more regular. As Bell Burnell subsequently revealed, she wondered aloud if she had indeed intercepted transmissions from an extraterrestrial civilisation. The idea of small green men seeking to interact with humans was never stated publicly by either she or her thesis supervisor, but the press couldn't get enough of them.

Thomas Gold and Fred Hoyle recognized the source of these signals a few months later, or at least provided an explanation that did not require aliens: neutron stars. When Walter Baade and Fritz Zwicky made their prediction in 1933, they referred to these objects as the final evolutionary stage of a supernova. We can only see the beam from a lighthouse on the shore because these objects produce radiation along their magnetic poles, which we can only see because of their quick rotation.

Arthur Conan Doyle, the British author who invented Sherlock Holmes, once said that "after you have excluded the impossible, whatever remains, however implausible, must be the truth." That the improbable is more likely than the impossible is a sound logical conclusion, according to the detective. It is, in fact, this delusion of reasoning that leads to so many erroneous reports of alien finds in the media, as demonstrated by Sherlock Holmes's argument. It would be arrogant to assume that we already know all the possible non-extraterrestrial occurrences that could contribute to a specific astronomical observation. The universe is wilder than we can conceive.

"Oumuamua," an unusually long object that traveled past our solar system not too long ago, is a nice illustration of this. ‘ As a reddish, palpitating, extremely faint splotch in the sky, Oumuamua appeared. It wasn't a normal object in any sense of the word. It was around 1,312 feet in length and 40 meters in width, and it was rotating rapidly. The name "first distant messenger" was given to it by a group of astronomers from Hawaii University, who were the first to observe it. Not only was it an anomalous object in terms of appearance, but it also defied Kepler's second rule of planetary motion by increasing its velocity as it got farther away from the Sun. Outgassing, which occurs when the Sun's heat melts the ice on comets and releases gases that propel them forward, has also been spotted in comets. 'Oumuamua, on the other hand, lacked a tail.

Astrophysicist Avi Loeb, a Harvard-educated physicist, has come out to declare that 'Oumuamua is an alien object, and more precisely that it could be an artificial thin solar sail driven by solar radiation pressure. According to a careful investigation by experts at the University of Arizona, it could be the result of a collision that catapulted it into the interstellar medium. On top of all this, Pluto can accelerate like comets because of nitrogen ice outgassing, which is common on these types of objects and gives it an orange hue due to the radiation processing its surface methane into hydrocarbons. It would, however, be completely undetectable. Though it's possible that this isn't the full and exact answer, it does demonstrate the possibility of otherworldly explanations for the 'Oumuamua phenomenon.

Another good example is Tabby's Star. Tabetha Boyajian discovered this star in 2011 and it had dips in light that had never been observed and for which there were no logical explanations at the time. Following the elimination of various theories, some scientists speculated that an extraterrestrial megastructure might be obscuring the star's light, something like to what are known as Dyson spheres, constructions that completely encircle a star in order to collect most of its radiation. For a time, this theory gained traction due to the fact that the findings could not be explained by any known natural phenomenon. The SETI (Search for Extraterrestrial Intelligence) network and the world's largest radio telescopes were swiftly pointed in its direction. Updated research shows that the light dips do not affect all hues in the same way as an opaque structure should and are remarkably comparable to the effect created by cosmic dust, which transmits more red light than blue light. Cosmic dust from a recently destroyed planet or satellite is the most plausible cause, although there are still many unanswered questions.

But let's not give up on the possibility of finding alien life and take a closer look at a few unsolved mysteries. In 1977, the Big Ear radio telescope at Ohio State University identified the Wow! signal, a peculiar narrowband radio emission. For the time being, there is no easy explanation for this signal, and no other signals like it have ever been detected. Or do you think they have? An emission peak was recorded on April 29, 2019, by the Parkes radio telescope when it was looking at our closest neighboring star, Proxima Centauri, and it continued to rise in frequency over the next three hours.

A student working on the Breakthrough Listen extraterrestrial search project re-examined the data and discovered the signal. More than a third of radio waves emitted into space originate from human activity. Breakthrough Listen, on the other hand, has a rigorous set of processes for removing them. When the telescope was looking at Proxima Centauri, this signal was discovered because of its frequency movement and not because it was detected at another location in the sky. To make matters more interesting, a world similar in mass to Earth orbits Proxima Centauri at at the proper distance from the star such that it could support liquid water on its surface. Is it possible that the Proximan invasion fleet is approaching us if the signal's frequency increases? There are a number of strong reasons why you should not believe this. It is improbable that a planet's atmosphere could survive the violent outbursts of Proxima Centauri, a red dwarf known for its frequent flares and CMEs. There are regular frequency gaps between the sounds, and it appears that these are multiples of the frequencies widely used in oscillators by our electrical gadgets. In spite of this, it shifts the balance back toward dullness. However, the fact that the signal cannot be caught when the telescope is not aimed at Proxima Centauri is undoubtedly strange.

As it turns out, the universe is always surprising us with new events, and while the idea of an extraterrestrial explanation is resurrected from time to time, in every case a natural explanation is found. Do we have to conclude that extraterrestrials do not exist based on our observations of the sky? When will we be able to say with certainty that a fresh piece of evidence points to the existence of life outside Earth's atmosphere? If the clue was supplied by aliens, there would be a mountain of evidence. When evidence indicates to the existence of extraterrestrials, scientists are the first to rejoice, and they will do so even more enthusiastically than everyone else. However, millions of dollars, many hours of work and a great deal of effort are being poured into trying to make it so that we can finally reveal that we are not the only intelligent beings in all of time and space.