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“able to support life“ ... as we know it. The universe being so vast and so diverse, most life forms will probably escape our comprehension: completely differe

“able to support life“ ... as we know it. The universe being so vast and so diverse, most life forms will probably escape our comprehension: completely different chemistry, environments (pressures, temperatures), time scales, state of matter (plasma based life forms?), or even energy based ones. We are not even looking for such different life forms, since we have already concluded that: - life must be water based - life must be carbon based - life must be based on dna (or simillar) Which leads (given our limited knowledge of the chemistry of these substances) to the conclussion that life must be extremely similar to Earth's. I see a lack of imagination here.

matthewmacleod 10y ago
I'm not sure that's fair. Researchers would be absolutely captivated to discover life forms that were drastically different from anything we've encountered. At the moment though, there's no clear understanding of how such life might form or what it could look like – and there are reasons to think that new life forms might be quite similar to known life forms. After all, we know at a high level what makes matter-based-carbon-water-life-forms work! It's a bit silly to try looking for something when we don't know what it looks like. Instead we can say with reasonable certainty that "life can evolve in this way, and we have evidence" – and look for life like that.
- gonvaled 10y ago
  My point is that there are vastly more environments different than Earth, than similar ones. And that while having proof that water based life forms are possible, we do not yet know how common they are. Maybe water is, considered in astronomical terms, an hostile substrate for life.
  - PhasmaFelis 10y ago
    It's really all just guessing, with only one data point. It may be that you're right, and alien life is all incomprehensibly weird in different ways. Or it may be turn out that only semi-Earth-like conditions can produce life, and it all looks rather familiar. Or it may be somewhere in between. I hope I live long enough to find out.
blauditore 10y ago
I've recently raised the same questions here, and there are indeed a couple reasons that favor searching for organic life. The short version is: - Complex structures are likely to require an element with 4 valence electrones, and carbon is the simplest one of them (lowest mass number), which also provides it with better properties like reactivity compared to e.g. silicium - Hydrogen and oxygen are two of the simplest elements, so probably more likely to exist than anything else with similar properties (if you hear hoof steps, you think of horses, not zebras) - The only life forms we know so fare are based on organic structures, so we know the requirements if its existence and what to look out for See my original comment[1] and its replies for more details. [1]: https://news.ycombinator.com/item?id=13668440 https://news.ycombinator.com/item?id=13668440
castis 10y ago
How do you imagine we would be begin to look for the things you're describing?
- gonvaled 10y ago
  I don't have a clue. But I would not pretend to know that life must be water based, as if this was an obvious fact. There are lots of things we do not know. I would still be excited when finding water in other planets, though. In general, approaches such as SETI seem to me much less biased by our own nature and much more likely to show results. A comparable aproach for simple life forms, looking for effects instead of causes, seems more sensible to me.
drjesusphd 10y ago
I'd be curious to see what elements (not chemical elements conceptual building blocks) are required for natural selection to take hold, irrespective of the physical form taken. Surely someone has looked at this on a more abstract level? Once you have natural selection, intelligence is a conceivable adaptation.
- gonvaled 10y ago
  Right. The first challenge is to have a clear enough definition of life. I do not even think that reproduction is a necessary property.
Pigo 10y ago
I think this every time I read something along the lines of "building blocks of life" in space news. I'm always hearing about how life could be so drastically different, but NASA seems to always be looking for the conditions you mentioned. We have life on Earth which oxygen is toxic to, for example. It would make more sense if their goal was to find an environment which is the most hospitable to relocate our life to.

matthewmacleod 10y ago

I'm not sure that's fair. Researchers would be absolutely captivated to discover life forms that were drastically different from anything we've encountered. At the moment though, there's no clear understanding of how such life might form or what it could look like – and there are reasons to think that new life forms might be quite similar to known life forms. After all, we know at a high level what makes matter-based-carbon-water-life-forms work! It's a bit silly to try looking for something when we don't know what it looks like. Instead we can say with reasonable certainty that "life can evolve in this way, and we have evidence" – and look for life like that.

gonvaled 10y ago
My point is that there are vastly more environments different than Earth, than similar ones. And that while having proof that water based life forms are possible, we do not yet know how common they are. Maybe water is, considered in astronomical terms, an hostile substrate for life.
- PhasmaFelis 10y ago
  It's really all just guessing, with only one data point. It may be that you're right, and alien life is all incomprehensibly weird in different ways. Or it may be turn out that only semi-Earth-like conditions can produce life, and it all looks rather familiar. Or it may be somewhere in between. I hope I live long enough to find out.

blauditore 10y ago

I've recently raised the same questions here, and there are indeed a couple reasons that favor searching for organic life. The short version is: - Complex structures are likely to require an element with 4 valence electrones, and carbon is the simplest one of them (lowest mass number), which also provides it with better properties like reactivity compared to e.g. silicium - Hydrogen and oxygen are two of the simplest elements, so probably more likely to exist than anything else with similar properties (if you hear hoof steps, you think of horses, not zebras) - The only life forms we know so fare are based on organic structures, so we know the requirements if its existence and what to look out for See my original comment[1] and its replies for more details. [1]: https://news.ycombinator.com/item?id=13668440 https://news.ycombinator.com/item?id=13668440

castis 10y ago

How do you imagine we would be begin to look for the things you're describing?

gonvaled 10y ago
I don't have a clue. But I would not pretend to know that life must be water based, as if this was an obvious fact. There are lots of things we do not know. I would still be excited when finding water in other planets, though. In general, approaches such as SETI seem to me much less biased by our own nature and much more likely to show results. A comparable aproach for simple life forms, looking for effects instead of causes, seems more sensible to me.

drjesusphd 10y ago

I'd be curious to see what elements (not chemical elements conceptual building blocks) are required for natural selection to take hold, irrespective of the physical form taken. Surely someone has looked at this on a more abstract level? Once you have natural selection, intelligence is a conceivable adaptation.

gonvaled 10y ago
Right. The first challenge is to have a clear enough definition of life. I do not even think that reproduction is a necessary property.

Pigo 10y ago

I think this every time I read something along the lines of "building blocks of life" in space news. I'm always hearing about how life could be so drastically different, but NASA seems to always be looking for the conditions you mentioned. We have life on Earth which oxygen is toxic to, for example. It would make more sense if their goal was to find an environment which is the most hospitable to relocate our life to.