These are not "good" answers to the Fermi paradox, and definitely not the only answers. Much better answers (in my opinion) are things like: their signals haven't reached us yet; they haven't developed interstellar communications or travel yet; they haven't developed intelligent life yet.
I would think an alien spacecraft carrying the energy and resources needed for interstellar travel (including the return trip) would be pretty obvious and detectable even by amateur astronomers. Instead what we're doing here is chasing at shadows and grasping at straws. Credible reports deserve to be looked into, yes. But what is Grusch alleging here? Existence of a UFO crash retrieval program. Presence of non-human biologics. OK, experimental Soviet or Chinese military technology with dog or cat DNA counts. Of course the US military guards those in secrecy. When we ask, "did you find aliens?" they aren't going to reply with "sorry no aliens, and to prove it, here are the details of all the experimental Soviet/Chinese/US military tech we recovered."
PBS Space Time has a number of great episodes on the subject of aliens, including questions like how do we know whether humans are among the first spacefaring species: https://www.youtube.com/watch?v=uTrFAY3LUNw
I don't think this is true. If an alien ship landed on the moon, we won't know about it. No equipment or resources put in to monitor something like that. Much less all the other planets, moons, and asteroids in the solar system.
My personal, unsupported belief, is that if there are aliens, Earth is like a nature preserve, and all the crashed ships are idiot tourists who, despite being told not to touch the buffalo, desperately want to touch the buffalo.
The problem with this stance for literally the past 20 years is that the Alcubierre drive, which has yet to be disproven in concept (despite requiring exotic matter and high amounts of energy) has been known about since the 90’s, and at least makes FTL travel, theoretically possible.
This is why I am skeptical about modern-day skeptics: Have they simply all collectively not read the Alcubierre paper, or the expert physicist responses to it, despite having had 20 years now to do so? Do they really think that simply not knowing how to implement it is an argument against it? How nearsighted would you have to be to assume that we’ve discovered all the loopholes already?
https://www.scientificamerican.com/article/star-treks-warp-d...
If, as you seem to be confidently asserting, the Alcubierre drive is feasible, has been built, and is what aliens are using to visit Earth, then given that even low estimates of the number of habitable planets in our galaxy runs into the millions (and there are more than trillions of galaxies in our observable universe) we must assume FTL travel is relatively commonplace. Even if only one species built a warp drive, they should have been able to colonize the entire observable universe by now. If one species has figured it out, it stands to reason that many more would have.
So where is the evidence? The Alcubierre Drive as theorized would give off an easily detectable signature. Where are these signatures? They should be everywhere. If the aliens visiting Earth are using Alcubierre drives, they should be particularly noticeable. But, of course, there is no sign of the effect of FTL travel anywhere in the observable universe, and even on Earth, the best anyone can come up with is conjecture and blurry photos.
Also, your mention of "expert physicist responses to it" fails to take into account the amount of criticism of the premise by the scientific community. You write as if the Alcubierre drive is proven science accepted by consensus and only engineering prevents us from building one, but of course that isn't remotely the case. As far as actual science is concerned, the Alcubierre might as well run on unicorn farts.
You're literally just taking one thing that doesn't exist, and "proving it" with another thing that doesn't exist. An argument that weak really doesn't merit the confidence you're putting out here. "But muh Alcubierre Drive" is not the slam dunk you seem to think it is.
Therein lies the rub. "As far as we know." Human knowledge only goes back, what, 2000 years? Industrialization started, what, only 150 years ago? The printing press is, eh, 500 years old? Ubiquitous computers began... literally an instant ago in cosmic timescales.
So while my argument might be summarized as "this one thing may be real because this other thing may be real but just 20 years ago wasn't even hypothetically conceived", your argument is basically "there's no way this one thing is real because this other thing is only distantly hypothetically real and still has flaws and besides, the whole concept is preposterous because there should either be aliens literally everywhere already or nowhere, because that makes about as much sense (maybe they're leaving our "incubator" mostly alone?), and because we simply don't understand how it's possible, despite the fact that we are basically 5 day old babies (and apparently VERY cocky ones) as far as science and human knowledge is concerned at cosmic timescales." LOL
We now have those technologies. It is trivial to extrapolate how effective they will be in say 10,000 years if we avoid blowing ourselves up. By then maybe we'll even have a sustainable Fusion reactor, general AI, and atomic matter deposition.
