Do you think any aliens exist in the universe?

Elon Musk talking about aliens:

1:39

I think it was Carl Sagan that said there either are a lot of aliens or none and they're equally terrifying

Click to expand...

Elon Musk has also said he thinks we're probably in a simulation/video game:


Then there is this:

it can be hypothesized that there are 11 billion potentially habitable Earth-sized planets in the Milky Way

Click to expand...

As a believer in the video game explanation my explanation for the apparent absence of aliens is to keep the costs of the video game low. I mean if you're looking at a typical distant star that apparently involves 10^57 atoms it can be approximated to us viewing it a lot more cheaply than if it had a Matrioshka brain attached or some nearby civilizations even though it might involve less than double the apparent atoms of the star on its own.

It is related to how likely evolution is. Either it is highly unlikely meaning that it rarely happens (e.g. once in the universe or our galaxy) or it is quite likely.... (or in-between)

My belief is that our simulation only started relatively recently and a virtual evolutionary history is worked out later on e.g.

Evolution isn’t just likely, it’s a certainty for any system that reproduces and competes for resources that some portion of the population is better at commanding.

The question is how commonly such systems arise, and it seems hugely implausible to me based on my knowledge of chemistry and molecular biology that they should be sufficiently unlikely as to have only arisen once in the entire universe.

The universe is big. No, much bigger than that. No, vastly bigger than that.

Even a galaxy is almost incomprehensibly large, and it would shock me if there weren’t several million planets (or moons) in our galaxy that host life, as an absolute lowest guesstimate.

It’s not at all certain that Mars doesn’t still host life, and seems fairly likely that it did in the past. Europa could also very easily have life beneath the ice. If either is the case, then we have two or three instances of life just in our solar system. That would strongly hint that life is endemic throughout the galaxy, and there’s no reason to think that our galaxy is unusual in that respect.

I strongly suspect that the universe is riddled with life, and hosts plenty of intelligent civilisations too. But the distances involved and the limit imposed by c mean that detecting it will be very hard.

We should be able to determine whether Mars ever hosted (or still hosts) life fairly soon - say, within a couple of centuries at most. Europa is harder to reach, but not that much harder that we couldn’t at least organise a sample return mission within a similar timeframe. If either or both hosts life, then the universe will inevitably be heaving with it.

bilby said:

Evolution isn’t just likely, it’s a certainty for any system that reproduces and competes for resources that some portion of the population is better at commanding.

Click to expand...

I initially meant abiogenesis (then evolution when talking about intelligent life)

bilby said:

I strongly suspect that the universe is riddled with life, and hosts plenty of intelligent civilisations too.

Click to expand...

1:17
It says that even if you are moving at 10% or 20% of the speed of light they could populate the entire galaxy in 10 or 20 million years - do you think they've tried visiting earth?

See also:

Let me start by offering my own opinion that Elon Musk is an insufferable idiot and a rotten person, and that we do NOT live in a simulation. There is no evidence for such a thing and no reason to believe it. I’m also aware of Bostrom’s classic paper on the subject and the fact that it has recently been debunked.

As to aliens, here is an interesting paper on the subject. First, it defines life as chemical system capable of undergoing Darwinian evolution and argues that the only strict requirements for life may be thermodynamic disequilibrium and temperatures consistent with chemical bonding. I haven’t finished the paper so I don’t know if it goes on to challenge these assumptions or postulates.

Thermodynamic disequilibrium may indeed be a strict requirement for life and it is found all over the place. I’m not sure about Darwinian evolution. Shall we dismiss out of hand the possibility that organisms on other planets may develop in accord with other paradigms, like Lamarckism? Or something we have not even imagined?

On earth, live arose very quickly after the planet cooled. This suggests that given the right environment, life is almost sure to arise. The problem, though, as I understand it, is that we have only one data point — earth. Maybe we’re a statistical outlier? Maybe life is very hard to arise under any conditions, or never arises anywhere except here? That’s possible, because without more than one data point, it’s not possible to calculate the probabilities of life arising.

