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> 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"

> 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 https://www.youtube.com/watch?v=uTrFAY3LUNw

kelipso 3y ago
> 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.
- DougN7 3y ago
  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.
  - thefurdrake 3y ago
    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.
- Fatnino 3y ago
  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.
CrispyKerosene 3y ago
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.
pmarreck 3y ago
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-drive-leads-to-new-physics/?amp=true https://www.scientificamerican.com/article/star-treks-warp-d...
- krapp 3y ago
  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.

kelipso 3y ago

> 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.

DougN7 3y ago
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.
- thefurdrake 3y ago
  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.
Fatnino 3y ago
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.

CrispyKerosene 3y ago

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.

pmarreck 3y ago

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-drive-leads-to-new-physics/?amp=true https://www.scientificamerican.com/article/star-treks-warp-d...

krapp 3y ago
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.