Do you accept that von Neumann probes are a realistic proposition and that they could have easily blanketed the galaxy by now?
https://en.wikipedia.org/wiki/Self-replicating_spacecraft
> It has been theorized[3] that a self-replicating starship utilizing relatively conventional theoretical methods of interstellar travel (i.e., no exotic faster-than-light propulsion, and speeds limited to an "average cruising speed" of 0.1c.) could spread throughout a galaxy the size of the Milky Way in as little as half a million years.
Half a million years. How long is that, really, in the grand scheme of things. And how close would we have to be to a civilization who released not one but millions of self-replicating probes for one to have visited us by now.
I am not saying this happened, but please consider it could have, it might have, and what if it did.
What if we are seeing these right now?
So this leaves a few possibilities:
1) No intelligent, technologically advanced civilization exists in the universe other than ourselves, because any such civilization would have developed Von Neumann probes, which would mean the galaxy should be covered by them.
2) No intelligent, technologically advanced civilization has yet developed Von Neumann probes.
3) Von Neumann probes exist, but they haven't blanketed the galaxy. Since the math says it should be easy for them to do so, either they were developed relatively recently and simply haven't had the chance to do so, or else confounding factors exist which make the process of unbounded exponential growth more difficult than the math would suggest.
None of these possibilities lead to the conclusion that UFOs (assuming the narrative presented by Grusch and other UFO believers) as described are more likely to be Von Neumann probes than not.
Any nearby civilization that released millions of self-replicating probes should be noticeable. We've studied nearby stars, there's no evidence of any of the telltale signs of energy usage or heat that should accompany something on that scale.
Also, there's no evidence of replication on the part of these objects within the UFO narrative. What are they feeding on? Where? Exponential replication means if they're here they should have stripped our solar system clean by now. Why haven't they?
All of the behavior described resembles conventional, piloted craft rather than the expected behavior of swarms of Von Neumann probes.
Without evidence, that's a really reasonable position that I can respect.
Edit - I wanted to point out that the probes need not strip the system of resources. They might exist to observe, document, and relay data.
Thank you for your response.
imo most likely is they exist, but space is just so unimaginable huge, and also Aliens can at most go close to lightspeed. They didn't beat physics nor invented portals / wormholes?
> They should be here already.
Least likely for me out of the three options.. just our tinfoil hat love :)
You're an expert in alien technology and civilizations far more technologically advanced than we are?
Now they might know some tricks around the limitations of our universes physics, but even those tricks must do something measurably.
Hard to know for sure.
He still works for intelligence, obviously. Aliens and UFOs are a well-known and obvious cover story for experimental aircraft. It's his job to spread this story.
Note that I'm not suggesting most things people claim to be UFOs are actually experimental aircraft. A few may be. But often it's a hoax, a piece of dust, an ordinary aircraft, a weather balloon, an artifact of extreme zoom, etc.
Without commenting on the likelihood of any hypothesis, I don't see how this makes sense. If we assume that it is a cover story for advanced tech programs, top secret programs in general are now going to have 10,000x more scrutiny by the media and Congress, and will be far more likely to have details leaked. Drawing attention like this is the exact opposite of what you'd do to keep something secret.
If "cover story" really is the explanation, it seems unlikely that Grusch is in on it--more likely would be that he was also fed the cover story, and that his going public really is resented by the military since it brings so much unwanted outside attention.
Given the limit of the speed of information and the expansion of the universe, there's a VERY small area that would even be aware of the signals we've started sending out over the past century to come looking.
But Earth would be an extremely interesting destination....for future Earth.
Though personally the most likely answer is that it's our own tech that the people sighting it don't have clearance to even know about which is why USINT is so against more attention to reports of sightings.
But if I had to put my money on outlandish claims, time traveling ships would get my best any day over extraterrestrial ones.
we should be able to come back, which means we would already be doing so? as long as the preconditions remain true... either way we would probably have some sort of "butterfly effect/grandfather paradox" laws in place
that said, the value of future earth visiting past earth would likely be 'kitsch' at best :P
Time travel (backwards) is not possible, only inter-universe travel.
