todofwar

I would say it's outright impossible. Too cold. If you have liquid methane, you can't have any bacteria grow, no chance.

These flow reactors don't tend to be aqueous, and there aren't intermediates in SN2 reactions, you're thinking SN1. I'm not familiar with these catalysts, but I believe you can oxidatively add an alcohol to a metal, than beta hydride eliminate and reductively eliminate to give water and ethylene. Ethylene will then oligomerize easily enough.

Your combustion products will be CO2 and H2O, in equimolar ratio I believe. So the ISP would probably be close to kerolox. A bit lower, since hydrocarbons spit out a higher ratio of water.

I question how much of an issue this is. There's a difference between bacteria surviving and bacteria actually growing and multiplying. Nothing from Earth is going to propogate on any moon of Saturn with the possible exception of Enceladus. Granted, said bacteria will mean you can never trust what you see within a certain distance of your landing site, but it's not like we aim for the same region twice usually. Unless we need someone to be able to have a back up way to communicate after losing their antenna and getting impaled.

So would you then "orbit" that point (probably not the right word, it wouldn't be eliptical) until you hit a side assuming you don't have the energy to exit the cylinder?

If I'm remembering mechanics correctly any point inside the ring will not feel a gravitational pull towards any side of the ring, same reason a sphere around the Sun would drift relative to the Sun. But extending it to 3d, I don't know about being inside a cylinder. I want to say you get an attraction to the plane intersecting the middle of the cylinder.

Just to address a few points and partly summarize (taking it from the reverse angle, if a new species evolves in 150 million years will they know about us assuming we all die tomorrow): 1 Mines: We've dug up enough key resources in specific places and that will leave a noticeable pattern, and the mines themselves will be clearly non-natural formations. Counter: I don't think we've dug up enough resources to really make it that obvious. Any oddities in terms of boreholes or shafts will be very distorted, and this hypothetical species will have studied these believing they are natural formations. I don't think Earth scientists have explanations for every feature, hence people keep finding "evidence" of lost cities that later turn out to be naturally formed. So, while their Earth science field is young, they might just assume all these sporadic features are simply natural formations and do their best to explain them in that context. They might even think our strip mines are the result of a series of meteor impacts and term it a "later bombardment" period. 2 Fossils: We have left a distinct impact on the fossil record, we will clearly show up as a dominant species and have caused such a change in ecology that will also be obvious. Counter: Average out over 100K years, and our impact is nothing. So, in 150 MY it will get very hard to distinguish antiquity from modern times, there may be enough of a trend in some species and clearly there will be a mass extinction event on the books, but they will start trying to form a theory to explain it without the need for an advanced civilization. 3 Isotopes: We have changed the isotopic patterns through our messing about with nuclear energy. Counter: They will see an anomaly for sure, starting at a specific time. But they may explain it other ways, claim it's the result of a meteor made of plutonium crashing into the Earth. This would even hinder their understanding of supernovae because they would think plutonium and other synthetic elements with long enough half lives are actually naturally occurring. So all their calculations would have to account for that. 4 Plastics: Similar to above, they would assume any plastics they find (not all would get preserved, tons of it is getting dumped into the ocean after all) are naturally occurring compounds. This would again hinder their Earth science a bit, they would start trying to figure out how it got naturally produced. But maybe, just maybe, this would start to lend to a new theory that they were not first. But is it enough? Or will it be a fringe theory like that guy who believes cell membranes don't exist? 5 Satelites: Once they go into outer space they will find our space junk. Counter: It won't last forever, but if a single piece survives long enough, with the weight of the previous evidence, maybe, just maybe they would start to think another civ came and went.

Pretty sure you're the one trolling this thread. No need to get accusatory or belittle people. This is the forum on the website of a video game that is targeted at all ages, so you will get all levels of knowledge on a range of subjects. And honestly, I'm pretty sure you're wrong about a few things, but I'm not going to add insults to my attempts to counter your points. This is supposed to be an interesting discussion about the realm of possibility, if you don't like it stop posting and this thread will fall off the front page in a day or two when the rest of us feel like moving on.

