Life in the universe.

Ryan_m_b

My signature encapsulates my opinion of the strong anthropic principle.

ImaLooser

Well expressed.

surajt88

bohm2

I came across an interesting thread/post discussing the debate between Carl Sagan and Ernst Mayr that relates to this thread and moreso with the probability of intelligent life:
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mfb

If you see "existence of species" as "success", the number of living animals does not matter. Humans exist, and as long as they do earth is a species with (quite) intelligent life.

Big animals are less numerous - that is not a matter of intelligence, but a simple scaling with available food, the ability to travel and so on.

I think exactly this time span shows the success of intelligence in terms of reproduction and survival of individuals.

Ryan_m_b

True but that is why bigger animals are more vulnerable. Relatively small disturbances in a trophic web can cause them to go extinct.
Bacteria can go from 1 to 7 billion in a matter of days. Point being that "success" has very different meanings and IMO when we talk about the success of intelligent beings we aren't talking abut their numbers or how fast their population doubles.

bohm2

Here's the relevant arguments by Mayr in more detail:

Can SETI Succeed: Carl Sagan and Ernst Mayr Debate
http://www.astro.umass.edu/~mhanner/...Sagan-Mayr.pdf

mfb

And compared to other big animals, humanity is less vulnerable.

Bacteria will likely survive any event on earth except a full destruction of the crust. When viewed as one big group of life, they are very successful in that respect. But that does not mean that no other group can be successful, too.
Humans are the first species on earth with the potential to take life to other planets.

The interesting point in the human population growth is not the growth itself, it is the self-made rapid increase in food production and habitable areas.

Scitech

Equation > Where are they Paradox = High yield Fusion is hard < my original idea too

As it would only take 3 million years may to colonize the Milkyway if mankind had high yield fusion and you only need one such inquisitive race to start intergalactic expansion on a significant scale then either Life is miraculous or High yield Fusion is hard to impossible.

Note, because the solar system is on the move colonization is more likely to look like milk swirls in a coffee cup than a spherical expansion thus the likely hood of any two civs being in close radio or physical contact goes up approx 100 fold.

No doubt genesis is clumpy too, life will spawn near to other within its local 'birth clump' , again more chance to meet so long as life isn't stupendously rare or miraculous.

my 2 cents

mfb

Do these numbers have any scientific background (if yes: source?) or did you just make them up? They look quite specific.

Why? I have doubts, can you explain this?

Why do fusion power plants imply colonization on a galactic scale?

Scitech

3 million years , is an oft quoted number for star hopping across the galaxy, you could do it in less, you could do it in more, but its a good mid point time-wise without making to many assumptions that stretch credibility or feasibility

colony ship + long journey + settle down build up period till it can spawn new colonies etc etc


The universe is clumpy at all scales, look out the window or thru a microscope, thus it stands to reason that as galaxies are clumpy and not random that some of those clumps will be more favorable to genesis than others


Fact 1 , we know for 100% sure that high yield fusion is not trivial

Fact 2, where are they ?, If life is not miraculous then there must be 1000s if not millions or billions of civilizations in the universe. If Fusion is very hard or impossible they may be mostly isolated and perhaps more prone to extinction as they cannot colonize other system with ease

I don't fancy your chances of inter stellar colonization without access to high yield fusion, its an exceptionally tricky venture

Thus it is highly improbable , indeed nigh on impossible for the universe to be inhabited by 1000s of civilizations all of whom have high yield fusion (and they will know by implication that other races will do to even if they do not meet) and not one of the decides to broadcast hello or colonize the universe....that is an absolute ridiculous assumption to make....it only takes a small % of these to be adventurous, most of space is empty so you might as well make use of it, at the very least you have a defensive buffer zone and made your race extinction proof.


So life is near miraculous OR high yield fusion is next to impossible
take yer pick, one or the other, because other themes don't really stand up to scrutiny. While there are 1000s of plausible themes obvious is obvious and simply wipes the board. Give me high yield fusion + a bit of time and ill make Darth Vader look like a garden gnome by comparison. With all that space confetti flying about, 'hello there' or 'lookout they are coming for' you messages would be flooding the airwaves in each and every direction.

