Is there realy life out there?

According to astronomers, the theory is that there are many planets in the universe other than Earth (see Earthlike planets ‘common in Universe’ ) and that many may harbor life. Some or many of these planets life forms might even be more “intelligent” than humans. I agree that this seems plausible based on our current knowledge but what I have been unable to reconcile, if this is so, is why at least a few of these advanced races haven’t openly visited Earth yet (like landed in Washington D.C… Moscow, Beijing or wherever).

Given that there IF there are a reasonably large number of other sentient life forms, statistically speaking, it would seem that at least a few should have passed through this region of space during our recorded history and should have dropped in and tried to say hello. Hell, at least we should have discovered a clear attempt at communication via radio or whatever.

Following classic science fiction, perhaps the good races really don’t want to influence our development, so they hide from us. But one would think that there must also be some evil races that would have said, screw it, let’s invade and take this thing/stuff that is useful to us.

So perhaps there really AREN’T any other life forms (at least in this galaxy)? Maybe we are all alone in the universe, an evolutionary stroke of luck? Or maybe interstellar travel isn’t really possible? Or maybe there were other races but as each race reaches a certain technological level, they wind up destroying themselves back into their equivalent of our stone age?

Anyone else ever ponder these questions?

We might genuinely be the first civilisation. For even the simplest life to develop, the “interesting” atoms from more than one generation of stars is required (ie. new elements produced in star core, then supernova scatters them, then new star including these elements produces further new elements, another BOOM! and so on). It is unlikely that there are too many other third generation stars like our sun in terms of a proportion of those visible, and so life might not have been all that likely until a billion years ago or so.

As for useful interstellar travel (ie. within years, but without the inconvenient time dilation which means your great-grandchildren die before you get back) I believe that this will require such incredible feats of engineering that a spaceship able to withstand “useful” space travel (eg wormholes/warp space) could fly through the sun. So millennia away, if ever.

Regarding transmissions, well, SETI tells us that nobody within 5 light years (see map) is broadcasting TV or radio, nobody within 50 light years (map) is using military radar, and nobody in this galaxy ever swept the skies occasionally with a high frequency gigawatt beam (eg. Arecibo) just to see if anyone sent anything back.

Now, this does not necessarily mean that there is nobody there, but the alternatives are all unlikely for one reason or another:[ul][li]There might be a ruthlessly enforced galactic silence policy, and nobody uses electromagnetic signals any more. However, each such civilisation could still not prevent the leaks from their technological infancy, and it is difficult to believe that nobody, not even a malfunctioning piece of equipment or a mischievous joker, ever lets slip an electromagnetic signal detectable by the incredibly sensitive receptors on Earth.[]The aliens might have encased the planet in a “shield” impermeable to transmissions. Unfortunately, this would require such enormous resources and manipulation of spacetime that we might as well suppose that they are keeping us in the Matrix.[]Perfect compression is indistinguishable from noise (ie. a signal which has been coded for optimum efficiency simply sounds like a detuned radio). This is a genuine possibility. However, again, there must surely be some leaks from way back when the coding was imperfect, and it would seem imprudent to code eg. emergency beacons so that they couldn’t be identified.[/ul][/li]
So, it is still possible they are out there in this galaxy. However, there are two definite facts:[ul][]The technology required to emit a galaxy-wide audible signal is only as advanced as that required to make a nuclear weapon. [] We appear to be the only ones ever to have done so.[/ul] One wonders whether the two facts are not unrelated

Also, out idea of what constitutes an “advanced” civilisation may not be in tune with the reality of those other civilizations. Advanced intelligence dosen’t necessarily lead to technolgical advancement. There may be some very highly intelligent and advanced populations on other worlds that just have no desire to send out radio signals or travel into space. There is no reason to beliveve that intelligent life on other planets would share any of our values – including the idea that exploration of space is beneficial and that technology leads to enligtenment. At least it is a toss up.

Which is why I think we should be cautious in sending out signals and probes. A look at life in action on our planet shows that the more powerful a living thing is the more power it will take. We have no problem exploiting the other living things on Earth for our own purposes – nor do other animals (and even plants). The laws of nature would lead us to believe that if a race of beings were powerful enough (“advanced” may be a human value) to make it here they would be powerful enough to exploit us for thier own purposes. Of course what are we going to do – stop using radio, sattelite technology?

Some say that is already happening - but I still can’t figure out how shoving a plastic rod up a person’s anus could be beneficial to an alien race. Although they probably have thier own values and if they want to anal probe some redneck then that’s better than them forcing us into slavery and strip-mining our planet.