I always thought that happened before the earth was capable of sustaining life, but if not I imagine that kind of impact would wipe any evidence out. Not relates to the quote above but this would get merged anyway. People keep asserting we leave behind enough evidence, but would it reach a critical mass? Again, any species that evolves would treat everything they find as natural formations. Anything useful they find will get mined and reused. Plastics would be burned as a useful fuel. So, at a certain point our left overs will stop being a complete record. And as @wumpus said, our civilization will be compressed geologically speaking such that you won't be able to tell the modern era apart from the neolithic era. So, if a civ grows under the assumption that they were first, they will decide all these odd fossilized bits of tech must be natural. They may not even find much depending on how long after us they come. Will there be a critical mass of evidence to overturn their belief they are first? I think if we found plastic sediment in the jurassic layers we would begin trying to figure out how it formed naturally, and probably wouldn't say it's the result of a distant species. And I don't think we've depleted enough resources yet for that to be noticeable until such a civ maps the earth completely and sees a pattern, something we have not done yet. Tldr: it's not just about the evidence, it's a question of how much evidence is necessary to force a civilization to change its mind about being first, considering their world view would presume every odd feature they see is natural including plastic and isotope patterns.

In my experience safety regs on chemicals are based more on how well known a chemical is vs how dangerous it is. Case in point: I was required to go through special training to handle 30% formaldehyde, but no training for HF or t-BuLi.

For someone who claims to hate this kind of thread you sure do seem to enjoy reading it. Interesting point though, since our entire civ will be compressed to a tiny layer in terms of strata, would we even be able to tell anything about our civilization? We'll have the odd bit of fossilized tech here or there, but as an example think about the Antikethera mechanism. I doubt that was the first of it's kind, seems entirely too refined for that, yet I don't think we have a clear "fossil record" for what came before it. So, from the perspective of someone 100 million years from now they'll see pottery, wheel, computer, rocket, all happening seemingly at the same time. There may be a sheet of plastic squeezed in somewhere, and odd deposits of metals, but it's not like archaeology is possible on such a long scale. So, getting back to what this thread was started to discuss, what would be left behind? We don't even know the full extent of ancient Egyptian tech (we have a very good idea, but the point is the record has already started to deteriorate in only 3,000 years) If every human dies tomorrow, and another civ arises in 150 million years, will they know about us? What will they know? They'll have a ton of fossils probably, will see a great extinction event, and can probably tell we became dominant, but what about technology? And don't forget stubbornness and skepticism play into this, what critical mass of evidence would be required? We find anomalies all the time, but since the weight of evidence tells us neanderthals didn't have toothpaste we find ways to explain them in our own context. So, if you found some odd geological formations, some depleted resources, and a few tiny patches of weird plastics here and there what conclusion would you draw? It took us a long time to figure out we move around the sun, because geocentrism was a good enough theory to account for the odd deviations. This hypothetical future race will have a theory that they were first, and as paleontology develops they will start to find more and more evidence that maybe something else was here first. But their theories will be built on explaining the world without that previous civ existing at all. So, any and all anomolies will first be forced to conform to the prevailing theory, until something breaks. That's how science advances after all. The question is, will we leave enough behind to break their theory? Or will future geologists be hopelessly trying to figure out how polyethylene forms naturally?

Pretty sure it was Carthage. But I think there were some remains left over after its destruction. Dan Carlin described ancient warfare as nothing more than a more labor intensive version of modern warfare, we always have obliterated cities, it's just easier to do now. Other examples include Assyria and whoever the Mongols didn't like.

I doubt there's a major risk of contamination from cassini. I mean, what from Earth could live on Titan? If it's cold enough for liquid methane it's too cold for any water based life form. We use liquid ethane for rapid freeze quench to study reactive enzymatic species, a technique that gets its name from the fact that it pretty much halts all chemical reactions. Now, Enceladus is a different story I suppose, but the surface ice is presumably thick enough to keep out any contaminants as well.

I thought I had read they had already planned out Cassini''s descent into Saturn. Of course, these kinds of decisions are going to come up again. I was always curious why funding continuing missions is an issue, God knows post docs and grad students aren't paid very much, I always figured you could at least hand the controls over to some academic lab for less than 500K a year in funding and they can squeeze some data out of it for a while. From what you say though I take it there are other factors at work for even controlling or accessing these probes beyond the manpower needed to run the probe itself.

