Good luck. I’d think it would be extremely difficult for an intelligent form of life to evolve in an area with so much radiation on every part of the spectrum.
Several people have stated that the universe is infinite. Since when? Since the universe has a finite age, it clearly cannot be infinite in size. Unless you are talking about as yet undemonstrated universes not stemming from the Big Bang.
Not that it matters much. Civilizations with which communication would take longer than the lifetime of a species aren’t very interesting.
I don’t recall anyone seriously offering a solution to the Drake equation that was > 1,000. Even if that upper limit were correct, that would not constitute “teeming”, considering how big the universe is.
This topic seems to have died down and there’s no better place to ask than in this thread, so …
What do you think the relative probabilities are of (a) us finding an intelligent civilization, versus (b) an intelligent civilization finding us?
Approximately 0:0.
No one really knows if the universe is infinitely big or not. All we can say is that it’s really really big. That it has a finite age doesn’t restrict it from an infinite size. When astronomers say the universe is expanding, they don’t really mean it’s getting bigger; a better way to think of it is that the density is decreasing. It’s like taking every integer and multiplying them by 2; you’re not really creating more numbers, you’re just increasing the space between each one.
Since space is really really big, even if there were 100 intelligent civilizations in our own galaxy, the chances of any of them finding each other are extremely small.
Well that would depend on what you meant. If we found an intelligent civilization at about the same technology level as us, they’d probably find us back pretty quickly. But finding other intelligences at our level of technology is very difficult, so I’d say odds are greater that a much more advanced civilization finds us.
If there are other advanced intelligent civilizations out there, they could have easily found us if they were at all trying to look. All it takes is one self-replicating probe capable of speeds of 0.1c, and I believe you can have the whole galaxy explored in less than a million years (which sound like a long time, but imagine if the dinosaurs on our planet had managed to evolve to a tool-using society instead of getting wiped out ; they could have explored the galaxy several times over by now)
Because it’d be so easy for an alien culture to explore the galaxy, the question remains, why have they not contacted us yet?
The only answers to this question are:
A. All advanced civilizations naturally become completely uninterested in physical exploration.
B. All advanced civilizations naturally destroy themselves at a certain point- either accidental, through warfare, or as some sort of planetary-wide “suicide pact”
C. They know we are here, but have chosen to ignore us at this moment in time.
D. Intelligent life is very uncommon and we are the only one in our galaxy/universe.
E. Intelligent life is common in our galaxy , but by some fluke of chance, and despite being in a relatively “young” part of the galaxy, we managed to become the first advanced civilization, or are among a group of “firsts” seperated by less than 1 million years of technological advancement.
No. Current thinking, at least when I left the field a few years ago, was that the planets moved inward due to interaction with the protoplanetary disk. That disk is gone by now, so the planet’s not moving any more.
Wait, a probe that self-replicates in space? 
F. We ARE the self-replicating probe.
(Very inefficient design.)
Unless it starts out infinite. As Yumblie says, the expansion of the universe is about the universe becoming less dense; the universe could well have started as an infinite one of immense density, not as a superdense point or finite region.
A Von Neumann probe could, as space is full of energy and debris. We can’t make one yet, but we probably will be able to within decades at most. Certainly some million year old culture should be able to.
Well, when a boy probe and a girl probe love each other very much…
Does anyone else read these aliens threads and think of Rimmer’s religious-like belief in Aliens?
I would add to these some others:
> We could be in a preserve or there could be something akin to Star Trek’s Prime Directive (non-interference) if more than one race has explored the galaxy, it would require a number of races to agree on this Directive (an interstellar United Nations) and someone be able to enforce these rules. Or we could be inside someone’s “space” (i.e. territory) & they enforce these rules here.
> A number of civilizations have been here, say one self replicating probe or generation ship every few 100K years from 600mil to 150,000. yrs ago and never found anything akin to intelligence & will be back in a few thousand years… to check on the Dinos and/or find out how Grog’s Homo Halibis monkey Clan is coming along…
> They could be here with technology that is almost akin to magic to us watching, observing, collecting and mining in ways that are environmentally sound (or some subset of the Prime Directive) and they chose that we just don’t see them.
I am not saying that any of this is so, likely, or “I think this”. But I think if we make a list of the answers to Fermi these need to be in the queue.
Infinite in the sense that it took up all the space there was, yes. Infinite in the sense of long distance between points in the space, no. Unless you have some recent findings I’m not aware of.
I’m no cosmologist, but last I heard the universe was believed to be open ( will expand forever ), which means it’s infinite.
