Of course, all life on earth is based on these things, but that doesn't necessarily mean that something considerable as a life form couldn't arise from complex chemical processes with different elements and at different temperatures.
For example, electronic circuits are non-organic and independent of water, but still capable of complex behavior. Something remotely similar to human-made robots using e.g. sun light as power source might have spawned on a planet with lots of metals and silicone. Of course this exact robots scenario is highly unlikely to occur - in reality their brains/circuits would probably work in a more evolution-friendly way - but you get the gist.
It's not just some sort of failure of the imagination. The idea that life might be really weird isn't a new idea; everybody's read and/or seen the same science fiction you have too. But if it's going to exist in this real universe, it has to follow the real rules of the universe, and it's not particularly obvious that there are any alternatives that can even theoretically work.
My point is precisely that this isn't just random chauvinism, which is rather than being some sort of way-cool open-minded "whoa" opinion is really rather insulting to the huge number of scientists who have considered this matter very carefully. There are a looooooooot of good reasons to think carbon is the only possible substrate for life in this universe, and a lot (still italicized, but with fewer "o"s) of good reasons to think water is the most likely choice.
Here's an article about it from this past summer: https://www.sciencedaily.com/releases/2016/07/160714120650.h...
A researcher at GA tech has built a simple computer out of neurons: https://en.wikipedia.org/wiki/Wetware_computer
And I remember reading about storing data in DNA strands, but I can't find the article at the moment.
Anyway, it's a really interesting area of research. I expect we'll only see more of this stuff in the near future.
For example, CH4 (methane) is a nice stable molecule. It exists underground for millennia. SiH4 (silane) is an unstable, pyrophoric (spontaneously ignites in air). There is no evidence to suggest that a silicon-based life form could exist.
I'm no chemist, and I buy the line of reasoning that Carbon is by far the most likely substrate for life, but this statement seems to assume an oxygen-rich atmosphere. That's another assumption that could, in theory I guess, be invalid.
This seems to, at the very least, discount silicon as a drop-in replacement for carbon.
In other words: given the fundamental particles and interactions of physics, it would be very surprising if the chance of abiogenesis for two different forms of life were within, say, an order of magnitude of each other, since there are so many conditional probabilities that need to multiply for a given sequence of improbable events. This implies that, looking across the universe, there is a preferred form of life that is much more likely to be generated than all other forms. Therefore, with high probability it will be the form of life that we are and that any aliens we meet are.
But how does one estimate probabilities of abiogenesis, or their relative magnitudes? Are there e.g. scientific papers published on this subject?
You probably covered some of this in school, though it tends to be an aside in your chemistry or biology book and easy to miss. But people have done the basic experiments with taking a bunch of likely looking chemicals, based on what we think the old Earth looked like, and shooting electricity through them and other such things that seem like they may have contributed to life.
Those experiments came up negative; life isn't that easy. That has been so thoroughly absorbed into modern consciousness that it can be easy to forget that they were perfectly legitimate experiments to conduct, and had they come out positive, that pretty much would have ended all debated about how common life is in the universe, moving the discussion firmly into the "intelligent" part of the issue.
You can also try to create "minimal organisms" that are sufficiently simple that they perhaps could be randomly created.
However, last I knew, computing odds of abiogenesis is still effectively impossible because there are still some steps that we simply do not know how to get past via random processes, such as ensuring the chirality of the molecules matches. That's not to say there's a lot of ideas out there on how to get over various elements of the problem, but at the moment I think it's fair to say that the best science we current have puts the odds of abiogenesis at simply "impossibly unlikely". Stay tuned for more "best science", of course.
To be clear, there is always a lower bound on this probability that comes from brute force randomness (e.g., a quantum fluctuation in which all the molecules of a bacteria assemble spontaneously). This lower bound is extremely, extremely tiny, taking the form 10^(-10^(large)), and there are almost certainly easier ways to make a simpler replicator that later evolves to become a bacteria. But since we don't have an upper bound on the volume of the universe, and we don't have evidence for life arising somewhere else in our observable universe, it's formally possible that it's simply that stupendously rare (but still not impossible).
