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Looking for Life in Light 140

Gearoid_Murphy writes "Earth-like planets around distant stars may be too far away to be reached by spacecraft but scientists could still investigate whether they harbour life. Telescope technologies are being developed that will probe the very faint light from these objects for tell-tale signs of biology. These are the same "life markers" known to be present in light reflected off the Earth - so-called "earthshine"."
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Looking for Life in Light

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  • by ScentCone ( 795499 ) on Wednesday May 24, 2006 @09:38PM (#15398657)
    For some real signs of life, try a little moonshine.
  • by account_deleted ( 4530225 ) on Wednesday May 24, 2006 @09:38PM (#15398661)
    Comment removed based on user account deletion
  • by El Cubano ( 631386 ) on Wednesday May 24, 2006 @09:39PM (#15398663)

    Telescope technologies are being developed that will probe the very faint light from these objects for tell-tale signs of biology.

    I am guessing that they are talking about optical observations, since it appears to be an extra-atmospheric telescope they are designing. However, at those distances, how can they discern the difference between the shine from a planet and the light given off by the star(s) near the planet? I would think that we observe the earthshine from small enough distances that we can see it in spite of the Sun. I am curious how this would work for distant bodies.

    • Probably will look at the shadow of the planet. What I am wondering though, is that if a planet is at, say, 700 light-years from here, and we're seeing a "civilization", or just plain life at least, then that life will be from 700 years before. Now with what we've been through in the last 100 years, put that a 10000 lightyears away and you have a heck of an evolution...

      PS: funny part is, if they see our earthshine from the same distance, we humans wouldn't even exist. Talk about being stealthy :)

      • That fact has always fascinated me. If we could travel faster than the speed of light with a huge telescope we could observe historic events. Thats pretty cool if you ask me.
        • Yeah, and if we could go back in time we could prove jesus never existed.

          Oh, I come here for the witty conversation.
          • But he did exist. You don't have to be a Christian, let alone a creationist or a fundamentalist one, to believe that.

            As to his legendary (miraculous even) efficiency in catering arrangements and the question of whether he was a threat to the vinicultural industry, that's a different matter.

            • As to his legendary (miraculous even) efficiency in catering arrangements and the question of whether he was a threat to the vinicultural industry, that's a different matter.

              Not necessarily a threat. Actually, there was a marketing opportunity there, if the competition'd had enough sense to see it:

              “Pick up some skins of Sea of Galilee® today. Our wine was never water!”

            • You may not have to be a christian to believ it, but that don't make it so.
      • Or we might see a death star heading our way in their "shine" and then blow up the day after :)

        Seriously though, it seems to me that we always have this idiotic need to find ORGANIC life. Perhaps it might not be light emitting or light modifying. Perhaps they're not even "corporeal" or light necessitating. Perhaps they'd find Pluto's cold more hospitable than the wet juicy nature of our own ball of mud. Everyone always thinks in their own paradigm. Why not think outside the box that someone always dema
        • "Perhaps they're not even "corporeal" or light necessitating."

          Unless it's a hyperintelligent shade of blue, that is.
        • Well certainly, there are alot of possibilities but the best geuss for life so far is carbon based, and any planet that'll support that has a good chance of showing up as having alot of the right stuff for life through a spectroscope. Anyway, look at it like this. We know carbon based life works, and we know it works reasonably well. That I'm typing this post proves that much. We know that alot of the reactions needed by an ecosystem we'd recognize need a certain temperature band to occcur. Now certainly, l
        • Seriously though, it seems to me that we always have this idiotic need to find ORGANIC life.

          This is not just a case of assuming everything has to be like us. The reason we look for organic life is the same reason we're made out of carbon and the same reason carbon (organic) chemistry is an entire subject separate from inorganic (non-carbon) chemistry -- carbon is an amazingly versatile element, totally unlike anything else. Sure, it's possible there might be life made of something else, in the same sense

          • There's a very cool article on alternative biologies on wikipedia. It's highly speculative, but a great read for anyone with an outsider interest in biochemistry.

