Search for Aliens: 5 Reasons We Still Don't Encounter Extraterrestrials

Researchers have been looking for concrete signs of extraterrestrials but haven't found any for multiple reasons.

Numerous sightings of rumored UFOs and aliens have occurred in the past years. However, no concrete proof exists that extraterrestrials have been around with us. Here are five reasons why we haven't encountered any of them.

1. Drake's Equation

The Drake equation, the second-most renowned scientific formula after E=MC2, is greatly simplified in the absurdly simple algebra above.

It was first proposed by radio astronomer Frank Drake in 1961. It determines the probability of intelligent, communicative civilizations by taking into account a variety of variables, such as the number of planets, the likelihood that life would arise, and the probability that life will advance in the future.

The formula is as follows:

N = R x fp x ne x fl x fi x fc x L

Drake equation isn't a new conundrum. In fact, it has long had a name - the Fermi Paradox, named after Nobel Prize-winning physicist Enrico Fermi. The Fermi Paradox is the lack of scientific proof for extraterrestrial life in the cosmos that, according to statistical calculations, should be teeming with it. But when we use our radio telescopes to listen for extraterrestrial communications, we don't find any proof of alien technology.

2. The Great Filter Theory

The Great Filter is just a theory, but it makes sense on many levels and may offer a solid solution to the Fermi Paradox. A recent study suggests that artificial intelligence (AI) is the great filter that makes it impossible for us to contact extraterrestrials.

Some argue that the Great Filter prevents technological species from evolving into multi-planetary. This is problematic because a single-home species is more susceptible to either extinction or stagnation. A species that doesn't have a backup world is in a race against time, said Michael Garrett from the Department of Physics and Astronomy at the University of Manchester.

3. 'Gaian Bottleneck' Hypothesis

This theory takes into account how difficult it is to establish the ideal circumstances for even the most primitive forms of life, let alone reach where we are at this time. Dr. Paul Byrne, an Earth, Environmental, and Planetary Sciences associate professor at Washington University in St. Louis, agrees with this concept. He believed that while it may not be difficult for life to emerge, it is very difficult for life to persist.

For instance, Venus possibly had Earth-like habitable conditions, and Mars once had liquid water flowing across its surface. Both the Moon and Mercury also once had a thick and moist atmosphere. However, things changed.

According to Byrne, a habitable environment might not be that difficult, but sustaining it is the real challenge, and Earth is probably the only planet in the solar system that has successfully managed to host life.

4. We Missed Their Signals

Given the size of the universe, one would think that extraterrestrial life must exist. However, it's also incredibly old-more than 13 billion years-so what are the odds that any of us exist at the same time?

Dr. Minjae Kim, an astrophysicist at the University of Warwick, said the timeframe when we developed technology capable of interacting with the alien civilization matters. For him, the most likely explanation for our lack of alien encounters is that time is long, and space is massive. Even if a sentient species evolved on a planet close enough for us to detect their signals, we would still miss them if their civilization lasted only a few millennia or if we had 10 thousand years difference.

5. Gamma-Ray Burst Destroyed Them

Dr. Frederick Walter offered a unique and morbid theory about aliens. According to him, it's possible that they no longer exist because the gamma-ray bursts (GRBs) have already wiped off their civilization.

Gamma-ray bursts are "the most powerful class of explosions in the universe." The light produced by a typical burst is one quintillion, or one plus nineteen zeros, times that of the Sun. It has enough energy to wipe out any alien civilization in its galaxy.

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