Although life arose early, it took billions of years for complex life, eukaryotes, to evolve. Human-style intelligence, capable of building spaceships and radio telescopes and asking these questions and searching for other life, took much longer to arise. If the history of the earth were condensed into a single year beginning on Jan. 1, humans did not arise on earth until about one second before midnight on the last day of the year, Dec. 31.

This might suggest that aliens with human-style intelligence are very rare but again, we only have this one data point and maybe the length of time for complex life and intelligence to arise on earth is an outlier. Maybe intelligent life arises very quickly on other planets. We have no way of calculating the odds.

Several years ago the philosopher Brad Monton posted a paper arguing that since the universe is probably spatially infinite (according our best evidence) and therefore infinitely larger than the observerable universe (our Hubble volume) we are justified to conclude that the universe contains an infinite number of inhabited planets, no matter how rare life is, including an infinite number of duplicates or near-duplicates of planet earth along with duplicates or near-duplicates of everyone who lives on our planet or ever has lived on it.

He reasoned from a dartboard analogy: Fred is really bad at throwing darts. In fact, he makes only one bullseye every billion throws. But how many bullseyes will Fred make if he throws infinite times? Answer: an infinite number of bullseyes.

In a spatially infinite universe it follows that if one planet in a billion or a trillion or whatever is inhabited, then there are an infinite number of inhabited planets. However, if life and especially intelligent live is exceedingly rare, these life forms may be so vastly separated in space and time that there will be almost zero chance of them coming into contact with one another.

pood said:

In a spatially infinite universe it follows that if one planet in a billion or a trillion or whatever is inhabited, then there are an infinite number of inhabited planets. However, if life and especially intelligent live is exceedingly rare, these life forms may be so vastly separated in space and time that there will be almost zero chance of them coming into contact with one another.

Click to expand...

Though I don't understand how a tiny point from the Big Bang could expand to be literally infinite.... I guess it would need to expand literally infinitely within within a particular time period...? Also if it was infinite would the density be very low?

I’m also aware of Bostrom’s classic paper on the subject and the fact that it has recently been debunked.

Click to expand...

Well this looks like it is from a reputable source:
Can you give the link to it being debunked? Do you mean that it is virtually impossible that we are in a simulation?

I will look for the debunking article. It appeared fairly recently but I did not bookmark it. As for infinite space and the Big Bang, if space is infinite (flat) and we now have empirical evidence that it is, it means that the universe has always been spatially infinite but at the bang it was infinitrely dense.

pood said:

I will look for the debunking article. It appeared fairly recently but I did not bookmark it.

Click to expand...

Nick Bostrom's article has been published (in Philosophical Quarterly). I wonder if the criticism of it has also been published....

pood said:

As for infinite space and the Big Bang, if space is infinite (flat) and we now have empirical evidence that it is, it means that the universe has always been spatially infinite but at the bang it was infinitrely dense.

Click to expand...

So that's quite different to the normal concept of the Big Bang beginning with an infinitely small point....

excreationist said:

pood said:

I will look for the debunking article. It appeared fairly recently but I did not bookmark it.

Click to expand...

Nick Bostrom's article has been published (in Philosophical Quarterly). I wonder if the criticism of it has also been published....

pood said:

As for infinite space and the Big Bang, if space is infinite (flat) and we now have empirical evidence that it is, it means that the universe has always been spatially infinite but at the bang it was infinitrely dense.

Click to expand...

So that's quite different to the normal concept of the Big Bang beginning with an infinitely small point....

Click to expand...

No, it’s not. Infinity is funny like that. A point with infinite density can have any internal spatial extent, including infinity.

I hope not. The problem is the Fermi Paradox--why don't we see them? The time it takes to colonize the galaxy is very short compared to the time life has been around, why didn't somebody beat us? And even if they leave habitable worlds alone why do we not at least see their works?

