Haystack posted:

Aliens don't have interstellar civilizations for exactly the same reason humans never will: it costs way, way, waaaay too much energy, and is way too slow. A physicist on another forum I frequent broke it down like this:

quote:

Everyone thinks that space is big, but they're wrong. It isn't big, it's big. People don't comprehend the scale. When I hear people talking about 'fast space travel' I start to itch a little bit. People that say that sort of thing don't mean 'fast' in the sense of being able to send a tiny unmanned probe to the nearest exoplanet in 'only' a few million years, they mean being able to hop a space-bus and have a family vacation in Betelgeuse. And that isn't going to happen, not ever. I don't care what kind of weird future technology and vast oceans of clean cheap energy you postulate. We are stuck on Sol forever, and let me show you why.

The closest terrestrial planet we know of is Gliese 876 d, which is 15 light years away. Sure, the atmosphere is well above boiling, but we are not very picky space travelers. Let's say that we have perfect technology. Our engines are 100% efficient, fuel weighs nothing, and accelerations are instantaneous. This is the thermodynamic limit. It cannot get better than this. What would it cost us to send someone or something to Gliese?

Here's a table. I have listed the energy cost of the voyage in units that I call 'Globes.' Globes are the percentage of the entire world's energy production per year. I chose three different masses for your edification. Use the globes per kilogram if you want to quickly calculate the cost of sending your favorite sci-fi starship on a 15 light-year journey at the speed of your choice. Use the 1,000 kilogram table if you want to launch your Honda Civic into space. Use the 500,000 kilogram table if you want to use the International Space Station as your ship (which by the way, is terribly cramped and unpleasant).

pre:

+--------------------------------------------------------------------------------------------------------------------------+
|Velocity (c)|Time, Earth's Frame (years)|Time, Ship's Frame (years)|Globes per kg|Globes per 1000 kg|Globes per 500,000 kg|
+--------------------------------------------------------------------------------------------------------------------------+
|0.01        |1500                       |1499.92                   |0.0000000095 |0.0000095         |0.0047               |
|0.1         |150                        |149.25                    |0.00000096   |0.00096           |0.48                 |
|0.2         |75                         |73.48                     |0.00000392   |0.00392           |1.96                 |
|0.3         |50                         |47.7                      |0.00000917   |0.00917           |4.58                 |
|0.4         |37.5                       |34.37                     |0.000017     |0.017             |8.65                 |
|0.5         |30                         |25.98                     |0.000029     |0.029             |14.69                |
|0.6         |25                         |20                        |0.000047     |0.047             |23.73                |
|0.7         |21.43                      |15.3                      |0.000076     |0.076             |38.00                |
|0.8         |18.75                      |11.25                     |0.000127     |0.13              |63.29                |
|0.9         |16.67                      |7.26                      |0.00025      |0.25              |122.86               |
|0.99        |15.15                      |2.14                      |0.0012       |1.2               |578.05               |
|0.999       |15.02                      |0.67                      |0.0041       |4.1               |2028.44              |
|0.9999      |15                         |0.21                      |0.0132       |13.2              |6618.27              |
+--------------------------------------------------------------------------------------------------------------------------+

There's a lot I want to unpack here.

Generous Assumptions

I can't emphasize enough how nice I'm being here. I'm granting instantaneous acceleration, which is huge. If you have to actually worry about thrust, the times become much, much longer, while still requiring the same amount of energy. I am also granting zero weight fuel, which is nuts. On top of that, we have perfect efficiency. We lose nothing by charging the engines nor by firing them (In contrast, we lose about 60-70% of the energy generated from burning coal by the time it reaches our homes). These numbers are also for fly-by arrivals. If you want to actually stop when you get there, then double the energy cost.

Scale: Earth Time

This is the only part of the chart that scales in a simple, intuitive manner. If you double your ship's speed, the guys on the ground have to wait half as long for it to get there. Nice and simple.

