That's a bit too broad of a statement to be plausible. It's likely there are no aliens near us in time, space, technology, and desire to communicate to make such a search fruitful right now. There could very well be aliens on the other side of the galaxy that we can't see. There could have been aliens nearby a million years ago that are now extinct or elsewhere. There could be aliens right now that are pre-industrial or advanced enough to not communicate with methods that resolve on the bands SETI looks at. There could be aliens that follow a game theory mindset of non-communication ala The Dark Forest. Etc.
Space is ridiculously big. The universe is ridiculously old. Talking in absolutes about such things is a poor strategy.
The universe actually seems surprisingly young to me. If the universe is a mere 14 billion years old, then dinosaurs ruled the Earth for 1/50th of all time! And life has existed on Earth for 1/3rd of all time!
When I was a kid, I figured the Earth itself would be a blip on a universal timescale. It's kind of disappointing that geological and astronomical timescales are so similar.
Of course, it doesn't really change your point. If a billion years is a surprisingly short period of time, then 21 years is an instant.
This was my original point: you can’t hide a Dyson Swarm. It goes the other way too. You can’t really hide from a K2 civilization either.
We’re getting into Fermi Paradox territory here. The beauty of a lot of arguments here is that you don’t need to prove or even assume that civilizations will, on average, “hide” because it just takes one to be detected. So the arguments is actually “do ALL civilizations hide?”
This is a much harder argument to make.
> There could have been aliens nearby a million years ago that are now extinct or elsewhere
In Fermi Paradox terms, this questioned is framed as “is there a Great Filter ahead of us?” This question predictably has a lot of discussion. It’s hard to predict what that might be because even apocalyptic scenarios other than extreme bad luck (eg a nearby star going supernova) are unlikely to completely wipe us out at this point, even nuclear Armageddon.
Okay, let me qualify: there are no aliens in the visible universe.
Of course what exists or doesn't exist in the universe that's not visible is pure unscientific speculation; might as well be made of blue cheese as far as science is concerned.
> Space is ridiculously big. The universe is ridiculously old.
This isn't true. Mathematical concepts of infinities and limits are "ridiculously big". Space is finite and thus ridiculously small.
> Of course what exists or doesn't exist in the universe that's not visible is pure unscientific speculation
If something can only be proven to a 99.999999% certainty, is that still "unscientific"? What if scientists predict something happening with only 0.1% chance, for example the likelihood of a particular asteroid hitting earth? Or what about 60%, like a typical weather report predicting rain.
Generally, the high, low, or intermediate likelihood of some event happening does not make it unscientific.
While it would be unscientific to simply say that aliens exist, it's plenty scientific to consider the rate of star formation and age, conditions for life around stars, and time it takes to develop intelligent life to say that there is a particular likelihood of there being alien life.
> While it would be unscientific to simply say that aliens exist, it's plenty scientific to consider the rate of star formation and age, conditions for life around stars, and time it takes to develop intelligent life to say that there is a particular likelihood of there being alien life.
Like I said in another comment below - you're assuming information is distributed uniformly across the universe, which we don't really know and can't assume because it certainly isn't in the solar system.
> Yes, I know I'm treading on some dearly-held religious beliefs ....
> what exists or doesn't exist in the universe that's not visible is pure unscientific speculation
I don't see anyone saying that the existence of aliens aren't speculation or that "aliens exists" (or your: "aliens don't exist") isn't just a personal belief as stupid to argue about as religion. But as countless wars have shown, people (like you) will try to create conflict from differing personal beliefs. Just because you drop "Occam's razor" doesn't make your belief the correct one.
OK, you know that whole big bang thing? That didn't start with a singularity the size of a golf ball, that was an infinitely large singularity that "exploded" and got bigger.
The singularity was infinite. Space is infinity, but bigger.
Like I said, I'm talking about observable space. Science only talks about things that can be observed (by definition), so as far as science is concerned, we must assume that we are alone in the (observable) universe until further evidence.
What's out there outside the observable universe is fun to speculate about, but it's armchair philosophy, not science. Maybe there's an infinite variety of life and somewhere out there right now Gandalf is wielding a light saber while riding a dinosaur. Maybe we're alone in the universe because the Earth so happens to sit right on the only information complexity singularity in the universe. (We really don't know anything about the information structure of the universe yet; all the "dude, the universe is really big" arguments assume that information is distributed uniformly across the universe, but this obviously doesn't match observed reality.)
I think you're using Occam's Razor incorrectly here.
Here are all the facts:
1) There's an incomprehensibly large amount of stars and planets in the universe
2) On one of these planets (Earth), there are conditions which have lead to the appearance of life
3) These conditions are not unique to this planet
We don't know of any fact that would exclude the possibility of life coming about on other planets with similar conditions, so using Occam's Razor actually tells us that there's probably lots of other life out there.
Use Occam's Razor: there are no aliens.
(Yes, I know I'm treading on some dearly-held religious beliefs now and will get lynched. Still, somebody had to say it.)