Absurdity of it is subjective, but it being consistent with the evidence is not. It's highly unlikely, but it's certainly more likely than explanations that have zero likelihood. In the past the government has put forth explanations of events that are patently false (read: lied) and never re-examined, so the extraterrestrial hypothesis is more likely than their explanations in those cases.
Edit: To be honest, I'm surprised the extraterrestrial hypothesis is considered so absurd by scientifically minded people. Clearly it's absurd to assume that we're the only 'advanced' civilization in the universe, the place where it's a grey area is if a much more advanced civilization would have the means or the interest to visit our planet, and if they did, if the phenomenon of UFOs jives with what we'd expect to see if they did. This is up for debate, obviously, but I am not sure why logic doesn't dictate that the odds are reasonable that such a scenario could exist. Fermi's paradox makes you wonder.
The problem with any hypothesis that involves Earth being visited by extraterrestrials isn't the almost unthinkably large distances involved, it's the timescales involved.
For any two given planets in the galaxy that could support intelligent life, in all likelihood the technological progress of those lifeforms will not align, and it won't be close. Imagine one civilization encountering another, except the first is 50,000 years more technologically advanced. Or 500,000 years. Or 5 million years. What would happen?
The more advanced civilization wouldn't be playing games to keep from being discovered, that's for sure. They wouldn't care. Even visiting the planet would be a total waste of time since with that level of technology they could certainly observe from afar.
I don't think you can dismiss the possibility of an as-yet-undiscovered end-run around these limits. The problem with a critique of a hypothetically more technologically advanced civilization than our own which is based on modern understandings of physics is problematic at best.
There are larger problems with the ET hypothesis, though, and that is why generally, descriptions of beings associated with lights in the sky, although also often associated with knowledge of new technology and with kidnapping, are described in physical details differently by different cultures. Even in somewhere as narrow 10th century Europe, you have at least three different, if you will, species of entity associated with this sort of thing.
So this leaves the ET hypothesis with two bad choices, which are either we are more observant than our ancestors which is patently false, or else there is some intersteller convention somewhere which divvies up cultures for observation and follows them as they move around, and stops when the culture changes sufficiently. That starts to sound very implausible.
What about: a scientific expedition to earth is expensive, so when it arrives here, the ship takes shore for a while, sends scouts, gathers data, and then moves on until another one arrives, possibly from another planet? Is it so far-fetched?
Also, things are always described in a sociological context. What we would call "automobiles" would have been called "chariots of fire" by our elders.
You still have near-exact boundaries between culture and portrayal of the entities involved. If you are in Continental Europe in the 8th Century, these are demons or even Satan himself. If you are in Sweden at the same time, it's the dwarves and they are the best metalworkers in the 9 worlds. Folk religion in England at the time still talked about elfs being associated with this sort of thing, and folk religion in Ireland was different yet.
I don't think you can have regional stability and such variation between regions with that hypothesis. I think an anthropological one makes more sense.
Making hypothetical statments about the motivations of an alien mind that may be millions of years ahead of us, and then using the implausibility of it as an argument to dismiss any contrary evidence, is the weakest argument against this phenomenon. But it is always repeated in every single discussion about this topic by someone!
An interview with Stephen Hawking was recently posted to HN. In the interview he states that UFOs are only witnessed by crackpots and that the laws of the universe prevent interstellar travel.
The "crackpot" statement aside, I think it's incredibly disturbing that a scientist of his stature makes absolute predictions like we'll never travel to another star. I believe he is pretty good at his job, but saying something is impossible -- based on our current understanding of physics -- seems silly. No one in the physics community could say that our understanding of the universe is complete. The most prevalent theme in physics today is still the incompleteness of our understanding. We can't reconcile our understanding of the largest things in the universe with our understanding of the smallest. Although we can measure gravity, predict and observe its effects, we have no consistent explanation for it.
I'd say that thousands of years of fiction (speculative or otherwise) remain largely unaffected by hundreds of years of physics. Our understanding of the universe is still in its infancy.
We also have a history of having our deepest beliefs overturned by progress. Why would the beliefs of the late 20th century be any different?
