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Comment by Razengan | Hacker News Reader

There is no way that we are "alone" in a universe estimated to have practically infinite planets.

However, the distances between stars and the very short windows of time in which life may thrive (remember that we may have never known about the dinosaurs on our very own planet if we didn't discover their bones, and we will never see them again) means that we may never meet any other life.

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This is a very optimistic view, but there are plenty of theories claiming otherwise. Check out the Fermi Paradox [1], or the Rare Earth Hypothesis [2] for a more detailed view on the problem.

To be honest the easiest explanation for the Fermi Paradox is that we are indeed alone as an inteligent civilization. If we were just an average civilization there should be plenty of evidence of more advanced civilizations across the galaxy, because probabilistically they would be millions of years more advanced than us.

[1] https://en.wikipedia.org/wiki/Fermi_paradox [2] https://en.wikipedia.org/wiki/Rare_Earth_hypothesis

Honest question: Do we have the means to detect conclusive evidence of life on Earth itself from even "only" as far as, say, Pluto, without knowing exactly what to look for?

You'd be able to detect radio waves from Earth. We can still communicate with the Voyager probes that are further out. We probably can't detect life on Earth from Alpha Centauri with our current technology.

> We can still communicate with the Voyager probes that are further out.

This is what I mean by "knowing exactly what to look for."

Can we place something at Pluto and have it listen to radio waves from the direction of Earth, and compare it to the background "noise" at that location? How different is it? How much of that perceived difference would be our own bias?

How much evidence about life on Earth is available to our own instruments from this range? -> https://www.bing.com/images/search?q=Pale+Blue+Dot

That's a cosmically trivial distance. Yes we could absolutely detect vast amounts of transmissions at that range, and even figure out how to decode a lot of them. For example video transmissions clearly have a tabular data structure, pixel data structure, timing encoding, serial frames, etc. Theres no way they could be natural. You could even see differences over time as video standards evolve and update. That's just one example. Bear in mind in wartime we manage to extract useful meaningful data from deliberately obscured and encrypted data, so determining useful data from vast ranges and quantities of non-encrypted transmissions would be comparatively easy.

> Bear in mind in wartime we manage to extract useful meaningful data from deliberately obscured and encrypted data

Yes, but data created and encoded by other humans. We would likely not even know where to begin when encountering data (assuming we even recognized it as such) from beings who may perceive reality completely differently.

99.9999999999999999% of radio waves we get from the rest of the universe is absolute garbage. There would be some kind of pattern with purposeful radio communications. Recognizing purposeful radio communication is a much easier task than interpreting the data. But we don't need to interpret the data to know it came from someone/something we should go and check out, because it could be intelligent life.

Maybe it’s encrypted.

The Voyager probes emit less radiation than your typical cell phone, so the Megawatts of emissions we produce would be very bright on typical radio telescopes on Pluto, I presume.

Voyager transmitters are in 10 watt range. On 2 and 8 GHz bands.

Lots of interesting reading, for those so inclined, at https://descanso.jpl.nasa.gov/DPSummary/Descanso4--Voyager_n...

Planets are not normally radio sources. You can detect Earth as a planet from Pluto, and you can say that this planet is a strong radio source in various bands. As a radio source it has changed over time in interesting ways that are very unlikely to be natural.

Planets can be very strong radio sources; there are astronomers who spend their entire careers recording and studying Jupiter in the 21 MHz band, for example.

https://www.spaceacademy.net.au/spacelab/projects/jovrad/jov...

We can detect atmospheric water and oxygen[1] on planets round other stars, so yes. Although your last qualifier is flexible enough to kill almost any possible answer.

[1] https://uanews.arizona.edu/story/oxygen-and-carbon-discovere...

I wouldn't say that water and oxygen are conclusive evidence of life. Neither are organic compounds (space is full of them).

Neither is the detection of those elements requirements for life. We know for a fact that for 2 billion years our earth had very very low levels of oxygen, but was in-fact full of life.