            As an aside, your signature brought to mind the high school I went to. Some silly idea about "self-directed" learning, which actually just meant that the school only had to pay its staff to mark papers and yell at kids who brought slurpees to the study hall, rather than actually teaching anything. The graduation rate was about 20%, most of who

            • Off topic, but (Score:3, Insightful)

              by DaedalusHKX ( 660194 )
              "Parents who Unschool [] should be charged with child abuse."

              Strange, since it seems to me that its mostly an American thing... our children are lazier than hell. And public school teachers are coerced into standardizing a shitty education, instead of making it engaging, interesting, and possibly controversial (as in the case of history, politics, language, physics? I once had a physics professor who began class by explaining that explosions are really fast burns, and, in fact, that flour, as
              • So I promote, less the unschooling, and more the MORE FREE TIME FOR KIDS AND MORE FREE TIME FOR PARENTS.

                That's not so much "more free time" as kicking kids' asses and making them work in the time they have. And that I totally agree with. The whole idea of "unschooling" is the ultimate expression of laziness. They don't want kids to be challenged, they just want them to do whatever the hell they want so the parents don't have to be parents and be involved.

        • Perhaps they're not even "corporeal" or light necessitating.

          what, like corporations? run for the hills... it's life Jim, but not as we know it...

        • Why do we always look for organic life? Because we know for a fact that that sort of life is possible.
        • 1903 Called. It wants to know why the Wright Brothers had this idiotic need to fly across a field. After all, perhaps time travel would have been more useful, than say moving people from place to place......
    • I am guessing that they are talking about optical observations, since it appears to be an extra-atmospheric telescope they are designing. However, at those distances, how can they discern the difference between the shine from a planet and the light given off by the star(s) near the planet? I would think that we observe the earthshine from small enough distances that we can see it in spite of the Sun. I am curious how this would work for distant bodies.

      I haven't studied the specifics, but when I hear about similar ideas, irt usually goes something along the lines of starting by just looking at the star. Based on the spectrum, the star has so much oxygen, so much hydrogen, etc. Then, calculate when the planet passes in front of the star. Then, see how the starlight changes. If there is a spike in the apparent amount of hydrogen indicated by the spectrum of the starlight whenever the planet passes in front, then the planet probably has a lot of hydrogen, and so forth.
      • I am no expert in this either, but I think it must be a little more nuanced to be accurate.

        First off, if the planet is partially obscuring the star, most of what we are seeing is the dark side of the planet. So, all we should see is a reduction in the total amount of light from the star, but not much change in the apparent percentage of constituent molecules of the star. Some of the light we are seeing is the star beaming through the planet's atmosphere, which might change the apparent spectrum signature
        • I just realized a mistake --

          When the planet is in front of the star, the total luminosity will increase, but it the star's light that gets beamed through the atmosphere of the planet will show absorption lines of the planet's elements. So, conveniently, that kind of works as a check -- when we see both the planet and the star, we will see extra bands in the spectrum corresponding to the planet's makeup, and when the planet is in front of the star, we should see absorption in those bands. Finally, when the
          • I recall hearing that another clue as to whether there is a nearby planet is a periodic, albeit slight, reduction in luminosity as the planet goes BEHIND the star, as the reflected light is blocked by the star itself. It is feasible that using very sensitive equpment we could check the differences in spectral emissions between these points and determine an approximate total reflectivity of the planet.

            If we would find earth-like reflection one could surmise that this planet would be a good place to look
      • My guess is that they will be looking for chemical signatures in the atmosphere of the planet, via absorption lines. That can tell you, indirectly, about the presence of life. For instance, one of the chemical indicators on the Earth is the presence of methane in an atmosphere containing significant amounts of oxygen. Ordinarily, methane "likes" to combine with oxygen to form water vapor and carbon dioxide. The reaction can go the other way, but it does so much slower. As a result, in a "dead" atmosph

    • by EmbeddedJanitor ( 597831 ) on Wednesday May 24, 2006 @10:16PM (#15398766)
      Of course I have not RTFA because that is cheating.

      If you do an spectral anaysis of IR etc reflecting off the earth, you'll get certain signatures for trees, grasslands, sea, coulds cities etc. So if observers see the similar patterns they will assume that the distant planets will have a similar biology, cities,...