Right, so if they decide to stop funding Curiosity tomorrow, cant they reactivate it later? Granted, it won't last forever, but instead of simultaneously funding both why not do six month or three month shifts for each project? I guess my question is, why does this have to be a final decision? Until we land a new rover or Curiosity breaks, why not just treat it as in storage if they can't fund it at the moment? People on this thread seem to be talking about it like they're planning on hitting the self destruct (I know for Cassini they kind of are). I'm very much an amateur when it comes to this kind of thing so I'm happy to hear the reasons why.

http://www.gizmag.com/ares-rail-energy-storage/28395/ @peadar1987 decided to find the article on this, because I knew I didn't come up with it. Looks like they're actually building it in Nevada. I don't know about how they're getting around track costs, I only quickly skimmed the article and they claim cost savings so maybe they are using existing track.

So what is the issue at hand here? Can't Curiosity chill out for a while until Cassini runs out of fuel for maneuvers and needs to be crashed? Once something is on target, especially a rover, what goes into maintenence from Earth? Midas can't upchare you that badly for a Martian oil change

Still, as you or someone else said, you need those reservoirs. What about somewhere like Norway? Rugged terrain, not allot of lakes, need to damn off or otherwise ruin large chunks of the landscape, and half the year your reservoir will be frozen. Or a desert, where water is a bit more precious than sand. Where you have the landscape to set up reservoirs they are the better option. But the railcar system is deployable anywhere.

I went with lead cause it's dense, but sand could also work and that's nice and cheap. And dont forget, Li systems dont recharge infinitely, while a lead ball will be a lead ball forever if you keep it oiled. The advantage over water is you get a denser system that is simpler to assemble and maintain vs hydro. Let's say you quarry out a big ditch and use the bulk of that material to also make a big ramp and the rest as material for your carts. So far you're at zero materials cost. You can set up a system that only requires a track and the generators instead of two large reservoirs and the pumps. If there's some natural terrain to take advantage of all the better, and all you need is a steep hill. Heck, you can go mountain scale which is infeasible for water based systems due to freezing.

Very steampunk but I think it might have some merit.

I saw something on this very recently, I think they're building a test case somewhere. But yeah, you can fill the cars with solid lead, really bump up your energy density from water. Not for individual homes, but how about this concept: attach really heavy lead weight to pulley system off the side of a skyscraper. Let it slowly descend as you use the pulleys to run generators. When you have a surplus you run the system in reverse to raise the weight again. By using lead you can get higher mass density and thus more stored potential energy per unit volume. If the building is high enough you can store quite a bit of energy this way. Of course, you wouldn't want them free floating out there, probably should encase them in some kind of shafts in case they snap and fall on someone. Even for an individual home, it would save space over a water pump system.

I meant as a hydrogen storage system, just add acid. Not for rocket applications

Hydrogenating benzene just gives you some cyclic alkanes, so basically back to gasoline (I know, not the same compounds but basically hydrocarbons). Boro hydride is pretty good in terms of mass density, but really a good tank will win out for storage. Granted, the tank will become brittle over time. And of course, the vast majority of our hydrogen is from natural gas and coal, not the clean energy everyone thinks. As was already stated we will eventually move away from one size fits all tech. Some places will use gravity, either with water or with railway cars on a hill (my personal favorite). For jets there will be hydrogen, for cars most likely batteries, for rockets the EM drive obviously (that last one was a joke). It's pointless to force one solution for everything.

Anyone have recommendations for scientific journals on planetary science? My university subscribes to pretty much everything so pay walls aren't an issue

Maybe the great dying was the result of terraforming attempts that got shot down by the alien greenpeace (greypeace?) after they had already killed everything. But I think a small couple oft thousand strong settlement could easily go unnoticed if the effort was abandoned early. We're looking at maybe a few thousand tons of refined material, that can easily vanish, with a low chance of being dug up. Even if it was, a small set of artifacts that we don't recognize would be dismissed as an anomaly. Studied and thought about sure, but unless you recognized the mun or bust graffiti on the side would you look at a twisted up bunch of metal millions and millions of years old and scream spaceship? There are lists and lists of weird things with no explanation out there. I suppose a global civ would leave behind enough evidence for us to speculate on, but one small outpost would probably not leave enough to prove anything. So, have humans permanently scarred the earth then? Are mineral deposits fixed or in flux? How long before it all gets scrambled again? Plastic is not a thermodynamic sink, it will ultimately decompose to something else with enough pressure and temperature (I read the paper on plastic sedement and was not impressed, classic case of overreaching). As for fossils, humans became dominant in the last few millenia, and if you look at mamallian biomass today we make up quite a shocking majority, but what about divided over all the time since mammals arose?