so does that increase or lower the chance that there is _any_ kind of life outside there? Maybe not carbon-based life but any kind. Next question would be I guess that what is "life"
Fascinating stuff nonetheless
Of course more stars increases the chance of life out there, but without a good handle on the chance of life arising around a random star, we cannot set any lower bound on the probability that life is out there on the stars we see.
You'd think that 94% of the observable universe not being reachable would get more of a mention. Granted, we can still look for artifacts such as radio signals or something similar, but it does seem to cut out why a type 3 civ hasn't shown up at our door.
Life started on Earth almost as soon as the surface was cool enough to support it. The surface seems to have been stable enough for life by 3.8 billion years ago, and we have some weaker evidence of life at 3.7 and stronger at 3.5. At any rate, based on what we can observe, life began relatively early and so it seems that as soon as the basic building blocks and preconditions are present, life evolves.
We now know that exoplanets are extremely common. Based on observations we can estimate that about 40% of stars have planets, but that’s just what we’ve been able to observe.
There are a lot of stars in our galaxy, 100-400 billion.
And a lot of galaxies in the observable universe, 200 billion to 2 trillion.
And that’s just the observable universe based on our local light cone. For all we know, there could be an infinite number of galaxies.
So we have n=1 where life started right away, and perhaps 10^25 planets in the observable universe. That’s a lot of rolls of the dice!
Hence the need for a proposed great filter that explains why we don’t get a visitor ever other week. Complex multicellular life seems like a possibility, that took quite awhile, a few billion years before the Cambrian explosion. Complex intelligence also took awhile, resulting in only us after 3.5 billion years of life. And yeah, given that we haven’t been around all that long and seem well on our way to destroying ourselves, seems like complex society could be a great filter too. But space is vast, EM signals attenuate quickly and the speed of light is a harsh mistress. They are probably out there, but we’ll probably never meet them.
If no one can afford the trip (due to what we currently know of physics), or survive as a complex civilization long enough (100k+ years), then… you see what you see right now.
If you're talking about sending alien drones, the light mass and lack of having to keep them alive makes energy requirements a lot lower, but they'd probably just be scouting us (if not trying to kill us) so we wouldn't be able to detect them
There is no evidence yet that anything we can construct (or a near peer) could make it to another system intact enough to know it had arrived, let alone DO anything regardless of the form any intelligence takes or how it is packaged.
Hell, as a species we still struggle to land probes on mars and Venus. And they don’t have to do anything but send data back.
Getting a toehold on a random solar system, or even arriving and taking pictures and sending them back is so many orders of magnitudes harder to do based on what we know now it’s essentially impossible. Even if we had a ‘fast forward’ button.
Hopefully we’ll find something out that we’re currently missing, but as of yet we have no reason to believe it exists.
[https://solarsystem.nasa.gov/missions/voyager-1/in-depth/]
"The twin Voyagers are the only man-made objects to have entered interstellar space. However, while they have left the heliosphere, they have not yet left the boundary of the Solar System which is considered to be the outer edge of the Oort Cloud."
[https://en.wikipedia.org/wiki/Heliosphere#Heliopause] [https://www.nasa.gov/press-release/nasa-s-voyager-2-probe-en...]
It's still in the area of things that primarily orbit the sun, even if it is no longer in the 'atmosphere' or 'shade' of the Sun (aka the heliopause, which is what was being used for PR purposes).
And it's nowhere near anything which isn't orbiting the sun, and nowhere near 'not being in' the area of things orbiting the sun.
So meaningfully, it's still in the solar system, and will be for a very long time. It's just out of the nice part.
Distance wise, Voyager 1 (the furthest) is ~ 22 light hours away, or .02% of a light year - after travelling for 45 years. Proxima Centauri, the closest known star to us is 4.25 light years away.
It would take ~ 73,000 years at Voyagers blistering pace (38,000 mph) to reach it, and there is essentially zero chance we could keep contact with it or it would be functional even 1/10th of that time - it's RTG is already nearly dead, and with a ~ 87 year half life, it would be a miracle if it even lasted another 50-100 years.
Hint: even with instant construction, even nutty ideas like Project Orion would be incapable of doing it, let alone anything else. We’re talking > 10% the speed of light for the entire trip.
I'm just saying our space faring objects would be fundamentally a lot different
If civilizations lasted for billions of years or their AGIs did the same, we’d have a lot higher chance of them expanding to fill the galaxy and converting the surface of all 8 planets and major asteroids into AGI probes and compute.
