Where is everyone?

[QED]

In the topic: Is Stephen Hawking correct about moving into space? the subject of other life in the universe came up. In response to my question about why our Galaxy does not seem to already be colonised Harvey introduced an idea that interested me...

...it does seem inescapable that some sort of exponential colonisation pattern should emerge to fill every available habitat in a trivial timescale. This presents us with the niggling question "where is everyone then?". So from a simple logical imperative we might have a reason to wonder at the fact that we seem to be alone in the universe.

My (optimistic) view is that we are like kids in a family growing up in a retirement village (the stars are the adults in this retirement village). We are the only kids in the village from what we can see, and we begin to ask ourselves why no other family has kids since the retirement village has been here a long time. I think the answer would be obvious in that example. There were kids of these other resisdents, but they grew up and no longer live with their parents. I prefer this view because that means that some great things are ahead of us, and that this home we call the universe is just a place that we are spending our childhood and adolescence. Perhaps we'll eventually meet others on the block who are around our age, and we'll all leave home together...

This seems to suggest that all life naturally reaches a point where is transcends the physical realm and comes to reside in some other realm that has no connection with the physical. Is this reasonable? Is it supported in some measure by any of the religious faiths? Is there any logic we could call upon to dismiss it as an explanation for why we seem to be the only kids in the village?

[otseng]

Actually, given the conditions on Earth, and the size of the Universe, it's very, very likely that life similar to ours exists somewhere. It's even likely that intelligent life exists... somewhere.

And also assuming that abiogenesis and common descent are true and the universe is around 15 billion years old. But, if we assume all these things were true, it would be reasonable to wonder why don't we see evidence of ETs. Why don't we detect other lifeforms? Surely we can't be special in the universe and be the only ones to exist.

For example some have suggested that the Earth is a "nature reserve" with aliens agreeing not to disturb things so we can be observed without the observation affecting us. The problem with this theory is, once again, that it only takes one alien civilization to ignore or be unaware of this agreement and the "game is up". This suggests that there are other reasons for it being so quiet -- it also detracts form Harvey's suggestion (as I read it) that existence for other lifeforms is conducted at a different level -- one which has no causal connection to our own.

This seems to me to be very unlikely. What motive would there be for any, let alone all, ETs to want to make sure we don't detect them? Also, how would they have first detected life on our planet? We have only been sending EMR recently. And I can't imagine being able to use a giant telescope from another planet to be able to see life on our planet. So, the only way they must've known is to have physically visited our planet. Why would they have not left any trace of themselves? In all our science fiction movies, none of them ever say, "Hey, we've detected life on this planet. Let's scram and add them to our blacklist and make sure they never detect us."

If we factor in intelligent life on earth, then it would limit the shy ETs only to our own galaxy. Assuming humans evolved around 2 MYA. And an ET happened to be on earth when it happened. Then it travelled back to its planet. Then it said, stop the presses, make sure we don't send any radio signals to Earth. Then the farthest the ET could've travelled would be within our own galaxy. The next closest galaxy, the Andromeda Galaxy, is 2.4 million light years away. So, nothing would prevent other galaxies from sending out radio transmissions and stop us from detecting them.

So, I would like to invoke the principle of parsimony. We have not any evidence of the existence of ETs. So, the simplist answer is that they don't exist. To theorize that they are simply hiding from us fails the principle of parsimony.

I must agree with Bugmaster, unless we find a way of bypassing the speed of light(hyperspace?) we are doomed to forever be restricted to our own solar system. Other intelligent life may be found, but time and distance means never being able to meet face to face.

Most likely we'll never be able to initiate contact with aliens. But, surely some other alien civilization got a head start on us and be able to initiate contact with us.

It always puzzles me, for instance, that there are so many of them. Sure, we think in terms of just one--even many of us who weren't raised religiously, simply because our culture is basically Christian and it seeps in. But other cultures have different gods, and other cultures before us had yet other gods. Looking at the actual data, the simplest explanation is that people imagine gods to fill in the gaps in their understanding.

And a twist on that, it intrigues me that so many people believe in some sort of god. Strange that humans that evolved from purely naturalistic means would almost all have a non-naturalistic solution to their questions.

Gods are pretty much defined as being outside the realm of science, and able to do things that are physically impossible for ordinary mortals.

Yes and no. Gods themselves are outside the realm of science. But if they've somehow left their mark on the natural world, then we can indirectly detect them.

True, we have no evidence, just as we have no evidence for or against gods.

I'd disagree that we have no evidence of the existence of some diety, but we've had plenty of other threads to discuss that.