Scale: Ship Time

For the ship, things are a bit weirder. As velocity increases, relativity becomes impossible to ignore. At 0.8c, it actually takes the ship less than 15 years to travel a 15 light-year distance. This might sound like FTL travel, but it's really nothing of the sort. Space is contracting for the ship. The distance between objects is shrinking. The 0.99c ship gets to Gliese in 2.14 years because in its frame, Sol and Gliese are only about 2.14 light-years apart.

Notice that the scaling becomes extremely non-linear towards the end. Increasing your velocity from .9c to .99c is only a 10% boost, but it cuts the travel time (for the ship) by about 70%. Welcome to space-time, you fuckers.

This also causes out-of-synch issues with your earth buddies. I was going to get into the heartbreaking consequences of this, but I'm not going to bother because the next section is going to render that moot.

Scale: Energy

And now we come to my point. Classically, energy scales by the square of the speed. So doubling your velocity doesn't double your energy cost, it quadruples it. That would be bad enough, but then relativity adds in an asymptotic scaling factor that goes berzerk as you start to approach c. Just look at those numbers. Really, look at them.

I chuckle a bit when I hear about space tourism. We aren't going to other planets. Not ever. The cost of sending even a small ship to our closest (and totally uninhabitable) terrestrial neighbor and having it get there before the crew dies of old age has to be measured in multiples of the earth's annual energy output. I don't care what kind of future tech that we have. How much more energy are we gong to be producing with our tri-lithium anti-phasing widgets? A hundred times as much? A thousand? Those both sound like wildly unrealistic numbers, and they both totally don't solve the problem. If you have to deal with issues like real acceleration, real efficiencies, and real fuels, then a million-fold increase probably wouldn't rescue the project.

We're not claiming other planets. We only have the one that we're on. We need to take care of it.

LtStorm posted:

In USPOL there was mention of alien microbes living among us, including the idea that tardigrades are that. Tardigrades are definitely from Earth, but, there's still potential that microbes of an alien source could be hiding all over Earth and we just haven't spotted them yet. More likely, but also yet unproven, is the idea there is life that evolved on Earth alongside the life we know, but that we haven't noticed yet--it'd all be microbial also, most likely.

The reason this is a question is because of how we study microbial life. To discover a new species of microbe a scientist has to:

1. Spot it in a microscope
2. Spot many of it
3. Figure out how to grow a colony of it
4. Study its biochemical and genetic composition

Right now the way we tend to study microbial life is by looking for biochemistry that works the same as it does in the macro life we can study much more easily; almost all microbes we know of have very similar biochemistry to us and all plants and animals. I say "almost" because recently scientists have nailed down an organism that is, to our knowledge, of Earth, but also differs more from all known life than we differ from fungi. The organism is hemimastigote and was first spotted in a microscope back in the 19th century but were only studied under a microscope before modern biochemistry had arisen which didn't reveal how truly weird they were until they were re-discovered now.

So where could alien (extraterrestrial or terrestrial) life be hiding on Earth? It could be anywhere in our biosphere. Say you were to collect a random sample of matter--much like what was done that lead to the hemimastigotes being rediscovered--and separated out the abiotic parts (which could also be where you accidentally throw out the evidence of alien microbes because it looks abiotic to you). What you were left with that you are sure was a living organism or came from an organism would include a portion of biological dark matter.

Biological dark matter includes things like junk DNA--which we can find even in our own bodies, but could also potentially contain remnants or genetic material of organisms with completely different biochemistry from us. As I mentioned before, most of our ability to study microbial life relies on it having the same biochemistry as us, which our cutting edge ways of analyzing biological material rely on more and more heavily. This all leads to a hypothesis that there could be a shadow biosphere that contains microbial life that works so differently than what we've identified and studied that it could be hiding in plain sight without us identifying it.