[Edited for language use]
[Edit]
He dismissed the idea of time travel in that article, not interstellar travel. My criticism still applies.
It won't be the first of the last time, that a famous scientist has made a statement or prediction that proved to be false. At the close of the 19th century, Lord Kelvin the most reputed scientist of that era, boldly stated, "heavier-than-air flying machines are impossible". This was in 1895, just 10 years prior to the Wright brothers proving him dead wrong. Those who advance the "seems impossble so it cannot be true" argument, need to remember this and all previously considered impossible stuff that became possible. These include airplanes, meteorites (yes, once considered impossible by scientists), analysing stars, existence of black holes, nuclear energy, space flight, and teleportation using quantum entaglement....
'by using "matter/antimatter annihilation," velocities just below the speed of light could be reached, making it possible to reach the next star in about six years.
"It wouldn't seem so long for those on board," [Hawking] said.'
I find the crackpot statement a bit problematic too. Basically he is suggesting that if you witness a UFO, you are a crackpot. I don't see any reason to think that. Indeed I have seen plenty of things I can't account for scientifically (no UFO's though), and I have had outright hallucinations induced by mystical experiences and meditation (those are terrifying believe it or not).
BTW, I don't accept the extraterrestrial explanation. I think when you look even over the last 50 years, descriptions and portrayals of UFO's have evolved with the times, and phenomena which are generally comparable in the outlines go way back, but are very culturally dependent.
The problem with the extraterrestrial hypothesis is actually remarkably simple and that is that one has to account why non-human entities which are reported to kidnap people, and have advanced technology, and are associated with lights in the sky, are so fundamentally culturally portrayed? Is it reasonable to think, really, that there is some great ET convention where they divvy up our cultures and follow them? That doesn't sound reasonable to me. I think it is more likely that there are multiple components to the sightings, some of which we may not know what they represent yet, and some of which may be our projection and making sense of what we see.
Just because it is seems unreasonable to you in human terms, is precisely why it may be perfectly reasonable to (what you admit) to be non-human entities! And just because it is unreasonale or implausible to you or anyone else does not mean it is not real or not happening. Quantum physics seems very implausible to me but that has no bearing on it being true.
I'm not familiar with Hawking saying we'll never travel to a star (well hopefully not in a star). I doubt he said that. We could build a space ark and travel for about 50,000 years and hit proxima centauri, no big deal. :)
but yeah, most are either crackpots or reasonable but naive people.
Since when are ad-hom's acceptable responses on HN? I never said I was sure such things were true, but like most true hackers, I'm curious and want to know more when things seem like they don't make sense. You're not very well read if you think UFOs are an open and shut case for all people who don't "need to see a psychologist."
Since at least 1303 days ago (for gfodor). Not that that's important, but just to dispel the "HN is declining" people. Your ad hominem response/insult is actually the kind of thing that could bring about HN's decline honestly.
I found gfodor's comments to be reasonable, though I have no idea if they're backed by real evidence. I wouldn't jump to conclusions myself unless I had more thoroughly looked at it.
Yes, sadly most people who dismiss UFOs, have not viewed or read - let alone examined the mountain of data and evidence that exist. Yes, evidence does exist - often as multiple cross-referenced radar readings, abnormal radiation levels, and even physical traces where UFOs have been observed. The true skeptic would not dismiss this out of hand, without some actual personal investigation into the subject.
Where are the aliens? There's apparently so many of them that there's "mountains" of data yet no definitive proof. Why is this the only sort of thing on history for which we have "mountains" of data but no definitive proof? I mean, come on.
Edit: To be honest, I'm surprised the extraterrestrial hypothesis is considered so absurd by scientifically minded people. Clearly it's absurd to assume that we're the only 'advanced' civilization in the universe, the place where it's a grey area is if a much more advanced civilization would have the means or the interest to visit our planet, and if they did, if the phenomenon of UFOs jives with what we'd expect to see if they did. This is up for debate, obviously, but I am not sure why logic doesn't dictate that the odds are reasonable that such a scenario could exist. Fermi's paradox makes you wonder.