A civilization doesn’t have to survive a billion years (do you know how long that actually is?) to not be ‘short lived’.
A billion year old civilization that isn’t expansionary will never reach us either.
Or one that doesn’t want to spend the energy ($$$) if other cheap energy forms we’ve speculated aren’t possible or as inexpensive/portable as would be needed.
They could just as easily be happy being billion year old zen masters, and we’d never know - even if they had warp drives.
They’d still exist though, and if we ever wanted to find them I guess we’d be able to do so. But we’d never know about them proactively.
Of course, there could be plenty of these floating around our solar system and we wouldn't know. They could be quite small and the solar system is quite big, and most of the proposed use cases for a civilization wanting to do this would not require it be in constant contact, so they might not even be broadcasting on anything resembling a frequent basis.
But in general there are a lot of theoretical technosignatures that we think we should be able to see if there was technological advanced life in the galaxy. (Should be able to see in that it is possible with our current technology - not that we would conclusively have seen it by this point.)
If you do the math, unless there are the aforementioned ‘cheat codes’, they frankly just don’t pencil out as worthwhile. No FTL/subspace? No ‘infinite cheap energy’ hack? No ‘infinite self replicating yet controllable builder of anything’ molecule?
No way to propagate, no way to energize, and no way to communicate at any real scale over the distances involved. Even gigawatt power, high efficiency, high precision aimed lasers aren’t going to have much luck at light year distances, and nothing is going to be useful for two way communication.
It’s easy to speculate of course, but like ‘grey goo’ it runs up against real issues with thermodynamics and physics if we stop and think about it much.
Worth investigating options of course, or talking about, but if physics is what it seems to be so far, that would perfectly explain the lack of us seeing them - they’re not useful/practical/worth the expense for anyone.
http://www.rfreitas.com/Astro/ComparisonReproNov1980.htm https://arxiv.org/ftp/arxiv/papers/2005/2005.12303.pdf
In general I do think it makes sense to not just contemplate interstellar visitors as living things making the trek or biological civilizations expanding, but there's a wide variety of artificial ~things~ that could end up in our solar system for whatever reason.
The only things we see self replicate are currently biological systems, and they can only do it under very specific circumstances and usually with a LOT of external help.
Circumstances which do not exist in space, let alone under the variety of environments on just the handful of planets we see in our solar system - except one, of course.
It's a very hard problem, and it isn't clear there is an actual answer that is economic to stick on the end of a rocket, even just to get to the moon. Something that survives 10k+ year journeys to unknown environments, and then does something useful? Even less clear.
Gets there AND then has the level of success necessary to transmit any sort of signal, or propagate itself further? Even less so.
Why we would do it, is also unclear.
Hopefully we'll figure out something that makes it less fantastical at some point - all the things that make it realistic would also help us in many other ways too!
We're in agreement that the 'why' is less clear, at least for probes exploring the galaxy. But there are some very clear reasons why this sort of tech in general is useful - mining the asteroid belt, building reflectors to better harness the energy of the sun, building all sorts of other infrastructure in space without having to use a rocket to get it there. At that point once we have the tech and are doing it - and I would be shocked if the human race is still around in 500 years and NOT doing that sort of thing - it's relatively cheap to kick off a bunch of probes doing similar things.
I'm still not sure if it's worth it in that scenario, but it's conceivable that it could be. And that puts us again on the question of why we don't see it. We think there should be a lot of intelligent life out there. There's a lot of very important 'if's in all of this, but if we can think of it and and conceive of some potential reasons, and if other intelligent life has these capabilities that we believe will be possible, and if it becomes as resource/energy/time efficient to do as it should be, then it seems like someone, somewhere, should have been able to convince their government or corporation or whatever to do it, even if the results aren't necessarily going to be super apparent. The Pioneer plaque is obviously much cheaper, but we knew beforehand that the utility there is basically 0%.
Like I said, I'm not necessarily arguing that these probes are out there. I'm guessing the answer is more likely "There's no compelling reason to colonize or even explore large swathes of the galaxy" and concerns around interstellar travel are on such large timescales that civilizations capable of interstellar travel would only care about their nearest neighbors. Maybe that changes as star formation spins down and the galaxy starts to slowly go dark and your local galactic resources are less and less abundant. I'm just saying that there are technosignatures that would indicate the presence of other intelligent life in the galaxy that have nothing to do with biological beings visiting us, and we would expect that some of these are possible for us to see now, if they're out there.