Is not there a book called *Rare Earth * that discusses the rarity of life in space? I’ve never read it – has anyone else? Is it some creationist crap or real science?

As much as Star Trek fans hate to hear it, interstellar travel is just not going to happen, with us or any other race. The distances are too far. So while it seems likely that there is other life out there, the chances that they would come our direction are extremely remote.

I think it’s more likely that there is other intelligent life on Earth. Octopi, dolphins, and parrots all have shown signs of it. I think it would be worthwhile looking at Earth’s species to learn how we would judge intelligence in alien species.

Imagine that we found ant-like creatures on Mars that created structures, “farmed” other lifefor food, had specialization, etc. How would we decide if they were intelligent?

Relatively instantaneous interstellar travel likely won’t happen. But otherwise there’s no physics that I know of that precludes long durration travel.

Why add the “without the inconvenient time dilation” qualifier? Why couldn’t advanced races send out robotic probes at near-lightspeed, dilating all they want? Sure, it would still be years before the signals came back, but it seems like something worth doing to me.

Maybe the intelligent lifeforms are just far enough away that they haven’t had time yet to hear us and get a ship to us (sending a ship to a planet without hearing signals from that planet seems rather imprudent). Or, of course, maybe they were convinced long ago that space exploration is foolish “while there are still problems here on Tatooine to deal with!”

Maybe I’m just reaching because I’m a sci-fi geek, but I still think it’s likely that there’s a civilization out there that’s more advanced than us.

We can speculate as much as we want, and our speculations will reveal something about our individual personalities (I for one will be disappointed if there is no life away from Earth), but really, the only honest and responsible answer is this:

Cannot yet say for certain. Not enough data. Ask again later.

The OP’s question even has a name - it is called the Fermi Paradox, first asked, I believe, by Enrico Fermi over lunch at Los Alamos.

You might be interested in reading some of Stephen Baxter’s books, which give several, fictional, solutions to this problem. The biggest problem is that the universe is very old, and life on Earth is relatively very young. If even one civilization spread through the galaxy, we should see the effects. Slower than light travel is not a limit, there is a lot of time to do it even if ftl travel is actually impossible.

As Cervaise said, the only real answer is that we don’t know. I’m working on an sf book also about this, so I have thought about it a lot. Here are a couple of possibilities.

  1. Intelligence is not a survival characteristic, and intelligent life forms don’t last long enough to get off their planets. But if even one or two did, we should see it.

  2. The aliens are deliberately steering clear of us, due to some non-interference directive. They either don’t broadcast, or don’t waste energy using radio-like methods. Say in the future all radio and TV broadcasts come over the internet and through a wireless network on the last hop. That would cut our radiation by a lot.

  3. They did visit, but so long ago we don’t have any indicators of it, and they have never come back.

  4. We got randomly skipped. Maybe they’ll show up next week.

  5. Sufficiently advanced intelligence is environmentally sensitive, and don’t mess stars in a way we can determine. So they are out there, but we won’t know until we meet them.

  6. After a certain point, intelligence evolves (self-directed) into a form where we wouldn’t be able to detect them. This doesn’t have to be mystical. One would think that eventually intelligent life would learn to download themselves to attain immortailty. Consider a sufficiently advanced computer running a simulation of the brain and other parts of the body affecting the personality. This might be easier to achieve than real AI.

The big weakness of Star Trek and other such stories is that they assume all life forms are roughly at the same level of development, to keep plots interesting. ST, at least, does have some more advanced forms, but none care about the universe very much. They don’t really appreciate the age of the galaxy, and how we are latecomers.

Of course, we could and probably have simply missed each other in time. Say that a radio using civilization arose 10,000 years ago but is 1000 light years away. And say that civilization lasted for 5000 years before it collapsed completely…maybe they wacked each other, maybe a stray commet or meteor hit them, maybe they failed to properly sanitize their telephones properly and died out. Whatever. In any case, their transmissions are long passed us and moving away at the speed of light. We missed them.

Chances are that life is relatively common out there in the great beyond. However, sentient life is going to be VERY rare. Sentient life that uses communications technology that we could understand and recognize is going to be ever rarer. Finally, we have to be within a certain time window to be in a position to hear and understand those transmissions. After all, if they were squacking when the Romans were running about, it didn’t do us much good, right? And if another civilization out there is, say 1000 light years away and has just discovered radio transmissions, and we aren’t here 1000 years from now, again we missed it.