      Of course these are all just assumptions. The scientists hope to make discoveries which they can publish for fame and glory. Luckily for them, they'll probably be dead long before they can be verified by eyeball technology.

      • It is actually simpler. You are looking for the spectrum of the atmosphere. Then, based on that spectrum determine the composition. If the atmosphere is of a composition that is stable in the absence of life then it is unlikely there is life. Although there could be life that does not interac twiith the atmosphere.

        If the atmosphere composition is unstable then there must be a mechanism maintaining that stability. One of those is life. The trick will be trying to exclude geological processes.

        None of thes
    • Light coming from a manned planet would be of a different frequency than natural light sources. Look at our incandescent, fluorescent and LED lights. All have certain spectra that show them to be the result of burning tungsten, ionized gas, or silicon junction spectra.

      There has to be life out there somewhere. But the distances are just so vast that without FTL transport we'll never get to meet them.
    • I am guessing that they are talking about optical observations [...]

      Yeah, and here I was hoping (from the ambiguous headline) that researchers were actually searching for intelligence patterns in photons.

      Fairly recently (a couple months ago; no longer in my posting history), someone on here and I were discussing converting ourselves into energy. If we could determine a way to make interacting photons, then we could beam ourselves at a patch of empty sky and "live forever", since photons do not expe

      • Ah, but some ARE looking for intelligence in photons. That is my future research interest, assuming that I graduate.

        Essentially the same arguments as regular seti, but using optical frequencies as the target "waterhole". This new recent effort is labelled optical-seti, or oseti for short.

        Instead of looking for narrowband radio broadcasts, we look for pulses of light that have an extremely short duration. With this kind of communication, you can use a typical earth technology laser in the megawatt output ran
    • I am actually working on this exact problem as an undergraduate astrophysics researcher. My mentor came up with the quite excellent idea of looking at the difference in luminosity of specific frequencies over the course of time.

      Technically, we use polarization-encoding to split a light beam into two right-angle polarized beams, run them through different color filters, and then recombine them back into a single beam. We then use a fast polarization analyzer to look at each beam independently at speeds close
    • by m0nstr42 ( 914269 ) on Thursday May 25, 2006 @06:42AM (#15400223) Homepage Journal
      I am guessing that they are talking about optical observations, since it appears to be an extra-atmospheric telescope they are designing. However, at those distances, how can they discern the difference between the shine from a planet and the light given off by the star(s) near the planet? I would think that we observe the earthshine from small enough distances that we can see it in spite of the Sun. I am curious how this would work for distant bodies.

      The project is called Terrestrial Planet Finder (TPF) []. I don't know a ton about the details, but I know some guys who were working on it. One of the technologies being investigated (I'm not sure how well this relates to TFA, but it addresses your question directly) is an optical trick called a coronograph []. The basic game is to design fancy Fourier optics that put more emphasis on small variations in off-center light. Like I said, not sure of the details, but it actually kind of works.
      • One of my buddies is working on this project. He had this to say about how the optics work:

        "The basic idea is that under Fourier optics, a wavefront with electric field E that hits a lens with focal length f will produce the Fourier transform of that field E at a distance f from the lens. This location is called the image plane. The location of the lens is called the pupil plane, and the idea is that if you block part of the light at the pupil plane (say with a piece of material in a particular shape,
    • To separate the light from a planet and it's sun you need a telescope with sufficent resolution. It's just like the problem of 'splitting' multiple star systems into their separate stars, you need a large enough telescope. In this case though, we need a REALLY BIG telescope. We can't make one large enough, but we can combine the light from several telescopes separated by a long base line to get the same result. In fact such scopes are already being built and the first ones have already seen first light.
      • Sure and while were looking through the telescope at them we see a telescope of their slide into view and discover their also looking at us!

        Only their's is higher resolution and we find out their looking at us in our homes in the tub or on the John!

        Intergalatic Perverts!

        What more reason do you need to build a fleet and wipe them out!!!@!

