'Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.' - Arthur C Clarke

I have to go with the Calvin & Hobbes quote - “The surest sign that intelligent life exists elsewhere in the universe is that it has never tried to contact us.“ - Bill Watterson

I love how quickly you dismiss the idea that our is lying to us, as if it’s impossible or there’s no precedence.

My absolute worst fear in this universe, in regards to finding "new" life, is that when/if we find someone, it's more humans

I swear, this guy has as many youtube channels as there are planets in the universe

My best friend passed away last year and he watched your videos every day. Always talked to me about them at night. Now I watch.

Part of the dark forest is also the not knowing. You don't know if that alien civ will be friendly. Let's say you're friendly and want to make friends, peace and love and stuff. But the other side isn't and tries to wipe you out the moment you make contact. So there is no reason for other civs to give each other even a chance instead of preemptively trying to wipe the other out before the other notices you're there and possibly wipes you out

I have to say the gorilla using the GPS analogy was awesome perfectly explained. And I refuse to believe there’s not life out there somewhere.

I believe it was Hawking who said you need only look at us to figure out why intelligent life might not be something you want to find

Even with all the effort mankind has spent on 'watching the skies' for extraterrestrial life, we have barely scratched the surface. I think it was Dr. Neil deGrasse Tyson who put it bluntly, "Go out into the ocean and pull up a bucket of water. If there are no fish in the bucket, does that mean there are no fish in the ocean?"

I honestly think the great filter is simply distance. Most of our current solutions rely heavily on the notion that we will one day be able to harness faster than light travel. But what if that is genuinely not a possible solution within our specie’s existence?

The universe is older and more vast than we can ever truly comprehend. The thought that we are the only, the first or the most advanced form of intelligent life in that seemingly endless sea of possibility is either ignorance or narcissism.

I support the "galactic trailer park" hypothesis. It's the theory that Earth is the interstellar equivalent of the the sketchy people in a Florida trailer park. They don't let us know they are out there because if they did we might slap together a space RV and show up on their lawn like cousin Eddie wanting to "borrow" stuff all the time.

Time scales may also be important here: consider how long it took humans to evolve, versus how long it took us to go from stones tools to space shuttles. This means that even a slight discrepancy could put all other civilizations hundreds of thousands of years behind us... or ahead; whether that makes them just too advanced to communicate, or too uncaring, or just eventually extinct somehow. It's entirely possible advanced civilizations come and go, but they just never overlap in time.

I feel like we can circumvent the problem that "We cannot communicate" quite simply: We have a massive surplus of things we want to get rid of, namely nukes in this case. Building a facility in space with a large parabolic mirror of like 3-5 km diameter, where we detonate nuclear weapons at the focal point would serve as a great way of sending signals: -The pulse energy is high enough to not be consumed by noise easily -The pulse is not narrowed to one wavelength and is rather broadband (IR, visible light, Gamma radiation, XRays, Radiowaves, etc) meaning it can be detected with a variety of instruments -We can repeat these pulses for a LOOOONG time (while simultaneously getting rid of the nuclear arsenal, so we are less at risk of exterminating ourselves) The only problem I potentially see is if this is seen as an attack and not an attempt of communication.

There was a short story a content creator did not long ago that depicted humans being observed by alien species after joining them among the stars and they talked about how they breathe what they consider to be toxic gas and drink poisonous liquids to sustain themselves that was interesting to think about. I put this in the same vein as the "all the wrong places" theory.

The biggest issue would be distance. If the nearest intelegent life is 500 light years away, which isn't far on a universe scale, even if they are listening with compatible technology, our first signal won't have reached them yet.