Of course, so far there's scant evidence to support this, which could be because it doesn't exist, but much like aliens not on our planet, could also be because we just haven't discovered it yet. And hemimastigotes are still having their biochemistry studied, they could still contain surprises even more amazing than they already do.

mycomancy posted:

Great topic LK! Here's my opinion as a molecular and synthetic biologist: there are three Great Filters of consequence, the Nucleosynthesis filter, the Intelligence filter, and the Synthetic Biology filter.

The Nucleosynthesis filter is the apparent requirement of heavy elements to do biochemistry. While life is made out of a skeleton of hydrogen, oxygen, nitrogen, and carbon, elements like phosphorous, sulfur, iron, manganese, magnesium, copper, and other elements are found everywhere and are essential to basic enzymatic function. Planets that form too early will have concentrations of these elements that are too low for complex biochemistry to evolve. This Filter means that life can only evolve once enough first and second generation stars have died to produce these elements.

The Intelligence filter is based on the fact that we've seen intelligence involve only once on our planet. Like many adaptations, intelligence evolved in response to a specific environment encountered by a specific species. The odds of this happening is likely very low, as the physiological cost and prerequdited of intelligence is high.

The Synthetic Biology filter is the one we're going through right now. We can't survive in any meaningful way in space, and evolution is too slow. We have to redesign ourselves to get off the planet, and now we have the tool to do it in RNA-guided nucleases like Cas9 and Cpf1. If an intelligent species evolved such that they could not engineer themselves for whatever reason, they'd be homebound.

Well, that's my two cents on the topic.

mycomancy posted:

Did you put my dumb, sleep deprived spelling error in there too?

To answer your question, here's the short list of animals we think of as being at least somewhat intelligent: us, pigs, dogs, elephants, various cetaceans, various apes, various corvids, and maaaaaaybe octopi. So we aren't crowding out intelligence at low levels. Despite these numerous examples of "low level intelligence," we don't seen other intelligence peers on the planet even though presumably the apes at least are as smart as our common ancestors were. So why?

There's a certain level of anthrocentricism when we discuss the evolution of human intelligence. WE'RE intelligent, and we see the good in it, so we think it'd be good for any organism to evolve. To borrow from Larry Niven's Known Space books, Finagle Was Right: The Perversity Of The Universe Tends Towards Maximum aka the Universe doesn't give a gently caress about what humans want, need, or think, and it's gonna do what it does without consideration towards us.

So, my expert opinion is that we're probably the first intelligent species in the observable universe, and likely we're the last. The spark of intelligence dies with us. And, with the way the world is going, that'll be in about 20 years.

VitalSigns posted:

Space predators being the resolution to the Fermi paradox seems unlikely to me because why would an alien species that doesn't share common descent like all life we've heretofore observed on Earth be able to naturally digest anything it finds here, let alone everything.

Even if you assume that only carbon-based life is possible and sugars are the building block of energy storage/release in every possible lifeform (or at least lifeforms complex enough to invent interstellar travel), there's still a bunch of proteins and possible carbohydrate configurations that you can't break down unless you evolved alongside the organisms making it so you have the enzymes you need.

There's an enzyme in our spit that breaks down the carbohydrates in starchy foods like crackers and potatoes, if you don't have that you can't get the glucose out of them, you just have to poo poo out all that energy untouched like we do with cellulose. The energy in cellulose is enough to sustain cows and even giant fat-rear end elephants if they eat enough of it, but even their bodies can't break it down, they rely on symbiotic organisms in their gut to ferment the cellulose down into something their bodies know how to produce the enzymes to handle.

Even to eat another mammal or even a nearly-identical human, I can't break down and use their proteins without special enzymes produced in my liver and a low-pH environment for the reaction to take place in, and of course all that needs to happen in a protected enclosed area of my body so the enzymes and acid don't get out and I don't digest my own muscles and organs. If you're born without one of those critical enzymes then eating meat literally poisons you. Or one of the most common dietary restrictions on earth is lactose intolerance where your body says "okay I'm not a baby anymore time to stop wasting energy on an enzyme to break down milk sugars since I probably won't encounter any" and so most people on earth can't eat the same food they ate as a baby unless they're from a few subpopulations of humans whose ancestors lived in a culture that depended so much on animal husbandry for survival that persistence of lactose tolerance into adulthood was selected for.

