Aitor

Thanks for your enthusiasm on the subject, Tyler. I noticed some of your facts are a "little" inaccurate: the Universe is actually only a bit less than 14 billion years old, i.e., about 3 times the age of the Earth. The solar system as a whole is rich in all sorts of elements heavier than lithium because it is born out of the remnants of a large star that died in a supernova many billion years ago, and it itself came from the enriched death throes of other rather primordial stars before that. After each stellar death, it takes time for the material to coalesce again to form new stars and planets, and these guys live for a few 100 to 1000 million years. All this to say: this is why the Earth only came to be about 4.5 billion years ago. Meanwhile, life will have appeared on other planets in other parts of the Universe. Whether some of the life forms it gave rise to had a chance to explore space around their world, let alone reach the early Earth, is quite debatable. However, life does not have to be intelligent to travel in space. Bacteria are rather suited to that activity. Maybe life on Earth was seeded by a stray meteorite contaminated with unicellular organisms or even just RNA created somewhere else in our Universe. As for the glassy terrain you mention: many things can do this: the most probable would be meteorite impacts, but natural nuclear reactors (arising from a critical concentration of radioactive material) exist or have existed, and can turn their surroundings into glass through super heating. Finally, I have the feeling that it may take many more years than 25000 to erase the first footprint of Man on the Moon.

Yes, plain old luck has a large part to play, but as far as fundamentals are concerned, if some are very advantageous to have, they should come around again after an initial obliteration. It's just chemistry, after all. Anything more complex arising from that would be more sensitive to random change. We can safely assume that we won't ever meet human-like creatures from other planets as a result, even if aliens may well have our life design. I definitely agree!

Apologies for my feeling touchy recently. I was not having a good week. I tend to have surges of paranoia when I am stressed. Rather embarrassing when it flares up. Anyway, I enjoy the feedback from everyone. The original question is indeed quite narrow in its formulation and we can now summarise the results of the debate as follows: Life as we know it is successful because its design has allowed it to be so over other life designs, and this explains why we cannot see other types of life. Other life designs may be occurring all the time, in various places, but their less "fit" form makes them vulnerable to "attack" from the dominant life around, therefore not allowing them to expand to significant numbers to be observable and self-sustaining. Current life is likely to have emerged through a rather chaotic build up from and exchanges of various "bits" that would not individually likely lead to a successful life form. When the current life finally emerged from all these trials and errors, it was able to take over everything else. However, it does not prevent this build-up process from occurring again, and it probably keeps occurring, but we wouldn't notice easily as it would not lead to anything different from what is currently observable. So now, based on the above summary of everyone's wisdom so far: are we entitled to state that the most likely life design aliens would take is ours? (This would almost support Star Trek writers' assumptions that aliens are biologically compatible enough to spawn hybrid progeny without any problem! What about that for lateral genetic exchange?! )

To those who mentioned that I am going about my question in a quite wrong way, like I am a moron, I say this: My question is meant to trigger a discussion on current debatable views of the scientific community, it is not meant to be perfect or to be free of misconceptions. It is meant to make people discuss these VERY misconceptions. There is therefore no need to demean me like I am an idiot who doesn't know what he is talking about. I think people here need to be careful how they formulate their reply, as it sometimes comes across as patronising, arrogant and rude. A bit more respect, please! We debate, we discuss, we don't judge. Thanks.

I'm having a problem with a photon not getting any closer or farther from us. A photon cannot ever be stationary, can it? Wouldn't this have repercussions on the bending of spacetime to make that photon travel at the speed c from or towards us?

Let us look at the problem another way. For a different life form to exist without us being able to realise it is there, what should it be like and not like? So far, we saw that it should have no measurable effect on our environment so we don't notice. It is has a measurable effect on the environment, it exists where nobody looks. And whatever it does, it must be small and probably in small numbers to evade detection, unless it consists of things that we do not see as life (rock? gaseous substance? etc?). Also, it should not be DNA based, as this is the criterion that defines our life type. So how else could it pass on its legacy of adaptations? Finally, which different internal structure could its cells have, assuming it has cells, so that scientists don't know what to make of it to test for genetic material?

Moontanman, you're a genius! Your link yields the perfect article for this blog. I feel I have asked a very sensible question, worthy of investigation. CharonY, I admit that I know not of a place on Earth where bacteria or similar unicellular organisms do not live. I guess the "we ate all the barbarians" assertion might be true!