The video game franchise Dead Space actually touches on the Fermi Paradox with its title, Dead Space. You see, if you take the first letter of all the chapters in the game: Chapter 1- New Arrivals, Chapter 2- Intensive Care, Chapter 3- Course correction etc, it spells out chchchchch, which is the sound of radio static, as in dead air, which is what the radio telescopes on earth has been receiving all this time. There are no signals from other species, because the Necromorphs killed and consumed them all. The lack of signals from other species in the galaxy is literally due to the space being dead, or Dead Space

some thoughts on... ... the dark forest: to deliberately hide, wouldn't you have to know there are predators out there to hide from? ... the great filter: who says there has to be just one filter? ... being alone: we might be the first, we might be the last.

I remember a great line from the first men in black movie where k says, "Human thought is so primitive it's looked upon as an infectious disease in some of the better galaxies. That kind of makes you proud, doesn't it?"

"The surest proof that intelligent life exists elsewhere is that none of it has tried to contact us." -Bill Watterson

"There must be some intelligent life somewhere in the galaxy, cause there's bugger down here on Earth" Monty Python, a true prophet

Really hit it out of the park on this one. From production to subject matter to delivery. A fascinating topic. Very well done. Thank you.

Chapter Six: The Gigantic Sand Box Space is Unbelievably Big and the Speed of Light is a REAL limit. The Universe might be teeming with intelligent civilisations. But each one is so isolated from every other one in space (and time) that each one might as well be alone. This seems to me to be the obvious answer to the Fermi Paradox. ----

Interesting ideas. I'm a firm believer that we are not alone in the vast universe, but had never thought about the last part where we could possibly be the front runners in evolution within the universe.

If we do make contact with other alien civilizations I sure as hell hope they don't have alien influencers. That would be terrifying.

Great video, love your channels. One point I notice a lot of people miss or forget about when discussing life on other worlds. When looking into the universe, you are looking back in time as well and it's not like it's a few 100 or 1000 years it's litterly lights years back in time. If I were a alien race looking back at "earth", what would I see? Depends drastically on the distance. You could see humans but more than likely not. You could see the moon's formation. You could see no planet at all. My point is chances are life has formed elsewhere, maybe even other intelligent life like ourselves, but we can't see it because of our point of view (looking back in time). I do wish more would include these facts in the discussions on the topic.

Another side of the Dark Forest theory is that perhaps there are no "hawks in the sky", but everyone's afraid there might be. Same result, just a little less unsettling. Fear of the unknown can be a powerful thing.

I think the fact we're seeing light in snapshots of the past makes 2 things possible: A. that the aliens are much closer to being concurrent or contemporary with our development timeline, so the signals haven't reached us yet, or B. that the time discrepancy for travel over long intergalactic distances means that we are the most recent civilization to form and all the preceding ones are already dead and gone and extinct.

Still the saddest thing to think about. An entire universe filled with countless wonders, unfathomable views, event beyond comprehension, an infinite space with infinite possibility...Empty. Lifeless. Dark...its depressing to think about. I dont know if we can actually handle that revelation as intelligent creatures

Government making contact and hiding it didn’t age well

I think life existing else where is pretty much guarenteed because of just how large the universe is, but i also think because the universe is so large it isn't a surprise if we never find them

One thing I always found interesting was the idea of the Great Filter being something good. Like "all intelligent species discover the ice cream dimension and go there by choice" or "all intelligent species ascend to a higher plane of existence and start making their own universes". But there's also the sadder ones like "all intelligent species upload themselves into virtual reality to live forever in computers" or "all intelligent life realizes life is pointless and stops having children" 😢

What people often forget is it’s not just space but also time. The universe is 12 billion years old. Our star didn’t even exist when it first cooled enough to be habitable. Entire civilizations could have evolved expanded, and eventually even wipes out without a trace. If it happened 3 billion years ago supernova and other astronomical phenomena or even just the expansion of space would have obfuscated or annihilated any real evidence of their existence.

These side project videos are fantastic. My favorite channel in KZfaq currently and I'm watching a lot of them I'm glad there are a lot of these side project videos

Glad you said "galactic" toward the end. It's hard enough to imagine detecting signals from the other end of our own galaxy, much less from one of the billions of other galaxies in the universe. And only signals from quite close to us (astronomically speaking) would have been sent recently enough to be at all useful. We're always forgetting or misunderstanding the enormous distances.

