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lifeform readings?

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Tue, 2012-09-11 23:31

It that must no... It that must not be named's picture

lifeform readings?

OK, we all know that in very soft SF there are always "life form reading" to be "picked up" on various "sensors". Now, my question here is "How do we define 'life form readings' exactly and what would it take to pick them up? I've tried to think of this in serious, scientific and technical terms and would like some feedback, especially from sources like this as I know there are some intelligent, knowledgeable people here. Now basically "life as we know it" will have certain characteristics, like heartbeat and respiration. I also know that in the real world there are security devices known as "heartbeat sensors" http://www.geovox.com/introAVIAN.htm I guess they could be fooled int a false positive reading by a special device. But what about remote lifeform sensors? Again motion can be detected, and warm blooded lifeforms may generate a certain heat image. So if it's warm and moving it may be a lifeform. Again, if it's just moving it might be a lifeform. If heartbeats can be remotely detected maybe respiration could to, so again a respiration detector might be possible. Also, as far as we know most significantly sized living things produce a faint EM field due to versios chemical reactions and such. Even cold blooded fish and crustaceans do, as evidenced by the fact certain fish use EM sensors to detect prey under sand. I'm just trying to make sense out of 'life form readings" and how to integrate them into serious SF settings. I'm fine with them being more limited than ones we see on star trek, and being less reliable. In fact false positives or false negatives can add to suspense and keep the players from becoming dependent on their gadgets too much.

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Wed, 2012-09-12 12:38

Arenamontanus Arenamontanus's picture

I don't think there is

I don't think there is anything like a generic lifeform detector, simply because life can be very different and the environments also very different. Consider trying to detect IR from body heat: it fails for trees. And underwater. And for liquid ammonia creatures. A self-replicating nanoswarm, should it trigger the detector? What about a synthmorph? I would think the best you can do is to have a comprehensive sensor suite and then look for non-equilibrium thermodynamical processes. If there is something that absorbs or has stored energy and releases it in ways that counteract entropy, then there is something curious going on. However, this may happen in more ways than you expect and the "inside" of the system might be rather subtle. So I would assume the detector would be running an AI trying to match what it sees with various templates of known or postulated possible lifeforms.

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Wed, 2012-09-12 15:20

nezumi.hebereke nezumi.hebereke's picture

I'd start by asking, how do

I'd start by asking, how do you define life? A lot of people would rule that nanoswarms are not life, and therefore shouldn't be picked up. And there will always thing that are in the grey area (like virii). Or better yet, define specifically what you're looking to detect. Do you want to detect bacteria, or only larger things? Once there, I'd establish a few things that most life does. Most life produces waste (i.e., 'everything poops'). Our understanding of how things metabolize is very primitive still, and in EP times is still quite primitive, but it gives us a baseline. Finding these chemical signatures suggests that there's some sort of chemical process which could indicate life (it could also indicate a number of other things, of course). With a long enough list in your checklist, and assuming some fantastic sensors and time to gather data, you may be able to say 'there is likely something here that coincides with how we understand life'.

Wed, 2012-09-12 15:53

nezumi.hebereke nezumi.hebereke's picture

I'd start by asking, how do

(double post)

Wed, 2012-09-12 15:31

Decivre

The easiest form of "lifeform

The easiest form of "lifeform reading" would be a simple air or water sample for viral or bacteriological presence. If there is some, then the planet has life. Barring that, detecting an atmospheric admixture of oxygen and carbon dioxide is another good sign that life is present, depending on the ratio. Lastly, I've read from some astrophysicists that the very presence of liquid water may, itself, be a sign of life.

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Wed, 2012-09-12 15:55

Arenamontanus Arenamontanus's picture

Decivre wrote:The easiest

Decivre wrote:
The easiest form of "lifeform reading" would be a simple air or water sample for viral or bacteriological presence. If there is some, then the planet has life.

But how do you sample that? On Earth you can try looking for RNA and DNA, but if it was alien you would not know what macromolecules to look for. Looking for small compartments (cells) might work better, but as the Mars meteor showed, there might be natural mineral deposits that looks like cells. The idea of the Viking probes was to put samples in a nutrient broth and see if there was any evidence of anything growing, but that requires you to get the nutrients right. Given the existence of mysterious transcript RNA that we do not know the source of, there are some people who think there may be an entire kingdom in seawater that we don't know about because we can't culture it and don't detect the right nucleic acids.