I’ve never thought much of the “invade and take your stuff” sci-fi plots. There isn’t a whole lot on earth that you can’t find orders of magnitude more of in places that don’t have annoying, heavily armed life forms on them. Even in our own solar system there isn’t one mineral on earth that you can’t get elsewhere in greater quantity and an interstellar-capable civilization would certainly be able to mine other, dead solar systems, or just dead parts of ours. But of course maybe they would just regard us as bugs and take what little we have anyway while strip mining the rest of the solar system too. Still, the idea that aliens might hear our radio signals and think “ooh, I’ll bet they have some titanium we could steal” is pretty far fetched.

Well, as I recall, SETI just looks for the presence of signal, defined as a high power, narrow-band transmission. Most of the things in nature that produce high levels of energy also produce very broad spectrum noise. So if you see a power peak at a certain specific frequency and nowhere else you can begin to suspect that it’s artificial. If the signal were sent to us unintentionally it might be part of their internal communications and would be optimized like you say, but if they wanted to talk they would send something that just screamed “we’re an intelligent civilization”. Beeping out the first 20 primes or something equally unmistakeable every now and then has been suggested.

Life on other planets and intelligent life on other planets are two very different propositions. Earth’s biosphere has an evolutionary history going back about two billion years. (If you’re a Biblical creationist you’re probably not interested in this thread anyway.) In all that time, encompassing multiple eras and epochs and ages and cataclysms and transformations in the nature of life on Earth, in all that time of randomly experimenting and trying out new life forms, this biosphere has, so far as we know, produced only one sentient species: Us. Homo sapiens. (And maybe some of our extinct hominid cousins, but that’s beside the point.) We have been here much less than a million years – by one account I read, only one hundred thousand – either way, an eyeblink in Earth’s history. Our existence would appear to be highly improbable.

Now, if we visit another planet, one that has life on it, we will be seeing only a snapshot of the long history of life on that planet – and the advent of an intelligent species there might be millions of years in the future, or the past, or never.

Even if life in the Universe is much more common than we imagine, intelligent life still could be freakishly rare.

It’s all in the Drake Equation ( We could use the Drake Equation to calculate the number of sentient, industrialized, radio-using races now alive and sharing the Galaxy with us, except that too many of its variables are not only unknown but imponderable – most importantly, the variable L, the length of time a sentient race sends transmissions into space – i.e., the length of time between the time it invents radio technology, and the time when it loses or abandons such technology or goes extinct. It’s possible that any sentient race is doomed to destroy itself within a definite period of time after developing a certain level of technology; possible, also, that a sentient race, unlike every other living species, has the potential to ensure its own long-term survival and never go extinct until the heat-death of the Universe. We just don’t know.

If another sentient race did exist, and had the resources and technology to cross light-years to visit us, I don’t believe that once they got here, they would just hide and watch and kidnap the occasional anal-probe subject. Of course, we have only our own psychology to use as a guide to theirs.

We’d have to have been looking at the right moment; this is not an insignificant factor.

Our galaxy is about 70,000 light years in diameter and I hear the stars number about 10,000,000,000. Even if life is fairly common it wouldn’t be difficult for the average distance between advanced civilizations to be 1000 light years. What if it is impossible to go faster than light? Would you be willing to make a round trip of 2000 years?

The sci-fi movies and stories make it look like habitable planets are a dime a dozen. Makes for interesting stories.

Dal Timgar

ummm… how about oil and other petrolium products? I don’t believe that any other planet in our solar system contains those as they are produced by carbon deposits from dead plants and animals. Actually Earth probably has a much greater variety of minerals than any of the other planets in our solar system. Because Earth is a living planet is has the ability to constantly produce varying mineral combinations over and over again. We don’t know much about the internal geology of the other planets but what we do know shows us that Earth is very rich in variety compared to the other planets. Mercury is made up of pretty much the same thing as the moon which is comparable to Earth’s limestone (chalk-rock). Mars (which we have quite a bit of information on including some very recent spectrographs from the surface and some actual rocks) is made up mostly of iron oxides, sulfates, and carbonates (none of which are really valueable to us). Venus is the best bet since it has an active internal heat source but the rest of the planets are dead inside and probably don’t have a lot of variety at least.

And who says they would just be after minerals? How about water? How about life? Any person who runs a business knows that the most expensive resource is the people who work for the company. Unless the beings have the ability to manufacture other living things to order then our lives and the lives of the other plants and animals could be considered a very valuable resource indeed. Living things are the only resource that self replicates – making living resources very valuable. And if life is rare than its rarity would make it valuable in an interstellar economy. Platimun is only valuable to us beacause of its rarity – Zog the alien could make a very valuable pet trade out of humans. We do it with rare birds and the like. – If we found some sort of wildebeast on another planet I guarantee that people would pay out the but to get a rump roast from it. Maybe we are inviting ourselves to dinner.