We've been blasting signals into the galaxy for over a century. Imagine if one day we finally received a response, but the message was simply "QUIET, THEY'LL HEAR YOU."

I like the idea that life could be such an incredibly rare occurrence that our planet is the only populated one. Its a scary thought that its nothing but empty space but it also helps make life all that more precious and enjoyable.

<a href="#" class="seekto" data-time="95">1:35</a> the dark forest <a href="#" class="seekto" data-time="236">3:56</a> the great filter <a href="#" class="seekto" data-time="456">7:36</a> impossible communication <a href="#" class="seekto" data-time="582">9:42</a> looking in the wrong place <a href="#" class="seekto" data-time="750">12:30</a> we are alone

I think we vastly underestimate the effort it takes for us to go from Step 8 to Step 9. It's more likely that even more steps ahead of us before we can actually travel toward the stars.

My man I follow all of your channels and this has been one of the best videos you've posted in a long time. I read before about the fermi paradox and the great fiiter, but this way to condense and present the information is unmatched throughout the internet. Thanks my man Simon from a Mexican fan

One theory that Simon didn’t touch on was simply the distance and scale of the universe. If life is rare its unlikely to statistically be close to other life. They could be nearly on the other side of the universe, and maybe only a few civilizations exist at any one time on average in the universe.

Dark forest, everyone’s being quiet. Humanity over here screaming into the woods…

I genuinely think that one aspect of the fermi paradox ignores is humanity's scale and failing to reconcile it with the size of the universe. It honestly shouldn't be that perplexing as to "where is all the life?" when considering the size of the universe. If anything, the point at which we should consider the Fermi Paradox to be "dumbfounding", would be when humanity has 'scaled' themselves up so to speak to better encapsulate our understanding of our neighbours, but also when the scope of our reach, observations, and science can help peer further out. Which is to say, it should come to no surprise that we are getting ahead of ourselves if we look at a sliver of grass in our backyards and the confusingly exclaiming "But where's all the life?!" We should honestly consider that scale a bit more, because even as an analogy, if you respond to it as "well we're a lot larger than a blade of grass, we know about the backyard, we know what's beyond the backyard, we know where the land of the backyard sits on..." etc... that's exactly the point! Our solar system is like that blade of grass, and yes, we've been able to look out from that sliver and make incredible observations. But we also know how exact our science can be when our locality can scale with our observations and instruments. None of this undermines any of the work or ingenuity of scientists or our progress as a species, but to think we would have the same understanding of our measurements here on Earth with our experiments and tools and minds put together because we are within reach of conducting much much more thorough observations and tangible handling of data, as we would when observing distances unfathomable to most of our relevant scale of understanding, I think is putting the cart before the horse. Again, none of that says that our current research in astrophysics or cosmology should be reduced; just look at the history of Quantum Mechanics and Black Holes to see the power of a brain and pencil in predicting things we understand better now and have 'imaged'. But when it comes to biology, prospects of life that would have implications of the entire universe (that scale I keep mentioning), I think something like the Fermi Paradox will forever and always be in the forefront of our spacing ideals and advancements. Because I think as humanity progresses as a space-faring species, the Fermi Paradox will become more and more relevant will absolutely scale with our discoveries in the future.

That final sentence was spooky, the thought of a completely empty universe is definitely unsettling, but it also means that it's all ours for the taking 😮

Even if another planet was using radio waves to communicate, how far could the signals go before being drowned out by cosmic “noise”? It might just be that intelligent life is rare enough that we’re the only species within earshot of Earth.

This hits different this month.

I think the most terrifying option is actually the Simulation Theory. That we are NOT alone, there are other civilizations far more advanced than us, but we exist as their playthings, created by them to run in a simulation of a universe, to maybe figure out how their own universe came to be. That would not just mean that we're isolated (effectively Simon's most grim option that we're alone), but also that we are not even "real" in the full sense of the word. That would indeed be terrifying IMO.

'Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.' - Arthur C. Clarke - I think he said this with the fewest words...

The most disturbing thing for me in thinking we might be unique as a planet is simply that if we cease to exist then the whole of the universe continues on with no one to observe its existence. Which in essence means it doesn't exist.

I believe it's one of two things. 1. Life is not as abundant as we may assume. Or my favorite and more terrifying , 2. It's a "Dark Forest" out there. And everything is in hiding. Trying to survive.

Aliens know there is no intelligent life here, so they are going to leave us alone.

A big problem is that most people only think of Carbon based lifeforms like us, not life forms based on other elements!

The great filter hypothesis. I always thought there would not be ONLY one filter but potentially many. There may be, for example, say 10 filters with a 1 in 10 chance of coming out a survivor. To get through all 10 filters would be a 1 in 10 billion chance, and even once leaving the planet there may be other filters out there. Interstellar colonisation may not make a civilsation immune to extinction.

<a href="#" class="seekto" data-time="70">1:10</a> how is that laughable? Congress just had a public hearing this week confirming we've made contact with aliens

I suspect chapter 3 is the most likely scenario, though there may bet to add, here. Distances may be too great for us to detect a civilization's incidental radio broadcasts. We may have a hard time detecting a civilization like us on a planet in the Proximal or Alpha Centauri systems, just because they get too weak for us to see. Use of neutrinos, or something exotic like subspace, may make detection nearly impossible. Also, unless they're specifically trying to send us a raw signal, any civilization that is advanced to our level or higher, or going to mostly use formats or CODECs to send signals, which may be encrypted. That's because transmitting data is far more efficient, and the same frequencies can be used for many parties simultaneously. To us, it would appear as noise. So even if the aliens could understand us, and vise versa, their signals will be encoded, because such encoding just works so much better. There may only be an 80-100 year window when a civilization uses raw analogue signals.before switching to CODECs and data packets. And of course, later, it likely gets sent as neutrinos or subspace, or whatever the future holds. So the reason we may not detect squat, is that there's nothing nearby (and it would have to be very nearby, like within a few light years), within the 80 year window when they would use analogue signals.

It's true that there are so many planets that life must exist somewhere else, but when you consider all the chance events that had to happen and all the conditions that had to be met for intelligent life to evolve, it's still possible that intelligent life is so rare that there are just no others near enough for us to see.

I'm going with: intelligent life is tremendously difficult to exist, given this, it's even harder to find two species in a level of development that allows for their encounter in the vastness of space and time

I think the "DARK FORREST" analogy is bogus. With our limited abilities we can discern if a planet millions of light years away has "pollution" in its atmosphere that would indicate industrial production. So any advanced civilization that could come here would be immensely more technologically advanced to look for signs of intelligent technological civilizations. It would be like hiding in a huge well lit room with no furniture.

I feel bad because I've been avoiding your videos purely because I thought you were vsauce and now that I've finally watched a video of yours I hit subscribe as a peace offering

This is one of the most well-made videos you've put out in a long time, loved the topic but also loved how well the editor did keeping it engaging. Keep it up!!!

Chapter 4 is and has always been my answer. Looking for water finds human-like life. Alien life might be fully alien to us and us to them. We might not have any concept of their type of life and again, they don't have the concepts of our kind of life.