If you have a species of intelligent squids then there will not be much of a radiation background - radio waves are no good in water. That would be a false negative.

I've never liked the Fermi paradox. It seems terribly contrived. It assumes way too much. That space colonization is inevitable and/or that strong AI is also inevitable.

What if it's not? What if it's an intractable problem?

What if technological advancement isn't exponential? What if it's more of an inverse tangent? A slow start, an explosive middle, then a long finish with an upper bound.

We have absolutely no other examples to base any assumptions of technological societies on, so why do we get "space colonization" and "independently thinking machines" for free?

To the single cell organism; the worm looks to be advanced and complex. To the worm; the human looks to be advanced and complex. Its possible we are still way down on the intelligence chain and too dumb to realize that we are in fact the worm in the scope of the universe

> To the single cell organism; the worm looks to be advanced and complex. To the worm; the human looks to be advanced and complex.

I don't think either of those is advanced enough to have a concept of anything "looking complex" to them. A cat or a dog would be a much better for comparison.

But we arent fundimentally more complex than the cat or dog. The only real difference is the relative size of various structures. We are both as complex as creatures come on this planet.

Probably there is some limiting factor to complexity, such as either the naivety to advertise existence, or the inevitably to halt creative destruction once we figure out how to not die.

> We are both as complex as creatures come on this planet.

Gaia says: Whatever, buddy. You're like a neuron comparing yourself to liver cells.

It is said that the wheat genome is five times the size of the human one...

A cell has no way to conceive of a worm, and worms probably can't conceive of humans. But they probably have some conception of birds, and birds can perceive humans. Where are our birds? As you go up the intelligence chain the ability to see beyond seems to increase, but we don't see anything beyond us.

We already have the concept of the eschaton, or the singularity. Is this a realistic concept? I don't know! But if you accept it, then the inability to see people at or beyond is is simple -- there is a large gap because progress past the point we are at is geometric up to physical limits that we are nowhere near today.

I didn't have the concept of the eschaton until today, looks like an interesting rabbit hole to explore.

Congratulations on your recent immanentization of the concept of the eschaton! ;)

https://en.wikipedia.org/wiki/Immanentize_the_eschaton

But that's the difference right there. Us speculating and imaging that there may be something beyond this plateau of intelligence is the difference separates us from worms and birds.

As well, metaphors for intelligence really falls apart when you are talking about very different scales, in the same way that some explanations for physical phenomena fall apart depending on the scale with which you are describing it.

Perhaps because what we are looking for doesn't want to be found.

For us, finding intelligent life would be a massive change in our reality and understanding of life because right now, the current state of affair is that we're alone.

But what if these other beings are used to a universe with billions of civilizations competing for resources of various kind (including biological, innovation, etc). Why draw attention to yourself?

Reminds me of this talk by Neil deGrasse Tyson:

https://www.youtube.com/watch?v=sLYorVnA44U

Paraphrased: "Everything that we have achieved which the chimpanzees can't, is in the 1% of the difference between our DNA and theirs. Imagine another species that is 1% different from us, in the same direction that we are different from the chimps."

You don't think that the capacity for rational thought makes a difference?

It seems to me that even with our limited intellects, we have already figured out an awful lot of what there actually is to figure out. We know all of the stable elements that make up atomic matter. We have identified and measured a huge range of the fundamental universal constants and it seems unlikely there are many more left undiscovered. So we can make reasonably good guesses about what the upper bounds of possible technology in our physical universe are. No FTL for example.

Of course you can refute that by appealing to ignorance - maybe there are technologies we can't conceive of and modes of existence beyond our comprehension. Well ok, but maybe there are fairies at the end of the garden path. That's not an argument that's tractable to rational analysis, no matter how rational you are. It can make no predictions and can never be tested so it's not much actual use.