When we take numbers and probabilities in consideration it's good to also note how many hostile to life events can occur on a cosmic scale. You have supernovas, gamma ray bursts, black holes, neutron stars, magnetars, solar flares and coronal mass ejections, and a host of other shit we don’t even now about that could destroy life at any stage.
There are tens of millions of magnetars in the milky way and we can and do observe their "hiccups" - we've traded a multitude of GRBs back to stars we believe to be magnetars.
They do not have anywhere near enough energy to sterilize an entire galaxy.
If not for that one mutation under specific conditions and abundance of easily freeable oxygen, we’d still be goo in mud today. We were for 1.4 billion years until GOE happened.
It doesn’t mean that it cannot happen elsewhere. But there’s no clear linear route from complex acids to democracy. And maybe complex enough life requires a set of very special catastrophes. We can’t write off that we managed to evolve, but we can’t write off the exact procedure either.
The thought that humans might be the only life in the universe to me seems like the 21st century equivalent of believing earth is the center of the universe.
Or it's an acknowledgment of the posterior data that has arisen over the past 30 years.
Every human has a camera 24/7 now and no one has documented visitors. Countless new missions and sensor arrays have found no evidence of life anywhere.
That doesn't prove no life, but it does make it more likely that the Drake equation is based on assumptions that are fundamentally flawed. Otherwise the Fermi paradox wouldn't still be a paradox.
Maybe it's all a simulation. Maybe it's something from a completely different paradigm. Who knows. But insisting they're out there as more decades pass with none found...that may be the real insistence that the sun revolves around the earth.
Take a few minutes to listen to Prof. Robin Hanson talk on this very thing.
The jist of what he says, is that there's very much weird stuff seen in the sky, like the McMinnville photos [1], but there's nobody as yet landing a craft on the White House lawn and posing for the cameras.
He puts forward a model for this kind of scenario, it's worth a listen, that any visitors would quite rightly be far in advance of the societies we currently live in, and may only show themselves fleetingly so we gain an acceptance of their presence.
[1] https://en.m.wikipedia.org/wiki/McMinnville_UFO_photographs
The "weird stuff" is always distant, blurry, shot under terrible conditions, etc. Yet when a research team, or random passer-by snaps a photo of some never-before-seen, or thought-extinct creature, there's no difficulty in getting a quality image, either on the initial sighting or shortly afterward. It's only the "aliens" that are so problematic.
As for the idea that "they" are doing it deliberately (and perfectly)... it reminds me of the TIGHAR folks and Amelia Earhart. TIGHAR knows that Earhart crash-landed on Nikumaroro (Gardner Island), so every piece of information they see is interpreted through the lens of how it fits with that interpretation. But they have no root basis for the conclusion, just that they really want to believe it.
When faced with the question, "Why are pictures of possibly alien UFOs blurry?" two (of many) possible answers are "because if they're not low-quality we can tell they're not aliens" and "because the aliens are carefully arranging circumstances so that pictures of them are always low-quality" I know which one I'm putting my money on.
"Only detectable by people with bad gear" is just not a technological state that makes sense in this context.
There is A LOT of stuff recording what's going on in the sky at all times. A lot of stuff that could give us detailed and high resolution images and other readings. Some of it is actively beholden to various governments so I guess you could argue it's being kept from us there - but are all of these governments going to be in lockstep on this issue? And even more aren't - are scientists going to all just keep quiet on this?
We've had all these declassified videos released recently, and they're some of the most obvious not-extraterrestrial-visitors ever. The one recorded on an aircraft carrier through nightvision with the flying triangles? Night vision goggles have triangular apertures. Bokeh takes the shape of the lens aperture - so bokeh lights become triangles. The blinking in and out of existence? Same timing pattern as a commercial jet.
The pill video from the jets? Parallax makes stationary things look like they move fast. The pill only ever looks to rotate/change direction when the actual recording device in it's housing also does. It's all stabilized so it's not readily apparent unless you know to look for it, but it becomes obvious when you do. What is the object itself? It could be a mylar balloon, it could be an IR hot spot from the sun reflecting off the water. Could be other things. What we don't have any reason to believe is that it is some sort of advanced craft with physics-defying maneuverability.