I thought about this one in university a bit and realized there's a missing variable. It's all spacial probabilities in every calculation that determines if there's life elsewhere but nobody takes the time dimension into account. When you take all of the probabilities and integrate them over time you get a much more reasonable and kinda traffic conclusion: 1. The number of sentient life sustaining planets tends to infinity as the universe feats older, until entropy reaches a critical point where complex molecules and crystals can no longer form. 2. The amount of the universe which is visible will infinitely increase, but will do so at a much slower rate than the rate at which life propagates through the universe. 3. Because distance and time are identical in astrophysics and sentient life takes billions of trials to form the probably that life has formed on another planet, while it was still within our observable range, and while we are capable of receiving communication from them, a number of light years away such that the transmission reaches us exactly when humanity is able to receive and identify it, is ZERO. In other words: Sentient alien life is a certainty, but it's a near certainty that it developed at a similar rate to what it did on earth, and that it exists far enough away that by the time their transmissions reach us we will no longer exist as a species. Keep in mind, humanity is about 100,000 years old; treat apes are only a few million, and "close" in astronomical terms is within a few THOUSAND light years of earth. Nearly everything in the night sky is millions of light years away, so if a civilization is out there, looking up at the stars, sending signals, as they likely are, Earth will receive them after the year 1,002,024; we're just too early to find that life; rather, the space we're looking at is too old.

I remember reading Greg Bear's "Forge of God," and the follow-up "Anvil of Stars." Ian Douglas' three military sci-fi series stemming from the Heritage Trilogy also deal with the Fermi Parodox as well. Great reads 😅

I always love watching stuff on the Fermi paradox. It is just fun to see how each person approaches it.

I used to think we just haven't come to appeciate the distances involved, but looking at our geologic history, a very unique set of circumstances led to our eventual evolution. Several extinctions, weird moon, well timed asteroids etc. Maybe we are a fluke.

Another possibility to the Fermi Paradox is the Rare Fire Solution.....fascinating idea. Great vid by the way.

I don’t know if anybody else said this already but I heard of the “grabby aliens” hypothesis that tries through a statistical explanation (exceptions are bad approach) to explain that we might be one of the early civilizations that appeared. I, for one, choose to believe that hypothesis.

I think the main reason for the Fermi Paradox is that life isnt as likely to develop intelligence as many people think, as many people think intelligence is some sort of "end goal" for evolution when there is no end goal, just adaptations to the immediate environment, and often intelligence proves to be more trouble than its worth. There is also the fact that intelligence alone isnt enough for a technological civilization to arise. For instance, octopuses no doubt have the necessary intelligence for that, as well as grasping appendages for using tools, but they reproduce by having their parents die to care for their eggs, making it impossible for them to share knowledge across generations.

What's so unsettling about being alone? That would be my preferred solution. Other humans are tricky enough to deal with...

The best part is realizing groups of beings were here before us, and some still are among us. Some even live within the Earth itself underground.

'Scientific thought is an inevitable path toward self-destruction' solves the question. As does 'the universe is really big and no civilisation survives long enough to travel any real distance'.

<a href="#" class="seekto" data-time="360">6:00</a> I think there are two great filters. One, in the past, was something like snowball suicide, where photosynthesis simply mopped up all the greenhouse gas. That may be related to the reason that green is the color of life: photosynthesis on earth isn't the most efficient. The other great filter is still in the future, with our ability to destroy ourselves and so many influential assholes denying a problem. I think that people are minimizing the size of space, and minimizing the time it takes for signals to travel or spacecraft to travel. Seriously, we shouldn't expect a response within the next few hundred years to any signal we send out. I believe that any conclusion based on the Copernican Principle is subject to revision by observation. Our place is special in a couple ways: our star is more massive than most stars, but not even close to the maximum mass of stars. We are in the disc of a giant spiral galaxy, a disc with lots of dust.

Simon, what about the fact of the sheer distance between us and the other stars? If a star is 1000 light years from us then it would take them 1000 years to hear our transmissions and then 1000 years for us to receive a reply. And if we use a telescope to look at that 1000 light year away solar system we would be looking 1000 years in their past and they might not have developed technology yet.

The reason we have never been contacted by aliens in 2024 is the same reason we have never been contacted by aliens in 1024.

