What are some theories on why we haven't been visited by aliens yet?

 Have Extraterrestrials Already Visited Us?

On October 19, 2017, Robert Weryk, a Canadian astronomer, was looking through pictures taken by the Pan-starrs1 telescope when he saw something peculiar. The telescope is located on Haleakala, a volcanic mountain on the island of Maui that rises to a height of 10,000 feet. Each night, it surveys the sky and uses the highest-definition camera in the world to capture its findings. 

Its purpose is to look for "near-Earth objects," which are large asteroids that move at an average speed of around 46,000 miles per hour and fall into our planet's celestial vicinity. Weryk noticed a dot of light traveling at over two hundred thousand miles per hour, which was nearly four times that speed.

Weryk informed his coworkers, who started monitoring the dot from several observatories. The more they observed, the more perplexing its actions appeared. It was a little object, about the size of a city block. It had to be extremely peculiarly shaped since the brightness of the object fluctuated so drastically (by a factor of 10) as it tipped through space. It was either flat and round, like a heavenly pizza, or long and thin, like a cosmic cigar. It was speeding away more or less in a straight line as opposed to circling the sun on an oval course.

Astronomers came to the conclusion that the brilliant dot was an entirely new phenomenon. It was an "interstellar object"—a transient visitor from a solar system far, far away. It became recognized as 1I/2017 U1 in the International Astronomical Union's formal naming. More poetically, it was given the name 'Oumuamua, which is Hawaiian for approximately "scout" and is pronounced, "oh-moolah-moolah."

Even interstellar objects are subject to the laws of gravity, but 'Oumuamua seemed to be being driven by an additional force as it sped forward. The gases that comets emit, which create their distinctive tails, give them an extra kick. However, 'Oumuamua lacked a tail. The telescopes pointed at it also found no signs of any of the byproducts of outgassing, such as water vapor or dust.

According to a NASA video, "This is undoubtedly an uncommon item." And, regrettably, 'Oumuamua is already too dark and distant for any additional observations to be made.

Astronomers carefully examined the evidence and eliminated one idea after another. The strange velocity of 'Oumuamua could not be explained by a collision with another object, by interactions with the solar wind, or by the Yarkovsky effect, which is named for a Polish engineer who lived in the eighteenth century. One team of scientists came to the conclusion that the best explanation for 1I/2017 U1 was that it was a "miniature comet" whose tail had escaped detection due to its "unusual chemical makeup.

Another group asserted that the majority of 'Oumuamua was made of frozen hydrogen. The appeal of this theory, a variant of the mini-comet theory, was that it provided an explanation for the object's unusual form. It had mostly melted away by the time it arrived in our solar system, just like an ice cube on the ground.

Avi Loeb, a Harvard astrophysicist, provided the report of 1I/2017 U1 which was by far the most amazing. Loeb contended that 'Oumuamua didn't act like an interstellar object would since it wasn't one. It was created by culture from another planet.

A year after Weryk's discovery, Loeb and a Harvard postdoctoral fellow named Shmuel Bialy proposed that the most cost-effective way to explain 'Oumuamua's "non-gravitational acceleration" was to assume that the object was manufactured. 

Their equation-heavy paper was published in The Astrophysical Journal Letters. It may be "floating in interplanetary space" as "debris," the extraterrestrial version of an abandoned automobile. Or it could be "a fully working probe" that has been sent to conduct reconnaissance in our solar system.

According to Loeb and Bialy, the second scenario was the more plausible one because the odds of humanity ever finding the item were extremely tiny if it were just some alien trash drifting across the cosmos. After considering the prospect of an artificial genesis, Loeb said in a blog article for Scientific American, "We should remember what Sherlock Holmes said: 'When you have dismissed the impossible, whatever remains, however implausible, must be the truth.'"

Unsurprisingly, a lot of attention was paid to Loeb and Bialy's idea. Faster than 'Oumuamua, the tale spread over the globe. At the Harvard-Smithsonian Center for Astrophysics, TV crews descended on Loeb's office and home. Film studios competed to produce a movie about his life. Not unexpectedly, negative media coverage predominated.

Paul M. Sutter, an astronomer at Ohio State University, stated that "'Oumuamua is not an extraterrestrial spaceship, and the authors of the publication demean honest scientific research to even imply it."