        Only problem is they'd see it and build one of their own to destroy it and then come here to subjugate us for their pe
  • by GillBates0 ( 664202 ) on Wednesday May 24, 2006 @09:39PM (#15398664) Homepage Journal
    Pardon me while I illuminate my GIANT blinking "Welcome to Earth" sign.

    If nothing else, it'll show up on the earth shine and indicate we're inhabited. On the other hand, they probably already know that...

    • Of course they know, that's why we haven't seen them yet.
    • Can they read morse code? ;] I question if the sun is really necessary for life on another planet. There is another world deep underneath the ocean where fish, crustations, and such live without light and can survive at extreme cold and hot temperatures. Pluto might even have some sort of life on there but it's a shame that we don't already know since it _is_ in our solar system.
      • I suspect that ultra-deep ocean life here still depends on light indirectly. For example, there's probably something light-dependent in their food chain. Maybe a deep dark octoplatyfungusapus eats deep dark selopodonkens, which feed on sunken plankton or which rise to feed on less deep fish who, in turn, feed on holy mackerel...

        That's not to say that light-free life couldn't evolve independently, ultimately getting it's energy geothermally. Aren't there bacteria that have been found sustaining on geothermal
  • Earthshine (Score:4, Funny)

    by Mr_Tulip ( 639140 ) on Wednesday May 24, 2006 @09:41PM (#15398672) Homepage
    We may call it 'earthshine', but advanced extraterrestrials probably call it 'signs of parasitic infestation', and warn tourists to stay away in case they catch something.
  • ...but not life. (Score:1, Informative)

    by JustinKSU ( 517405 )
    From the article:

    "'This gives you some information on habitability,' said Wesley Traub, chief scientist on the US space agency's (Nasa) Navigator Program..."

    ...but not life!
    • If we find oxygen in the atmosphere, we have found life. Oxygen is very reactive, without some process to constantly replenish it, any oxygen in an atmosphere would very quickly bind with other chemicals. The only process we know of that can do that is life. There could be others, but it is a very safe bet that where we find oxygen, there's life. Here's a link to the wikipedia article about earth's atmosphere, [] specifically the part about it's evolution.

      P.S. Anyone else first learn about this stuff through S
  • Seems primitive. (Score:5, Informative)

    by jd ( 1658 ) <> on Wednesday May 24, 2006 @09:53PM (#15398709) Homepage Journal
    If/when the kilometer array is built (it's an array of small radio telescopes, where the array has a diameter of a kilometer and a density of one dish every couple off metters or so), they will be able to resolve Earth-sized planets at a distance of 100 light years.

    How will this help? Radio telescopes can look at the absorbtion spectrum of the planet for the tell-tale lines of water, methane, oxygen (both O2 and O3), and other markers of highly reactive chemicals - especially when they will react with each other. When you have an atmosphere that is chemically violently unstable (as is the case on Earth), it must be being maintained by some process.

    That's the first clue, but only the first. The second clue is that "dead" planets will be in equilibrium with their surroundings, but "living" planets will always be in opposition. (Organisms will always create a dynamic equilibrium that suits them, so must always counter any and all natural phenomena that would push the system away from that preferred state. Simple negative feedback.)

    Simple radio telescopes can do all this now, no new optical technology need be developed, and no assumptions about the type of life need be made. (All the above assumes is that life can never be inert and that any specific organism cannot function equally under all potential conditions. That's broad enough, although there will probably be exceptions even then.)

    The Km array proposed (and the hectare array already built) are just a huge stack of ordinary satellite TV dishes. This could be done by anyone at any time. A mile array would give you 2.5x2.5 pixels ast 100 lightyears - enough to discern if weather patterns exist, though not enough for any long-range forecasts.

    • Uh, hi, welcome to earth. We're primitive.

      Nice to meet you.
    • "The Km array proposed (and the hectare array already built) are just a huge stack of ordinary satellite TV dishes. This could be done by anyone at any time."