My main theory would be simple economics. Interstellar travel is mind bogglingly expensive with little potential return on the investment. The distances are so great that a mission could fail at any point and we'd never know. Even at relativistic speeds, we're many talking years before any information would be relayed back. In that time, politics and budgets could change drastically. Add in that there's no effective way to test the equipment over interstellar differences. Just look at all the steps from Mercury to Gemini to Apollo. There were numerous missions to test various phases before putting them all together to land someone on the moon. With that, we still had Apollo 13. There's simply no way to communicate effectively over such distances if there's an emergency and who's paying for that. Even aliens would have some semblance of economics in that any task has a cost in time, labor, materials, etc. It may simply be too hard and expensive to really attempt. Edit: When you look at the history of expansion and colonialism in human history, there really aren't cases of completely independent colonies past simple tribal splits. Successful colonies, even in mostly agrarian societies, maintained contact and got supplies from the mother country. Travel time was long by today's standards, but was months, not years or decades. You can't set up supply lines over interstellar distances.

The "Three Body Problem" trilogy is a mind-blowing read on this very topic, as a matter of fact the second book _is_ called "The Dark Forest" and the characters within it talk about the exact same stuff in the video. It's about advanced aliens from the Alpha Centauri system that make contact with Earth and set out to invade it because their home planet gets tossed around the three stars and thus leads to crazy climate changes. Even though humanity has 400 years to prepare, and they waste a whole lot of resources building fancy warships and planetary defense systems, the aliens send one single probe that destroys everything and erases human technological progress while their main fleet is still halfway enroute. The second book's main character basically states that civilizations grow exponentially, but the amount of resources in the universe never changes, so it's inevitable that they will fight each other and conquer stuff.

Fantastic, thought provoking video. Simon's delivery on the "We are alone" part was chilling, the editing was awesome and the topic was extremely thought provoking.

I think the other factor in the Fermi Paradox is that the universe is still expanding...meaning all those stars, planets and galaxies are still (generally) getting farther away from each other, meaning interstellar travel & communication is just getting more difficult. Although the probablility of other intelligent life existing in our own galaxy must be reasonably good...but given the size of the Milky Way that would still be a hell of an undertaking.

We are ALONE. Which makes ANY loss of life that much more sad.

A wonderful solution to the Fermi Paradox that I ran into that I'm surprised isn't more well known is the Phosphorus Precursor theory. Basically, all of the energy bonds that make everything in carbon organics work requires phosphorous bonds, and we've recently discovered that phosphorus is extremely rare in our galaxy. We have an insanely high percentage of the known phosphorus. Phosphorus is a heavier element meaning it must be created through supernovae which means that there will be more eventually. But for now the reason why we aren't finding any other life could very well be that we are the precursor race, we are the first intelligent species because we lucked out on the early phosphorus lottery. The odds of being the first or among the first is low, but the amount of phosphorus we're seeing in exoplanets and stars makes it look like our planet has a lot more than it should.

The size of the known universe is too large for us to ever know that we are alone. The great distances may also serve as protecting various intellegent lives from each other.

I honestly hope we are not alone in this galaxy because if we are the damage we would cause “would” wipe out out whole solar systems because we are arrogant as a species and we are incredibly destructive in are explorations of everything. If we are the only ones out here then it truly is a sad state

Considering the universe is estimated to around for 100 trillion years it could be that we’re one of the first civilizations. We are existing less than a percent into the universes total estimated lifespan.

Always thought Alistair Reynolds had the best response to the 5th fermi paradox, about us being alone. The guy said if thats true, it would be our duty to seed life in all worlds, and become the skybfathers we always sought.

"Thinking about paradoxes is the way human understanding advances. I think the Fermi paradox is telling us something very profound about the universe, and our place in it." -- Stephen Baxter

It's not a paradox since the statements do not contradict each other. It's a quip that two other people argued about. He wasn't talking to himself! It was a conversation with Edward Teller and Emil Konopinski. You can't even start the story right.

Randomly saw this video while looking for stuff on the Fermi Paradox, I think this is the awesome dude who did the videos on the romans, usually emperors. If so, I love your Octavian video.