Can we speak about how bothersome it is that Avi Loeb promotes wild speculations about the extraterrestrial origins of 'Oumuamua, making the rest of us undertake the laborious scientific effort of refuting these rumors? University of Arizona astronomer Benjamin Weiner tweeted.

Loeb increased his efforts instead of backing down. He attacked the frozen-hydrogen idea alongside Thiem Hoang, a scientist at the Korea Astronomy and Space Science Institute. The pair claimed that it was unrealistic to think that solid hydrogen would be floating around in space in another article that was jam-packed with equations. 

And even if a frozen piece did manage to form, a block the size of 'Oumuamua could not possibly survive an intergalactic voyage. According to Hoang and Loeb, "sublimation by collisional heating" would destroy any H2 objects that could manage to form before they could, in a sense, take flight.

With the publication of "Extraterrestrial: The First Sign of Intelligent Life Beyond Earth," Loeb has done away with the scientific notation (Houghton Mifflin Harcourt). He tells the well-known tale of how Galileo was accused of heresy for claiming that the Earth revolved around the sun. Galileo allegedly retracted his testimony at his trial in Rome in 1633 and then mumbled, "Eppur si muove" ("And yet it moves"), according to folklore. 

Although Loeb agrees that the phrase is likely apocryphal, he nevertheless believes it to be pertinent. Even while the astronomical establishment would like to keep him quiet, it is unable to explain why 'Oumuamua deviated from the planned course. And yet, he says, "it changed."

Loeb explains his thinking in "Extraterrestrial" as follows. Without resorting to some form of undetected outgassing, the only explanation for 'Oumuamua's peculiar acceleration is to postulate that the object was driven by solar radiation, or more specifically, photons bouncing off its surface. 

The item could only be pushed by solar radiation if it were very thin—no thicker than a millimeter—with low density and had a sizably vast surface area. Such a thing would act as a sail, but one propelled by light instead of wind. People make sails, not the natural world. Therefore, 'Oumuamua must have been created, created, and launched by an alien intelligence, according to Loeb.

In 1995, Swiss astronomers Michel Mayor and Didier Queloz discovered the first planet to be discovered orbiting a sun-like star. The planet was given the official name 51 Pegasi b because its host star, 51 Pegasi, was in the constellation Pegasus. It was later given the name Dimidium thanks to a different naming scheme.

The "Oumuamua" of its day, the finding of dimidium generated international news. Mayor and Queloz subsequently received a Nobel Prize for their efforts. The planet's mass, which is around 150 times that of Earth, proved to be extraordinarily huge. It had to be near its star because it was whirling around it once every four days. 

It was also likely incredibly hot, with a surface temperature of up to eight hundred degrees. The discovery of such a massive planet so near to its parent star shocked astronomers, who had to create the term "hot Jupiter" to describe it.

By measuring the gravitational pull of Dimidium on Pegasus 51, Mayor and Queloz have discovered it. The Kepler space telescope, which was created to find exoplanets using a different approach, was launched by NASA in 2009. A planet's passage in front of its star causes a very minor dimming of the star's brightness. 

(At the time of Venus' most recent transit in 2012, observers on Earth could see a tiny black dot move across the sun.) More than a hundred and fifty thousand stars near the constellations Cygnus and Lyra had their brightnesses tracked by Kepler. It discovered 1,000 exoplanets by the year 2015. By the time it ceased operations in 2018, sixteen hundred more had been exposed.

The eta-Earth, or, the figure was the telescope's ultimate objective for NASA. This is the typical number of planets that are rocky and around the size of Earth that can be discovered circling a typical sun-like star at a distance that might theoretically make them habitable. Researchers have come to the conclusion that has a value between.37 and.6, after spending two years reviewing the data from Kepler. The Milky Way has at least four billion sun-like stars, which implies that there are theoretically between 1.5 billion and 2.4 billion planets in our galaxy that may support life.

Nobody is certain of what percentage of potentially habitable planets are really populated, but even if it's a negligible number, there are still millions—possibly tens of millions—of planets in the galaxy that may be teeming with life. A few years ago, Ellen Stofan, who is currently the director of the National Air and Space Museum and was previously NASA's chief scientist, stated at a public event that she thought "definitive proof" of "life beyond earth" would be discovered within the next two decades.