This basically says there must be something phenomenally unlikely about a race reaching starfaring status. Have we been phenomenally lucky and passed that barrier, or does it lie in the future--and note there's very little future between now and starfaring.

bilby said:

excreationist said:

So that's quite different to the normal concept of the Big Bang beginning with an infinitely small point....

Click to expand...

No, it’s not. Infinity is funny like that. A point with infinite density can have any internal spatial extent, including infinity.

Click to expand...

Well I heard it was about a dense state that expanded.... also it involved the emergence of spacetime and is called the singularity so I thought it involved a tiny speck.... so then does that mean that infinite spacetime just emerged everywhere at once?
I am familiar with the idea of it involving the surface of a balloon.... i.e. it begins a lot smaller and isn't infinite....

Loren Pechtel said:

I hope not. The problem is the Fermi Paradox--why don't we see them? The time it takes to colonize the galaxy is very short compared to the time life has been around, why didn't somebody beat us? And even if they leave habitable worlds alone why do we not at least see their works?

This basically says there must be something phenomenally unlikely about a race reaching starfaring status. Have we been phenomenally lucky and passed that barrier, or does it lie in the future--and note there's very little future between now and starfaring.

Click to expand...

The barrier to starfaring is c.

You can talk about seeding the galaxy with automated probes, but as that’s both expensive and utterly futile, we shouldn’t be shocked that nobody in our galaxy has bothered to do it.

It’s a big universe. Our total ‘works’ outside low Earth orbit amount to basically fuck-all, and outside the heliosphere, even less - two 800kg lumps of metal and plastic within cooee of our home star aren’t going to be detectable to aliens; We can only detect them ourselves because we know exactly where to look, and because they are deliberately beaming a directional radio signal directly at us.

There could be half a dozen Voyager sized alien probes in our Solar System today, and we almost certainly would never spot one. But there probably aren’t any at all, because sending a crewed probe is impractical, and sending an uncrewed one is futile. If Voyager ever reaches another star, neither we, nor any local alien residents, are likely to know about it.

bilby said:

....It’s a big universe.

Click to expand...

The main focus is our galaxy - which apparently has around 11 billion potentially habitable Earth-sized planets....

You can talk about seeding the galaxy with automated probes, but as that’s both expensive and utterly futile, we shouldn’t be shocked that nobody in our galaxy has bothered to do it.

Click to expand...

Well what about: https://en.wikipedia.org/wiki/Self-replicating_spacecraft
When self-replicating it is basically for free. As far as being futile goes, they could see for sure if there is life on other planets by visiting them....

excreationist said:

pood said:

I will look for the debunking article. It appeared fairly recently but I did not bookmark it.

Click to expand...

Nick Bostrom's article has been published (in Philosophical Quarterly). I wonder if the criticism of it has also been published....

pood said:

As for infinite space and the Big Bang, if space is infinite (flat) and we now have empirical evidence that it is, it means that the universe has always been spatially infinite but at the bang it was infinitrely dense.

Click to expand...

So that's quite different to the normal concept of the Big Bang beginning with an infinitely small point....

Click to expand...

That may be different than the *popular* concept of the Big Bang theory, but in a spatially infinite universe the singularity is in density. Obviously, the physics break down and we won't solve the problem until we can merge GR and QM.

excreationist said:

bilby said:

....It’s a big universe.

Click to expand...

The main focus is our galaxy - which apparently has around 11 billion potentially habitable Earth-sized planets....

You can talk about seeding the galaxy with automated probes, but as that’s both expensive and utterly futile, we shouldn’t be shocked that nobody in our galaxy has bothered to do it.

Click to expand...

Well what about: https://en.wikipedia.org/wiki/Self-replicating_spacecraft
When self-replicating it is basically for free. As far as being futile goes, they could see for sure if there is life on other planets by visiting them....

Click to expand...

Yeah, but they couldn’t.

Their probes could. But they themselves would never know.

And self-replicating probes ain’t free, because if they were, I would have a dozen of them.

bilby said:

excreationist said:

bilby said:

....It’s a big universe.