      Imagine a Beowulf cluster of satellite TV dishes....
    • by ookabooka ( 731013 ) on Thursday May 25, 2006 @01:19AM (#15399429)
      Are you sure about the capabilities of such an array? There are two main properties to a radio telescope (or any telescope for that matter) and that is Resolution and Lightgathering. By increasing the diameter of the collecting dish you increase both the resolution and lightgathering capacity. By creating an array using interferometry you can increase resolution to create a "virtual" dish with a diameter equal to the distance from one end of the array to the other. This doesn't, however, increase lightgathering capacity the same way. Let me propose a crude analogy: think of dishes as buckets, you can put two buckets 50ft apart and infer how much rain fell between them by adding them and dividing by two, but if it was just a drizzle, your data wont be so hot. If however, you have a 50ft bucket, you're gonna collect a lot of water.

      So an array of a bunch of teeny TV sattelite dishes wont have as much surface area as a dish a kilometer wide. So yes we could resolve a planet, but it would have to be bright enough to be seen.
      • And with a really big single dish we could see planets that aren't bright enough to be seen? ;)
      • by jd ( 1658 ) <> on Thursday May 25, 2006 @03:10AM (#15399689) Homepage Journal
        Yes, I'm certain.... but it is why you need the density of dishes. If you had one dish on each corner of a square, one kilometer on a side, then you would have the collecting area of those four dishes. Which, if they are TV dishes, is very little. If, however, you have that same square but one dish every five meters, you would have 200 x 200 dishes, for a total of 40,000. If each dish has a collecting area of one square meter, you then have a total collecting area of 40,000 square meters.

        In practice, the Square Kilometer Array [] is intended to have a collecting area close to the physical area of one million square meters - requiring almost no gaps to exist between dishes.

        My first calculation would be for dishes with a wider gap, which would give you much greater flexibility on pointing the damn thing, as you can't see through the other dishes. Personally, I consider this to be a much superior design, even though it would cost on the collecting area. Unfortunately, they are the ones being paid, even if I am the one who is right...

        By way of comparison, Jodrell Bank Radio Telescope [] is a paltry 76 meters across, for a total collecting area of 4560 square meters, and that's one of the largest single steerable telescopes out there.

        I'm going to guess that a collecting area about nine times that of Jodrell Bank, combined with a resolving ability that is, well, astronomical, you would get a very respectable image of Earth-like planets around other stars. If we accept the SKA group's claims, then you've a collecting area 250 times that of Jodrell Bank.

        I first heard the 100LY=1 pixel resolution with SKA from Jill Tarter, head of the SETI Institute [] at a talk she gave at NASA Langley. From crunching the numbers, I can see nothing that could seriously contradict the claim. Even if you assume my model is the more reasonable implementation, the complete MERLIN [] network that has been detecting jovian planets for some time has only a fraction of that collecting area - probably something like a quarter or a fifth. (Aside from Jodrell Bank, the next-largest radio telescope in the UK is a paltry 32 meters across.)

        If we go with SKA's claims, then we're talking about collecting possibly hundreds of times the total radiation, which would definitely be enough to spot even the tiniest of worlds - provided it had some characteristic reflected in the radio spectrum.

        (It's also worth bearing in mind that networks such as MERLIN, which are hundreds of kilometers across, are set up for VLBI - very long baseline interferometry. That's fine, when you're talking about gas clouds or stars, but is probably none-too-hot for spotting very fast pulsars or rocky inner planets. On the other hand, a kilometer would let you use regular interferometry, which means these things would show up quite nicely.)

        There are three drawbacks to all of this, and I'm surprised none of the posters has commented on them (so far). First, interferometry requires very exact timing of all the delays in the system, or it won't work. Let's go with the SKA estimate and say the dishes are 1 meter apart. Your clock must count an integral number of ticks for every meter the signal travels from the dishes, even after allowing for the natural variation in the data lines varying the speed of the signal. This is some astonishingly serious timekeeping.