Right, so a different kind of life is not prevented from appearing at any time, providing there are resources for it and the right conditions. The Earth is a pretty diverse place, and where our type of life cannot exist, there must therefore be a niche for another type. Why aren't we observing this? As for my assertion that making life is easy, it comes from our knowledge that fossilised remains of bacterial activity were found in a rock 3.8 billion years old somewhere on this planet (my memory is failing on that location detail), but at that time Earth was a pretty nasty place to be and it had just about managed to cool down enough to have primitive shallow oceans with volcanoes and gashes gushing lava everywhere, and an unbelievably violent and lethal meteorite shower lasting a few million years had just about started to decline. Basically, the Earth was so dangerous that nothing would be able to survive on it, and yet, life had already started to leave its trace as carbonates, which we can see today. Which is why I said that life-creation must be relatively easy since in the worst possible environment it still appeared and thrived. With the much more tame conditions nowadays, it should therefore be dead easy to create life (pun intended because it is silly) anywhere, one would think, especially where our type of life has not managed to set a foothold thereby leaving resources intact for something else to emerge and thrive on.

Galindo, it's not what I mean by tree of life. Evolution transforms species into others. Ultimately, the primordial organisms yield a vast array of new species that are completely different from each other. However, they remain related, because their fundamental building blocks and inner workings are exactly the same. Tracking the evolution of the complexity of these inner workings in reverse brings one back to just one primordial ancestor to all current living things, were they a tree, a leopard, a human, a bacterium, a virus, a archaeum, or a slime. This is the root of just one tree of life. No other parallel life structure is observable on Earth. Actually, could prions be part of that hypothetical other tree of life? One wonders... Come on, geneticists and biologists and paleontologists out there! I need your contributions! Thanks in advance.

SOrry for having made my question unclear. My question is: "If life formed so early in the history of the Earth, thereby implying that it was a more likely event than we think, how come we see only evidence of 1 type of life on the Earth? Why does the tree of life only trace life's history only to one primordial life form? Why aren't there more trees of life?" Are the above questions clarifying my original question? Thanks for your contributions already. They are very pertinent and I am happy to accept them as valid answers. Anybody would know of (likely very recent) research about potential life-creating chemical systems different from ours?

Evidence suggests that life appeared very soon after the Earth formed. Right. This means that life can form easily. OK so far. But if life formed so easily, why has it appeared only once in Earth's history? Surely, if it can be produced easily, it should have come up in several places in various forms and the descendants of each life strand would somehow have left evidence of their existence. But there is only evidence of the current life. The only 2 things I can suggest are that: 1) Life appeared at the beginning in many ways and many places on the primordial Earth, but only the current one was selected by evolution. Which then would suggest that the conditions at the time of the birth of life were so alien to what we see now anywhere on the Earth that only 1 strand managed to evolve quickly enough to stay around until the present day. It also means that not a single one of the different environments on Earth today are good enough to produce life from inert material, otherwise there would be places on Earth where life comes up from non-living stuff all the time. So what is it likely to take to make life from inert material? Where else in our solar system could we find these conditions? How likely would these conditions be found in other stellar systems? 2) Life appeared in many chemical forms, but somehow all had in common the cellular structure and the ATGCU bases of RNA, which were the sine qua non of what turns inert stuff into living structures. This would imply that if life is found somewhere else in the Universe, it would also use the same stuff and basic structure as "our life", and would be not-so-alien to us. Is there really nothing else that could yield life? So, to conclude: Am I missing something? Have scientists already managed to answer part of my Question? Has anyone ever asked my Question?

My name is not Aitor and I love all sciences. Yes, I do. There. I am a Maths lecturer and I adore my job (talk of being sad!). My passion though is whatever pertains to Astrophysics, from star formation to planetary discoveries, through black holes, dark matter and just beautiful pictures from the Hubble Telescope, because science is the right amount of logical and imaginative endeavours. (cheesy but true) And because I am not necessarily well in my head, I have created a world and let everyone enjoy it on my own website. How cool is that? (Do nerds do cool?) Cheers Aitor Pastomeytinn (not his name) Merged post follows: Consecutive posts mergedUh, nmicroscope, your link is like, so an advertisement for your products! Are you for real on this forum?