Today I saw this article and a funny coincidence struck me: on the day this article was posted, rd95 and I were on a long drive, and one of the podcasts we listened to was the 9/27 episode of Point of Inquiry, Lee Billings on the Search for Life in a Silent Universe. http://pca.st/0wxk
The premise of this article is that we may not be finding other intelligent life because it is buried in planets and moons like Enceladus with subsurface oceans. If intelligent beings evolved on such a world, would they even know the rest of the universe exists? When taking these frozen over oceans into account, we effectively move the boundary of the habitable zone of our solar system out potentially as far as Pluto. I brought these points up while we were listening, and now I'll pose some questions to you:
What are your thoughts on Fermi's paradox?
How likely do you think life might be on subsurface ocean worlds?
Where else might we not be thinking to look?
If by "intelligent life" you mean lifeforms either A) not of sufficient intelligence to broadcast detectable radio/light signals or establish surface-level architecture (at least, within our solar system) or B) of an intelligence so advanced that they use a method more advanced / less traceable than light signals. Maybe they'd use neutrino beams, or maybe they've hacked quantum entanglement. Or perhaps they're just hermits. Otherwise, I guess the most "intelligence" you could hope to find is something akin to dolphins. Anything of a higher level of intelligence would have deduced that their world is spherical in shape, and we can venture a guess that some of them would've had enough curiosity to start exploring upwards. The most I'm expecting to find in our own backyard is complex organic molecules. Even microorganisms would be a shock. But for other solar/planetary systems, well, that's where things start to get interesting. Especially with how common extra-solar systems are, apparently (thanks, Kepler mission!). Oddly enough, I ran into Alan Stern yesterday. He was giving a quick speech at a memorial service for one of the space engineering community's greatest minds that was recently laid to rest. :( Edit: Ah, right, the other questions: 1. Re: Fermi's Paradox: What incentive would an alien race have to make their presence known to us? Benevolence? Were I an advanced alien, I would let Earth keep incubating without interfering until they'd proven themselves deserving of assimilating into any existing galactic order. Granted, this is all presuming intelligent aliens exist, and I'm not sure that they do. 2. Very likely, but not in our own backyard. Now that I think about it, I'll bet that the challenge of space travel is even more daunting for liquid-dwelling lifeforms, because liquid (in general) isn't as compressible as gas, and compressibility is handy for transporting finite resources during space travel. 3. When we develop the imaging capabilities, we should look for alien space stations in orbit near the cloud tops of large gas giants with large magnetic fields. A strong magnetic field offers protection against solar flares, cosmic rays, and nearby supernova explosions.
I agree with you that it's unlikely that we will find anything else here in this solar system, or if we do it will be very simple. This was meant more as a thought about other star systems, but I don't suppose I clarified that very well. 1) There really isn't any, I think the issue with Fermi is that there's an assumption that intelligent life elsewhere in the galaxy would be easily detectable to us but I am not so sure that is the case. How far out into the galaxy do our own signals travel before they dissipate or become no longer recognizable as being "not natural?" How far away are we visible to anyone who is looking? And when are we visible there? Did the advanced life-forms look at our star with their version of SETI and just see dinosaurs? Or maybe they looked right after Toba, the supervolcano, erupted and saw only a world covered in ash and cloud? 2) The life-support system for an aquatic species would be a nightmare on its own. Then there's the question of how would you build and launch a spaceship from a world where you live in liquid under a mile of ice? If you can launch from the surface that's easier but could potentially damage your world's ice crust if it isn't thick enough. But how do you get all that machinery through the ice? Maybe there's a natural vent you can go through, but if not, do you risk cutting through? 3) Would the moons of such a gas giant, if close enough to the planet, benefit enough from the magnetic field to be used instead of building a space station?