> we have already figured out an awful lot of what there actually is to figure out

that's very presumptuous. As we learn more, every time, more phenomenon shows up that's even more intriguing. We can't explain many quantum effects (tho there's a good theory on how to do some predictions), we can barely manipulate 2 of the 4 fundamental forces, etc.

theoretical knowledge frequently fails to capture the engineering possibilities of exploiting a phenomenon.

example: we understand all of the relevant theories to explain how an ant can carry something that is many times heavier than itself.

but would we have thought to use those theories in the way that the ant's body does if we had never seen it nor had a concrete need to produce a similar result for ourselves using technology? clearly not. even after the fact, knowledge of the way the ant performs its feats does not let us replicate it easily. engineering is not something to dismiss with a hand wave, it's the meat.

put differently: our imagination for the upper bounds of technology is with certainty nowhere near the actual upper boundary because we are always thinking too narrowly when we consider the application of the laws of the universe, even when we know the laws deeply.

that doesn't mean FTL is possible. it means we might might create a way to make the problem of a speed limit irrelevant using what we already know.

> It seems to me that even with our limited intellects, we have already figured out an awful lot of what there actually is to figure out.

Really? It seems just as likely that our brains are fooling us into believing that they are universal knowing machines.

We understand that there are real things that we cannot see. Microscopes and telescopes and other sorts of detectors outside the visual spectrum allow us to "see" them. That is we have technology which present reality as a simulacrum our eyes can see. Similarly with sound, we know that there are sounds which we cannot hear, but through technology we can represent them in a form which we can consume. But to be clear, we are still not seeing or hearing these things, we are seeing and hearing artifacts of our technology which we accept as corresponding with reality.

Is it that hard to imagine that there are true thoughts that we literally cannot think? And any sort of technology which would help us, would really just be showing us a pale representation of the reality?

Maybe the oldest and most advanced civilizations decided to go tribal.

Maybe they are so advanced that they can hide their trail so belligerent civilizations like ours do not encounter them.

I don't think the easiest explanation is to assume that there is any sort of naturally occurring event in the universe that is one of a kind, save maybe for the big bang.

There are civilisations on earth (uncontacted tribes) who are completely unaware of the existence of modern society. With this in mind your view seems incredibly naive.

Yes, https://en.wikipedia.org/wiki/Uncontacted_peoples

And we collectively decided to leave them alone, ostensibly for their own good.

True, but all these assumptions are probabilistic. What are the chances of us being one of those uncontacted tribes. We have found thousands of other tribes, leaving only a handful hidden. The probability of a tribe to remain hidden is almost 0. And this probability decreases more and more with time.

There might simply be no way to travel at, or even near, and much less faster than, the speed of light, in which case the universe could be full of life that we will never contact or meet. Life might be rare enough that it's unlikely in any single galaxy.

Even at very low speeds, a civilization with a 10 million year "head start" (which is nothing on the timescale of the universe) would be able to send autonomous robots across the galaxy. At least that what we would do if we had sufficient enough technology. This is essentially the paradox.

So many assumptions here. Maybe they’d be able to, but why would they want to? What’s the point of probing a galaxy that you can only ever explore below the speed of light, at the cost of ungodly amounts of energy and eons of time? Why wouldn’t that same civilization stick within 1-100 light years instead? There is only a paradox if an advanced civilization with high tech is so irrational that they can’t control their breeding and doesn’t care about time dilation and efficient use of resources.

It also assumes that it’s safe to broadcast your presence to the whole galaxy that way. It assumes a lot of unproven ideas and then hand waves at a “sufficiently advanced” species that has only apparently enjoyed technological advancement rather than personal or social advancement. Maybe humans as we know them would spread unmanned probes across the galaxy for the sake of doing it, but I have doubts that humans capable of th feat would do it. I suspect we’d be wiser, or we’d be dead.

That so-called paradox takes the following assumptions:

• That it is possible for a region as large as even a single galaxy to ever be "full" of one species or their creations.

• That anything can keep spreading indefinitely, and remain intact, not only across the gargantuan distances involved but also over potentially millions of years for other species to encounter them.

• That intelligent life wants to keep spreading or exploring indefinitely. As opposed to, say, creating VR universes of its own and attaining contentment within them.