If we crack high yield fusion this century or indeed within 1000 years then life must be near miraculous,( exceedingly rare ) ....either that or an exceedingly improbable alternate scenario that explains the silence must somehow true.


If you've not considered these matters deeply then there is plenty of scientific literature on the topic

mfb

I would not use the number as an upper limit then.

The universe is clumpy, but different clumps are often quite similar, so you don't expect that some clumps have a higher probability to get life than other, similar clumps.

Neither is the detection of gravitational waves, but I do not expect that this will help to establish colonies.

There are so many possible reasons, some of them are listed here. The evolution of life and a powerful energy source are just 2 points in the list. Other reasons why we did not see extraterrestrial life are listed here, for example.

Maybe many species communicate with each other, and we simply do not see it as most traffic is highly directed and the "hello" broadcasts are not in the tiny frequency ranges where we look for signals.

Fusion power is not magic. It is fuel with very high energy density, but it does not allow you to simply teleport to other stars in no time and no costs.

D English

Hi Folks, I'm new, very glad I found this place.

It would be shortsighted to think there's no life out there. I dare say there are billions of life-forms on the earth itself. This shows how prolific life is. Only one life form is capable of contemplating this.

So mathematically, it is a sure bet that life is out there. But also mathematically, it is a sure bet that 99.99999% of that life is not intelligent- as we define it.

I've come to think that any extraterrestrial life that we may be able to communicate meaningfully with does exist, but is so rare, and the expanse of space so vast, that we will never meet.

enceladus_

I am beginning to think that Earth is an incredible miracle of a planet. Life as developed as ours is an incredible miracle as well.

The Earth survived to incredibly chaotic formation of the solar system. At one point, the Earth was almost destroyed by an impact during this time. Not only that, but it just so happens to coincide in a perfect temperature zone, not too hot, and not too cold. As astronomers and astrophysicists discover more and more planets today, they are finding that the vast majority of them are completely terrible. That alone gives us reason to believe that the Earth is an extremely rare coincidence.

Additionally, Mars appears to be in the past, a planet that was destined for greatness. However, it had one very fatal flaw - it was unable to keep its atmosphere. Because of the solar wind, it was unable to keep its water and life (as we know it) supporting capabilities.

As for life, the origins of life could have come from a comet. From the tests I have seen, it takes a specific type of collision for amino acids on a comet to survive the impact. Life as we know it is very fragile as well. Another aspect that makes the Earth so perfect, is that we have Jupiter to protect us from comets and meteors. A comet or meteor could strike the Earth and completely wipe out life. In the epic span of the universe, human life of planet Earth would be completely meaningless. Only lasting for thousands of years.

There is probably some kind of life on some of the moons in our Solar System, but they will be a far cry from human beings. To me, out form of life is an amazing coincidence, originating from another amazing coincidence, one very low probability event following another.

mfb

The number of species or living creatures is not (directly) related to the probability that life appears at all.
How did you get that number?

@enceladus_: It is not surprising that earth is habitable - otherwise, we would not exist to discover this. Current methods to detect exoplanets are more sensitive to big, hot planets, which do not allow life as we know it. This does not mean that earth-like planets are uncommon, we just do not have the technology to discover most of them yet. Statistical analyses of the Kepler collaboration are promising, and planets with the mass and orbital parameters of earth around sun-like stars are probably quite common.
I wonder how non-fragile life would look like then. How can life be more robust than "survived every threat in the past 4 billion years"?

adjacent

Yeah imaginable.Looking into the size of our universe; that is not imaginable.There can be at least one or many life forms.Our technology doesnt let us discover all the universe as a whole I reckon never.Why should someone say we are alone?There are many things yet to be discovered.

enceladus_

The dinosaurs are extinct, are they not? My point is, it isn't hard for us to be wiped out. In fact, once the Sun begins its red giant death march, all life on this planet will be dead. That will be in a long time, but it is conceivable that life in the past was wiped out due to cosmic events, which would give the impression of their being no life in the present.