Searching for extraterrestrial life
Discussion
Like many no doubt, I sometimes wonder if we are alone in the universe. Statistically, it seems almost impossible, but every single scientist who speaks on the subject, talking about the hunt for life, seems to define life only as we know it. They talk about things like water being prerequisites for life and base their assumptions around this.
Surely life developed on Earth to make use of the resources available and life on other planets might well make use of the elements available there. It just seems short sighted to define life in the same way as we do on earth?
Surely life developed on Earth to make use of the resources available and life on other planets might well make use of the elements available there. It just seems short sighted to define life in the same way as we do on earth?
Life is mainly about energy acquisition - if you can derive energy from a process, then you can achieve something. Move one step down the periodic table from Carbon to Silicon. Less reactive (less energy) but the same ability to bond and make complex structures. In a high energy planet (hotter) could Silicon replace carbon? Possibly. Then you have the interesting possibility of a life form whose chemistry is based on Silicon being able to make natural semiconductors. Unlikely, but I wouldn’t count it out.
Eric Mc said:
Let me know what your theories are on how bio-chemistry and biology can work WITHOUT water molecules and complex carbon compounds.
You are talking about processes and compounds that we know about because earth. Is it really possible that these processes & compounds are exclusive to the whole universe or is it more likely that there are elements that are not on the periodic table yet, (and ergo compounds, processes etc) perhaps because we don't know they exist?The main thing people seem to do when trying to answer this question is state what elements / biology / chemistry might be required for life as we know it on earth to exist somewhere else.
But I think you have highlighted my point perfectly Eric, your response is very typical of how the vast majority seem to think about this - i.e. to base everything that might be out there on principles learned from a proportion worth 0.0003%
Edited by cashmax on Saturday 19th December 11:53
I would suspect that the basics of chemistry and compounds would be identical on planets because the laws of physics are (hopefully) the same. We may or may not have discovered all/most of them but the ones to be found are generally massive and a bit fragile - yes “islands of stability” for super heavy atoms are possible, but as we’ve found none, they are likely to be very rare and not really suitable for life.
Put yourself in the shoes of some alien species. Could you conceive it was possible for life to be made of hydrocarbons and water? Yes. If you’d never seen DNA, could you imagine such a biological process exists? Well, yes, but repeatably reliable over generations of a species - that’s a stretch. It is amazing that our genetics is powered by basic chemistry underneath everything. If we weren’t made of it, I doubt we’d have thought of it.
Put yourself in the shoes of some alien species. Could you conceive it was possible for life to be made of hydrocarbons and water? Yes. If you’d never seen DNA, could you imagine such a biological process exists? Well, yes, but repeatably reliable over generations of a species - that’s a stretch. It is amazing that our genetics is powered by basic chemistry underneath everything. If we weren’t made of it, I doubt we’d have thought of it.
cashmax said:
You are talking about processes and compounds that we know about because earth. Is it really possible that these processes & compounds are exclusive to the whole universe or is it more likely that there are elements that are not on the periodic table yet, (and ergo compounds, processes etc) perhaps because we don't know they exist?
The main thing people seem to do when trying to answer this question is state what elements / biology / chemistry might be required for life as we know it on earth to exist somewhere else.
But I think you have highlighted my point perfectly Eric, your response is very typical of how the vast majority seem to think about this - i.e. to base everything that might be out there on principles learned from a proportion worth 0.0003%
That's not how the periodic table works. It's a table of what elements could exist give the way atoms and molecules behave. It's perfectly possible to include elements without finding them in the lab or even knowing whether they actually exist.The main thing people seem to do when trying to answer this question is state what elements / biology / chemistry might be required for life as we know it on earth to exist somewhere else.
But I think you have highlighted my point perfectly Eric, your response is very typical of how the vast majority seem to think about this - i.e. to base everything that might be out there on principles learned from a proportion worth 0.0003%
We are basing our ideas on 100% of the life found so far. Yes, perhaps life can exist based on silicon, but it can certainly exist based on carbon so carbon based life is the obvious thing to look for first. The carbon based life we know about also needs liquid water, so lets prioritise our search further by starting with the wet places.
Rich1973 said:
Yes. Not the first time I have heard mention of silicon based life.
Arthur C Clarke postulated this a few times. Methane based life in the clouds of Jupiter in 3001 if memory serves. The notion of water & life being indivisible is true. Here. We know that where we find water, we find life & vice versa. I don't see how logically other forms of solvent preclude life arising elsewhere, given, as mentioned above, source(s) of energy.
If there is life out there based on chemistry or biology that we can't understand and have no possibility of understanding or even recognising that what we are seeing is "alive", then we wouldn't know whether we'd found life or not - so we would be wasting our time looking for it.
We can only look for the type of life we understand to be life.
We can only look for the type of life we understand to be life.
Eric Mc said:
If there is life out there based on chemistry or biology that we can't understand and have no possibility of understanding or even recognising that what we are seeing is "alive", then we wouldn't know whether we'd found life or not - so we would be wasting our time looking for it.
We can only look for the type of life we understand to be life.
Maybe. Even then, that doesn't preclude its existence.We can only look for the type of life we understand to be life.
Spitwad said:
Rich1973 said:
Yes. Not the first time I have heard mention of silicon based life.
Arthur C Clarke postulated this a few times. Methane based life in the clouds of Jupiter in 3001 if memory serves. The notion of water & life being indivisible is true. Here. We know that where we find water, we find life & vice versa. I don't see how logically other forms of solvent preclude life arising elsewhere, given, as mentioned above, source(s) of energy.