It could be because of the Star Trek prime directive theory.I mean if the writers of a 1960's sci-fi show figured out that it was a bad idea to introduce a civilization to alien technology before they are ready then it is likely that more advanced civilizations figured that out as well.

The idea that we are simply the most advanced in terms of technology is the one I like best as it offers the hope that in the future other civilisations will make (hopefully) peaceful contact.

I personally like the idea that we may be the first civilisation, being the forerunners is interesting.

<a href="#" class="seekto" data-time="160">2:40</a> is such a tired old argument that no one went against simply because Hawkins said it. If you look again, we also have animal conservation efforts and actively protect ecosystems. Any civ more advanced would just be more efficient in those efforts, no? Why should we assume doom?

Deadspace presented the most horrific solution to the fermi paradox. That humanity already lost before our species even began. Our whole universe is just one big farming ground for another apex predator species. In that way we are not very different from cows, just waiting to be slaughtered in the galactic grazing field

I feel that #4 (or a variant of) is the most likely. I feel like our own experiences create a bias toward what life should look like that may be preventing us from seeing our neighbors. Very reasonable and understandable, after all conceptualizing something completly outside of your experience is very difficult if not impossible.

We really need to update our theoretical underpinnings with new data. Fermi was using data we now know to be obsolete. It was assumed that if life evolved on a world, eventually it would evolve into complex life. But we've now discovered that even here on Earth, the basis of complex life, the Eukaryotic cell, was a 1 in a billion fluke. If it was something that would happen as a natural course of things, we would think that it would have happened multiple times here on Earth, but it didn't. It happened ONLY ONCE. Every Eukaryotic cell on Earth traces its lineage back to the same single Archaea that ate a bacillium but failed to digest it. And then it took over 3 million years before it evolved into multi-cellular colonies and another 3 million years before it became what we would call simple complex life forms. So that last option, that we are "special" does seem to be the case given what we now know. But if something can happen, it probably has and in the case of Earth, we know it happened here. It's probably happened elsewhere too. But the problem is like being a farmer in Nebraska. You've never seen your neighbors but you're pretty sure, somewhere beyond the back 400, they probably exist. 300 trillion stars in our galaxy and maybe 45 civilizations, each and every one of them a fluke of nature. So the answer to the Fermi Paradox is likely that there are people out there but needles in haystacks are easier to find.

Isn't it possible that we are just too far apart and you can't travel faster than the speed of light? At best they could send a probe but they may have sent it 10,000 years ago and it still has another 1000 years to arrive.

At the end, Simon mentions the time difference at which different species evolve. This suggests that there is a relatively short window during which species may be aware of the other and could communicate with the other. Imagine two transcontinental trains travelling in opposite directions. As the trains pass each other, a person standing at a door on each train attempts to the other. The time to do so is very short.

The answer is simply spacetime. At a certain distance the issue is not only space, but also time, since the image the universe shows us at a large distance is an image from the past. And it is not only time in relation to distance, but also in relation to history, because the age of the universe allows many civilizations to exist, but not necessarily at the same time and long enough in time to overlap to allow communication, with both being close enough and advanced enough at the same time.

"Where is everybody?" pondered Enrico Fermi "as he peered into the night sky," is certainly more poetic than "as he peered into his copy of the New Yorker."

I would argue that Hanson wasn't the first with the Great Filter idea. David Brin published a short story in Jan 1984 called "The Crystal Spheres". In it, mankind's first starship cruises out of the solar system and slams into a barrier, a crystal sphere that encloses our planets like an eggshell. With the shell now broken, mankind's subsequent starships can get out into the galaxy. They find a number of planets with their own crystal spheres, but it's not possible to communicate with civilizations inside them. Eventually they discover a broken sphere, but the aliens have moved on to hang out on the event horizon of a black hole, along with several earlier species. The explorers fidn a message saying, "when you outgrow planets, come join us".