And all those problems exist among creatures that have evolved to eat each other, planet earth is filled with organisms with weird proteins and strange sugars and other chemicals that might as well be alien compounds from another planet because you can't do anything with them, at best you excrete them out untouched, or maybe they blister your skin or maybe they just kill you, or maybe they mimic or block neurotransmitters and do weird things to you like make you hallucinate or get you high or paralyze your nervous system and suffocate you to death.

Even if everything goes well you can have unexpected problems if your environment provides too little of an important nutrient (iodine deficiency was common in isolated landlocked areas before we added it to salt to supplement everyone's diet) or too much (if you eat a dog's liver you will die from too much vitamin A, this was a problem when early arctic expeditions ran into trouble and started eating their pack animals).

When you look at how digestion works you have to conclude it's hilariously impossible that a predator alien could show up and just start eating earth life. Even if we don't lack a single element they need nor contain any elements in lethal overdoses for them, their bodies wouldn't be able to digest the life they found here just like we can't digest a lot of life we find here. And digestion has to evolve this way. Energy efficiency is extremely important, if you can expend 1% less energy than the neighboring species to obtain the same food you're going to outcompete them. The purpose of enzymes is, like all chemical catalysts, to lower the input energy required for a chemical reaction. You can't carry around a reactor in your stomach to incinerate everything you eat into its constituent parts because the energy requirement would be enormous and you'd lose out to the animal using specialized enzymes to break down food at cold temperatures (and how would you protect your own body from it, we can coat our stomach in pus that the acid and enzymes can't break down, but a universal digestor by definition would break down anything organic it touches). And you can't make enzymes for every conceivable energy-rich molecule you might ever encounter because (a) if you've never been exposed to a given molecule there's no selection pressure to create a way to digest it, and (b) creating enzymes costs energy so making ones you never use makes you less competitive than the next guy who only makes the ones they need for the food they eat (again why most humans become lactose intolerant at ages when their ancestors stopped drinking breastmilk, or why humans are the only animal susceptible to scurvy. Most animals make their own Vitamin C, but at some point in our and our great ape cousins' history we lost that ability because we stopped making a critical enzyme in the chain, most likely Vitamin C was so readily available in our immediate environment that apes who didn't bother to make the enzymes survived better than the ones who did).

It makes for a fun creepy sci-fi premise, but practically speaking it's biologically impossible that we would make a good food source for a lifeform that evolved from an independent line of descent, and that's before you even get to the practical problems of the insane amount of energy expenditure it takes to come here versus just growing food on your home planet or in artificially constructs in your own solar system or manufacturing it from base elements or whatever (these are the same problems behind theories that aliens would conquer us for our natural resources, all of which are more plentiful and easily found in space without having to lift them out of a planet-size gravity well)

LtStorm posted:

I take issue with your issue. There's no guarantees silicon-based life would be rock anemones or stuck at the bottom of oceans. Well, no more guarantee than it'd be anything because we haven't met it yet. Now I get to talk about what I think about silicon chemistry!

Carbon is super-flexible, you are correct, but silicon is the second most flexible atom next to it (and is literally next to it on the Periodic Table meaning their properties are similar). Silicon is flexible enough to make macromolecules just like carbon, which is possibly the most important thing for it plausibly being a cornerstone of life and why we talk about silicon-based life. Macromolecules are, as the name suggested, large molecules; at their low end a macromolecule contains hundreds of atoms while at the high end it contains thousands of atoms. Small molecules, like the nucleic acids in our bodies (dozens of atoms each), come together due to their chemistry to form macromolecules such as DNA (thousands of atoms). The proteins in our bodies and any polymer we use in our lives are composed of macromolecules.