Like others said, we’d have to be around at the right time to detect radio waves. There could be intelligent species a million light-years away that are emitting radio signals right now searching as desperately for us for another species out there and we won’t get them for a million years.

Additionally, faster-than-light travel could very well be a constant limit. Sci-fi counts on there being some way to travel huge distances in short amounts of time. This could be impossible. That easily explains why there haven’t been any visits.

And if there isn’t intelligence life, for whatever reason, there could very well be unintelligent life. There could be a planet of dinosaurs out there. There could be planets with oceans teeming with fish-like creatures.

I think the scales that we are talking about here are much too large. We can only survey our own galaxy for the most part, how many billions of galaxies are there out there in the universe?

Thought someone might mention that. But if you can cross the distances between the stars you already have a power source that renders fossil fuels a complete anacronism.

All true but I was actually thinking more of the asteroid belt as a mineral resource. What I’m getting at here anyway is that the galaxy is composed of most of the same stuff everywhere. If you can find a dead solar system with an asteroid belt and maybe an “earth” or two to mine/colonize/terraform why bother with us?

Well again, I’m assuming that if they can get here they probably have long since transcended any need for slave labor, farmland, etc. and would have advanced nanotechnology, fusion power and so on. It’s probably very unlikely that we would encounter any interstellar capable civilization that was close to us in technological development. They would likely be FAR beyond us. This is just based on the idea that when you meet the aliens you do so at a more or less random time in their evolution as a civilization. If the average technological society lasts, say, 100,000 years then the probability of our encountering them when they are in our stage of development is very small since we have only even had radio for about 100 years.

Nope for petroleum products you need carbon and hydrogen. Both are abundant in C class asteroids and comets. From here

bolding is mine

The Earth is not alive. Perhaps you’re thinking of metallic ore loads created by the presence of water?

Mercury is denser than the Earth (i.e. there’s a lot of iron and nickel over there). The Moon is primarily composed of Earth crust type rocks like silicates, though it has a wealth of Ti, Al, etc that can be smelted out of the regolith.

Venus is pointless unless you really like saunas. No water, no volatiles no nitrogen. Mars on the other hand has carbon, water and nitrogen. Yeah sure Zog may not need those but we do.

Hydrogen and oxygen are common in the universe and especially in comets and icy moons like Europa. No need to drop into a big gravity well when you could empty the Oort cloud.

The odds are pretty good that even if a) spacemen evolved elsewhere, and b) they cared about earth vs. other places, that there still would be only a short window geologically speaking where they could have noticed us.
Perhaps they came, took a few amoebas home and moved on to the next planet.
Or perhaps they are arriving tomorrow, having been delayed for a century trying to find water on Mars.

Even assuming a relatively high number intelligent lifeforms, say a dozen per galaxy, which are all broadcasting English in the FM band, it’s not a simple matter to ponder whether we’d catch on. Radio telescopes have not been around for a significant amount of time. You have to take the fourth dimension into account in SETI, radio may seem instant but in terms of interstellar distances it travels at a crawl. So the question of how close another species is or how long it has been broadcasting are very relevant. The universe could be temming with advanced interstellar civilizations, but if their signals are still a week out we’d have absolutely no idea they existed until they finally made it here.

Or to turn the idea around, imagine we knew somehow that there was an intelligent species somewhere in a neighboring galaxy, how would we give them a call? Forget two way dialogue, how would we even send out a one way hello?

Then you have the other major problem with SETI. The idea that we would doubtlessly recognize an alien civilization’s radio broadcasts as an intelligent signal is a bit on the scifi edge of things. At best we’d be dealing with some serious gray area, and in all likelihood we could have easily misidentified the signals as coming from a star or other source. Our current identification algorithms are based on things like narrow band frequency spikes, but aliens may not used fixed frequency broadcasts. They may encrypt all their broadcasts such that they don’t appear as simple repeating patterns. They may intentionally mimic natural radio patterns of their star. There’s no real reason to expect they would do things just like we do.

Deriving any meaning from the signals is another ball of wax entirely. The problem with long range radio communication between two species is that we would basically be limited to displaying basic mathematics and maybe a bit of novice science if we really got creative. To display Shakespeare you need context, and context doesn’t broadcast well. Especially with a few decades of lag between speakers.

The bottom line is that unless humans invent FTL travel, or someone else does and drops in to see us, the whole question is academic. Important, valid, but academic.