As I’m sure you know, that isn’t the theory. Instead the galaxy would be colonised by an exponentiating wave of self-replicating devices, which take thousands of years to replicate, and millions of years to cover the entire galaxy. This possibility was suggested by Frank Tipler, among others, and amplified by Carl Sagan, who suggested that this possible was so likely that other civilisations would act to prevent such waves from occuring. A very good summary of the debate is available in the relevant Wiki article. https://en.wikipedia.org/wiki/Self-replicating_spacecraft#Implications_for_Fermi’s_paradox
None of this seems to have happened, or if it has, we can detect no sign of it. Which is encouraging, I think.
You are overestimating the travel times and harshness of conditions, as well as underestimating the engineering capabilities of a space faring civilization.
And our first probe to Mars scraped a bit of sand and delivered weather reports for a few years until we stopped listening. Now we fly helicopters.
Starshot is a step, it’s not the journey.
Mixed minds on that. Encouraging if that means that we are the first, and the galaxy and even supercluster is our oyster. Discouraging if it means we are simply one more in a long line of failed civilizations.
Fair enough, however, one can use the ‘they thought powered flight was impossible’ style of argument to support anything you want, regardless how possible it actually is. It’s certainly interesting to look at things now possible, once thought impossible, but it does not follow that every problem will yield in the same manner.
If it’s possible, we will do it, one way or another, or die trying.
Unless it is actually impossible, then it will be done, if not by us, then by any other civs that are out there.
Those who thought that powered flight was impossible were proved wrong every day by the birds flying over their head. Just as anyone saying that interstellar travel is impossible is proved wrong by objects like Oumuamua and 2I/Borisov. Anything that can occur naturally, we can do, and we can do better.
For instance, I don’t think that FTL or time travel are possible. What we know and understand of the universe tells us this. There are no natural phenomena that do this. So no, not anything that is thought to be impossible will one day be possible. But, anything that cannot be shown to be impossible probably isn’t.
I think we should be discussing something quite different, to be honest. For more than ten years the US Navy in particular has been the source of significant numbers of reports about unidentified aerial phenomena, and indeed for the last couple of years Navy personnel have been actively encouraged to report such events.
In some ways this is a good thing, but these reports are really not very good quality (look at the triangle video for instance- it is just triangular bokeh caused by the shape of the iris). Mick West and others have investigated every photo and clip so far, and found convincing explanations for just about all of them.
To me the mystery is why the Navy themselves can’t come up with these explanations. Could it be that the constraints of secrecy and security are preventing them from confirming these explanations, because they may give away details of the sensitivity of these detection systems? Secrecy sometimes demands extreme discretion, as demonstrated by the May incident during WWII.
May just thought he was sharing an amusing anecdote, but his free speech killed a significant number of people.
There may be a lot to that. In analyzing and debunking claims, they very well may disclose sensitive information about their capabilities. Rather than spend a whole bunch of time vetting their debunking to avoid security slips, they may just refuse to do so at all.
Some people on the internet thinking that there are aliens flying around is not as important to them as making sure that our enemies are not aware of our capabilities.
Which leaves internet denizens to speculate and debunk. I’ve seen pretty thorough debunking and explaining of many of the videos.
Frasier Cain did a pretty good interview with one of the more prominent and respectable debunkers.
I’ve very happy to, but I simply don’t understand why you’re carrying this on.
From the point of view of the Fermi paradox, it’s not enough to say that some problem is difficult. It’s necessary to actually show it’s physically impossible. You have no argument for why there is any restriction on how far a probe could hypothetically travel, or why that restriction would be less than 100k light years.
And that’s that. In a reasonable discussion that should be the end of this tangent.
As a former believer of the “it was aliens” explanation I have to note one item that was pointed before in one article or book I read when I was young.
Paraphrasing, the observation by a UFO believer of them being of extraterrestrial origin, was that their appearance through the ages was a way to “induce” or predict progress among humans, that is that UFOs looked in the past as balloons, then dirigibles, then planes and then crafts with impossible looking wings, or no wings at all. Just before the technologies were revealed to the public or deployed.
The point was lost for me when I realized that such a point of view ignores a simpler explanation: That our nation’s military and allies wanted to keep new technology and its capabilities secret, or that the enemy’s progress on new technology did/is allowing them to just get around our defenses. An explanation that fits many of the unexplained sightings. There are many things that our military would also want to keep secret, not only to discourage enemies from learning how good their tech worked or failed; but also to avoid, as others pointed out, the capabilities that we really do have. And then there is the item about trying to avoid embarrassing questions from taxpayers.