Making macromolecules requires a flexible atom able to form lots of bonds (lots in this context being four) as a base. Both carbon and silicon can form four bonds with four different atoms; they're both about equally good at that. One important feature of these flexible atoms is how they form long chains. Carbon has no problem forming long chains of itself; if you have a long chain of carbon with only hydrogens in every other available bonding position, you have a hydrocarbon; modifying them can make things important to our biochemistry like fatty acids. The silicon equivalent is a silane, which is hilariously flammable like hydrocarbons, but not nearly as stable. So while silanes, which are highly reactive in general, may be important to the biochemical reactions of a silicon-based life form, it's probably not going to around as a stable molecule. What silicon can do that carbon can't is form silicones. A silicone, as in the polymer we see in our every day lives, is a chain of alternating silicon and oxygen atoms. Silicones are highly stable and flexible with the theoretical ability to modify each silicon in the chain with up to two other atoms. Carbon doesn't form an exact equivalent of silicone--alternating carbon with oxygen in a chain makes an ether functional group which has its own complex chemistry. You can put ether functional groups in a chain but they tend to form a loop instead of a straight chain, which oddly enough is important to how Febreze and other odor eliminating products work.

Another thing you would need for life is a set of functional groups that have a variety of chemical properties they can imbue macromolecules with. For our carbon-based life, most atoms used in our functional groups are near carbon in the Periodic Table: nitrogen, oxygen, phosphorous, and sulfur. Other atoms used in our biochemistry are on the left side of the Periodic Table (hydrogen, sodium, magnesium, etc.) or near the center (iron, zinc, manganese, etc). While we don't know exactly what other atoms silicon-based life would use in its functional groups, it's easy enough to speculate it would share a lot of the atoms with us based on what we know about basic chemistry, the chemistry of silicon, and our own biochemistry. We know, for instance, that in our own biochemistry the elements carbon, nitrogen, and sulfur have a complex interlocked chemistry. Silicon does not interact with nitrogen directly, but has chemistry with carbon and sulfur. So functional groups for silicon-based life would have access to nitrogen as a key micronutrient much like we need iodine--or they may not use nitrogen at all. With carbon, we know silicon can form some functional groups and that they have a complex chemistry with each other because of the study of organosilicons. With sulfur, we know silicon can polymerize with it in a way that carbon can not, which would be an important difference in how silicon-based life works. Silicon does not interact with phosphorus much at all under Earth-like conditions, so if we found silicon-based life using phosphorous we'd probably learn something new about that chemistry. Lastly, one thing silicon is hands-down worse at than carbon is the ability to form double and triple bonds. Carbon is very good at both of those things which means they're a big part of the functional groups in our own biochemistry.

So silicon is flexible enough to plausibly build large macromolecules with, and we know from basic research into the chemistry of silicon that it can form functional groups with carbon, oxygen, and sulfur at the least. Once you have functional groups you need a set of molecular building blocks using those functional groups that fit together in a flexible way to build a macromolecule. As that macromolecule gets bigger it will start demonstrating unique properties due how its functional groups interact with each other and with functional groups in other small and macromolecules. In carbon-based life this would be where you building blocks like nucleic acids that are assembled to make a self-replicating macromolecule like DNA and RNA which is able to facilitate the synthesis of other macromolecules like proteins and other structures that make up the cells organisms are composed of.

So from this perspective there's nothing clearly standing in the way of silicon-based life being just as complex as carbon-based life. Silicon has its own bag of tricks to offer but we only poorly understand them because we haven't studied silicon and its ability to form macromolecules (this is something basic research would do, FYI) nearly as much as we've studied carbon and most importantly our own biochemistry. Most of our research into organosilicons is due to polymer research--so how to make different and better plastics (this is something applied research does, FYI).