If there were a number of different civilizations then the chances of at least one managing to evolve the sort of technology being discussed as a possibility today (self replicating and repairing machinery) then a sort of "pyramid" effect would take over: probes arriving at hospitable (in terms of necessary resources to construct more probes) solar systems would release multiple copies towards other systems. Note that it only takes one civilization to accomplish this but once the process was started it would spread out at an incredible rate.

If self replicating machines that were able to travel through space did exist, it would seem likely that they should've shown themselves to us by now. If I were to build one, I'd design them to occasionally send me back a message on their status (how many it has replicated, where it's been, what it has detected, etc). And unless they use some other form of communication besides EMR, we should be able to pick those up.

Also, I've noticed something, am I the only a-alienist here?

[McCulloch]

Also, I've noticed something, am I the only a-alienist here?

Well, I am not quite an a-alienist but an agnostic wrt aliens. I also believe that the probability of an advanced alien civilization close enough to us to become known is quite low.

[juliod]

But, if we assume all these things were true, it would be reasonable to wonder why don't we see evidence of ETs. Why don't we detect other lifeforms?

For the same reason that any other civilization wouldn't be detecting us.

Thirty years ago it was assumed that we could detect the alien equivalent of our high-intesity radio emmissions. But even now we are falling silent in the radio spectrum as we switch to low-power, smaller communications devices.

And interstellar travel my never be possible, so we shouldn't expect to ecounter aliens even if they do exist.

Surely we can't be special in the universe and be the only ones to exist.

I expect we'll find life of some sort on the moons of Jupiter and Saturn. Mars might have some too, probably had life in the past, but may be sterile now. There is tentative evidence from mars-originating meteorites of fossile bacteria.

What motive would there be for any, let alone all, ETs to want to make sure we don't detect them?

My feeling is that if some alien civilization conquers all the problems of interstellar travel, etc, then we'll realize they are here when they begin wiping out all life on earth to reform the planet for themselves. That's what we'd do.

Also, I've noticed something, am I the only a-alienist here?

As Mac said, alien agnosticism is the correct position to take. We can clearly see that under the current conditions we cannot make a decision as to whether aliens exist or not. There is no evidence that they exist, yet there is good reason to think they could exist. We can make no posative statements one way or the other.

Alien agnosticism differs from theo-agnosticism in that aliens are remote. All god concepts posit a local, involved, active deity. People who believe in aliens that are local, involved and active are similar to theists, but equally fail to show significant evidence.

We can exect to cease being alien-agnostic once we are capable of examining the outer planets and their moons for microbial-type life, or are visited by genuine extra-solar advanced aliens.

DanZ

[Bugmaster]

And also assuming that abiogenesis and common descent are true and the universe is around 15 billion years old.

We have some pretty good scientific evidence of both.

But, if we assume all these things were true, it would be reasonable to wonder why don't we see evidence of ETs. Why don't we detect other lifeforms? Surely we can't be special in the universe and be the only ones to exist.

I believe I answered this in my post above. The reason we don't detect other lifeforms (actually, other intelligent lifeforms) is that the speed of life is so slow. Given the probability of intelligent Earth-like life evolving -- which is fairly small -- all the other intelligent lifeforms probably live too far away for their light to reach us. The Universe is huge, which means that there are probably tons of intelligent aliens out there... they're just too far. They're not hiding on purpose, they're hidden by the speed of light.

[harvey1]

The Universe is huge, which means that there are probably tons of intelligent aliens out there... they're just too far. They're not hiding on purpose, they're hidden by the speed of light.

There's lots to speculate on. Here's another... The universe continues to be a breeding ground for fighting over resources, and planets where the ecosystem is rich enough to support intelligent life are also attractive for invasion and takeover. In this scenario, you don't announce your presence for the same reason that mammals didn't make noises when T-Rex was in the neighborhood.

I don't favor this possibility, but it's a fun story to enhance upon around summer late night campfires when people are telling scary stories.

[QED]

It's certainly true that our technology has turned away from the use of high-power, narrow band broadcasts of the sort that will propagate far across the galaxy. Wide-band directional signals from orbiting satellites and distributed cellular networks have taken over in just 100 years - a very narrow window for ET to catch our accidental calling card. To pick up these early, more primitive, signals of ours means being "in the right place at the right time" -- an unlikely occurrence given the huge disparities in time and place between potential havens for civilization.

And also assuming that abiogenesis and common descent are true and the universe is around 15 billion years old.

Well, with all due respect to the more unconventional interpretation of the world that some hold to, the physics behind Nucleosynthesis is very clear on the matter. The universe has to be billions of years old and billions of light years in extent (as a minimum) otherwise there would be no heavy elements around to make everything from -- only hydrogen and helium. Even if we turned out to be the only players on the stage, the stage would still have to be as big and old as this to have given the stars time to do their stuff.

