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Why do we assume extraterrestrials might want to visit us?

scientificamerican.com

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Re: Why do we assume extraterrestrials might want to visit us?

#291

Post by b112 »

bluGill wrote: post #92
b112 wrote: post #76

Earlier quoted context omitted.

I find it difficult to respond without emotion, to such a comment. We likely know very very little about physics right now. My point with Newtonian physics is that at the time, it was The Physics. According to observation capable at the time, it seemed to make sense, with a few little oddities. To them, they thought they had a small hole in current physics. Does that sound like your "small hole" in current physics to…

The reality is newtonian physics is still taught in college because for the vast majority of what people need physics for it is close enough to correct as to not matter. I come back to this: even if we are wrong, whatever is correct still needs to fit all the observations that we have done to date. I don't know what we will know in 1000 years. Euclidean geometry is over 2000 years old and still considered correct (th…

There's not a lot to discuss here I guess, when your world view is so bracketed by infallibles.

Re: Why do we assume extraterrestrials might want to visit us?

#292

Post by simiones »

cnity wrote: post #289
simiones wrote: post #129

Earlier quoted context omitted.

The problem with this train of thought is that it fails to account for the observations so far. We know that the amount of energy required to accelerate an object increases as its speed approaches the speed of light. We have observed this effect. New physics will never contradict this - they may just put it in a new light, or perhaps discover a new dimension. But they will not invalidate the measurements we have so f…

> Note that the observations done in Newton's time were never proved wrong - we just discovered that with better measurement precision and in different regimes of speed, they turn out to have additional small terms. This is not quite the right way to look at it. The general theory of relativity isn't just some unmeasurable difference in the margins of the calculations. There are _real_ situations (e.g. near a black h…

> The general theory of relativity isn't just some unmeasurable difference in the margins of the calculations. There are _real_ situations (e.g. near a black hole) where the predicted properties of relativity totally overwhelm the predicted movements under newtonian physics.

A much better example of the practical consequences is special relativity's adjustments of the laws of motion, which are necessary for example to synchronize GPS. However, my point is that no such observations had been done in Newton's time (they had no satellites in orbit, nor any black holes to study).

> It's not insane to think that there equally are not-yet-predicted situations in which FTL speed is possible, under conditions that have never been possible in the natural universe but are possible with human intervention.

I do think that imagining we could create conditions that have never happened in the natural universe before in such a way that we overcome what seem to be fundamental constants is a bit insane. Remember that our current understanding is essentially that all objects constantly move with speed c in 4D Minkowsky space time, and that acceleration can only switch the direction of this movement, not the actual length of the movement vector. Moving faster than c in any of the space directions would then require negative speed in the time direction.

It's of course not impossible that this theory is wrong. But there is also no reason to believe that it isn't wrong and that c is just a fundamental constant of the universe that is impossible to go past. The fact that the maximum speed we can travel or measure has increased constantly over humanity's evolution is much, much weaker evidence than all of the data that have led to the theory of special relativity and our understanding of the fundamental limits of speed.

In other words, while it is of course impossible to predict how our science will evolve, my money would be firmly on the c limit being fundamental. I would bet that 5000 years from now, there will be no change in this observation (though the exact nature of the equations of motion, gravity, its relation to particle physics and so on will likely all be significantly different).

Re: Why do we assume extraterrestrials might want to visit us?

#293

Post by psadri »

volkk wrote: post #267
psadri wrote: post #232

Earlier quoted context omitted.

Maybe not humans, but they probably do get visits from other insects and animals.

an interesting point which begs the question of what is a threshold of intelligence required to lose interest in a species. and if intelligence isn't the only parameter, what are the others? predation is an obvious one, curiosity comes with a form of intelligence, what else is there?

I think a sense of curiosity is a pre-requisite or perhaps co-emergent with technological advancement.

They also need to be advanced enough to be send an interstellar probe or ship to visit other disntant planets.

Re: Why do we assume extraterrestrials might want to visit us?