The bigger hurdles to us imagining silicon-based life, from our perspective as carbon-based life, is what their basic building blocks and fundamental chemical reactions for them would be--which we have to completely guess at. For example, their biochemistry would definitely have several reduction-oxidation reactions somewhere in it (which doesn't have to involve oxygen in spite of the name of the reaction); for us one of those is carbon (solid) and oxygen (gas) forming carbon dioxide (gas). The equivalent for a silicon-based life form would be silicon (solid) and oxygen (gas) forming silicon dioxide (solid). So how they use that reaction would have to be completely different than how our form of life uses the equivalent. And of course because silicon reacts well with carbon it may just be that they use the same carbon and oxygen redox reaction as us.

When we think about silicon-based life we need to remember it doesn't have to exist at the same conditions as we do. What if they were on a planet halfway between Earth and Venus in conditions? I say this because one idea is that silicon-based life could exist at much hotter temperatures than carbon-based life. Going to a much higher temperature and pressure would mean changes to chemistry that would both make some reactions we benefit from unfavorable and unusual and vice verse. One other big question that also relates to the reactions that make this life possible is what solvent that silicon-based life would use as at a higher temperature water isn't going to work. Sulfuric acid is one suggestion because it boils at 300 C; so if silicon life using that would exist somewhere just below that temperature. Using sulfuric acid as a solvent would also make the chemistry happening completely different than how our life works and might have the benefit of making silicone-based macromolecules much more stable. An example in the difference of conditions is silicon nitride, an inert industrial chemical under Earth-like conditions. On a hot planet covered in sulfuric acid, silicon nitride would not exist as a compound--it would be dissolved so nitrogen would not risk being locked up in an inert compound and would go elsewhere in their environment and be available for biochemical reactions.

Living at a higher temperature than us hardly would stop a silicon-based life from space-faring anymore than we do from the perspective of life support--it's trivial to make a hotter box than what we do for traveling the delightfully insulating depths of space where you have more trouble getting rid of heat than generating it.

Of course, what kind of technology is possible on the planet they might live on is another question. The important thing is that if silicon-based life could form from abiogensis, there's nothing fundamental that we know of standing in its way of being as complex as us.

Citations: A lot of chemistry textbooks I've read because I'm a chemist. I like this one which is about supramolecular chemistry, the study of molecules--especially macromolecules--interacting with one another.

Zophar posted:

Great thread idea. One of my favorite resources is Isaac Arthur's Youtube channel/audio podcast, where he makes long-form videos breaking down the science behind insterstellar travel, building superstructures/massive, interstellar projects, and he also spends a ton of time on the Fermi Paradox. Each video can be 45 minutes long, but you get clearly organized videos that walk you through the theories, the scientific principles under-girding them, and even the calculations needed to make it happen.

https://www.youtube.com/watch?v=channel?UCZFipeZtQM5CKUjx6grh54g

The short version of his outlook is that he's an endless, Utopian optimist about the possibilities of mankind in space, but also makes very convincing arguments to the effect that there is no real answer to the Fermi Paradox other than intelligent life being ridiculously rare.

Zophar posted:

Thanks, should work now.

Demon Of The Fall posted:

space aliens ate my balls OP

Kerning Chameleon posted:

That's adorable, you still believe in Asimovian fairy tales of human existence extended beyond the Oort Cloud. Don't worry, dear, one day I'm sure you'll realize the situation you described in that post is exactly as realistic as the literal events of Lord of the Rings.

zoux posted:

Check out the Revelation Space books.

It'd be nice if it was because of invisible crystal spheres set around each habitable system by a mysterious progenitor race that protect a civilization until it's ready to go out into interstellar space

Kerning Chameleon posted:

Nothing about space is "fun": it is silent, it is dark, and it is completely hostile to anything we can identify as life. I'm sick of the romanticization of the fundamentally horrifying and humiliating situation we find ourselves in, and I'll fight it here as well. If that means I have to be the ice-cold water dumped on your rocket boners, so be it.

Kerning Chameleon posted:

This is why discussions about the Fermi Paradox that don't end with "we simply can't detect them with our lovely instruments" get real facile real fast.

