PDA

View Full Version : Why extraterrestrial life exists, but we haven't made first contact yet.



planetaryscience
2014-Jul-15, 04:35 PM
I suppose this would belong in the Against the Mainstream section as much as this, but I suppose I might as well choose one to post in.

There are many theories, hypotheses, and bits of discussion about just how common extraterrestrial life is, and why we haven't seen any. There's the group convinced that we're alone, the group who ponders distant existence of advanced civilizations, and the group who thinks we've already been visited. So far, none in particular have gotten the upper hand, and any thought or discussion is just pure speculation, so here's mine.

Quite frankly, the universe is still very young astronomically. 13.8 billion years may seem like a very long time, but at it's current age most stars in existence are only second or third generation, with a select few being fourth or fifth, but the universe is still in its juvenile stage compared to its eventual gigantic age. Most of the first billion years of its age were spent getting calmed down, with the first possibility for life having only started recently.

First of all, based on common knowledge, the first stars began to form some time between 0.15 and 1 billion years after the Big Bang, or about 13.7 to 12.8 billion years ago. Most of these stars probably couldn't have sustained any life early on anyways, but assuming that a few of these first-generation stars were F, G, or K-type stars, and that they had planets orbiting in stable orbits in the habitable zone, and were isolated from dwarf galaxies in their own void areas, it might take about another billion years (12.7 to 11.8 billion years ago now) for the beginnings of simple life to arise from chance interactions with different molecules, and begin the course of evolution. Assuming that it continues at the same rate that Earth's does, intelligent life would arise something around 3 billion years later (now 9.7 to 8.8 billion years ago) still assuming that the star was free of the early chaos involved with early dwarf galaxies and the big bang. Within a few million years, whatever intelligent life formed would have begun interstellar space travel and by now would have conquered much of the known universe if they invented faster-than-light travel, which we can of course say is impossible as a result.

Now the previously-mentioned civilization(s) would be among a very small group of life-favoring worlds. The majority of first-generation stars would otherwise be careening around each other, trading off planets and asteroids in a gravitational game of dodge-ball. These stars would eventually congregate into dwarf galaxies, and the first O, B, and A-type stars would form into stellar-mass black holes, which would merge together in the center of these dwarf galaxies. Eventually, floating clouds of hydrogen would fall into these black holes and cause them to emit waves of particles, baking any would-be-life-favoring systems in clouds of radiation. Any life that did or could have formed in these planets in these galaxies would either be thrown out of solar systems as rogue planets, cooked in radiation, or experienced its host stars stellar evolution much too quickly to ever have complex life arise. Unfortunately these planets make up the majority of those orbiting around first-generation stars, so I can say based on the previous two paragraphs that any interstellar life that arose then is long-dead or surviving as a simple type I or II civilization around its second star.

By around 3-8 billion years ago, the first second-generation stars would have begun to form. The earliest would have been caught in the same chaos mentioned above, so I might say that stars that formed only 3-6 billion years ago could have formed any life. The sun, being one of these, evolved somewhere around the middle of that, and about 4.5 billion years later we sit here pondering how we got here.

At present-day, we are already looking for other life nearby. Scientists listen for chance radio waves or signs of Dyson Spheres from places near our galaxy, but as my theory guesses they are not to be found. At our current technological capability, most messages we've sent outside the solar system will decay into static far before they reach much further than the local interstellar cloud. Of course, we also look for the same radio waves from other civilizations, expecting them to have gotten them further than us, but surprise! none to be found. Dyson Spheres are of course out of the question. The reason we haven't found any extraterrestrial life is because they are at the same level of technological advancement as us. Perhaps in a few million years, the nearer habitable planets will be found to have life on them, but for now the only way to be sure is to make a space ship and sail right to the civilization for however long it will take, because I doubt we're going to be hearing anything any time soon.

DaveC426913
2014-Jul-15, 05:18 PM
The reason we haven't found any extraterrestrial life is because they are at the same level of technological advancement as us. Perhaps in a few million years, the nearer habitable planets will be found to have life on them,

What is a few million years on the scale of a few billion? What is one hundred years on the scale of a few billion?


Our solar system has been around for 5 billion years. Life started within the first few billion years.