        The second problem is to keep the signal noise-free. Easy, for a giant single steerable dish - you plunk it in the middle of nowhere and surround it with a huge Faraday cage that only obscures the horizon. When you've a few tens of thousands - or millions - of very small dishes, the problem isn't so easy. The terrestrial radio sources will be far harder to screen out - not just

    • Just recently, I was considering that I could probably do something cool with discarded satellite dishes on three houses, internet-linked to one computer. My house, my parents' house, and my best friend's house form an almost equilateral triangle, roughly 20 miles on each of two sides and 24 miles on the third. I wonder what could be done with that idea...
      • Ok, you won't have much in the way of collecting power (too few dishes) but the resolving power would be amazing. Now, you don't need much in the way of collecting power to see "bright" radio sources - electrically active planets, for example, nearby stars, or globular clusters.

        Your resolving power, however, should be pretty damn amazing at 20 miles diameter. Ok, so what's wanted here is something nice and noisy, where your ability to isolate a region of sky and/or track an object would be of value.

        You coul

  • by talkingpaperclip ( 952112 ) on Wednesday May 24, 2006 @10:16PM (#15398770) Homepage
    I can't understand why these guys are searching so hard for life in light. There have to be at least a dozen half-dead bugs in the ceiling light about 7 feet away from me.
    • Because it's easier and better than searching for life in the dark!

      Dead or alive it is or was life, When was the last time you saw a corpse of a bug in the dark?

      Besides looking for a bug zapper is a better way of finding out theirs life out their than looking in the dark for life looking for light to zap itself on anyway.

      If you ask me it's killing two bugs with one light to go about it this way. :D

      Ok enough with the bug zapper enaligies i got mor
  • News? (Score:3, Informative)

    by brian0918 ( 638904 ) <> on Wednesday May 24, 2006 @10:17PM (#15398774)
    Where's the news? NASA's had the Terrestrial Planet Finder in the works for years now. Is it a slow news day at BBC?
    • Because TPF has been cancelled so that the ISS can be finished so we can deorbit it into the ocean, thus honoring our commitments to our international partners (and screwing over our international partners on TPF). The scientists who are interested in trying to find life on other planets like Wes Traub are out there trying to drum up support for TPF so Congress might bring it back.

      So maybe it's a slow news day, but maybe some scientists are engaging in public relations.

      • IMHO, a Terrestrial Planet Finder is an inevitability, whatever form it finally takes.
        • Only death and taxes are inevitable. NASA had two viable TPF candidates and had spent tens of millions of dollars building up teams and hardware and labs and knowledge. Most of that has disappeared, except for a few papers and a couple of labs. "Deferred" means "cancelled" means "start over from scratch" if it ever gets started up again. Wasted money, mostly.

  • What's the point? (Score:3, Insightful)

    by rm999 ( 775449 ) on Wednesday May 24, 2006 @10:31PM (#15398806)
    We want to:

    A. attempt to detect life on a planet that is too far away for us to determine if we are correct any time in our lives
    B. using a method that has an unknown accuracy
    C. despite the fact that we don't even have an idea of the *order of magnitude* of the chances of life out there

    What's the point?
  • by Kozar_The_Malignant ( 738483 ) on Wednesday May 24, 2006 @11:05PM (#15398964)

    Is communication from Commander Znetab of Zygort Interstellar Death Fleet:

    Radio frequency wavefront from your planet is passing through our fleet causing much physical distress. Auditory awfulness of "Wayne Newton" voice recordings we are considering weapon of mass destruction. Is reducing all fleet radio operators to disembodied protoplasmic goo. If not stopping immediately, destruction of your insignificant planet will be accomplished. You have been warned!

    Is ending communication.

  • Last time I checked, there exists a project already doing this. It's called SETI. They very thouroughly comb a large range of the EM spectrum for any data representing intelligent life. This proposal instead takes hazy samples from a very narrow band of data (the visible spectrum), to guess at the chemical composition of other planets. So we've replaced listening to white noise with looking at faint blue dots.
  • and tried to find intelligent life by the light signature. All they'd see are the blue darters...
  • ...too far away to be reached by spacecraft...

    It will just take a while to get there. Weapon systems are robust. Of course, we don't know when they detected us so we don't know how much time we have to set up defenses.

  • You light up my life
    You give me hope
    To carry on
    You light up my days
    and fill my nights with song []
  • I'm all for looking for more earthshine, after all, that was the best song of of Vapor Trails [].

There's no such thing as a free lunch. -- Milton Friendman