At the same event, NASA astronomer Jeffrey Newmark added, "It's clearly not an 'if,' it's a 'when.

When—not if—life is discovered on other planets, what will it look like? This issue is addressed in "The Zoologist's Guide to the Galaxy: What Animals on Earth Reveal About Aliens—and Ourselves" by Arik Kershenbaum, a researcher at the University of Cambridge. It's a common misconception that alien life is unimaginable, he writes. "I don't concur.

Natural selection, according to Kershenbaum, is the key to comprehending cosmic zoology. He claims that this is the "inevitable method" by which life arises and that it is consequently "not merely confined to the planet Earth" or even to creatures made of carbon. Regardless of how extraterrestrial biochemistry operates, "natural selection will be at work."

According to Kershenbaum, it follows from this assumption that life on other worlds will have developed, if not along similar lines to life on our planet, then at least along generally recognizable ones. Feathers are a helpful trait, for instance on Earth where the atmosphere is primarily composed of nitrogen and oxygen. Feathers presumably wouldn't develop on a planet where the clouds are ammonia-based, but "we should not be shocked to see the same functionalities (i.e. flying) as we witness here."

Similarly, according to Kershenbaum, alien life is likely to have evolved some form of land-based locomotion—"Life on alien planets is very likely to have legs"—as well as an equivalent of sex for reproduction and a method of communication: "Aliens in the dark will click like bats and dolphins, and aliens in the clear skies will flash their colors at each other."

If there is extraterrestrial life out there at all, most of it is probably minuscule. Stofan responded, "We are not talking about tiny green guys," when she claimed we would locate it shortly. We're referring to tiny bacteria. However, Kershenbaum, who specializes in animal communication, skips right to complex creatures, which rapidly places him in Loebian terrain.

Many creatures on Earth exhibit what humans may generically refer to as "intelligence." Given the benefits that this feature offers, Kershenbaum contends that natural selection will favor its emergence throughout the galaxy, and as a result, there should be many life forms out there that are at least as intelligent as humans are, if not more so. According to him, this opens up a whole can of interplanetary worms. 

Will we provide "human rights" to aliens? Will they provide us any privileges that they do, if any, grant to their small green (or silver or blue) brethren? Such inquiries are challenging to answer in advance, according to Kershenbaum, "without any evidence of what type of legal system or system of ethics the foreigners themselves may have."

Even more unsettling than coming across sentient aliens is, possibly, the fact that we haven't heard from any of them yet. The Fermi paradox is the name given to the puzzle of why this is the case.

Enrico Fermi, a scientist, turned to several coworkers one day in 1950 while eating lunch at Los Alamos National Laboratory and inquired, "Where are they?" (At least that's how one account of the incident goes; in another, he inquired, "But where is everyone?") Years before Pan-Starrs 1 and the Kepler mission, this occurred.

Fermi believed that despite this, Earth was a reasonably ordinary planet orbiting a fairly common star. He reasoned that there should be civilizations that are far older and more developed than our own, some of which should already be skilled in intergalactic travel. Strangely enough, nobody had arrived.

Since then, a great deal of human ingenuity has been spent pondering Fermi's query. Frank Drake, an astronomer, developed the eponymous Drake equation in the '60s, which provides a means to estimate—or, if you prefer, guesstimate—how many extraterrestrial societies there are that we may expect to speak with. The number of potentially habitable planets, the percentage of potentially habitable worlds that will develop advanced technology, and the persistence of technologically advanced civilizations are important variables in the equation.

The "Where are they?" conundrum has only gotten more complicated as the number of possibly livable worlds has increased. A French researcher by the name of Jean-Pierre Rospars advanced this theory during a symposium on the topic conducted in Paris in 2019: Aliens haven't contacted us because they're keeping Earth under a "galactic quarantine." They understand that "learning about them would be culturally damaging for us," he added.

Loeb suggests that Fermi may provide the solution to his own conundrum. Only in the last century or two has humanity developed the ability to communicate via radio waves with extraterrestrial beings. The atomic bomb was developed by Fermi and his Manhattan Project coworkers seventy-five years ago, and the hydrogen bomb was developed a few years later by Edward Teller, a lunch companion of Fermi's at Los Alamos.