Why is it a plausible assumption that all other civilizations started at a similar time and take a similar length of time to reach technological status? By similar, I mean - "within one-tenth of one percent" (that's to be generous. It's one-ten-thousandth-of a percent to be specific).

It's like suggesting that several wildly different animals (say, a tortoise, a hare and an ant) all cross a thousand mile wide desert, starting at wildly different times (say, days or weeks or even months apart) and expecting that when the winner crosses the finish line, and rest will be no less than one mile behind. When the 2nd place doesn't show up within a mile, you're starting to ask why there's only one entrant in the race.

(Actually, to more accurately reflect the analogy of time-to-distance, the finish gap isn't a mile, it's more like an angstrom. We've had this window of opportunity for less than 100 years. That's 100 years over 10 billion.)

primummobile
2014-Jul-15, 05:49 PM
I wouldn't say they are at the same level. I would believe that most other life, assuming it exists, is probably behind us when it comes to technology.

planetaryscience
2014-Jul-15, 05:57 PM
Dave, I was considering what you mention and how we have rapidly advanced against the slow evolution of the animals before us, and how in the billions of years that separate us that we would somehow all contact one another very quickly, and retort with what primummobile says. Compared to habitable planets around us, we're in a fairly good place to live. On this planet, simple survival as an ecosystem is much easier, and we were able to get intelligent life relatively quickly, while other habitable planets would still be one or two billion years behind us, with several of those not being able to sustain life much more complex than that.

molesworth
2014-Jul-15, 06:30 PM
Dave, I was considering what you mention and how we have rapidly advanced against the slow evolution of the animals before us, and how in the billions of years that separate us that we would somehow all contact one another very quickly, and retort with what primummobile says. Compared to habitable planets around us, we're in a fairly good place to live. On this planet, simple survival as an ecosystem is much easier, and we were able to get intelligent life relatively quickly, while other habitable planets would still be one or two billion years behind us, with several of those not being able to sustain life much more complex than that.

With a sample size of 1, I don't think we can make any suppositions about whether the appearance of intelligent life on Earth is fast, slow or average, or whether other planets are behind, ahead or level with us.

My own feeling is that there are likely a considerable number of planets, even within our galaxy, which are well ahead of us technologically, but the difficulties of detecting them, or even of eventually communicating with them, are a fairly big hurdle to proving their existence. (And as for interstellar travel, well that's a whole other level of difficulty...)

primummobile
2014-Jul-15, 06:32 PM
My personal feeling is that intelligent life is a rather extraordinary development. Assuming that and the young age of the universe, I would believe empirical evidence that we were one of the first intelligent civilizations to arise, should such evidence ever be presented.

Swift
2014-Jul-15, 06:39 PM
<snip>
Dave, I was considering what you mention and how we have rapidly advanced against the slow evolution of the animals before us,
This is almost a nitpick, but I have to disagree a little with that statement. I think you are mixing apples (biological evolution) and oranges (cultural and technological development). Though rates of evolutionary change are highly variable, I don't know of any evidence that humans are biologically evolving particularly rapidly, as compared to other animals.

As others have said, I don't know that we can make too many conclusions about rates of technological or cultural change given a data set of 1.

planetaryscience
2014-Jul-15, 06:57 PM
That's exactly the problem. We only have us to work with, and as a result - like I said at the beginning of the thread - all of this is just pure speculation.

John Mendenhall
2014-Jul-15, 07:30 PM
Your general approach I agree with wholeheartedly. We might be the first technological civilization hereabouts. There certainly is no evidence (yet) of any other.

We may also be incredibly lucky. Try this article if you're feeling comfortable about going to sleep tonight:

http://en.m.wikipedia.org/wiki/Cretaceous–Paleogene_extinction_event

Jens
2014-Jul-15, 11:06 PM
I think the idea that we are pioneers is one of the realistic explanations of Fermi's paradox. What bothers me a bit is that it appears that life has not followed a linear process of development, but rather one of advances and then extinction events, which are fairly random. So for example, if the K-T event hadn't taken place, then perhaps intelligent life could have merged ten million years earlier. But it certainly is a possibility, that intelligent life is still very rare.

Jeff Root
2014-Jul-16, 12:34 AM
There is no indication whether intelligent, technologically
advanced life is extremely common or extremely rare in our
part of the galaxy. It could be either, and there would be
no obvious signs telling us which.