That first one is difficult to answer. It's a matter of resolving a signal awash in noise created from natural planetary, astrophysical, and galactic processes. And extraterrestrials might have come up with some pretty clever ways to do such a thing, but we've still gotta consider the time delay of the signal. Humans have only been making radio waves for ~150 years, so only extraterrestrials within ~75 light years away would have had time to receive them, respond, and send a signal back at us (if they chose to, of course). Anything further away than that, well, we wouldn't know if there's something there yet. And it appears that there are plenty of planetary systems (likely with moons, too!) within 75 light years, but I'll bet that intelligent life is quite a bit more sparse than that. Now, if you're talking optical detection, and presume that extraterrestrials are looking for man-made structures, I think the pyramids might be our best bet. So that's ~4500 light year radius of signal, only 1/10th of the radius of the Milky Way. And we'd have only just heard back from anything within ~2250 light years. To give you an idea of where we are with optical wavelength resolution, I'd estimate that it could take us another 200 years-ish before we're able to resolve pyramid-size surface features on the planets orbiting Proxima Centauri, and that's only ~5 light years away. And hey, if they'd seen "only" dinosaurs (my quotes/italics, for emphasis), that would have absolutely warranted sending shittons of probes here. Probably a continuous stream of probes. Definitely an argument against aliens, at least in the Milky Way, and intergalactic exploration seems downright impossible. Sucks :(. Shoot, they could figure something out, I have faith in our hypothetical intelligent species! Maybe! I just checked, and although Jupiter's four largest moons (Io, Ganymede, Europa, Callisto) all intersect the deadly radiation belts, there are some captured asteroids that supposedly orbit in the sweet spot just above the cloud tops. One of those with a small orbital inclination (so that it doesn't intersect the high latitude portion of the rad. belts) might be perfect. And I'd wager that systems like Jupiter and it's moons are relatively common. We already know that Jupiter-like planets abound, but don't know much about how commons moons are, and the distribution of magnetic field strengths, orientations, stabilities, etc. Of course, the planet has to orbit within a habitable zone... ugh, so many variables.1) How far out into the galaxy do our own signals travel before they dissipate or become no longer recognizable as being "not natural?" How far away are we visible to anyone who is looking? And when are we visible there?
2) Then there's the question of how would you build and launch a spaceship from a world where you live in liquid under a mile of ice?
3) Would the moons of such a gas giant, if close enough to the planet, benefit enough from the magnetic field to be used instead of building a space station?
That part I can answer at least. We look, to the best of our ability, because of what a shame it would be if someone, something somewhere, was trying to reach us, and we weren't even trying to listen. If you try and fail at a noble goal, there is some honor and dignity to be had. Nothing but shame if we don't even try. Plus the search for ET has lead to lots of advances in radio telescopes.why
We're looking at earth like planets because the only conditions we know of that support life is this one. Sciencey logic right there. See above. But to go further, the instances that we know that supports life as we know it involve water, adequate heat, a magnetosphere to protect from radiation, stable orbits, stable atmosphere, and probably a bunch of other stuff that someone like Dala or francopoli could pull out of their butts cause this is their area of interest and not mine but I don't have a lot going on this morning and I'm trying to draw a hut (feel like breaking down and just ripping off this guy but I'm actually not a fan of drawing stuff that's already existing) and it's not going well, so here I am, looking for a distraction. SO MANY FUCKING WAYS IT'S MIND BLOWING!!! Off the top of my head, people figure out orbits of planets through the flickering of stars, bending of light, and voodoo science. If a planet is too close to a star, they can probably surmise that solar wind is ripping away the atmosphere and I might be wrong, but I think they can actually take infrared pictures or something to see if it's actually happening. They can also surmise that it might be too hot, too radiated, or in some other way fucked up. As for determining a planet's atmosphere, they have these special spectrometers that look at chemical makeup of shit. I might be wrong, but I think it only works on stars at the moment cause maybe planets are too small or too far or something or maybe we actually do spectrometers on planets, I dunno. That said, if we can see the gas makeup of atmosphere on planets, there might be some tells. For example, the presence of oxygen means it might support life and Dala says that methane is a byproduct of biological chemical reactions so if there's methane there's a chance there's a herd of alien cows farting away to their hearts content. And, as usual, in trying to look something up I find a Wikipedia Article that basically makes an feeble attempt of mine to figure something out, moot.I'm not even sure where, how and why we are looking right now.
Why
How
That's a great point. Of course our "habitable zone" might not be so habitable to another lifeform born of an entirely different environment than Earth's. And think of how weird things might get when you consider regimes far from standard pressure... The recent arsenic-based DNA sham comes to mind (edit: not 'cuz it required non-STP conditions), but hopefully we don't use that to reinforce the notion that our exact organic makeup is the only possibility.
And to expand further, such a quest appeals to our innate humanity. We're naturally inquisitive and to discover other life out there has the potential to answer questions we've had as well as bring about new questions for us to ponder. Despite all of our struggles with each other, we have a natural desire to make connections, to communicate and share our lives with other people. The more life that could be out there for us to discover, the more potential connections we can make. Most importantly though, successful in our endeavors or not, sometimes our attempts to explore outwards allows us to find answers about ourselves inwards.
It was a very interesting podcast, which I think could be summed up as "We won't know until we do." It was particularly interesting where modern day instances basically canceled out mid 20th century sci-fi ideas. For example, more efficient and direct means of communication could rule out the possibility of radio chatter or better use of materials and more efficient use of energy might mean that concepts like Dyson Spheres are unnecessary, etc. It was a fun little listen.