• That there are only a few "directions" into which species or machines can spread across the universe, for them to run into each other.

• That there are no "stabilizing" forces – natural or adversarial – which counter rampant expansion.

As others have pointed out there are 50 thousand assumptions being made here, but one of the biggest is why you assume technology can ever be efficient enough for this?

The entire universe is limited to the periodic table. You would need to have a device made entirely out of material that has a half life greater than millions of years, and a battery that can last that long without sunlight. I'm not saying it's impossible because technology is often surprising, but that's a fundamental limitation that so far we know cannot be overcome.

Edit: Even if the robot behaved in a self-sustaining manner, this further assumes a perfect, unobstructed trajectory and asteroids full of essential materials are on the route to earth.

> Even at very low speeds, a civilization with a 10 million year "head start" (which is nothing on the timescale of the universe) would be able to send autonomous robots across the galaxy.

I see this sort of statement all the time, and we have no empirical evidence it is true.

As this article says, even this simple "Starshot" concept is "a monumental engineering challenge that will require huge leaps in technology for spacecraft design, propulsion and communication."

And all the challenges are fundamentally physical, involving issues of weight, strength, density, power density, thermodynamics, etc. Unless they make some near-magical breakthrough in physics, a civilization one million years older than our own would find it just as difficult as we will!

And what if some galactic civilization has already done this? Are we likely to detect a spacecraft "just 3 to 12 feet across and weigh as little as a thimbleful of water" passing somewhere through our solar system at 20% C?

It's usually the explorers who do the detection and contact, while the lesser civilization simply acknowledges their presence.

I don't think physics is a roadblock for space exploration at this point. We just need to figure out asteroid mining and building in space, after that we can send robots driven by AI to other systems, at low speeds. Once they reach other systems they would refuel, build more robots and carry on.

It's a massive engineering challange, but it's quite predictable within a few thousand years (if we don't destroy ourselves by then).

That theory doesn't account for the fact that the laws of physics prevent anything from traveling faster than the speed of light. because our galaxy is 100000 lightyears long by itself, it would take 100000 years for an advanced civilization just to get to us let alone cross their own galaxies. It's highly possible other life doesn't exist but the reason we can't see them is because space is way larger than you think it is and takes a long time to travel across.

It's easy to speculate when there are infinite "what-ifs". If AGI (artificial general intelligence) development is technically possible and if they're really able to recursively self-improve themselves to become semi-gods and if there are really N number of civilizations out there, then there should be N number of AGIs too, it would make sense that we should be able to see their traces of existence across the universe.

This makes a lot of cherry-picked assumptions: https://news.ycombinator.com/item?id=17829840

Which is a very short amount of time for a species to be in existence. Alligators have been around for 2000x that amount of time. If you take a max speed of 0.01c which is possible with technology that we will probably have in the next 100 years (fusion power) that means the galaxy could be colonized in 10 million years. If 200 million years ago humans had evolved instead of alligators (can’t see any reason this is not possible on some alternate earth) then we could have colonized the galaxy 20 times over by now.

"Unrestrained colonization just because we can" relies upon a lot of assumptions: https://news.ycombinator.com/item?id=17829840

For example, we could have begun building a base on the Moon by now if we wanted to, but we have decided not to.

My point was in response to WilliamEdward above so really only dealing with showing that travel time is not a constraint. That said, your points are good, but knowing humans I think "Unrestrained colonization just because we can" is probable if not certain, for anywhere that a self sustaining society can exist. It certainly holds for Earth. The moon is not a great example because it isn't habitable. Same as Antarctica. We have sent a few expeditions and have a few bases but have not colonized it. If the moon was earthlike then I would bet that colonization would have started shortly after the Apollo program. Right now there are no habitable planets we can get to. If we ever develop interstellar travel, finding habitable planets we can reach is a near certainty. More likely we first develop technology that allows terraforming and a self sustaining colony on Mars. And at that time I would bet that it happens.

> The moon is not a great example because it isn't habitable.

It could actually serve well as a strategic and logistic launchpad for subsequent missions.

