Do aliens exist? That’s a tough question. It’s obviously possible that life can evolve because here we are on Earth. Has it happened elsewhere in the universe? Probably, given the number of worlds out there, but there’s no way to be sure. Scientists have made attempts to calculate the likelihood of extraterrestrials existing and estimate the number of alien civilisations that could be out there.
Astrophysicist Frank Drake created an equation, the Drake Equation, to estimate the number of active civilisations in the Milky Way galaxy that could communicate with us. It’s just an estimate so we can’t read much into it but you can be quite conservative with the inputs and it still suggests there should be plenty of other civilisations and that’s just in the Milky Way, which is one in hundreds of billions of galaxies.
So if it’s likely we’re not the only civilisation capable of sending out communications across interstellar space, why aren’t we hearing from anyone else? It’s one thing to not be visited, but to not even hear anyone else’s chatter out there? This is known as the Fermi paradox named after Encrico Fermi. There are billions of stars like our sun in the Milky Way and many will have Earth-like planets (estimates suggest there are 100 Earth-like planets for every grain of sand on Earth). Some of those planets will develop intelligent life. Many of these stars have been around for billions of years longer than our own so aliens have a head start at interstellar travel. So, what gives?
Humans have been around for just a moment in terms of the history of the universe. We appeared practically yesterday and we’ve only been using computers and spacecraft for a few decades. Douglas Adams put it best:
“Far out in the uncharted backwaters of the unfashionable end of the western spiral arm of the Galaxy lies a small unregarded yellow sun. Orbiting this at a distance of roughly ninety-two million miles is an utterly insignificant little blue green planet whose ape-descended life forms are so amazingly primitive that they still think digital watches are a pretty neat idea.” – Douglas Adams, The Hitchhiker’s Guide to the Galaxy
But we’re already developing technologies to make interstellar travel possible. It took 66 years to go from the Wright brothers to the moon landing and now we’re working on solar sail nanoprobes to travel to other stars in mere decades. There are plenty of star systems out there that are billions of years older than ours so aliens have had more time to become interstellar. Sure, the distances are extreme but what’s a few million years of travel for life that’s been around for billions of years? Why haven’t we been visited? Here are some of the possible reasons.
The rare Earth hypothesis
The most obvious solution to the Fermi paradox is that we really are alone. The sheer number of worlds in the universe make it seem possible that life can evolve more than once but the Rare Earth Hypothesis suggests biogenesis is simply so complex it’s literally one-of-a-kind. For life to exist on Earth as it does today, many complex events had to occur and in the right place at the right time.
It’s not just the complexity of biogenesis itself; it’s the many factors that make Earth ideal for life. Our planet is a relatively stable environment. Sure, we lose most of our species every time we get hit by a giant rock from outer space but generally things are calm. We’re a good distance from our star and even our moon to keep conditions stable enough for life to prosper. Some people think that all of these factors coming together might be too rare for life to have evolved elsewhere in the universe, despite the staggering number of worlds.
The signals are there, we just haven’t spotted them yet
We’ve been listening for extraterrestrial communications for decades and haven’t heard anything and this is a big part of the Fermi paradox. However, not finding communications from aliens doesn’t mean there aren’t any. We haven’t been trying very hard, to be fair. We don’t put as much resources into searching for extraterrestrial signals (e.g. SETI) as we do into space exploration (e.g. NASA). We only listen to small parts of the sky and usually at limited times on borrowed equipment. We also don’t know exactly what we’re looking for.
Another possibility is that the signals are everywhere but we’re far too primitive to recognise them. We tend to think aliens will kind of look like us, think like us, count and talk like us, and have similar technology. We look for radio signals because that’s what we’re sending out but aliens could be sending communications using neutrinos, gravitational waves, or something we can’t yet comprehend.
The Great Filter
Perhaps life is abundant in the universe and intelligent civilisations aren’t exclusive to our own planet, but they don’t survive long enough to travel or communicate across interstellar distances. Perhaps there is always some barrier or stumbling block, either technologically or naturally, that wipes out species before they can explore the stars.
Looking at our own planet we know that mass extinctions happen fairly regularly and wipe out most of the species on the planet. The Earth might be just a tiny dot in space but there are enough asteroids out there to ensure that most species are wiped out every few hundred million years. We’ve had 5 major mass extinction events so far, the worst being the Great Dying that occurred between the Permian and Triassic periods and destroyed 96% of all species.
Maybe the rate of extinction for intelligent species means that they never quite develop the technology to reach other stars. Another possibility is that the development of technology itself leads to civilisations destroying themselves before they develop interstellar technology. The go-to explanation is nuclear war. It’s sad to think that every single alien civilisation would always destroy itself.
All of this makes us wonder what stage we’re at. We’re already beginning development of technology to travel to other stars so are we one of the only species to make it past the barrier and escape The Great Filter? Or are we heading towards it, full steam ahead?
The weird theories
There are too many really weird theories to list here so we’re clumping just a couple together to give you an idea of how bizarre some of the explanations are for the Fermi paradox. One of the more reasonable weird ideas is that interstellar travel is so difficult and takes so long to develop that species figure out how to explore other dimensions and universes before they can even reach other stars. By that point who cares about stars, right? To cosmic beings of pure energy, why waste time with carbon-based bipeds on some watery world in the middle of nowhere.
Even weirder is the Planetarium Hypothesis, which suggests that we’re living inside of a computer simulation like the Matrix and that we’re all artificial intelligences within the system. If the observable universe is just for us, maybe other species haven’t been programmed into it and that’s why we don’t find evidence of anyone else out there. If this sounds insane then you’re not alone, we’re right behind you. But an alarming number of physicists and philosophers take the hypothesis seriously and debate how we could actually test it.
The aliens are already here
One answer to the Fermi paradox is that the aliens have already found us and are living among us but keeping quiet about it. It’s seems extremely unlikely that species would travel interstellar distances only to chill on our rock in secret, despite prominent politicians like a former Canadian prime minister claiming that 80 alien species live on Earth. Some hide away because they look like movie aliens while others live among us because they look very similar. Some of these people claim that Nordic males are actually an alien species. Seriously.
Never trust anyone who says aliens naturally look just like us. We look the way we do because of our ancestry as primates, and reptiles, and fish etc. To think that aliens could be identical to humans is like believing that aliens not only develop spoken languages but specifically 21st century Engish. We got modern English through years of language evolution over generations. English is shaped by its past. What are the odds that we find an alien species using English? Unlikely, yes? Well, biological evolution is much the same. Humans won’t be found elsewhere.
Why do some politicians claim that there are aliens? Who knows. Attention most likely, or they’re mistaken, which are perfectly reasonable explanations and more plausible than the conspiracy theories. Also this just in: politicians can lie.
For the best?
We feel it would be immensely sad if we’re truly alone but some people like Stephen Hawking think it could be a blessing, suggesting that we should lay low if we do hear from aliens as we might suffer from their interactions. History is filled with entire peoples being wiped out by colonisers. We might not want to attract other civilisations in case the same thing happens on a planetary scale.
Arthur C. Clarke once wrote, “Two possibilities exist: Either we are alone in the Universe or we are not. Both are equally terrifying.”
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