Quote:
Barring that, detecting an atmospheric admixture of oxygen and carbon dioxide is another good sign that life is present, depending on the ratio.

Only our kind of life. Before the cyanobacteria Earth had a thriving biosphere that would not have registered on this detector.

Quote:
Lastly, I've read from some astrophysicists that the very presence of liquid water may, itself, be a sign of life.

Astrophysicists don't know much about biology :-) There is evidence of liquid water occasionally on Mars, but that hardly constitutes evidence for life.

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Wed, 2012-09-12 19:53

Decivre

Arenamontanus wrote:But how

Arenamontanus wrote:
But how do you sample that? On Earth you can try looking for RNA and DNA, but if it was alien you would not know what macromolecules to look for.

Wouldn't macromolecules be a very easy clue to look for overall? Even if we found a macromolecule that wasn't DNA or RNA, wouldn't it be safe to say that the macromolecule was either a simple sign of life, or likely artificially built (and therefore [i]still[/i] a sign of life, to some degree)? How many non-biological non-artificial macromolecules are out there?

Arenamontanus wrote:
Only our kind of life. Before the cyanobacteria Earth had a thriving biosphere that would not have registered on this detector.

Admittedly this wouldn't work to detect sea life. But there aren't any anaerobic organisms that exist outside of liquid environments, and land life would no doubt lead to atmospheric presence of some electron acceptor gas... of which there aren't a dramatic amount of common natural ones to choose from. Unless you had some really crazy life, like anaerobic land animals that eject waste into an electron-accepting ground material.

Arenamontanus wrote:
Astrophysicists don't know much about biology :-) There is evidence of liquid water occasionally on Mars, but that hardly constitutes evidence for life.

So I'm guessing you disagree with the current hypothesis that Europa might harbor simple life under its ice sheets?

—

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Wed, 2012-09-12 20:29

NewtonPulsifer NewtonPulsifer's picture

Decivre wrote:So I'm guessing

Decivre wrote:
So I'm guessing you disagree with the current hypothesis that Europa might harbor simple life under its ice sheets?

Myself, I can't agree or disagree with a hypothesis that has zero evidence - like life on Europa. I need evidence to form a conclusion.

—

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Thu, 2012-09-13 04:30

Arenamontanus Arenamontanus's picture

Decivre wrote:Arenamontanus

Decivre wrote:
Arenamontanus wrote:
But how do you sample that? On Earth you can try looking for RNA and DNA, but if it was alien you would not know what macromolecules to look for.
Wouldn't macromolecules be a very easy clue to look for overall? Even if we found a macromolecule that wasn't DNA or RNA, wouldn't it be safe to say that the macromolecule was either a simple sign of life, or likely artificially built (and therefore [i]still[/i] a sign of life, to some degree)? How many non-biological non-artificial macromolecules are out there?

Well, there is an infinite number of macromolecules out there. Plastics are good examples. If you saw something like epoxy in the environment, would you think that is a life sign? The problem is that it could be artificial, it could be weird biochemistry, it could be due to a weird non-biological process. I'm not sure what a macromolecule detector would actually be. Maybe a nanodisassembler picking apart samples atom by atom. There is nothing unifying them chemically.

Quote:

Arenamontanus wrote:
Only our kind of life. Before the cyanobacteria Earth had a thriving biosphere that would not have registered on this detector.
Admittedly this wouldn't work to detect sea life. But there aren't any anaerobic organisms that exist outside of liquid environments, and land life would no doubt lead to atmospheric presence of some electron acceptor gas... of which there aren't a dramatic amount of common natural ones to choose from. Unless you had some really crazy life, like anaerobic land animals that eject waste into an electron-accepting ground material.

Exactly. And it is not obvious to me that moving electrons around in oxidation/reduction reactions is a reliable sign of life. (I expect it to be common, though) A life detector for our kind of life is likely doable (somehow), but there doesn't seem to be any way of incorporating unknown forms - mostly because we do not have a strict definition that can be operationalized.

Quote:
Arenamontanus wrote:
Astrophysicists don't know much about biology :-) There is evidence of liquid water occasionally on Mars, but that hardly constitutes evidence for life.
So I'm guessing you disagree with the current hypothesis that Europa might harbor simple life under its ice sheets?