But still, you highlighted a key point yourself: That it's not always going to be possible (or desirable) to continue expanding through the galaxy because we may run into a "dead end" with no stepping stones (i.e. habitable planets) within our range of travel.

Another related example: We don't have the abundance of resources to do so. Whether or not the universe is infinite, while it does mean there can be infinite resources, our direct radius of galaxies is finite and it gets harder to travel as the distance gets further so the infinite planets are not all the same distance from earth.

The other way of looking at that is that it would only take a few hundred thousand years for a technologically advanced civilization to permeate the galaxy. But the galaxy is billions of years old and that has not happened.

The other thing is that the paradox isn't just that they aren't physically here with us. It's that there's no evidence of intelligent life whatsoever. We're at the point where we can take direct optical images of exoplanets. At some point we have to conclude that if they are out there, we would have seen some indication of it.

> it would only take a few hundred thousand years for a technologically advanced civilization to permeate the galaxy.

Why? How? How soon would they be able to start? Why haven't we begun doing so ourselves? Why haven't we even established a presence on our neighboring moons and planets, even though we are technically capable of already doing so?

At the risk of sounding like a broken record, the "we should have met someone by now" argument relies upon a bunch of thin assumptions that have been brought up elsewhere in response to other instances of it:

https://news.ycombinator.com/item?id=17829840

The Fermi paradox assumes that there is infinite progress, what if going interstellar is just too hard? (Warp drive too hard and going such distances directly just impossible) What are the incentives to go interstellar once a species has colonised it's solar system?

The incentive would be to escape the eventual heat death of their sun or insure their race against any other solar system wide extinction event, I guess

This assumes that the civilization would be able to prevail for an extremely long time.

The universe is 13.8 Billion years old, so we can only observe the universe 13 Billion light years away. However the universe is practically infinite and much larger than the observable universe. It's not possible for us to detect a galaxy and a civilization (if it exists) in the said galaxy outside the observable range. Similarly, for the said civilization we lie outside that observable range and they can't detect us because nothing can travel faster than the speed of light.

Now imagine, how huge the unobservable universe is. Probabilistically, it is quite possible for a civilization (or multiple) more or less advanced than us to exist far, far away, or may have existed some point in time. But none can detect each other. Its even possible for a civilization to exist in the spheres of observation of other civilizations but so far away that its almost impossible to make contact. 13.8 Billion years is not a long time on the scale of the universe, but it is also a long time on evolutionary scale for a civilization to have existed and have been extinct.

The problem is that humans, you and me included, are very bad at extremely large and extremely small numbers.

We don't have infinite planets. We have 10^21 stars, roughly, and some constant P average planets per star.

If the odds of life are 10^-14 per planet, and the odds of intelligent life are 10^-7 per life hosting planet, and we presume every star has one planet that might support life, then in the 10^21 stars in the universe, we'd expect only one intelligent life. That is one possibility!

But we simply don't know what the odds of life and the odds of intelligent life are in the slightest. We don't even know what range of possible values are reasonable. And humans are so bad at contemplating numbers like 10^21 and 10^-14. They're too extreme for one to think of them rationally.

And saying "well, it happened here, be it must be common" is selection bias- we can only contemplate the problem because it happened here.

The right answer is to get more information to improve our estimates of the probabilities. If we can find life at Alpha Centauri, that would either be a hell of a coincidence, or a very good indicator that the probability of life given a planet is high.

> If we can find life at Alpha Centauri, that would either be a hell of a coincidence, or a very good indicator that the probability of life given a planet is high.

Why would finding life on just one more planet – out of the 195 or so "worlds" that we know about, including moons – suddenly make "the probability of life given a planet" high?

By your own reasoning, whether we find life at Alpha Centauri, or do not find any life there, will not really change the probability of discovering future life or intelligence among the rest of all the 10^21 * P planets.

We could always just keep saying that "There are only 2 planets in the universe with life. No more." "There are only 5 planets in the universe with life." and so on and on.