#294

Post by kyriakos »

chii wrote: post #56
drclau wrote: post #48

What bothers me quite a bit, both in more-or-less scientific conversations and in Science Fiction, is that we virtually always assume a human-like psychology for aliens, and we judge what they may want or not based on our thinking. Even when we think about potentially highly advanced aliens, we still assume they'll have a psychology similar to ours, and they'll just be more advanced technologically (ie. the aliens an…

The "Three Body Problem" trilogy ( https://en.wikipedia.org/wiki/The_Three-Body_Problem_(novel) ) makes an argument for why the behaviour of an intelligent species is going to mimic humans (or more accurately, humans' behaviour converge towards a universal set of behaviour - one of survival of the fittest). I don't want to spoil the books so i won't discuss any further, but worth a think about if you have read the bo…

Great books. Apparently they ate being turned into a Netflix TV series.

Re: Why do we assume extraterrestrials might want to visit us?

#295

Post by drichel »

cortic wrote: post #290
drichel wrote: post #268

Earlier quoted context omitted.

There is indeed as far as I know some evidence that we are early bloomers https://hubblesite.org/contents/news-releases/2015/news-2015... Half of the stars might be 9 billion years old, but for heavy emelents fo form, you need already certain conditions like neutron star mergers need to have occured. Our galaxy might be just old enough for that.

That is interesting, and it changes my math a bit, though not to your favor; >Based on the survey, scientists predict that there should be 1 billion Earth-sized worlds in the Milky Way galaxy at present, a good portion of them presumed to be rocky. That estimate skyrockets when you include the other 100 billion galaxies in the observable universe. So for us to be near the first, near enough not to trip on Fermi's par…

Well actually you are starting to convince me of the opposite.

My horizon is limited to the galaxy. The hypothesis here is that the Earth is an early bloomer in the Milky Way. Then we are dealing with 1 billion Earth-sized planets, only a fraction of which is orbiting stars capable of sustaining life, only a fraction of which in the habitable hone around their stars... They also need to be in the right region of the galaxy in which heavy stars were formed and died with the right conditions to produce heavy elements. Candidate planets also need to be far enough from sources of gamma ray bursts. And finally, even if they have life, it still needs to develop in the right direction for it to be complex enough and interested in reaching out and colonizing the galaxy.

So, the odds are a billion times a tiny fraction to one, a sustainable hypothesis as far as I am concerned.

I believe I saw a model somewhere, predicting that most habitable planets are yet to form in our galaxy, but I did not bother to look hard enough for references.

Re: Why do we assume extraterrestrials might want to visit us?

#296

Post by karaterobot »

jjk166 wrote: post #278
karaterobot wrote: post #266

Earlier quoted context omitted.

Upvoted for a thoughtful response, but I want to be clear that I'm not saying the Fermi paradox is valid or even useful. What I'm saying is that the author of the original article argued that the paradox assumes humans are fascinating to other species, when it makes no such assumption. There may be many reasons to dismiss the Fermi paraxox, but the one he leans on the most heavily is a non sequitor.

But the whole point is that it does implicitly make that assumption. The fermi paradox is a paradox if and only if we would actually expect to see evidence of aliens. We would only expect to see evidence of aliens if they are actively trying to communicate with us. All other scenarios would require us to be extremely lucky (in which case there is no conflict with our lack of observation and thus no paradox). If we as…

> All other scenarios would require us to be extremely lucky

I think I understand your position now, but I don't agree with this part. The paradox is asking "if intelligent life is common, and intelligent species invented space travel billions of years ago, wouldn't we have seen some evidence of them?"

It seems like you may disagree with the premise that it's likely we'd see evidence of them in any case. And that may be so. It's completely reasonable to say the Fermi paradox is invalid, for this or many other reasons. I don't think it was all that serious to begin with.

My objection isn't to dismissing the question, it's to the author presenting it as though it was fundamentally about human or Earth exceptionalism. I see no reason to assume that's the case.

As an illustration, does it change the nature of the question to remove Earth entirely and ask "given the age of the universe, etc., why haven't we seen evidence of alien civilizations visiting Mars? Or Titan? Or Kepler-16b?" I think it's the same paradox, it's just harder to make the point that way, since we've never been there ourselves. Asking it about Earth doesn't necessarily presume Earth is special, as the linked article suggests.