Like, we have people itt that seriously think we actually live in a Lovecraft story, I mean come on.

Kerning Chameleon posted:

Every single intelligent species clings for dear life to its slowly dying mother sun. The luckier and more canny ones might be able to ride out the star's expansion by island hopping planetary orbits until it settles into brown dwarfhood, but the idea any of us in the Big Brain Club could personally visit even a single extrasolar planet (given what we now know about physics and the realities of existing in space) is the real laughable idea.

Kerning Chameleon posted:

Yes, my choice for Great Filter is "laws of physics makes interstellar travel en mass impractical if not impossible", I consider that the most reasonable stance to take on the matter.

We're in a cage, but so is everyone else. We are effectively is not actually alone in the universe, just like everyone else.

Deptfordx posted:

I think his point is that it may not be practical to do it even the slow way. That entropy and interstellar radiation etc mean you just can't build a craft capable of slowboating it between the stars over a couple of centuries without it failing.

Kerning Chameleon posted:

The big question is... Why would anyone do that? My island hopping idea would be plenty for a species to survive a longass time on, if they live sustainably and accept limits and periodic culls in population. Trying to send colony ships you'll never hear from again gets you nothing but inaccurate warm fuzzies about your species specialtude, and it's so unlikely they'd survive the journey, much less the destination...

It's just a huge buy-in for enormous risk with basically no payoff. I can't imagine anyone but the Alien Elon Musks of the universe seriously considering it at that stage.

Kerning Chameleon posted:

Let me know when you can design a space station in orbit around Io capable of comfortably housing all of Earth's current population to escape Creeping Red Giant Sun.

And we kind of have to assume aliens think like us, because otherwise we have to assume Star Trek energy cloud alien morality, which isn't very useful for discussions.

Kerning Chameleon posted:

Okay, so you're fine with abandoning some humans to a sun-baked hellscape to save the rest. That's culling.

Yes, but at that point, I can make my theoretical aliens believe anything I want to to make my case, no matter how absurd that may be, and then expect you to disprove my angel aliens or Stay-Puft Gozer Aliens, or whatever. It's rhetorically useless.

Owlofcreamcheese posted:

or that there is plenty of intelligence all sorts of places and there was no actual rule that it'd reveal itself by 2018 or we would know there was none.

We have barely done any seti stuff and have completed like, a couple radio frequency searches on like a small percentage of the stars near us. The idea we searched so hard and so completely the entire universe that we need to start coming up with explanations is pretty absurd.

Deptfordx posted:

That it may not just not be possible to build machines with the kind of reliability that would be required over centuries of slower than light travel.

That all the fancy handwavy, basically magic, Nanotech self-repair you see in SF shows are not compatible with the actual laws of physics.

Ytlaya posted:

This exactly lines up with my feelings on the issue. There is no natural law stating that all our wildest technological dreams must be possible, and it's entirely possible there just literally isn't any way for life to practically travel interstellar distances.

This doesn't mean we shouldn't still keep exploring the idea, but a lot of people just kind of treat it as a given that we'll figure out how to do this stuff someday.

axeil posted:

I read a pretty interesting thing a bit back that Venus might be a more workable 2nd Earth than Mars, provided we live in essentially a space station. Venus has Earth-like atmospheric pressure and temperature a few miles up and you wouldn't need a spacesuit, just something to provide oxygen, unlike Mars where it's basically a vacuum and terraforming isn't real technology right now.

Owlofcreamcheese posted:

Doesn't this apply to basically everything? Isn't this literally how ecosystems work? Just constant churn of different species killing each other and hiding from being killed and fighting back from being killed over and over till it settles into slowly shifting ongoing patterns forever.