> Why would finding life on just one more planet – out of the 195 or so "worlds" that we know about, including moons – suddenly make "the probability of life given a planet" high?

Because sampling. It's like election polling. If you ask one person who they're going to vote for and they say "Candidate A", you really have no idea how likely it is that candidate A has massive support. Perhaps you just happened to find the only person voting for that candidate! But if you ask the next random person and they say the same thing, well, the odds that you found the only two people voting for candidate A in your first two random asks is very low. On the other hand, if the second person is not supporting candidate A, that also helps you get a better guess at support levels.

You can never know the true level without asking every single person, but with every additional piece of data you can better estimate just what the truth is.

Just the same, as soon as we find another star with life, the number of stars we had to search to find that second one gives us a fantastic start to coming up with an estimate on how common life is. We presume that our corner of the universe is a good sampling of the rest, and extrapolate based on what we know here.

The key point is that extrapolation from a single data point is wildly innacurate.

> As soon as we find another star with life, the number of stars we had to search to find that second one gives us a fantastic start to coming up with an estimate on how common life is. We presume that our corner of the universe is a good sampling of the rest, and extrapolate based on what we know here.

We currently know of at least 8 or 9 planets in our system + at least 185 moons (new ones were discovered around Jupiter last month.)

So, finding life on 2 out of 194~ places will take us from "There is only 1 planet in the entire universe with life!" to "how common life is"?

> The key point is that extrapolation from a single data point is wildly innacurate.

But extrapolating from 2 points out of (100 billion x 200 billion) is not?

–

Why wouldn't people continue to use the same arguments they do now to say Earth is the only planet with life, to say there are only 2 planets in the universe with life?

> Because sampling.

Sampling requires a random selection from the universe of interest.

It's certainly possible if the probability of developing intelligent life is Infinitesimal.

We don't know all the forms that "life" or "intelligence" can take.

We certainly do not have any proof that it's impossible for life to be different from us, and we're already in the process of creating intelligence that's different from ours.

Our understanding of where life can thrive still gets challenged by discoveries on our own planet, or the experiments in our own labs, like the one on metal-based "cells" [0] that I read about recently.

[0] https://www.newscientist.com/article/dn20906-life-like-cells...

Your basic argument is just not solid, sorry. You're pointing out that one variable in the Drake equation is large and admitting that we literally have __no clue__ about several others. No clue means no clue, we don't know the mechanism by which they happened. They could under present knowledge turn out to be precisely as small as space is big, or even smaller.

The "space is big argument" is not good but hopefully it leads you down the rabbit hole of more interesting arguments.

https://en.wikipedia.org/wiki/Drake_equation

Honestly, the Drake Equation, Fermi Paradox etc. feel like "One-eyed kings in the land of the blind" type of reasoning.

The "otherwise we should have met someone by now" is an absurdly weak criteria, given the distances and timelines involved.

––––

We know that life and intelligence are possible and that there are plenty of places for them to occur on:

We know the universe must be practically infinite. [0]

We know there must be practically infinite planets (here "infinite" being a substitute for trillions upon trillions.) [1] multiplied by [0]

We know that even lifeforms on the same planet may never come into contact with each other. [2]

We know that intelligent lifeforms can decide to leave other intelligent lifeforms alone. [3]

We know life can take forms that do not occur naturally on Earth. [4][5][6]

We know intelligence can take forms that do not resemble human intelligence. [7]

We know that lifeforms do not require humanoid bodies to be able to use tools. [8]

We know we don't have the technology necessary to conclusively detect life at distances beyond 2-3 planets adjacent to our own.

We know we don't have the technology necessary to disprove life – present or past – on other planets.

There is more evidence to support extraterrestrial intelligence than there is to infer that this is the only planet to harbor intelligent life.

––––

[0] https://en.wikipedia.org/wiki/Galaxy

[1] https://en.wikipedia.org/wiki/Milky_Way

[2] https://en.wikipedia.org/wiki/Dinosaur

[3] https://en.wikipedia.org/wiki/Uncontacted_peoples

[4] https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi...