I’ll confess I had misunderstood your initial comment as being one that probes could have radiated directly from a single origin to everywhere else. That, I think is probably prohibited by the damage and degradation that would occur during the journey time.
In terms of the spread happening more like an infection - with an incubation period on each system before the next hop - well, I guess that could be how we got here - if the probes are, for example, very simple self-replicating organisms in spore, or their precursors.
The simpler and more numerous the probes, the greater the chance they will succeed on any given hop - for example if they are just chunks of cometary ice with primitive bacteria inside, but the simpler they are, the longer the incubation period per hop, and the less it becomes about ‘aliens spreading’ vs ‘life spreading’; that is, there’s no guarantee it produces any kind of uniformity.
However, if we treat the matter as if it were a spreading infection, there are factors in those sorts of phenomena that can and do tip it into decline rather than advance - distance and factors affecting the difficulty of distributing copies. Social distancing and masks.
Indeed, but you shouldn’t use such argument to automatically wave away the idea that limits can and do actually exist. The half life of isotopes isn’t likely to be something we’re just going to work around, for example.
“Oh, but people thought their breath would be sucked away if they travelled more than 30mph” is often used as an argument against c being a fundamental limit of speed, but the two ideas are not the same at all.
A major problem that has not yet been discussed in the thread, as far as I can tell, is the real issue with deep time. It’s not simply a matter of engineering a device that can survive for the million-year flight between stars (which is itself not a trivial challenge). It’s that the million years represents something like 0.007% of the generally accepted lifespan of the known universe.
One of the assumptions of looking out among the stars for other civilizations is that they are there right now. (Well, “right now” meaning the arrival of their light in our neighborhood where we can see the evidence.) But who’s to say the extraterrestrial civilization has reached a peak in its development, such that its technologies and other impacts can be observed, simultaneous to our ability to observe them? They could have arisen at any point in the last several billion years. It seems vanishingly unlikely for any such civilization, once it appeared, to have persisted for so long. More likely that they would have destroyed themselves, or transcended their original form, or naturally died out, or something else that exceeds our capacity to imagine because we are simply not equipped to think about events on this kind of time scale.
In my own mind, I think about it like this: You’re at the top of a skyscraper with a bucket of ping-pong balls. You spend the next month randomly throwing them off. What are the odds that two of them will hit the ground at the same time? It’s not impossible; you can speculate on a number of local factors that could influence the falling times of all the different balls and create a simultaneous landing. But it’s wildly improbable.
Even if the universe — hell, our own galaxy — is home to other cognitively advanced critters, we are essentially a ping-pong ball that has just hit the ground, looking out across the surface and hoping to see another ping-pong ball that’s bouncing at the same time we are.
TLDR — there’s a lot of discussion in the thread about interstellar distances, which are vast, but the mind-melting scale of billions of years is just as significant, if not more so, for creating gulfs of inaccessibility between hypothetical pan-galactic cultures.
Sure, but again it’s important not to confuse present day engineering limits with fundamental limits of physics.
Not really, no. It’s not like megastructures or probes are going to decompose*. They don’t need to be simultaneous to us at all.
* Ok, when we’re talking millions of years then even materials that seem stable to us are not, eg diamond will become graphite. But the engineers making a ship designed for millions of years will be aware of this.
On the other hand, megastructures such as Dyson Swarms are dynamically unstable, and they will tend to collide with themselves and become orbiting piles of rubble. We might be able to identify them by their unusual composition, but they won’t be in very good shape after a billion years.
*indeed, they will probably collapse into disks, and maybe even form new planets.
Millions of years is an infinitesimal fraction of the overall scope of time within which civilizations would need to overlap for the engineering even to matter. That’s the key point and it can’t be handwaved away.
I’ve never really liked the idea of Dyson spheres / swarms. It seems weird to me for aliens to use incredible technology and expertise to make…a big wall of parasols.
It’s just a gut feeling, but if they require significant maintenance / risk of collisions then that’s a more specific reason to not consider this an elegant solution.
This is not to discount searches for Dyson swarms. It’s worth a look, and such surveys of stars would be likely to detect other unusual data which be a signature of a megastructure that we have no yet conceived of.
Fine, change “millions” to “billions” in my last post and the point remains.
Besides, this could only ever be a partial solution to the Fermi paradox. The existence of Homo sapiens within our window of time proves that intelligent species can appear within our window of time. And the existence of ancient intelligent species would prove that intelligence species can appear on other planets than Earth.
So why don’t we see other intelligent species in our window of time? If the answer is “because they are so unlikely to appear, and the ones that do, don’t build probes” then that is the main solution being proposed to the Fermi paradox, the deep time is beside the point.