If a trillion civilizations have been expanding their cultural volume at the speed of light, and for an average of fifty thousand years each, and are constantly replaced as they become extinct, and that has been true since a billion years after the big bang. they occupy only a tiny fraction of space, in fact so tiny that it is unlikely that two would coincide in space and time in the same galaxy.
It’s a very large universe.
Most of it is so far away that only Supernovas are noticeable, and you pretty much have to be looking right at them even then.
Tris
My favorite thought experiment in this line is Freeman Dyson’s Astrochicken.
Because the universe is expanding at what is now believed to be an accelerating rate, it can be considered effectively infinite insofar as there will be points in spacetime that are unreachable from other points in spacetime (at least, without going into some kind of multiply-connected space or allowing for some form of superluminal travel). This doesn’t mean that the circumference, if you could sit back from some omnipotent viewpoint and measure it, would be infinite, but rather just too large and expanding to rapidly for light (or anything else) to get from one “side” to the other in any amount of time. So as a result we have the observable universe, out to the boundary of the cosmic event horizon, and…everything else.
Like everything in cosmology, this is poorly understood and will probably end up just as wrong as luminiferous aether, but it is what we collectively accept at this time.
As for extraterrestrial life: from an empirical standpoint, we have only one data point; all extant life on Earth arose from a common ancestor. However, we have observed the existence of essential amino acids–the building blocks of DNA and RNA–in locales that could not have possibly come from Earth, and by laboratory experiment have produced them in environments similar to primeval Earth, Titan, et cetera. So the basic molecules and conditions that presumably resulted in life on Earth are probably very, very common throughout the universe. In addition, we’ve seen and created artificial ribozymes which are, while not alive by any reasonable assement, self-catalyzing. While we don’t currently believe that ribozymes were the path to abiogeneis, the fact is that processes that support life and self-replication are pretty easily reproduced in natural conditions. And this, of course, is only talking about carbon-based life using something similar to DNA as the encoding and protein mapping structure; it is entirely possible that a self-replicating singularity could occur in some other stable fashion which we would recognize as being alive.
So why aren’t be being buzzed by aliens with books entitled How To Serve Man? (I’m assuming that UFO and abduction believers are as full of hot air as they appear.) There could be any number of reasons. Sapience may be rare, or ultimately detrimental to survival. It may be that a great galactic culture spawned across the galaxy but fell into barbarism 2500 years ago. Maybe they’re just to busy playing cosmic pinocle and have little time for hairless apes who can barely cope with multivariable calculus and hyperbolic topology. Perhaps they are afraid of the prophesy that says that mankind will rise up and rule the world after crushing the Thetan menace. Maybe they can’t figure out what we could have to say that would possibly be of interest. Maybe they just really, really hate Robin Williams movies and don’t want the rest of civilization polluted so they’ve quarantined Earth until he dies. There could be any number of reasons why we’re not on the Christmas card list of the Supreme Galactic Emperor, including the fact that they have made long and involved efforts to communicate with the dominant lifeform on the planet only to receive no positive response from the now-extinct Chevy Corsica.
It seems improbable that we’re so incredibly unique, so astonishingly lucky, that of all possible conditions on worlds around billions of suns over billions of years that only life has arisen here. Of course, we again have only that one data point, and if we weren’t so special we wouldn’t be around to ask the question.
Stranger
For the most part, and for a very long time, the only accessible parts to us, on a scale that will be large enough for us to detect, will only be in our immediate galactic neighborhood. Forget the rest of the universe and other galaxies. If there isn’t intelligent life around us in a radius, probably no bigger than 50 to 100 LYs (perhaps even smaller than that), we’re not gonna find shit until we advance our technology so far, that we’re creating wormholes or some such seemingly science-fiction method of space travel.
If intelligent aliens are out there, and have been actively looking for others like us for eons, still the chances of them finding us, at this point in time are so vanishingly small that, for all intents and purposes, you’ll never know before you die.
Shoot, our galaxy may indeed be teaming with life, but the laws of physics are set up that traversing the immensity of space is the ultimate problem, such that engineering will never overcome it (unless they brute force probe the galaxy by sending one to every star they can see).
Now, I’ll be out on my lawn, still watching the heavens… hoping…
Now we’ve evolved from a species of apes who use tools, into a species of apes who get used by tools.
As to the question in the opening subject line, I think it’s actually a reasonable and safe assumption to think the universe has a large number of intelligent species. All the points made above seem to support it.
The fact is it’s possible. Perhaps once a life-form reaches tool using, the natural evolution is to become self-aware. Then exploration is probably inevitable.
One thing I think is certain: All this talk about odds and chances of discovery, isn’t going to stop humanity from trying. We’re naturally curious (to a fault), and we won’t stop until every rock on every planet has been overturned.