Haystack posted:

Aliens don't have interstellar civilizations for exactly the same reason humans never will: it costs way, way, waaaay too much energy, and is way too slow. A physicist on another forum I frequent broke it down like this:

DrSunshine posted:

On the same note, is anyone else as as I am about NASA's focus on Mars, when the biggest, most interesting focus for interplanetary exploration would be to send a mission to Europa or Enceladus to search for life under the ice?

https://en.wikipedia.org/wiki/Europa_Lander_(NASA)

It's not even on the mission plan yet, it's just a proposal. I think it's a big mistake to be all gung-ho about sending a manned mission to the Moon or whatever when the biggest potential discovery is with submarine missions to the watery moons.

Shaddak posted:

Between 4 minutes and 20 minutes for Mars, depending on orbital position. Current ly 35 light minutes to europa, don't know the distance for farthest approach.

mycomancy posted:

The Intelligence filter is based on the fact that we've seen intelligence involve only once on our planet. Like many adaptations, intelligence evolved in response to a specific environment encountered by a specific species. The odds of this happening is likely very low, as the physiological cost and prerequdited of intelligence is high.

mycomancy posted:

Did you put my dumb, sleep deprived spelling error in there too?

mycomancy posted:

Well, take a look at it this way: if we're the first, then we have a duty to wake up the "dumb" universe and spread intelligence to every point of light in the sky. We can turn anything on Earth capable of supporting the neurology into an intelligent animal, we can build AI in our image, we can try to bring our dead ancestral species back to life, or we can augment our own intelligence to the point of becoming alien.

mycomancy posted:

Sure, there's a ton of ethical concerns with in essence birthing a new species into realization that they're trapped in a rotting meat cage on a planet that has a maximum of 500 million years left before it gets roasted and that we're never leaving this solar system.

mycomancy posted:

Sorry dude. It IS a depressing topic when you weed out the sci-fi and get to the hard facts.

mycomancy posted:

There's no concept of progress or advancement in evolution, there's just survival.

BardoTheConsumer posted:

I for one think that, once we can be reasonablly sure there isnt anything alive on Mars, we ought to be exporting extremophiles.

Owlofcreamcheese posted:

Do you think the discovery of LIFE ON OTHER PLANETS would be some minor footnote you couldn't remember? That would be nearly one of the largest discoveries in all of human history.

Nail Rat posted:

No they found organic compounds ie compounds that could be the building blocks for life like that on Earth. Not actually any life or direct evidence of it yet.

MSDOS KAPITAL posted:

I'm astounded that you've been walking though life thinking we had discovered microbes living on the surface of Mars until just recently

Revelation 2-13 posted:

I can't remember where I read it, but someone was saying that the discovery of complex life on Mars would basically be the worst news ever written in a newspaper in the history of the world. 1) because if life evolved independently (important caveat) on two different planets in our own solar system, it would mean life is infinitely more abundant than we ever thought possible. 2) which again would mean that the great filter is most definitely ahead of us.

E: it was a little more complex explanation, but that was the basic gist of it.

silence_kit posted:

Cosmology is definitely worth studying pretty much purely for the reason that knowledge in and of itself has an abstract value. It is worth spending some money on, but it really isn't very useful and doesn't really change how people live their lives.

physeter posted:

Some people think the Earth-Moon arrangement is a little too convenient to be a natural accident. IIRC Jeff Bezos was tip-toeing around that in an interview a couple years ago, which I thought was funny.

VitalSigns posted:

Kerning Chameleon posted:

How hard would it be for you to go to Pluto, then build a receiver to pick up your old local news broadcast stations, with the stipulations that you have to build the decoder for the digital signal from scratch with absolutely zero documentation about it and your degree in communications is from the 1940s?

We'll assume getting you to Pluto, making so you don't immediately die, and giving you the semi-raw materials for the equipment are the freebies in this experiment.

Kerning Chameleon posted:

https://www.cnet.com/news/chinas-moon-lander-sprouted-a-plant-but-now-its-dead/


Of several seeds sent, only one had actually sprouted, and then promptly died afterward.

Yet more evidence organic life has no business ever being in space, and a rather poetic one at that