Evolution does not inevitably tend toward intelligence.
Nearly all species of life on Earth have not led to more
intelligent critters, but have instead stayed at about the
same level of intelligence. Nevertheless, intelligence
clearly can be evolutionarily advantageous, and advances
happened often enough to lead to us after a few billion
years. It seems pretty clear that it would take at least
two or three billion years to get to our level from the first
appearance of life, but if three billion years is enough,
then the first lifeforms similar to our level of intelligence
and technological development could have existed more
than five billion years ago. Maybe closer to ten billion
years ago. So it seems very likely that at least some
technological civilizations more advanced than ours have
come and gone in the intervening eons. But there is no
reason to expect there to be any obvious sign of them.

-- Jeff, in Minneapolis

PetersCreek
2014-Jul-16, 12:36 AM
I suppose this would belong in the Against the Mainstream section as much as this, but I suppose I might as well choose one to post in.

Just a quick note about your opening statement: Given the tone and content of your post, LiS was the right call. Since you mentioned that you have a LiS-related theory...not that I see a problem yet...I'd like to point you to the sticky thread at the top of the LiS forum entitled, "Rule 13 and the LiS forum". In short, if you move from general discussion to making definite assertions about finding ET life (or not), you'll be expected to support and answer questions about them with some rigor, as would be required in the ATM forum. Either way, have fun with it.

Jeff Root
2014-Jul-16, 12:54 AM
the first stars began to form some time between 0.15
and 1 billion years after the Big Bang, or about 13.7 to
12.8 billion years ago.
....

By around 3-8 billion years ago, the first second-generation
stars would have begun to form.
I'll estimate that second-generation stars must have begun
to form less than a billion years after the first generation
began to form. So less than two billion years after the Big
Bang, or more than eleven billion years ago.

-- Jeff, in Minneapolis

.

DaveC426913
2014-Jul-16, 03:17 AM
I have solved this problem.

I know how many extraterrestrial civilizations there are.

It is a simple application of the German Tank Problem (http://en.wikipedia.org/wiki/German_tank_problem).

We take our single observation, which is 1. According to GTP, our observation is statistically most likely to be in the middle of the full set of values.

So, with an observation of one, we can say that, statistically, it is most likely that there are two intelligent civilizations in the universe.

QED.

Where's my Nobel Prize. :D

Noclevername
2014-Jul-16, 03:25 AM
At least you didn't say that we were the maximum, then there would only be 0.5 civilizations.

Jens
2014-Jul-16, 03:49 AM
I have solved this problem.
I know how many extraterrestrial civilizations there are.
It is a simple application of the German Tank Problem (http://en.wikipedia.org/wiki/German_tank_problem).
We take our single observation, which is 1. According to GTP, our observation is statistically most likely to be in the middle of the full set of values.
So, with an observation of one, we can say that, statistically, it is most likely that there are two intelligent civilizations in the universe.
QED.
Where's my Nobel Prize. :D

I think you might have miscalculated. You said "extraterrestrial civilizations", so the one you counted doesn't count. So there are 0 in the sample, and so 0 x 2 = 0. So there are none.

I'll settle for the Kavli prize.

kzb
2014-Jul-16, 12:19 PM
What is a few million years on the scale of a few billion? What is one hundred years on the scale of a few billion?


Our solar system has been around for 5 billion years. Life started within the first few billion years.

Why is it a plausible assumption that all other civilizations started at a similar time and take a similar length of time to reach technological status? By similar, I mean - "within one-tenth of one percent" (that's to be generous. It's one-ten-thousandth-of a percent to be specific).

It's like suggesting that several wildly different animals (say, a tortoise, a hare and an ant) all cross a thousand mile wide desert, starting at wildly different times (say, days or weeks or even months apart) and expecting that when the winner crosses the finish line, and rest will be no less than one mile behind. When the 2nd place doesn't show up within a mile, you're starting to ask why there's only one entrant in the race.

(Actually, to more accurately reflect the analogy of time-to-distance, the finish gap isn't a mile, it's more like an angstrom. We've had this window of opportunity for less than 100 years. That's 100 years over 10 billion.)

