Comment by kahnclusions | Hacker News Reader

Comment by kahnclusions | Hacker News Reader

Parent Full thread

> Fermi’s paradox has two good answers — we don’t see aliens because they don’t exist, or we don’t see them because they are here already.

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 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.

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.

Even if we couldn’t detect them, with tech as advanced as they would have to have, are they going to be crashing on our planet so often that we need a full on program for collecting them? If it happened once, maybe. Multiple times with that level of tech? No way.

Maybe they've been in space so long that atmospheric flight is problematic for them? That seems unlikely, though.

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.

Any craft coming from outside our solar system and trying to stop inside it would leave a huge energy signature as it slows from some significant fraction of c.

The presumption among all of this skepticism is that the speed of light is the ultimate limitation.

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...

The most obvious argument against the validity of the Alcubierre drive (besides the exotic matter and energy requirements, and spacetime not working that way as far as we know, all of which which are substantial issues despite your handwaving them away) is the Fermi Paradox.

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.

> as far as we know

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

First of all, the Alcubierre drive only works if several things that have never been confirmed to exist do in fact exist. Secondly, even if it turns out that exotic matter and such exist somewhere in the universe, the Alcubierre drive only works in their presence. So, it can't be used to travel FTL to a place where they don't exist, such as the Earth.

When von Neumann probes were proposed, we did not have working AI or 3D printers. They were merely concepts with some proof of concept systems in various states.

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?

Obviously Von Neumann probes haven't blanketed the galaxy as if they had, it would be obvious. Not to belabor a point I made in another comment, but the Fermi Paradox is a harsh taskmaster.

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.

So you are unwilling to consider what we have these people reporting are those 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.

The problem with all things like this is that they are simple mathematical models being used to argue for highly advanced physics and engineering. I find it extremely likely that the real world would quickly turn this half a million years into many billions of years once you add in various inefficiencies and limits. After all, life is a self-replicating machine and it has taken slightly longer than that to consume a fraction of the resources on this planet.

You don't know what you don't know. I'd assume any significant timeline involves broadening our understanding of thermodynamics and material science. I don't think its far fetched to presume that another species is further along on the Kardashev scale.

Reply on news.ycombinator.com