@Khethil,
Khethil;92721 wrote:
- We define life in terms of its similiarity to how life has developed here. Who's to say there aren't other based-lifeforms other than carbon?
The stability/reactivity, and structure of carbon when bound to other elements is a property of period 4 elements that is a requirement for the complex compounds we see in all life on earth. Of course other elements have been considered, but carbon chemistry is simply the only way to create compounds with the necessary complexity (at first, amino acids and some form of RNA) for natural selection to being. Silicon is the next group 4 element, and has similar properties to carbon, hence some people say that silicon based life may be possible. In an oxygen atmosphere, silicon is too reactive as I understand it, so it's not possible on earth, but a more inert (nitrogen/CO2) atmosphere may harbour some variant of silicon life.
But chemically speaking, these are the only choices if life developed "naturally".
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[*]What might our period table of elements look like if we could add every other substance out there? What might the characteristics of other substances be?
The thing about the atomic model used by the periodic table is that it is, theoretically, complete. With increasing energies one can make more massive and less stable elements, which quickly become practically meaningless because their atoms exist for minute fractions of a second. I don't think there is any "new" substance that could be reasonably expected to exist. Of course, scientists have already posited the existence of some pretty strange stuff, but not amongst the elements.
Further, the very nature of its "periodicity" makes the table predictable. Scientists have, since the table was first formed, correctly predicted elements and their properties, and as the models became more accurate, so did the predictions. I don't think there are any surprises left here. (Any physicists to verify??).
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[*]We sense with our 5 senses; there are other visual, sonic, radiometric means of gathering input; what other avenues might there be that we can't even sense, see or are aware of?
Physics makes things pretty simple on this front, too. Just look at what machines detect nowadays... EM photons, mechanical air vibrations, changes in electrical potential, magnetic field strength, etc etc. If its there, we are detecting it already, for some reason or another.
Besides, what you detect does not fundamentally change the workings of the mind, merely the information sources on which its thoughts are founded.
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The point is - the one I'd like to echo - is that the possibilities that Nero spoke about are vast... VAST. Ideas, physics, elements, substances, chemicals are likely to exist that we can't even conceive of. Of all these unknowns, the ways in which they may interact to spawn something living are, for us, unknowns iterations for unknown phenomena in unknown environments. Therefore, like he alluded, anything we come up with in terms of chances is just a shot in the dark, dark within a dark.[INDENT]
Actually, I think most scientists would agree the biochemical and physical conditions for life are incredibly small. Not only that, but the evolutionary requirements for sentience (including but not exclusive to group behaviour, tool manipulation, warm blooded energy requirements?) mean that humans could represent something of a "norm" for biological, natural, manifestations of sentience.
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I fear our species will never overcome the barriers to interstellar travel and exploration. Such would be a necessary first-step to even beginning to understand the varieties of phenomena and elements out there requisite for any concept of life.
In his
book on sci-fi science, Michio Kaku concedes that it is entirely possible that we may never break the light barrier for travel. But hey, if we can we can, we can't we can't. Either way, we know people will try.
Quote:On this issue its good to dream, imagine and kick around. But we don't know anything about the non-terrestrial phenomena we don't even know exist. Thus, it's all academic - very difficult to argue for or against life's existence when we don't even know what's involved.
I agree that it would be scientific arrogance to not expect anything new. If we do encounter alien life anytime in the next few years, logically speaking they should be decades/centuries ahead of us in science just to get here, in which case there patently would be something new to discover.
What we need to be careful not to do is ignore science. We know more about the universe because of science,
not because we imagined things like our ancestors did. Nowadays, any hypothesis, which scientists make all the time too, must be founded on scientific evidence.
---------- Post added 09-24-2009 at 02:47 PM ----------
EmperorNero;92755 wrote:
If there are neighbors, they are likely not going to be nice.
It's an irrefutable scientific fact that a species cannot evolve to dominate its planet unless it is made up of merciless killing machines. Any civilization with access to the resources necessary to reach us, has, by definition, gained that access by slaughtering its biological competitors. If they turn up here tomorrow, it's only because they've found out, say, that our ground-up spleens are an aphrodisiac for their women.
This is not particularly logical; would you put humans in this class of "merciless killing machine"? Before you say, "yes", which I might be tempted to do myself, lets look at what unites people today; science, technology and global culture. Science is the great equaliser, it puts everything and everyone on an impartial, level platform. I would argue that any culture of sufficient advancement would, as equally if not more so than be homocidal, be peaceful and appreciative of the value of life and sentience, precisely because they understand what it is.
The idea that a developed sentient species has destroyed all competition may well be true, in the case of homo sapiens it is widely thought we killed off the neanderthals thousands of years ago. But this is the same species that at the dawn of the space age sends out probes with peaceful messages telling anyone and everyone who and where we are.
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The main idea of this thread was that life will likely expand exponentially, even if it's so different we can't imagine it. An an expanding life form will in a fraction of the age of the universe fill the entire galaxy. That they did not, since we don't see any, should be an indicator that in the last 13 billion years (age of the universe), nowhere in this galaxy life developed.
It has been proposed, for some time now, I forget by who, perhaps von Neumann, that self-replicating robotic drones travelling at sub-light speeds would exponentially colonise the galaxy and could quite easily and relatively quickly reach all the stars by harvesting some resources and launching more drones onto adjacent systems. When they detect life or a habitable planet, they simply send a message back to their creators at the speed of light.
If this actually happened in galactic history then, like 2001, there should be some factory or beacon or something on a body in the solar system (some people think this is true).
As per the picture posted earlier, around earth there is an EM shell expanding at the speed of light, telling any sentient that has a radio receiver we are here, and by now it is about 60-70 light years away from earth. In terms of the volume of the galaxy, this is a pinprick of space.
Either way, if we are detected actively or passively, and both are certainly possible, there is nothing more than educated guessing that can be brought to bare. The question of alien life is, without evidence, un-answerable.
Also, the assumption that life can break the light-speed barrier and therefore expand forever is also quite un-answerable... it is equally likely, moreso based on current physical knowledge, that we shall be stuck in this solar system forever, communicating delayed messages to other civilisations lightyears away, islands of life flashing torches at each other.