What has happened has always happened and will always have happened.
Please tell us more about it!
If both events have occurred at the same time then that means they can't exist in the same timeliness.
Pretty freaking simple ain't it?
No one on HN "throws it out" because this is ostensibly a rational community and time travel is an even more absurd, less scientifically plausible solution than FTL or interdimensional travel. At that point we're just discussing comic book plots. If you believe we live in a universe that runs by comic book rules that's fine - it seems a depressing number of people here do, but there isn't much viable, intellectually grounded discussion to be had about that. You either agree with it or you don't.
I mean hell, let's throw Jacques Valee onto the pile and say maybe UFOs/aliens are fae taking on a modern form in order to feed upon humanity's collective fear of the other. Makes about as much sense as time travel.
So simple, in fact, that all of us are already doing it.
Others try to calculate and predict the position. But they didn’t use enough floating point precision bits and ended up in the earth’s crust or somewhere in the ocean.
In the story the scientist takes a friend forward 22 hours, but outside the time machine door there's nothing. Total darkness.
The friend asks if the scientist forgot the movement of the Earth and the galaxy, but the scientist assures him that no, that motion has been accounted for.
Instead it appears they've arrived between quantum periods, stuck forever out of phase with ordinary time like an elevator stuck between floors and frozen by the lack of momentum.
I ask because that's the first story I read that drew attention to needing to travel in space to keep up with the planet.
What inspired me to write the comment is was thinking about time travel and how people in movies and stories seems to always materialize on a nice level surface, somewhere in a building with the their feet exactly on the floor, in a nice meadow outside the city, on a sidewalk etc. Then, remembering how earth and galaxy move through space I thought how extremely hard would be to get a safe set of future spacetime coordinates to land on.
If the universe has, on the scale of potentially uncountable trillions of years, just barely reached a stage where the probability of life appearing has risen above "infinitely small" then there's nothing chauvinistic or anthropocentric about speculating that we're it.
Yes, and for any given species, it is incredibly unlikely they are the first.
> If the universe has, on the scale of potentially uncountable trillions of years, just barely reached a stage where the probability of life appearing has risen above "infinitely small" then there's nothing chauvinistic or anthropocentric about speculating that we're it.
That is a humongous if that you have to prove, and it still would mean that it's very unlikely we are the first.
The argument "there's lots and lots of stars, therefore it's unlikely we are alone" is mathematically bogus. It presumes the chance that life arises at any given star can't be "too small". But there is little basis for making that assumption.
> if other life exists, the chances of us being first would be really low given the size and age of the universe
I assumed that I didn't have to re-state the assumption that other life exists as the basis for my argument.
We can think or imagine whichever option is more fun and exciting. Without a single example of at least one confirmed alien life a lot of interesting possibilities are open.
The Fermi paradox assumes intelligent life is common. However, perhaps its not. It certainly was not rare on the one planet we know for sure life exists. Biodiversity on earth right now nears 9 million forms, with probably at least that many now extinct. So out of all of those forms of life there is one that evolved the intelligence necessary to detect life outside of this planet.
So even with the age and size of the universe…and knowing the conditions necessary for life to evolve being somewhat rare, and the conditions necessary for intelligent life to evolve where life is being also some rare given our experience here on earth, it is not a huge leap to say that while life might be common in the universe, intelligent life could be uncommon, and if it is uncommon, we could be early enough to be one of few intelligent species out there. So we may not be detecting anybody because there is nobody out there to detect…just yet. Especially given distance and time and the fact that evidence we are capable of detecting is coming to us from an intelligent species may still be quite a time away since we are seeing their past.
That's the argument I would like to make regarding the existence of angels and the coverup by the secularists to hide their involvement in humanity.
Watch this 5 min clip for additional context: https://www.youtube.com/watch?v=2FrloSlst1A
If we expected to see them far away, how would them being here prevent us from doing that (and also from seeing other presumably existing alien species that are not here)?
How could you possibly know that?