Please literally explain it like I’m 5! TIA
Edit- thank you for all the comments and particularly for the links to videos and further info. I will enjoy trawling my way through it all! I’m so glad I asked this question i find it so mind blowingly interesting
In: 4425
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Come up with an estimate for how many stars are likely to have habitable planets. Then of those, how many will form life. Then of those, in how many will that life become multicellular, then complex, then sentient, then sapient, then civilized, then industrial, then nuclear, then space-faring, and so on.
Take the combined percentages of all those things, multiply by an estimated number of stars in the entire universe, and according to those estimates, you should come up with something like hundreds of thousands of galactic-level civilizations popping up over time leaving evidence everywhere that alien life exists.
But we have no evidence of any of them existing. That’s the paradox.
edit – and sorry, this was a fairly quick reply that melded the answer with the Drake Equation and I could have gone into a lot better detail. Wasn’t expecting it to blow up
Our solar system is pretty young, and our galaxy is big, so some other intelligent life should have taken over the galaxy by now. We see no evidence of that happening. The most common response is that intelligent life is extremely rare, so it probably hasn’t happened in our galaxy before.
There are so many stars in the universe that we cannot count them. It’s a very very high number that is hard for us to contemplate! Because there are soooo many stars, some scientists think that there just HAS to be other life out there. Even though there are soooo many stars, and we are pretty sure there must be life out there, we have not been able to find evidence or proof other life exists outside of our planet.
The Fermi Paradox can be thought of like this: If there are so many stars, why haven’t we found other life out there in space?
I found Kurzgesagt’s series on the Fermi paradox explained things really well: https://youtu.be/sNhhvQGsMEc
For how quickly our technology has progressed and how long the universe has existed for, literally any civilisation that has survived has had the time to fully colonize a significant portion of the Galaxy. But we see nothing, not even a trace. We’ve had civilisation for maybe 4-12k years depending on your definition/sources which is an insanely small fraction of the time the universe has been around. So the paradox is if we got from monkey to space in that amount of time and the universe has been around for millions of times more time, why do we see nothing?
Other responses have gotten the basic framing correct: Our galaxy is large, and much of it is much older than our Solar System. Taking basic wild-ass-guesses at various parameters that model the probability of intelligent life forming in the galaxy, we’re left in a position that it seems likely that it has developed. If the civilizations don’t die out, it ‘should’ be possible to have some form of probe/ship/exploration spread out over the galaxy in something on the order of 100’s of thousands of years, which really isn’t very long in comparison to the age of the galaxy.
We don’t see any evidence of this type of activity at all. This is the ‘paradox’ – it ‘should’ be there, but it isn’t.
Where the Fermi Paradox gets it’s popularity though is in the speculation around “Why don’t we any signs”. There is seemingly endless debate possible. To wit:
– We’re first. despite the age of the galaxy, we’re among the first intelligent civilizations, and nobody has been around long enough to spread.
– We’re rare. Variation on the above – intelligent life just isn’t as common as we might think.
– There is a ‘great filter’ that kills off civilizations before they can propagate across the galaxy.
– The Dark Forest: There is a ‘killer’ civilization that cloaks themselves from view but kills any nascent civilizations to avoid competition. (Or, an alternative version is that everyone is scared of this happening, so everyone is hiding)
i think the Fermi Paradox frequently seems to get more attention than it deserves, largely due to the assumption that spreading across the galaxy is an inevitable action for an advanced civilization. I’m not entirely convinced of this – if FTL travel isn’t possible (and I don’t think it is), then the payback for sending out probes/ships to destinations 1000’s of light years away seems to be effectively zero, and so I don’t see how it’s inevitable. But, there’s no question it generated a lot of lively debate.
It goes like this
1. Earth has intelligent life on it.
2. Even if intelligent life is extremely rare, the galaxy has hundreds of billions of stars, so there should be other intelligent life elsewhere. Even one other planet with interstellar travel technology is enough.
