Limits for the habitable zone

mfb

An asteroid cannot destroy a whole solar system, but intelligent life can destroy (or even use) an asteroid.

The average lifetime of intelligent and technological species is a completely unknown factor. Is it of the order of 100-1000 years, because they all tend to kill themselves as soon as nuclear power and similar things are available? Is it of the order of millions of years? Is there a reasonable probability that the species (or some descendants) will exist for billions or trillions of years?


Life exists everywhere on our planet (excluding the molten interior), and there are indications that life from earth might be able to live permanently on Mars. I would not call this "sensitive" - we don't even know where the limit of our life is. Life which evolved in different conditions would be able to adapt to different conditions.
Sure, you cannot take a bacterium which is adapted to live in rocks 3km below the surface and expect it to survive somewhere in the antarctic ocean. So what?

julcab12

Not really. All P-life 'as we know it' has that degree of sensitivity until given the opportunity(It will happen eventually) to adapt gradually under conditions(local/General) while most of them died and became extinct. Case of Mars. In general. It is different to earth but such local criteria has similarity to earth which is compatible to certain life. We can say that simple lifeform thrived and has lesser biological limitations compared to most complex P-life that requires a larger condition to exceed.

I agree we don't know the limits to life but we do have a positive hint and a critical analysis on conditions to life (P-based life)to which we can draw local limits like biological potential and/or multiple adaptations of certain species. Question like; "Do they have the intermediate profile that enable them to adapt in those conditions?"
.

Well. Adaptation-mutation is a gradual process you don't expect a fish to develop limbs or wings overnight (Tiktaalik roseae) or drain your fish tank and expect them to grow limbs or more so survive . Same is true with bacterium adaptation?

mfb

I don't get your point. There is no place where all organisms can survive. How does that matter if we consider places where life is possible?
There is no place on earth where life is impossible (again, excluding the molten interior).

What is "P-life"?

If Mars is similar to Earth, there are similar planets on many stellar systems.
http://www.digitaljournal.com/article/343021

Sure. Life on other planets will be adapted to the conditions of that planet, as it always faced those conditions during its evolution.

julcab12

...In some sense it is sensitive, opportunistic, economical and adaptive. All Organism (complex chemical system) are 'step' condition dependent. You can't achieved chaotic complex form of structure without the abundance of other complex elements. It is the basis of complexity. Our solar system is abundant with carbon and elements. Whenever they made contact they will surely bond; first step to what we describe as life is met. To enable multiple bonds. Other complex conditions must be met and so on increasing, exceeding to what is needed. If it were simply a repetition of same complexity it will end up structure of repetitive bonding (diamond graphene etc).

Point is we don't exactly know the boundaries to life but we certainly have intermediate steps before reaching a given level of evolutionary complexity. And be able to make hypothetical prediction of its minimal requirement and possibility of 'stepping' further; extremophiles can thrive on other planet given the same minimum conditions and possibility of a step in evolving to a more complex form if given the right mixtures and 'chances'.

We are carbon based and probably phosphorous dependent life.

Expect possibility of life and 'how complex can it handle'. Quick question. "Are their any paper on spectral or any chemical analysis related to the article?". Sorry for being noob and bad english

. Thanks.^^

Damo ET

I agree, a single asteroid connot destroy a whole solar system, but as an intelligent species in which we gauge all possible others against ourselves, our entire 'intelligent' civilization could be wiped out by a single asteroid! It would take a civilization probably 100 years more advanced than ours is now (at the same rate of technological change in the previous 100years) to first detect all potential strikes, and then to eliminate the threat. We are a long way from being able to spot much which doesn't orbit the sun inside Jupiter's path.
Possibly at an advanced stage where we can see all threats at a distance, we may also be able to (and be willing to) ensure our long term survival as a species by setting up colonies on Mars and other potential moons. Until then, we are just another species on the path to an inevitable extinction.

I would think that although we may 'destroy' ourselves, the human species wouldn't be completely wiped out. We may delay ourselves technologically for a while, but we would still have the runs on the board to progress again quickly.


Damo

mfb

Sure, but you were taking about interstellar travel as (potential) barrier. Interplanetary travel is easy compared to that.

Most dangerous objects are within the orbit of Jupiter, and we know most of them already.

A restart might be tricky - raw materials would be harder to obtain compared to the initial development, as the cheapest sources are exploited now.

Vierstein

Earth was still full of life then, just think of the Oceans.

Damo ET

Yes and definitely, but 'Intelligent civilizations' like ours are far from being advanced enough to be able to firstly:
repeatedly send enough start-up materials to anywhere but low altitude orbit, or
have the technology to be able to create a self sustainable and self propagating biosphere for colonists to live and expand into.
So being able to achieve interplanetary travel is not enough. We need to advance in many other areas first which I would imagine is a good 100 years away.
So I would maintain that a 'civilization as advanced as our own' would be wiped out by one suitably sized rock, see or unseen.


Damo

DHF

Good points Damo,

considering how difficult it is to extend ourselves into low orbit and at this point technologically and logistically unrealistic to colonize outside of out planet. Assuming other nearby civilizations were comparable to our own contact would still be slim. Even if they didnt get wiped out.

Consider there is an as of yet undiscovered planet circling one of the three stars in Alpha Centuri and assume there is an intelligent society there with comparable technology. Assuming their astronomers have discovered our world (its questionable considering how close we are to our sun) they might send signals our way but we might not understand them as anything other then background noise. they might send a probe but if they are on the same level we are that would take millenia to reach us.

4.36 light years away and even if we each knew the other existed we would probably not be able to do anything more then guess if there was life there.

assuming we dont throw physics out the window and invent warp drive ;)

mfb

SETI looks at a frequency range where we have sent signals as well, I think. If those aliens would think in a similar way about the frequency ranges (at least physics is the same there), we probably would have seen them now. If they send at completely different frequency ranges... well, bad luck.
Planets close to the sun are easier to detect, not harder - the Doppler shift increases. In general, the transit probability goes up, too, but for earth and Alpha Centauri no transits happen.

With an established frequency to transfer data, we would be able to get a reasonable data rate even with current radio telescopes.