Re: Why do we assume extraterrestrials might want to visit us?

#297

Post by jjk166 »

karaterobot wrote: post #296
jjk166 wrote: post #278

Earlier quoted context omitted.

But the whole point is that it does implicitly make that assumption. The fermi paradox is a paradox if and only if we would actually expect to see evidence of aliens. We would only expect to see evidence of aliens if they are actively trying to communicate with us. All other scenarios would require us to be extremely lucky (in which case there is no conflict with our lack of observation and thus no paradox). If we as…

> All other scenarios would require us to be extremely lucky I think I understand your position now, but I don't agree with this part. The paradox is asking "if intelligent life is common, and intelligent species invented space travel billions of years ago, wouldn't we have seen some evidence of them?" It seems like you may disagree with the premise that it's likely we'd see evidence of them in any case. And that may…

The problem is there is no way to remove earth and earth exceptionalism. The question "why haven't we seen aliens visiting mars" presupposes that we ourselves have observed mars so thoroughly that we should have expected to see such evidence. Given that we have only been closely observing mars for a few decades, either we'd have to get very lucky to see an alien visiting mars right when we just happen to be looking, or they would have to visit mars on an extremely regular basis. The fermi paradox is fundamentally about our specific lack of observation, for all we know the martians have already made contact and thus there is no paradox for them.

Re: Why do we assume extraterrestrials might want to visit us?

#298

Post by sliken »

bluGill wrote: post #38
teekert wrote: post #7

Earlier quoted context omitted.

Indeed, Ants do some pretty fascinating stuff, TIL we have stuff like "Ant colony optimization algorithms" [0]. Even if we are as the aliens were 2 millions years ago, there must be something of interest in what we do? I mean, we'd be interested in life 2 billion years ago. I find it more likely that they just don't want to interfere. [0] https://en.wikipedia.org/wiki/Ant_colony_optimization_algori...

Perhaps, but I think it is far more likely they can't overcome the limits of the speed of light to do any useful observing. They can't cross the distance to observe us, even robots take so long to arrive that their star dies before it gets here (not to mention our star was still forming when they sent the probe out...) They cannot observe us directly, light just doesn't have that resolution at the distance. They can'…

Quite a few stars and usable solar systems started out 1 billion years ahead of ours. The sun is relatively late to the game. If a race was curious it could well seed the galaxy with small, smart probes, that could watch for certain signs life, record, and report back to the galaxy wide cloud, sure speed of light means that takes a long time. Sure that may take 50k years for light speed communications to reach a central location, but it would collect whatever was of interest.

Might even just be a few 100 bytes of info along the lines of somewhat evolved bipedal warm blooded beings with a basic grasp of electronics, quantum, chemistry, and atomic sciences. Haven't transitions to artificial life forms, and unlikely to succeed because of short sighted environmental policies that are systemically causing a extinction event by destroying the food chain and decreasing fertility world wide. Check back in 10,000 years and see if they surprise us.

Re: Why do we assume extraterrestrials might want to visit us?

#299

Post by jkingsbery »

chrisseaton wrote: post #235
jkingsbery wrote: post #227

Earlier quoted context omitted.

Given that horses run faster than 30 mph [1], and people have been riding on horses for a while before trains were developed [2], this seems unlikely. [1] https://horseandrider.com/western-horse-life/fastest-a-quart... [2] https://en.wikipedia.org/wiki/Domestication_of_the_horse

> this seems unlikely Well duh nobody thinks it's likely now! Obviously I don't believe it so don't explain it to me, explain it to people at the time! https://www.mentalfloss.com/article/67806/early-trains-were-... (This article says 50, which is still slower than a horse in your link, but I've read 30 in books.)

No, the claim "early in the development of trains people were sure it would be physically impossible for humans to travel over 30 mph or so" cannot be correct, because people had been traveling faster than 30 mph on horse back for at least centuries. There's no way anyone can think was true given that they had many counterexamples.

The article you sited says that some people thought there might be issues at 50 mph. Evidently there were some people who thought this, but that doesn't say anything about how wide-spread that thinking was.

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