The question of whether we are alone in the Universe is one that has perplexed humans for centuries. Reports of unidentified flying objects, alien encounters, and Government conspiracies have led many to believe that there might be Alien visitors that have come to the Earth. But are these reports really accurate? Is it really likely that foreign visitors from distant planets have visited us on Earth?

The Fermi paradox proposed by Enrico Fermi and Michael Hart in the 1970s postulated that with the vast size of the Universe, there must be other intelligent lifeforms abound. This was related to the Drake Equation, an equation postulated by Frank Drake, which assigned probabilities to various likelihoods, such as the fraction of planets that could support life that actually do support life. Using their probabilities, these scientists all concluded that intelligent alien life must exist and that it would be likely that those lifeforms have visited us.

The calculations created by the scientists made various assumptions about the probabilities of various facts with which we really have no idea regarding their accuracy. All we really have as evidence is our own knowledge of life on Earth. I would argue that our knowledge should lead us to have serious doubt that alien civilizations have visited modern humans.

In order for alien lifeforms to be visiting us on Earth, the following questions must all be answered in the affirmative:
1. Does life exist outside of Earth?
2. Are any of those life forms complex?
3. Have any complex lifeforms reached the level of complexity of humans?
4. Have any human-like or more intelligent lifeforms been able to leave their planet and explore other civilizations in distant solar systems or galaxies?
5. Have those intelligent lifeforms come across or near Earth at precisely the moment that Humans have ascended to having the capability to record their presence.

1. Does life exist outside of Earth?

The probability that there are living things outside of Earth is almost a certainty. Recent astronomical research has revealed that there are thousands of nearby, observable planets just in our galaxy. With over one hundred billion stars in the Milky Way and over one hundred billion galaxies in the observable Universe, there is almost a certainty that the process that occurred on Earth which brought about life could also have happened on other planets as well. There are too many planets for it to be a one-time occurrence.
That being said, we only have one concrete example of the formation of life, and we still haven’t been able to replicate the process, so we don’t really know how likely it is for sure. But, it is pretty safe to say that whatever natural process occurred on Earth could likely have occurred on another, similar planet.

2. Are any of those life forms complex?

Assuming that the Universe is crawling with bacteria or similar simple life forms, how can we know for certain that any of these bacteria have teamed up to form multi-cellular organisms? For over two billion years, life on Earth was perfectly content to remain in a single cellular form. It wasn’t until the Cambrian explosion, 542 million years ago, that we started seeing the abundance of complex life begin to form.

Life needed billions of years of uninterrupted prosperity to reach a point in which it started evolving to complex levels. One asteroid could have wiped out the whole process. All we know is that life takes a long time to advance from simple, unconscious forms into breathing, conscious beings. We know that the Universe is 13.8 billion years old, and thus it took about one fifth of the total duration of the Universe for complex life to form on Earth.

Knowing that it did happen here, we can probably safely say that over that time, some of those living beings on distant planets formed into complex lifeforms, but even with the vastness of the Universe, we really can’t know how often the conditions were perfect enough for long enough to facilitate that occurrence.


With hundreds of millions of years of various evolutionary paths taking place between the Cambrian explosion and the evolution of early humans, we can see that the path to intelligence is riddled with unintelligent dead ends. There are millions of species of animals on Earth, but only one has the complexity necessary to communicate with language, let alone travel throughout space (although we out-survived any competitors like Neanderthals, but they were part of the same unique evolutionary path).

There could be billions of planets in the Universe that meet the requirements of question 2 above, but only feature animals with the intelligence level of the rat or lizard.
We can see how unique our intelligence is by observing our closest living relative, the chimpanzee. Only seven million years ago, the ancestors of chimpanzees and humans were the same people. A very unique, small set of genetic mutations for the ancestors of humans separated the two of us over that short time. Without those specific mutations, we could still be living in a world of chimpanzees.

Given another seven million years, would the descendants of chimpanzees have human-like intelligence? We have no idea. All we know is that there are many more possibilities leading to non-intelligence or moderate intelligence than there are to human-like intelligence.

Based on our earthly observations, I would say that we can’t assign a more likely than not probability to the fact that human level intelligence could evolve on multiple occasions, even with the trillions of possible worlds in the known universe.


Maybe the evolution of beings with human intelligence isn’t incredibly improbable and we are not alone in the Universe? Maybe there are thousands of civilizations throughout the Universe that have been capable of the exact technological capabilities that we currently possess- sending out signals to the cosmos, flying non-living objects to the reaches of our solar system and sending living beings to orbit and nearby moons?

In that case, it is still highly improbable that we would ever make contact with those other civilizations. We can only hypothesize based on the level of our current technology, not based on some future technology that we may have. Our first radio waves are 100 light years away, relatively close in the grand scheme of the Universe. In order for us to be able to contact another civilization it would have to be really, really close, and that’s just to get a radio signal.

As of right now, we have no way of travelling beyond our solar system. We would have to hypothesize a civilization much more advanced than our own that would be able to send space ships that could arrive here from distant stars and galaxies.

An alien species capable of reaching us is thus a purely theoretical one, with no substantiation in our actual known Universe.


Perhaps an alien species somewhere in the Universe is (or was) more advanced than humans, satisfying all of the requirements in questions 1-3. Perhaps this alien has surpassed all known human technology and created space ships that travel near the speed of light, sending probes to the distant ends of the Universe to search for life.
Even still, the probability that this species would have stumbled upon Earth during the precise period of time that humans evolved to our current level of intelligence seems highly improbable. The dinosaurs were around for hundreds of millions of years. It would be much more likely that an alien species would have stumbled across the dinosaurs, seen no evidence of intelligent life, and continued on their journey.
Humankind has only been interesting from an intelligence perspective for a few thousand years. The odds of the alien species leaving its planet in search of distant life forms and coming across Earth at the exact moment that humans have ascended to technological advancement seems almost ridiculous.

In conclusion, the possibility that we will be visited by aliens during our lifetime seems so remote and improbable that the rational belief would be to conclude that we are “alone”. There hasn’t been a credible enough account of an alien encounter, and the unidentified flying objects spotted in the sky almost certainly have a terrestrial or celestial origin (not an extra-terrestrial one).

We have no idea how life forms and how likely that occurrence is. The Universe is relatively young when compared to the known gestation period for complex life. Even on Earth, a planet abound with life, intelligent life is incredibly rare. Humans are still incapable of traveling outside of our solar system, and thus aliens would have to be far more advanced than we are. Even if these aliens have more advanced methods of travel, the odds of them stumbling upon us at this exact moment are minuscule.

We still have no idea how many planets in the Universe are capable of supporting life, but even if that number is high, we should not believe that aliens are visiting the Earth.