So, not long after mankind developed the ability to communicate with other worlds, it also developed the ability to exterminate itself. We have continued to devise new means to destroy ourselves since the development of nuclear weapons, including unchecked climate change and synthetic microorganisms.

The next few centuries of our civilization might very well be its last, says Loeb, if we do not take precautions. He implies that alien civilizations that have the technical capacity to explore the cosmos are also "susceptible to extinction by self-inflicted wounds." Perhaps the absence of attendees is due to the fact that no one is available to travel. This would imply that "Oumuamua" was the cosmic version of a potsherd—a relic of a long-since-dead civilization.

This (albeit extremely hypothetical) line of reasoning may be seen as a warning to earthlings to be cautious of new technology. For his part, Loeb comes to the exact opposite conclusion. He believes that mankind should be attempting to create a photon-powered vehicle that is exactly like 'Oumuamua. He serves as an advisor for the Breakthrough Starshot Initiative, a project whose stated goal is to "show proof of concept for ultra-fast light-driven nano crafts," in order to achieve this.

The team wants to "build the foundations" for a launch to Alpha Centauri, the star system nearest to Earth at a distance of around 25 trillion miles, in the long run. (The effort is supported by Russian-Israeli billionaire Yuri Milner, and Mark Zuckerberg serves on its board.)

The day when we will be able to "create synthetic life in our laboratories" is something else that excites Loeb. Then he envisions "Gutenberg DNA printers," which "might be spread to create copies of the human genome out of raw materials on the surface of distant worlds." He proposes that by dispersing our genetic material around the cosmos, we could reduce the likelihood of total extinction. 

We could also conduct a huge evolutionary experiment, which may produce results that are considerably more amazing than those we have observed so far. According to Loeb, "There is no reason to suppose that terrestrial life, which arose under accidental conditions on Earth, was ideal."

Chariots of the Gods by Erich von Däniken was one of my favorite novels as a child. The premise of the book, which was adapted into the Rod Serling-narrated television documentary "In Search of Ancient Astronauts," was that Fermi's dilemma had long before been resolved. "They" had been here before. 

Von Däniken, a former hotel manager from Switzerland who is now an author and who in the program was oddly referred to as a German professor, made the case that aliens had visited Earth in the distant past. Legends and relics, like the Nazca Lines in southern Peru, bear witness to their travels. If not to communicate with entities in the air, why had humanity made these large images?

I contacted von Däniken because I believed he would be intrigued by the first recognized interplanetary object. He is 85 years old and resides not far from Jungfrau Park, a theme park he built and which was once known as Mystery Park until being renamed as a result of a string of financial setbacks. Seven pavilions make up the park, one of which is fashioned like a pyramid and another like an Aztec temple.

Von Däniken admitted to me that he had been keeping up with the 'Oumuamua' debate. He often sided with Loeb since he believed that Loeb was a really bold man.

He answered, "He requires bravery, and certainly he had courage. "No scientist likes to be laughed at, and anytime they deal with UFOs or aliens, the media laughs at them." But "the circumstances will change," he asserted.

"Exceptional claims deserve extraordinary evidence," is a common adage. The astronomer Carl Sagan, who perhaps accomplished more than any other scientist to advance the hunt for alien life, popularized the phrase. Loeb's assertion plainly falls short of what is frequently called to as the "Sagan test," and the strongest support he offers for his argument that 'Oumuamua is an extraterrestrial vessel is that the competing ideas lack merit. 

However, Loeb expressly rejects the Sagan standard and turns its reasoning on its head: "Exceptional conservatism keeps us extraordinarily stupid." He adds, "It is not evident to me why extraordinary assertions demand extraordinary evidence."

We'd be idiots to ignore the possibility that 1I/2017 U1 is an extraterrestrial probe as long as it's a possibility. He states that "whole new horizons of research for proof and discovery open before us if we recognize that 'Oumuamua is probably of extraterrestrial-technology origin."

Loeb undoubtedly took a risk by publicizing his hypothesis and paid the price in derision. Extraterrestrial looks far more likely to be ranked with von Däniken's work than with Galileo's. Even so, it's exciting to consider the possibilities, as Serling observes toward the conclusion of "In Search of Ancient Astronauts": "Look up into the sky some clear, starlit night and allow yourself the freedom to wonder."