It might, but we don't know yet. Claiming that water *implies* life is a classic Dan Quayle quote. My personal guess is that life can be surprisingly common, perhaps due to at least local panspermia. But I also think life can be surprisingly weird. I am not going to rule out anything - not plasma-based organisms, not life on neutron stars, not cryo-life on gas giant moons or in their oceans, not weird biochemistries, not solid state machine life - until we have strong arguments against them.

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Thu, 2012-09-13 05:02

#10

Smokeskin

NewtonPulsifer wrote:Decivre

NewtonPulsifer wrote:
Decivre wrote:
So I'm guessing you disagree with the current hypothesis that Europa might harbor simple life under its ice sheets?
Myself, I can't agree or disagree with a hypothesis that has zero evidence - like life on Europa. I need evidence to form a conclusion.

You shouldn't ever agree or disagree with a hypothesis (or a theory for that matter) - you have a belief in how likely it is to be true.

Thu, 2012-09-13 21:10

#11

Decivre

Arenamontanus wrote:Well,

NewtonPulsifer wrote:
Myself, I can't agree or disagree with a hypothesis that has zero evidence - like life on Europa. I need evidence to form a conclusion.

It depends on what you consider evidence. Researchers base the idea on extremophiles that survive in conditions that they view as very likely under Europa's ice crusts. The toughest question isn't so much about whether life could be there, but whether life could [i]start[/i] there. Biospheres and life as a whole tend to become more hardy as evolution carries on, but we have little clue as to how durable it is in a post-abiogenetic state; where life is likely still relatively fragile.

Arenamontanus wrote:
Well, there is an infinite number of macromolecules out there. Plastics are good examples. If you saw something like epoxy in the environment, would you think that is a life sign? The problem is that it could be artificial, it could be weird biochemistry, it could be due to a weird non-biological process. I'm not sure what a macromolecule detector would actually be. Maybe a nanodisassembler picking apart samples atom by atom. There is nothing unifying them chemically.

Actually, I would assume that epoxy was a sign of life. The odds of a collective soup of natural, non-biological polyamines just happening to encounter a natural epoxide on a lifeless planet near unimaginable with our current understanding of the universe. Even in the oddest case, I don't see plastics occurring naturally without either some artificial process or at least a biological compound to precede it. Admittedly, I could be wrong. That said, it shouldn't be dramatically hard to examine a suspected macromolecule, especially if we're working under the theoretical assumption that this "life detector" exists in a time period of nanotechnology and hyper-advanced computer systems. A nanoswarm can disassemble and digitalize the compound's structure, after which it can be put through a battery of simulations and tests to determine just what it is and what it might be a sign of.

Arenamontanus wrote:
Exactly. And it is not obvious to me that moving electrons around in oxidation/reduction reactions is a reliable sign of life. (I expect it to be common, though) A life detector for our kind of life is likely doable (somehow), but there doesn't seem to be any way of incorporating unknown forms - mostly because we do not have a strict definition that can be operationalized.

Well, of course. But that doesn't mean it wouldn't be feasible or useful. A life detector would be good for cursory examination of new worlds, meant to detect whether the planet has signs of already-known life. From there, exobiologists will know whether to expect something they've probably already seen to some degree, or to be wary of something new altogether. Plus like any good technology, it will likely be in a perpetual state of development. While version 1 might only detect all RNA/DNA-based organisms, version 5 might be able to detect isotope-based lifeforms, organisms that exist in wave form, and creatures with a fusion-based metabolism.

Arenamontanus wrote:
It might, but we don't know yet. Claiming that water *implies* life is a classic Dan Quayle quote. My personal guess is that life can be surprisingly common, perhaps due to at least local panspermia. But I also think life can be surprisingly weird. I am not going to rule out anything - not plasma-based organisms, not life on neutron stars, not cryo-life on gas giant moons or in their oceans, not weird biochemistries, not solid state machine life - until we have strong arguments against them.