Yea. The argument is actually independent of whether the probability of abiogenesis is large enough for life to independently arise multiple times in the solar system or (conversely) small enough that it's very unlikely for it to exist elsewhere in the observable universe. I think all it requires is that abiogenesis is a combination of several small probabilities distributed over several orders of magnitude. (If the probability is large enough that multiple forms routinely develop on the same planet, then we probably also have to assume something about, say, the first-mover dominating.)
> But how does one estimate probabilities of abiogenesis, or their relative magnitudes?
It's really hard.
> Are there e.g. scientific papers published on this subject?
Yes, but I don't know them off the top of my head, or whether any are any good.
So, what could that mean?
If you claim that those elements (or at least a subset) are essential for any kind of life, then by the anthropic principle, it's not surprising to see the distribution that we see in our home galaxy.
Alternatively, you could claim that life can evolve with all sorts of combinations of elements, but that it makes sense that it would evolve to use the most common elements in any given area of the Universe.
Either way, it seems like the fact that the life we know uses the most common elements in the galaxy is a good reason to expect non-Earth-based Milky Way life to be similar.
This is just a thought I've had in the past; I haven't done a whole ton of research into this correlation. And of course, there's a whole other set of arguments involving the chemical properties of elements, which I'm just skipping over in this comment.
EDIT FOR CLARITY: The sentence mentioning the anthropic principle used to read: "By the anthropic principle, you might say that those elements (or at least a subset) are essential for any kind of life, and given that life exists on Earth, it's not surprising to see the distribution that we see in our home galaxy."
The second claim seems much more sense to me (like horses vs. zebras). However, actively searching for organic compounds in search of life would lead to circular reasoning.
After all, organic life is probably the easiest one to search for because it's the only one we know so far.
Maybe a silicon based life-form is possible, when temperatures are around 1000K or even higher, for example.
So when we search for "life" you really need to read "life as we know it"
A new form of life would be a massive discovery, but is by nature almost impossible to target as to a of the research.
Silicon and ammonia share some of these properties, so they potentially are competitors, but what we observe not just on earth, but as gas in interstellar space, is that complex molecules are all carbon-based.
For eg: Life on neutron stars.
There for you have to settle for a search space and look there.
"Indicating a surface containing distinct locations iron-bearing minerals, bound water, trapped carbon dioxide, silicates, organics, nitriles and cyanide compounds. Phoebe is one of the most compositionally diverse objects yet observed in our Solar System. The only body imaged to date that is more diverse is Earth!"
So... there's a chance!
I know we're just supposed to accept click-bait headlines, but it bothers me more with space exploration because there is nothing more fascinating than the final frontier dammit! It doesn't always have to be about finding life, especially for people like me who doesn't believe there is any.
I blame Orson Welles.
I only made my first comment because I have a passion for space, and believe it's the greatest human endeavor. People being constantly teased with finding life does a disservice to a pure science that is unequaled in majesty and wonder.
Does it not seem statistically improbable that in the entire universe, life only occurred once?
Personally I think if I believed that, I'd have to accept a creator deity of some kind as well.
You can probably manipulate the odds by changing both life-time and life-probability to be anything you want. Add restrictions of life being able to interact causally (i.e. they coexist long enough for a light round-trip) and things get even harder. Then consider how long it takes for life to be capable of interstellar communication and things probably get even more tighter.
To get even closer to foolproof, presume a correlation between sufficient technology for interstellar communication and sufficient technology for self-caused extinction-events (nuclear, climate or otherwise).
So, there is a very big difference between 'did other life ever exist?', 'does other life exist right now?', 'will we ever have any kind of interaction with other life?' and, 'will we ever meaningfully communicate with other life?'
Don't get me wrong, life on other planets would be super cool, and liberating in a certain way. In the meantime, we have life right here, let's nurture and take care of it.
please stop shit posting