With recent advances in the scientific community, we've been able to discover that the universe is MASSIVE. There are billions of galaxies with billions of stars that harbor billions of planets. According to some estimates, there may be more Earth-like planets in only Milky Way than grains of sand on all of our beaches.

That makes it sound impossible for Earth to be the only planet harboring life and boosts the chances that humans may not be the only intelligent life forms in our galaxy. The Drake Equation, a mathematical calculation to estimate how many communicating intelligent civilizations are in the universe, asserts in even its most modest solutions that the cosmos are teaming with life. But there seems to be a problem... where is everyone?

This was the question atomic scientist, Enrico Fermi, asked himself and his colleagues in the 1940's. If there is a likelihood of millions of advanced civilizations that may be thousands, possibly millions of years more advanced than us how come there is no tangible proof? Since Fermi addressed this odd paradox, many solutions have been created but they generally fall under three categories: aliens are here, aliens exist but haven't communicated, and aliens don't exist all together. Let's begin with the most controversial of the three.

They Are Here

According to millions of recorded UFO sightings, thousands of alien abduction accounts, and the History Channel, Earth is being visited by alien life forms. Ancient Astronaut theorists point to past artifacts, structures, and religions to affirm that extraterrestrials have played a role in human history. Other theorists believe that humanity is the remnant of a past advanced civilization from another planet. Lastly, the zoo theory states that aliens are on Earth but are keeping humanity under a sort of quarantine to prevent outside contact with other civilizations. These claims may sound interesting but they ultimately aren't backed by tangible evidence and can't be tested in any scientific way.

They're Out There But It's Complicated

This bundle of theories asserts that aliens are out there but offer up more scientific answers as to why we haven't heard anything. One states that the sheer massiveness of space makes a message from ET take hundreds, even thousands of years to reach Earth. Another explanation is that we are receiving signals but don't know how to hear them. The civilization may be so advanced that they no longer communicate with radio waves, never have communicated with radio, or could've developed an entirely new mode of communication unknown to mankind. Or maybe they just don't want to communicate all together. An alien life form could be so advanced that us humans may seem like primitive ants in the grand scheme of the galaxy or the universe. But each of these theories contain different fallacies that mainly state that the sheer number of different civilizations that should be spread across the galaxy are no excuse for not a single one using radio waves or having some curiosity about Earth.

Catastrophe

This solution to the paradox is even one of the variables considered in the Drake Equation, the lifespan of advanced civilizations. The human race, much like every other species on Earth, will become extinct due to natural causes or ourselves. With nuclear technology alone, humans have developed enough weapons to destroy Earth several times over. Also don't forget that global climate change may lead to famines, plagues, and natural disasters that could easily end humanity. An extraterrestrial civilization may have destroyed themselves millions of years before even the dinosaurs roamed Earth. Also asteroids or solar flares could easily decimate life on a planet within minutes. The reason we may not see any extraterrestrial life is because they're long dead.

Aliens Don't Exist (Or At Least Intelligent Ones)

For all we know, the creation of life may be much rarer than we originally thought. One theory asserts Earth may be the first and only place life has ever come to being. Other theories state that the human evolution of being intelligence, using tools, and language may be extremely rare. But these explanations receive hefty debate in that microbial life has been found in space, the universe is billions of years old (plenty of time for evolution), and animals on Earth have demonstrated language and tool making skills.

I know that one day we will have a definitive answer to the paradox but until then all of the theories are up for grabs. I personally align with the theory that they are trying to contact us but the distance and the technology at our disposal make it difficult for us to receive the message. What are your toughts on the Fermi Paradox and what solution do you feel explains it best?