BUT, the fact that we have the Fermi paradox with no fully satisfactory explanation makes us think this is the most plausible theory. To borrow off Sherlock, when you have eliminated the obvious what is left must be the truth, even if it seemed implausible initially.

What it means is, the theories saying that the early galaxy was habitable are actually incorrect. The galactic habitable zone has only very recently come into being, and not billions of years ago as in much of the literature.

That being the case, it becomes more reasonable to say we are amongst the first. There has not been time to colonise the galaxy since habitable conditions have not been around for long enough.

That leaves us with the problem of explaining exactly why there was no galactic habitable zone until 4.5 billion years ago, but perhaps something will come up.

R.A.F.
2014-Jul-16, 12:34 PM
...if you move from general discussion to making definite assertions about finding ET life (or not), you'll be expected to support and answer questions about them with some rigor, as would be required in the ATM forum.

Personally, I think that we will never discover an advanced intelligent ET civilization, as the distances involved are just too great.

...now...am I expected to "support and answer questions" defending this opinion?...doesn't the boldened portion "cover" that?

Noclevername
2014-Jul-16, 12:35 PM
BUT, the fact that we have the Fermi paradox with no fully satisfactory explanation makes us think this is the most plausible theory. To borrow off Sherlock, when you have eliminated the obvious what is left must be the truth, even if it seemed implausible initially.


Eliminated the possible, not the obvious. It may seem like a nitpick but the difference is very important.

At this point we have not eliminated all or even most possibilities, we aren't even close to doing so. We just know that we have no evidence of contact, we don't have a clue as to why.

Strange
2014-Jul-16, 12:35 PM
I would believe empirical evidence that we were one of the first intelligent civilizations to arise, should such evidence ever be presented.

Does that imply that you wouldn't believe empirical evidence that we are not one of the first intelligent civilizations to arise, should such evidence ever be presented? :)

primummobile
2014-Jul-16, 12:41 PM
Does that imply that you wouldn't believe empirical evidence that we are not one of the first intelligent civilizations to arise, should such evidence ever be presented? :)

I know that was a joke, but I generally believe any empirical evidence. I guess I was just saying that, given the relative youth of the universe and then absence of evidence to the contrary, that I would be inclined to believe that we are among the first. Relatively speaking, that is.

KABOOM
2014-Jul-16, 02:35 PM
I think the idea that we are pioneers is one of the realistic explanations of Fermi's paradox. What bothers me a bit is that it appears that life has not followed a linear process of development, but rather one of advances and then extinction events, which are fairly random. So for example, if the K-T event hadn't taken place, then perhaps intelligent life could have merged ten million years earlier. But it certainly is a possibility, that intelligent life is still very rare.

In fact the contrary is really the case. Heretodate, it has been the extinction events that have allowed for intelligence to evolve and flourish on Earth. Mammals would have remained small and subordinate to the dominance of the dinasaurs had there not been an extinction event ~ 65M years ago. It is the aftermath of extinction events that allows for an explosion in new species, new niches etc. We or anything resembling us wouldn't be here today if it weren't for likely all of the precedent extinction events.

primummobile
2014-Jul-16, 03:21 PM
In fact the contrary is really the case. Heretodate, it has been the extinction events that have allowed for intelligence to evolve and flourish on Earth. Mammals would have remained small and subordinate to the dominance of the dinasaurs had there not been an extinction event ~ 65M years ago. It is the aftermath of extinction events that allows for an explosion in new species, new niches etc. We or anything resembling us wouldn't be here today if it weren't for likely all of the precedent extinction events.

I think that some dinosaur species would have had a reasonable chance at evolving intelligence if the K-T extinction had not happened.

DaveC426913
2014-Jul-16, 03:52 PM
I think you might have miscalculated. You said "extraterrestrial civilizations", so the one you counted doesn't count. So there are 0 in the sample, and so 0 x 2 = 0. So there are none.

I'll settle for the Kavli prize.

No, the sample is of observed civilizations. (I did not state this, but it is implicit).

We have counted one civilization. From that, GTR predicts two as most likely.

One of those is extraterrestrial.

Sticks
2014-Jul-16, 05:53 PM
Personally, I think that we will never discover an advanced intelligent ET civilization, as the distances involved are just too great.

