Where Are All The Aliens?

In this short explainer video, Universe Today publisher investigates the riddle of the Fermi Paradox; if the Universe is big, and old, and there are countless habitable worlds, why do we see no evidence of life? Where are all the aliens?

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Consider this. The Universe is enormous.

There are as many as four-hundred billion stars in our galaxy: the Milky Way. And there are more than one-hundred-and-seventy billion galaxies in the observable Universe. Most of those stars have planets, and many of those planets have got to contain useful minerals and fall within their star's habitable zone where liquid water is present.

The conditions for life are probably everywhere.

But where are all the aliens?

And think about this.

The Universe has been around for thirteen-point-eight billion years. Human beings originated two-hundred-thousand years ago, so we've only been around for zero-point-zero-one-percent of the age of the Universe. An intelligent species could arise on any one of those countless worlds, and broadcast their existence to the entire galaxy.

Once a species developed interstellar travel, they could completely colonize our galaxy within a few tens of millions of years; just a heartbeat in the age of the Universe.

So where are they?

As far as we know, Earth is the only place in the Universe where life has arisen, let alone developed an intelligent civilization.

This baffling contradiction is known as the Fermi Paradox, first described in nineteen-fifty by the physicist Enrico Fermi.

Scientists have been trying to resolve this mystery for decades, listening for radio signals from other worlds. We've only sampled a fraction of the radio spectrum, and so far, we haven't detected anything that could be a signal from an intelligent species.

How can we explain this?

Maybe we really are the only planet in the entire Universe to develop life. Maybe we're the first civilization to reach this level of advancement in the entire galaxy. But with so many worlds out there, that really seems unlikely.

Maybe civilizations destroy themselves when they reach a certain point. Nuclear weapons, global warming, killer epidemics, and overpopulation could all end humanity. Asteroids could strike the planet and wipe us out. But would this happen to every single civilization? one-hundred-percent of them? Even if ninety-nine-percent of civilizations destroy themselves, we'd still have a couple that made it through and fully colonized the galaxy.

Maybe they're just too far away, and our signals can't reach each other. But then, self-replicating probes could traverse those distances and leave a local artifact in every single star system.

Maybe we can't understand their signals or recognize their artifacts. Maybe, but if aliens constructed a series of artifacts on Earth, I think we'd notice them. The aliens would have experience creating obvious structures.

Maybe they're just too alien and we just can't understand them. Maybe we're too insignificant, and they don't think we're even worth talking to. We don't need to talk to them to know they exist. If they flew through our Solar System, ignoring us, we'd still know they're around.

Maybe they're not talking to us on purpose, and we're really in some kind of galactic zoo. Or aliens have a Prime Directive, and they're not allowed to talk to us. Again, all the aliens? Not a single one has gotten through and snuck us some evidence?

There are many other potential solutions to the Fermi Paradox, but I personally find them all insufficient. The Universe is big, and old, and if extraterrestrial life is anything like us, it wants to multiply and spread out.

Perhaps the most unsettling thought is that something happens to one-hundred-percent of intelligent civilizations that prevents them from exploring and settling the galaxy. Maybe something good, like the discovery of a transportation system to another Universe. Or maybe something bad, like a destructive technology that has destroyed every single civilization before us.

How do you feel about the Fermi Paradox? How do you resolve the contradictions? Whatever the solution, it's really fun to think about.

[frasercain]

The Reapers was a fantastic way of handling the Fermi Paradox. I love Mass Effect.

[frasercain]

I think that's a reasonable answer to the Fermi Paradox, that there's an obvious communication technology that everyone uses, and we just haven't worked it out yet. But you might expect a few aliens to keep using the old tech radio signals, just in case.

[datikro]

“Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.”

- Arthur C. Clarke

[rickysmyth]

The speed of light is too slow, and the distances are huge

[frasercain]

I always tell people that Mass Effect is the best science fiction movie I've ever played. Regarding the Fermi Paradox, do a search for the "Great Filter". I find that idea compelling: Reapers.

[abagofsunshine]

I love the moment where he says where are all the aliens and a text pops up and says "and why don't you ever call? "

[frasercain]

The closed captioning [CC] should be exactly the same. Are you looking at that?

[frasercain]

Sure, if it's happened once, it could happen again. There are several really intelligent species that could become as intelligent as humans in a few million years.

[frasercain]

It seems pretty hard to believe. If a civilization can make that journey, there won't be any possible cover-ups.

[frasercain]

NASA actually released a comprehensive document discussing alternative liquids that could theoretically support life as well, like ammonia-based life, or methane-based life. They're using this to expand their search parameters.

[chichimus]

Scariest idea I have come across is that there are lots of civilizations out there but they are keeping quiet because they do not want to draw the attention of a malevolent group intent on wiping everyone else out (think BORG or Krikkit)

[Chris-hpbe]

I personally think its the extreme vast distance between stars not to mention galaxies that is the problem. Even if there is intelligent life somewhere in Andromeda (the nearest galaxy) it would take so long to reach and explore us even for a more advanced civilisation. Although it's only a matter of time till we eventually get to know other aliens so terribly far away

[SkatingToy]

To me, it is truly beautiful how we can ask questions with unknown answers.

[tecm]

Your best one yet. Very comprehensive, succinct and well enunciated.

[danielfarrell]

After listening to pretty much every Astronomy Cast episode in the last few months, great to discover these videos.

[frasercain]

That's a great question. Maybe they could be microscopic with the right technology, and then they construct larger facilities when they arrive.

[rstrosah]

What you have to remember is that ‘Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is.’ Intelligent species (For the sake of the argument I’ll define intelligent as capable of sending interstellar signals) may simply be fairly rare and the galaxy alone could probably maintain a handful of them without us being able to detect them.

And then there’s other galaxies I mean would we even notice if the Sombrero Galaxy had a Von Neumann infestation?

[EricPouhier]

Great video about the Fermi Paradox, to me the main possible explanation is about maths. As you know we use the continuum in maths while we know that the universe is purely quantic (the opposite of the continuum hypothesis). When THIS mathematical terrestrial paradox will be solve and that we get some discrete maths. I bet that we will realise that we have been receiving signals from extraterrestrial intelligences like forever. And we will be able to decrypt them properly.

[luminousstrawberries]

Text notes on video were all great, well done

[Bombdodger]

Fact is, we just don't know and might not for several hundred generations to come. There are so many variables. We are probably the first civilization to reach this level of intelligence within the reachable universe. Notice I said "reachable". Other civilizations might be out there but might as well not even exist if we cant see or communicate with them. Lets keep out collective ears open and just focus on finding life elsewere in our own galactic neighborhood. That notion might not seem as fantastic as looking for intelligent life, but just imagine seeing a complex animal from a distant planet for the first time. So exiting to me. Great channel by the way Frazer. Im a subscriber now!