It's not a question of ruling anything out. A life detector likely isn't going to be an end-all, be-all means of finding life. It will be a first-resort cursory examination of a locale, likely done simultaneously alongside tests to ensure that a planet has a tolerable atmosphere, temperature, etc. to (trans)humans. Even if life isn't detected, any good exobiologist will still be trying to spot various theorized forms of life once the research team arrives on site. And while water might not be a guaranteed sign of life (especially if the planet is largely hostile to complex compounds forming), it's a good starting point to search, especially while we work with limited detection systems and technologies. Hence why astrophysicists are looking for so-called Goldilocks planets; it's not about the idea that every other planet is inhospitable, so much as it's making the best use of the limited means of searching the universe that we have. As for machine life, wouldn't that be a sign of natural life by proxy? A machine is likely to have been produced artificially, which would automatically imply some organism preceded it (whether that organism is still existent or extinct).

—

Transhumans will one day be the Luddites of the posthuman age. [url=http://bit.ly/2p3wk7c]Help me get my gaming fix, if you want.[/url]

Fri, 2012-09-14 11:15

#12

Gantolandon Gantolandon's picture

There exist some generalized

There exist some generalized [url=http://en.wikipedia.org/wiki/Living_systems]definitions of life[/url], it's just that they are quite tricky to apply. You would need a field lab at least and it still would be quite tricky to do. I would imagine like that: 1. Find some concentrated matter which looks at least a bit patterned (and, possibly, organized). It's best if you can find several similarly looking lumps of matter, which could indicate reproduction. 2. Try to find the boundaries of the potential system. 3. Try to account for any matter and energy that enters and leaves the boundary. A lifeform will use up significant amounts of energy to maintain its internal stable states, so watch for large differences and increases in entropy in matter being extruded. 4. Try to isolate the system (if you have similar samples) as completely as you can. It should begin to detoriate quite fast, its internal entropy increasing. If it does, it's probably a lifeform. 5. Try to disrupt the system's environment a bit to see if and how it reacts. It should cope with relatively minor changes, adapting to them. Try to emulate stresses which are quite probable in the system's environment first, then proceed with more uncommon ones. Of course, there are still many things that can go wrong here. For example, bacteria endospores wouldn't be recognized as lifeforms, because they have no detectable metabolism. Viruses also don't have any, but according to the definition of a living system, they are not alive anyway. And I'm not even sure how to tackle infolife with that - a server running a bunch of infomorphs could be treated as a part of the system maybe?

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Sat, 2012-09-15 12:19

#13

Quincey Forder Quincey Forder's picture

what about brainwaves?

Could there be, in the time of EP, a technology to detect certain brainwaves from a distance? By tuning it some, it could focus on human typical wavelength, with a margin of a error for the variation from individual to individual Another possibility would be derivated from T-Rays coupled with doppler to detect heartbeats. by calibrating the detectors to display only certain BPM coherent with human ranges

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Mon, 2012-09-17 08:11

#14

Smokeskin

Bah, ping a laser rangefinde

Bah, ping a laser rangefinde on the hab and you can see people move. Even a 500,000 ton hab would move 1/1,000 of a millimeter if a single person walked 7 meters inside it. In EP, remember to pee before you try to hide. How accurately can you measure distance (or rather changes in distance)?

Mon, 2012-09-17 08:30

#15

Arenamontanus Arenamontanus's picture

Quincey Forder wrote:Could

Quincey Forder wrote:
Could there be, in the time of EP, a technology to detect certain brainwaves from a distance? By tuning it some, it could focus on human typical wavelength, with a margin of a error for the variation from individual to individual

Human brains produce waves from up to 40 Hz, but they are in the microvolt range already on the scalp, and fall off faster than the inverse square of the distance (plus, they are a mixture of many broad frequencies). Detecting brainwaves over normal electromagnetic noise is not going to be easy beyond a few centimeters, no matter how good your detector is. Muscle signals are about 100-1000 times stronger, but still likely easier to detect through noise or actual motion. Thanks to laser interferometry one can in principle detect subnanometer motion. Again, the problem is figuring out what is signal and what is noise. Looking for heart rhytms might work, assuming there are no other things rhytmically moving at around 1 Hz. If you know exactly what you look for, detection can be fairly easy. Unfortunately, living beings are fairly approximate and changeable, so they are tricky in many cases - and life in general is so general that you don't have any good templates to try to match. Meanwhile detecting characteristic emissions of synthmorph nuclear batteries or the stray mesh traffic from smart objects is so easy...

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