[Bugmaster]

There's lots to speculate on. Here's another... The universe continues to be a breeding ground for fighting over resources, and planets where the ecosystem is rich enough to support intelligent life are also attractive for invasion and takeover. In this scenario, you don't announce your presence for the same reason that mammals didn't make noises when T-Rex was in the neighborhood.

Yeah, like you said, it's a neat story, but it's just not very likely. For example, the closest star to us is Alpha Centauri; IIRC, light takes 4.5 years to get there. This is already too far away for any practical conversation; and it is much too far away for a starship maintaining a constant 1g acceleration to visit. And, as far as we can tell, there aren't any habitable worlds there, either :-(

[McCulloch]

Also, I've noticed something, am I the only a-alienist here?

[sarcasm]Please note that most philosophers would agree that an a-alienist is one who believes that it can be proven that there are no aliens. Simply not believing in the existence of aliens is not enough. If you do not believe that there are any aliens, you must be content with the label alien agnostic. However, if you believe that there are not any aliens, then you may properly wear the title of a-alienist. What is it about being an a-alienist that makes so many alien agnostics want to falsely use that title? [/sarcasm]

[QED]

Yeah, like you said, it's a neat story, but it's just not very likely. For example, the closest star to us is Alpha Centauri; IIRC, light takes 4.5 years to get there. This is already too far away for any practical conversation; and it is much too far away for a starship maintaining a constant 1g acceleration to visit. And, as far as we can tell, there aren't any habitable worlds there, either

We keep coming up with the disappointment that people have about the time/distance problems, but isn't it naive to put this forward as a limit to what might be achieved? Surely there are other timescales that apply, not just our own pathetic three-score and ten? Apart from the more fantastic speculations about worm-holes in the fabric of space-time I believe there are more realistic scenarios built upon the technology of self-repairing mechanisms and a fusion between biology and mechanism. The idea of seeding the galaxy with probes containing explorers who emerge into consciousness after journeys lasting for hundreds of thousands of years might sound like pure SF today, but given the present rate of technological advancement I find it hard to rule out in the future.

The main obstacle to all these enterprises is money. Money has a habit of buying you things that you couldn't dream of affording ten years or so ago. Using this simple projection it would suggest that, in time, personal resources could come to meet those that are the preserve of Nations today. I don't think it far-fetched to imagine people funding their own space probes to the inner planets sometime in the next century for example. I can remember setting up a very early DEC PDP8 computer at work (in 1969) and being hooked on it to the extent of wishing I had $25,000 to buy one to have at home... I can remember it got me thinking about the future and wondering if computers would ever find their way into homes. I think I foolishly concluded that it would not be so. I should have given more consideration to the little voice inside my head that made me wish I had one.

This makes me think that it's not so much the technology, but the will to do this sort of thing. Natural human curiosity and drive to explore seems to me to suggest that the will is there -- and therefore that the barriers of time and spatial separation will be overcome by adopting a different approach to the problem.

Returning to the theme of this topic, I would suggest that the reasoning I've set out above would apply to any technological civilization and ensure that the galaxy was already seeded with living explorers if we were not the first and only intelligence to have arrived on the scene. We have a lower bound to the emergence of intelligent life in the galaxy due to the distribution over time of the heavier elements. I've not managed to find an agreed estimate for this but it's looking as though around a 10 billion year gestation period might elapse before life emerges. This could place us in the first wave of life. The upper bound is defined by the point in time when all stars have moved off their main sequence which, IIRC is many orders of magnitude greater than the lower bound. So maybe the show simply hasn't started yet?

[Scrotum]

I would like to say some thing i personally see as obvious, duh, so listen up.


Considering the size of the Universe (infinitive in Human eyes), its very very unlikely there would not be other similar life out there. But, we also have something called Reality thats against us.

Lets pretend we WOULD have a neighbour "pretty close" to us, If they would be advance enough to space travel, it would still take them thousands of years to get here. This is not Starwars, we cant go into "lightspeed" or whatever they call it on the movies, there is a Very limited speed we CAN come up to, and thats the END of it, we as humans cant handle more, and its against physical reality.

So, we would have to wait thousands and thousands of year for them to come here, or we to them, and as you can assume, they will be as curious as us about other life, but would also be aware of the lackof possibility of a "quick ride over there". This is a Millennia job.


But thats just HOW IT IS (reality), then maybe you guys have personal oppinions that make you dislike his reality. But thats how i is.