@manton Exactly what I’d expect a covert agent for an alien civilization to say. 🤔👽🛸

I’d never looked at it that way. Space and number of planets may be effectively infinite, but time is not. Doesn’t leave as much room for infinite possibilities as I’d long imagined.

Also, oxygen is probably poisonous for most aliens, as it was for early single-cell Earth organisms before photosynthesis evolved.

@manton But what if that’s what the aliens *want* us to think?

“Here, we’ll catch them off guard with this. Humans seem to have a fascination with balloons! We’ll just disguise it like one!”

@manton I think it’s virtually certain that there are other civilizations at our technological level or higher. Possibly many.

I think it’s also virtually certain that none have visited our solar system, let alone Earth — and probably never will.

@jeff I can believe that. To me, it’s the combination of how long it takes for intelligent life to develop plus how long it takes to get anywhere in the universe (compared with the age of the universe and a visitor’s probably short lifespan) that makes an alien visit nearly impossible.

The Earth is 4.5 billion years old while the universe is 13.7 billion. I think that’s enough time for others to be ahead of us. No telling by how much, though.

@SamHawken I checked the numbers before I posted and stand by them. 🙂 It could take similar billions to evolve elsewhere, leaving little time to explore the universe given how slow travel is. But who knows!

@acfusco Yeah, they’d have to so far ahead that we can’t imagine it. Or they’d have to have impossibly long lifespans to make the trip.

@manton so what you’re saying is that balloon-based time travel isn’t totally impossible!!!

aliens aeronauts from the future!!!

The assumption is aliens equals beings like us. Where I would postulate that it’s likely very few aliens are, in fact, anything like us (bipedal or even carbon-based). It’s more likely – as bacteria and viruses came first here – that this is predominantly the state of life elsewhere. Think mould or mycelial systems.

@manton Much more likely, IMHO — and nearly as amazing — is finding primitive life elsewhere in our solar system.

I wouldn’t be all that surprised if we eventually found some sort of (very simple) life swimming in the oceans of Enceledus, for instance.

Not quite what people think of when they think of “aliens,” but…

@alexink That makes sense to me.

it’s all just a simulation anyway 😉

@acfusco There is plenty of space and time for other civilizatios to rise and fall, and never touch us. Even if a civilization spans a big part of the galaxy and lasts a million years there is still plenty of time and space for that civilization to disappear and never leave a trace that we can find.

Another possibility is that the chances of intelligent life evolving is so incredibly rare that it’s only happened a few times in the universe, even though there are billions of Earthlike planets. Consider the number of snowflakes in the world, and yet every one is unique.

@camacho Thanks, added!

Silica based-life is another option.

@manton There’s plenty of time for other species to have developed beyond our capability (if it weren’t for the asteroid that wiped out the dinosaurs, something sentient may have arisen in our place, and far sooner, for example), but I agree that instellar travel is vanishingly unlikely to happen frequently among civilizations, let alone on a space-timeline that intersects ours.

@manton The universe is ~13.8 billion years old. Our galaxy is about that old, but our solar system within it is about 5 billion years old. So there are a staggering number of systems out there that are much older than ours and have similar conditions that it is very likely that other civilizations advanced a whole lot more, notwithstanding the great filters.

@Antichrista Fascinating to imagine a different timeline without the asteroid. And what setbacks other civilizations may have faced.

@manton The universe is young but still old enough that many civilisations could already have lived and died out. Assuming that microbial life is far more abundant than complex life in the universe, how likely is it that more than a few advanced civilisations are alive around the same time so they can say "hi"!? And how likely is it that either would have capability to bridge vast distances? I think microbial life quite likely. Chances of 2 advanced complex civilisations connecting is far lower.

isn’t it roughly 10 billion years older than earth?

one of my absolute favorites!