It’s natural for us to have an anthropic bias when considering what constitutes life. A clear definition of life still eludes us, so I’m not sure we’d know some forms of life even if they existed alongside us.
In terms of intelligent life, again, how do we define intelligent?
If we’re hoping to find a civilisation somewhere out there that we could easily recognise as an intelligent species, I think we might be disappointed. I suspect intelligence, as we know it, is rare. And the rare Earth hypothesis is probably my chosen solution to the Fermi Paradox.
In terms of intelligent life, again, how do we define intelligent?
If we’re hoping to find a civilisation somewhere out there that we could easily recognise as an intelligent species, I think we might be disappointed. I suspect intelligence, as we know it, is rare. And the rare Earth hypothesis is probably my chosen solution to the Fermi Paradox.
Eric Mc said:
Spitwad said:
Maybe. Even then, that doesn't preclude its existence.
But all rather stupid if we can't spot it. If we are looking for life in the universe, it's not worth the effort (and money) if we cannot recognise it even if it's staring us in the face.It rather depends where we are looking for life and for what purpose.
If we are searching on Mars it makes sense to look for something based on water - after all, we think that Mars used to have abundant water, so something may be kicking about still. Again, on say, Titan, you’d be looking for conventional organic life.
At a greater distance, you’re looking at planets and saying “that could support life as we know it, maybe”.
More importantly there is a chance that we might observe something manipulating energy in a manner that suggests intelligence, but we have no idea what it is. Perhaps a species that decides to move a planet to make it more habitable. Can we do that? No. But if we saw that happening we could conclude that life was out there, but draw no conclusions as to its characteristics, other than it was far more advanced than we are.
If we are searching on Mars it makes sense to look for something based on water - after all, we think that Mars used to have abundant water, so something may be kicking about still. Again, on say, Titan, you’d be looking for conventional organic life.
At a greater distance, you’re looking at planets and saying “that could support life as we know it, maybe”.
More importantly there is a chance that we might observe something manipulating energy in a manner that suggests intelligence, but we have no idea what it is. Perhaps a species that decides to move a planet to make it more habitable. Can we do that? No. But if we saw that happening we could conclude that life was out there, but draw no conclusions as to its characteristics, other than it was far more advanced than we are.
Rich1973 said:
Yes. Not the first time I have heard mention of silicon based life.
This is where I first heard of it:/https://public-media.si-cdn.com/filer/c6/ae/c6ae3738-8518-487d-9bc8-d620a7825f9c/horta.jpg)
https://www.airspacemag.com/daily-planet/silicon-b...
Spitwad said:
Eric Mc said:
Spitwad said:
Maybe. Even then, that doesn't preclude its existence.
But all rather stupid if we can't spot it. If we are looking for life in the universe, it's not worth the effort (and money) if we cannot recognise it even if it's staring us in the face.I'm not interested in mindless and idle speculation. Tell me the science that can be used to identify alien life.
Off you go.
I can't because by definition, I don't know what it is. But that's not quite the pedantic trap you think it is.
What I do know is in the example I gave above, questing minds, which are a defining characteristic of our branch on the tree of life, were sufficiently curious about the composition of the sun that they eventually came up with the spectrometry apparatus to measure it. And similar advances have happened repeatedly throughout human history, so it stands the sniff test for me to suggest at some point, some form of advance will come along to help us see what we could not previously see & that may or may not include life in a different form.
This really isn't particularly contentious stuff, I'm not sure why you would want to pursue the argument but it takes all sorts, some of whom we can see
What I do know is in the example I gave above, questing minds, which are a defining characteristic of our branch on the tree of life, were sufficiently curious about the composition of the sun that they eventually came up with the spectrometry apparatus to measure it. And similar advances have happened repeatedly throughout human history, so it stands the sniff test for me to suggest at some point, some form of advance will come along to help us see what we could not previously see & that may or may not include life in a different form.
This really isn't particularly contentious stuff, I'm not sure why you would want to pursue the argument but it takes all sorts, some of whom we can see
Looking for something when you don't know what you are looking for is the definition of a pointless exercise.
For the moment, all we can look for are the signs of life we can recognise.
It's not that hard a concept to follow.
And, of course, if you are a scientist or a researcher looking for funding to embark on such a project, you are not going to get much backing when your pitch is along the lines of "I'm looking for signs of life on an alien world but I won't recognise it even if I find it".
For the moment, all we can look for are the signs of life we can recognise.
It's not that hard a concept to follow.
And, of course, if you are a scientist or a researcher looking for funding to embark on such a project, you are not going to get much backing when your pitch is along the lines of "I'm looking for signs of life on an alien world but I won't recognise it even if I find it".
To spot life we don’t even need to know how it does it. We just need to spot signs that are highly unlikely to come from natural processes. Could be chemicals that can’t easily exist without constantly being synthesised - oxygen, for example - or electromagnetic signatures with complex patterns, such as a radio signal or starlight being modulated by a massive structure.
Wouldn’t need to know if I they were produced by a silicon-based jellyfish the size of a sixpence, a carbon based crustacean the size of a house, or a methane-based cloud the size of a continent. If it couldn’t exist without being ‘made’ by something, it’s probably life.
Seems likely to me that within the next 50 years we’ll see such a signature. Whether we could understand what they’re saying or doing is another matter.
Wouldn’t need to know if I they were produced by a silicon-based jellyfish the size of a sixpence, a carbon based crustacean the size of a house, or a methane-based cloud the size of a continent. If it couldn’t exist without being ‘made’ by something, it’s probably life.
Seems likely to me that within the next 50 years we’ll see such a signature. Whether we could understand what they’re saying or doing is another matter.
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