I fully believe that there is intelligent life out there. Probably in our galaxy, but near certainty in the universe. I also believe that the chances we have had intelligent visitors from another place is the barest fraction of a fraction of a percent.
1. We are likely amongst the earliest of advanced space-faring civilisations that have ever exists, which is why we haven't established evidence of other life,
2. There are 'quiet' civilisations and 'loud' civilisations. We will never see evidence of 'quiet' civilisations, and the other 'loud' civilisations haven't expanded sufficiently to be observable at this point in time.
3. Assuming we don't die out ourselves and are therefore a 'quiet' civilisation, we should encounter the other 'loud' civilisations sometime in the next hundred million years or so :-)
However I don't think it makes sense for any civilization to be 'loud'. Just seems naive to blunder about and risk your civilization. However monitoring new civilizations for intelligence, fairness, open mindedness, lack of religions that justify killing outside their religion or species, treating the less fortunate of their/other species well and the like. Then once they hit some developmental milestones for compatible civilizations you introduce yourselves. Possible milestones include practical fusion, returning your ecosystem to baseline, practical anti-matter production/use, making a blackhole, traveling to the nearest star that you don't orbit, quantum computing at scale, etc.
Might well be something on the moon, well stealthed, a few meters down, with receivers capable of decryption RF traffic, and sensors to see how quickly we are poisoning ourselves.
If you think about it, if you were an alien watching earth, would you want to meet us? Or terminate us, at least the humans, and wait for something else intelligent to appear.
https://physics.stackexchange.com/questions/245505/from-how-...
Furthermore, Andromeda galaxy is on a collision course with the Milky Way. If there’s an intelligent alien culture there, they might get here just by waiting.
You are being willfully obtuse. There have been thousands of documented sightings over the past 80 years. Audiovisual recordings abound, not infrequently matched with radar or other secondary corroborating evidence.
The typical response to this is:
1. “They are faked.”
2. “That doesn’t mean it’s aliens.”
3. “It’s a secret government program.”
Fine. Nevertheless some percentage of documented events cannot be explained. There is a non-zero chance that they are caused by things that were not made by humans. They deserve to be scientifically investigated in good faith, without the arrogant dismissiveness that is so frequently encountered.
Something mysterious is going on in our skies.
It seems plausible to me that by the time a civilization can quickly travel to other stars, it becomes so different that it doesn't need to interact or even be visible to advanced monkeys on a distant planet, just like we aren't really striving to talk to exotic monkeys on isolated islands. And the only reason those exotic monkeys and birds haven't become our food, like cows or pigs, is that there is very little protein on their bones (speaking bluntly).
We also wonder why we don't see alien activity in radio spectrum, while at the same time we use encryption to make radio wave communication indistinguishable from noise. More advanced civilization might have learnt that not getting noticed is vital to survival, so they scramble all signals. That background microwave noise might be those signals scrambled.
https://en.wikipedia.org/wiki/List_of_potentially_habitable_...
More generally on the subject considered seriously, without taking into account the various factors involved in predicting the probability of life it is unwise to talk of certainty and scoff at sceptics of its abundance.
There is also an important distinction to be made between life in its simplest form and at its apex; it is the latter that perhaps most people think of when looking upwards in wonder, and there is no reason to think that the distribution of intelligent life is such that we have good chances of contact and interaction, however we may wish it to be so.
So this argument gets repeated slot (because people like repeating things they hear) but it's completely fallacious.
Yes, the amount of planets is astronomically large. But it might be that the probability that life appears on a planet is astronomically small. If there are 10^50 planets in the universe, but the probability that life appears on a planet is 10^(-60), then we're probably the lucky one.
In other words, we don't know, but please stop repeating garbage.
And more specifically the Drake equation (a subsection of the wikipedia article).
I personally think anyone's "answer" to the paradox just reveals their personal opinion/ what they want to believe, rather than any meaningful result from data.
> When the model is recast to represent realistic distributions of uncertainty, we find a substantial probability of there being no other intelligent life in our observable universe, and thus that there should be little surprise when we fail to detect any signs of it.
https://arxiv.org/abs/1806.02404
SSC has an article on the paper as well
https://slatestarcodex.com/2018/07/03/ssc-journal-club-disso...
The article says they "incorporat[e] models of chemical and genetic transitions on paths to the origin of life" -- I'm not an expert but that sounds like the territory of some very unsettled science.
https://www.npr.org/sections/krulwich/2012/09/17/161096233/w...