...now...am I expected to "support and answer questions" defending this opinion?...doesn't the boldened portion "cover" that?

This is seen as arguing moderation in thread. If you wish to contest a moderation you are directed to PM another moderator or one of the administrators.

RAF receives a (Should have known better) 2 point infraction

Jens
2014-Jul-16, 11:25 PM
In fact the contrary is really the case. Heretodate, it has been the extinction events that have allowed for intelligence to evolve and flourish on Earth. Mammals would have remained small and subordinate to the dominance of the dinasaurs had there not been an extinction event ~ 65M years ago. It is the aftermath of extinction events that allows for an explosion in new species, new niches etc. We or anything resembling us wouldn't be here today if it weren't for likely all of the precedent extinction events.

That may be true, but I think it still supports my point that (whether it's in a negative or positive direction) the progress is not linear but is driven by stochastic events, so it's hard to make a time schedule of how long it takes for intelligent life to emerge.

Jens
2014-Jul-16, 11:28 PM
No, the sample is of observed civilizations. (I did not state this, but it is implicit).

We have counted one civilization. From that, GTR predicts two as most likely.

One of those is extraterrestrial.

OK, then I'll concede both the Nobel and the Kavli. Prize, and I'll console myself with an Ignobel.

Dave12308
2014-Sep-26, 06:50 PM
Personally, I think that we will never discover an advanced intelligent ET civilization, as the distances involved are just too great.

...now...am I expected to "support and answer questions" defending this opinion?...doesn't the boldened portion "cover" that?

Wouldn't the burden of proof be on you to prove to us that the theoretical physics that would allow for wormhole travel are false? Because in theory, according to physics, the distances involved are NOT too great given the technology to travel in a way that bends space-time. Or am I misunderstanding the principles of wormhole travel?

primummobile
2014-Sep-26, 06:55 PM
Wouldn't the burden of proof be on you to prove to us that the theoretical physics that would allow for wormhole travel are false? Because in theory, according to physics, the distances involved are NOT too great given the technology to travel in a way that bends space-time. Or am I misunderstanding the principles of wormhole travel?

No, the burden of proof is on whoever says FTL travel is possible.

Jens
2014-Sep-27, 12:12 AM
No, the burden of proof is on whoever says FTL travel is possible.

I'm not sure how there could a burden of proof on either side in this case, since we're talking about the future not the past. People who think it is likely to be possible should conduct experiments, and those who don't shouldn't bother.

Noclevername
2014-Sep-27, 12:45 AM
Wouldn't the burden of proof be on you to prove to us that the theoretical physics that would allow for wormhole travel are false? Because in theory, according to physics, the distances involved are NOT too great given the technology to travel in a way that bends space-time. Or am I misunderstanding the principles of wormhole travel?

Both General Relativity and Special Relativity say that c is the maximum speed limit of the universe, no matter the means of arrival. You can travel the space, teleport, take shortcuts, etc., and the limit is still there.

Personally, I don't think that eliminates the possibility of interstellar travel for a very advanced, high-energy civilization. Still, we have seen no evidence of such travel, and it would not be easy or common even for an extremely powerful society.

Jens
2014-Sep-29, 01:05 AM
Both General Relativity and Special Relativity say that c is the maximum speed limit of the universe, no matter the means of arrival. You can travel the space, teleport, take shortcuts, etc., and the limit is still there.


You probably know that I'm not a believer in this type of thing, but although the theory says that you can't travel over c, a wormhole by warping space could theoretically allow you to travel from point A to point B at a speed higher than c if you were to travel normally (not through the wormhole). And I emphasize "theoretically" because it would require matter with negative mass.

Noclevername
2014-Sep-29, 01:10 AM
You probably know that I'm not a believer in this type of thing, but although the theory says that you can't travel over c, a wormhole by warping space could theoretically allow you to travel from point A to point B at a speed higher than c if you were to travel normally (not through the wormhole). And I emphasize "theoretically" because it would require matter with negative mass.

Well, yes, that's what I mean by "taking shortcuts". Causality is causality, no matter how you "get" there.

alromario
2014-Oct-20, 08:34 PM
I reckon the Von Neumann like probes in our solar system sent out a signal or something in the 60's or so,
Reckon we'll here back from them in the next 500 years ��