3. Even at slow speeds, an technological civilization can visit every star in the galaxy in less 50 million years. (The 50 million is actually a bit of an *over*estimate)
4. The galaxy is old enough that there were planets as old as Earth is now at the time the Earth first formed.
5. That’s plenty of time for a technological civilization to get to the solar system and leave evidence of that.
6. There is absolutely no evidence that this has ever happened, so where the hell are they?
There are plenty of answers to the paradox, but they generally fall into assuming that aliens choose to not come to the solar system. Remember that they can visit literally every star in the galaxy, so them not coming here makes us a special case that needs explanation. There’s an idea called the Copernican principle that we should assume we’re average without evidence otherwise.
Alternately, there could be no other life in the galaxy which is odd for two reasons. The first is that life isn’t made out of anything special. You’re pretty much made of methane, ammonia, water, and carbon dioxide linked together in complicated ways, and the ancient Earth was covered in those chemicals. Life also appears at pretty much the earliest time it could, so it seems reasonable to assume that any planet like the early Earth will end up with life like the Earth.
Other folks have explained the *what* question really well. My answer will include my personal preferred *solution*. Other folks will have theirs, or they might certainly be able to provide counterpoint to what I’m about to write.
My personal educated opinion is that life in some form is abundant throughout the galaxy. Intelligent life is rare, but my optimistic side says it’s greater than zero (in addition to us humans).
Assuming that much, my brain has chosen to divide those potential alien civilizations into three logical groups, depending on how their advancement level compares to ours.
The first group are the normal Star Trek-style aliens who are roughly on par with humans technologically (maybe within a century or two). Those aliens would be exceedingly hard to find — our solar system is about 4.5 billion years old, but humans have been using radio for about a century. To find some other civilization in the middle of that equivalent microscopic snapshot would be extremely unlikely. So they can be logically disregarded in any traditional SETI radio search.
The second group are the aliens who are less advanced than we are. They’re the ones who haven’t discovered radio yet. We can also disregard them — if they exist, they’re not talking in ways that we can hear.
That leaves the third group of aliens, who are *more* advanced than we are. The question then becomes, how *much* more advanced? At least on the order of thousands, probably on the order of *millions* of years more advanced. Their data requirements in communication are probably so large, and their data compression needs so extreme, that any transmissions we overhear are probably indistinguishable from background noise if we’re limited to Earth-modern technology.
To find a civilization communicating at that level (assuming they’re even using radio in the first place, as opposed to some more advanced kind of physics we haven’t yet discovered) would be a lot like tapping into a copper wire, looking for Morse Code pulses, and finding Modem static instead.
If all you knew was Morse, would you even recognize the Modem static as intelligent, let alone have any way of deciphering it? Probably “no”, either way.
On Earth it took about a century to graduate from telegraphs to Modems, and Modems themselves are already obsolete even within our lifetime. Add another million years to that development rate and you can start to see the problem.
TLDR: if aliens exist, either they’re not talking, or we haven’t learned how to listen.
In [1950](https://youtu.be/zqzMAnPKa_s) at Los Alamos a scientist was talking with his friends
The conversation had them all fully engrossed about this universe that almost has no end
And as they were all about to return to their study
[Enrico](https://en.m.wikipedia.org/wiki/Enrico_Fermi) suddenly shouted: *Where is everybody?!*
And he sat down and did a few simple calculations
That indicated we should’ve been visited thousands of times
At least based on his estimations
Well, that’s the Fermi paradox, if they’re out there why don’t we hear them talk
And the galaxy just keeps on spinning, with 400 billion stars in it
And I just can’t believe that we could be unique
When there’s so much space in this galaxy
I want Pandora’s box-
-to be open but instead we’re stuck in Fermi’s paradox
—
That’s a bit “for fun”, but it gets at the idea. For the amount of *stuff*, there *should* be intelligent life, but we’ve never seen any indication of its presence.
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