Click to expand...

The main focus is our galaxy - which apparently has around 11 billion potentially habitable Earth-sized planets....

You can talk about seeding the galaxy with automated probes, but as that’s both expensive and utterly futile, we shouldn’t be shocked that nobody in our galaxy has bothered to do it.

Click to expand...

Well what about: https://en.wikipedia.org/wiki/Self-replicating_spacecraft
When self-replicating it is basically for free. As far as being futile goes, they could see for sure if there is life on other planets by visiting them....

Click to expand...

Yeah, but they couldn’t.

Their probes could. But they themselves would never know.

Click to expand...

I thought they could send a message back - perhaps through a network of probes

bilby said:

And self-replicating probes ain’t free, because if they were, I would have a dozen of them.

Click to expand...

Well I think it involves nano-technology or something though at the moment there is only natural self-replicating technology like living cells.

excreationist said:

bilby said:

excreationist said:

bilby said:

....It’s a big universe.

Click to expand...

The main focus is our galaxy - which apparently has around 11 billion potentially habitable Earth-sized planets....

You can talk about seeding the galaxy with automated probes, but as that’s both expensive and utterly futile, we shouldn’t be shocked that nobody in our galaxy has bothered to do it.

Click to expand...

Well what about: https://en.wikipedia.org/wiki/Self-replicating_spacecraft
When self-replicating it is basically for free. As far as being futile goes, they could see for sure if there is life on other planets by visiting them....

Click to expand...

Yeah, but they couldn’t.

Their probes could. But they themselves would never know.

Click to expand...

I thought they could send a message back - perhaps through a network of probes

bilby said:

And self-replicating probes ain’t free, because if they were, I would have a dozen of them.

Click to expand...

Well I think it involves nano-technology or something though at the moment there is only natural self-replicating technology like living cells.

Click to expand...

And as far as we can tell, those natural self-replicators can’t survive interplanetary, much less interstellar, travel without non-self-replicating support equipment.

bilby said:

And as far as we can tell, those natural self-replicators can’t survive interplanetary, much less interstellar, travel without non-self-replicating support equipment.

Click to expand...

Well the galaxy is only 100,000 light years wide and they could go from earth-like planet to planet to gather resources and it could only take less than a few decades each time.... they don't need to be strictly/automatically self-replicating....

excreationist said:

bilby said:

And as far as we can tell, those natural self-replicators can’t survive interplanetary, much less interstellar, travel without non-self-replicating support equipment.

Click to expand...

Well the galaxy is only 100,000 light years wide and they could go from earth-like planet to planet to gather resources and it could only take less than a few decades each time.... they don't need to be strictly/automatically self-replicating....

Click to expand...

Sure.

But ‘could’ covers a multitude of sins.

Is there any reason to think that any civilisation in the galaxy will develop such things?

We don’t know how, we don’t have much incentive to learn how, and we don’t have any particular reason to do it even if we could.

Nor would any putative aliens.

‘Could’ is a flight of imagination.

“I can imagine quite a bit” - Han Solo

bilby said:

Is there any reason to think that any civilisation in the galaxy will develop such things?

We don’t know how, we don’t have much incentive to learn how, and we don’t have any particular reason to do it even if we could.

Click to expand...

Well it seems more than $100 million has been spent on SETI

If the probes were sent from orbit or from the Moon I think they would be a lot cheaper to send. Elon Musk thinks 1 million people could be sent to Mars in the coming decades. Planets in other solar systems could be extremely similar to Earth rather than have problems like Mars. Sending probes with the chance of finding life is worth it - I mean if they did it could be one of the greatest discoveries of all time. Earth-like planets that have oceans, etc, would be more likely to have life I think.

BTW in a simulation it is an advantage for time to slow down in dense masses - dense structures could become a lot more "CPU intensive" than sparse structures....
Also there are warp drives that could be possible but they aren't very "CPU intensive" because the craft is mainly only interacting with itself.... (and I guess the warped spacetime has sparse particles)