[5] https://www.newscientist.com/article/dn20906-life-like-cells...

[6] https://en.wikipedia.org/wiki/Genetically_modified_organism

[7] https://en.wikipedia.org/wiki/Artificial_intelligence

[8] https://en.wikipedia.org/wiki/Octopus#Intelligence

Terms like "practically infinite" are meaningless (my finger is practically infinite from an atomic perspective). We don't strictly "know" hardly anything about our universe, rather we have certain models which make predictions which have so-far not been falsified. Drake equation, Fermi paradox, etc., fall under the umbrella of philosophical speculation. They aren't proper science until they make concrete predictions that we can test experimentally.

If only one in a thousand stars have planets that can support life, only a thousandth of them develop complex life, only a thousandth of them avoid extinction events, only a thousandth of them develop technology, only a thousandth of them avoid destroying themselves somehow.

That would give us about one civilisation in every 10,000 galaxies. There are actually a lot more possible stages than that too, I've seen estimates that reasonably put our existence in the observable universe at all as a low probability event and maybe they're right. I've swung either way over the decades. There is a reasonable case that long term technological civilizations might be extremely rare. It's not a foregone conclusion that we are one of many.

Personally, I have no idea. It could go either way, but the Fermi Paradox does tend to indicate in the pessimistic direction at least with regard to our own galaxy. The problem is once you say technological life is rare at the one galaxy level, it only takes a few extra stages and a few extra low probability multipliers to make any life anywhere pretty unlikely.

You leave out the time dimension. The universe is what, just under 14 billion years old, and intelligent life on earth that can meaningfully seek out such things is what, 100 years?

That's another remarkably small window in time for us to discover anything - what if a civilization died out a million years ago?

> You leave out the time dimension. What if a civilization died out a million years ago?

This is what I keep bringing up when referring to dinosaurs, and I'm surprised that this point doesn't get presented more often when considering the chances of encountering life on other planets:

We have proof right here that life on the same planet can be separated by time and never contact each other, without even bringing cosmic distances into the equation.

You’re talking as though the dinosaurs and us are deparate life though. We are descendants of the dinosaurs - were the same life.

Fair point, the odds I gave are for these things to happen in the lifetime of a star. It seems likely though that Stars of previous generations than ours are unlikely to have had enough heavy elements to have a rich enough material environment to develop life. An abundant supply of heavier elements such as iron, potassium, calcium, etc is a relatively recent development in the universe. Planets lacking plentiful supplies of mid-weight elements seem like they would be dramatically less likely to develop life.

> There is no way that we are "alone" in a universe estimated to have practically infinite planets.

Maybe there is a lot of space out there, but not enough time? Maybe the universe is still pretty young and it takes a lot of time to go from zero to intelligent life that knows how to contact each other over great distances.

> but not enough time?

Or too much time, between different epochs even on the same planet.

We are intelligent. We know dinosaurs existed. They stood where we stand. We cannot contact them, we will never touch them, and we will never fully learn about them, nor they us.

Maybe each galaxial species is given the perfect planet for them. Distance to other life is so great to avoid one planet species from destroying another.

Which considering the appalling job we are doing of caring for our home planet is a good thing. Because if humanity ever finds another species, our track record is pretty abysmal. God only help them if their planet contains a resource we covet

> There is no way that we are "alone" in a universe estimated to have practically infinite planets.

What if we are a random sample of conscious life in the space of all possible universes in a multiverse? Many of them will have intelligent life in many places, but the majority have the parameters just tweaked enough to touch the edge and only produce one. Couldn't we live in one of those?

(And there is near certainty a given tuning of the parameters produces none but obviously we can't be in one of those.)

This is exactly why we need to invent a device that allows us to travel, or "slide", between alternate universes.

> There is no way that we are "alone" in a universe estimated to have practically infinite planets.

That's very frightening on its own. Assuming the universe is practically infinite, there is another identically similar earth in this universe where another guy that has the same microscopic details as me writing this comment.

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