Warhorse
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Posts posted by Warhorse
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Engine part corrosion won't be an insurmountable problem. Some US ICBMs used red fuming nitric acid as an oxidizer in Real Life . As an FYI, the Kethane mod already contains a jet engine that can use non-oxidizing atmospheres.
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First you'll need a way to capture the hydrogen. Secondly purify it and extract the deuterium. (Regular hydrogen isn't very useful in fusion, the isotope deuterium is.) And thirdly you'll need a fusion reactor. I see a lot of extra weight in this.
Actually, regular hydrogen fuses just fine; it is, after all, what most stars run on. You just need a bit more energy to get it started.
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Well done, India, keep up the good work!
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Interesting ... My major concern would be that in order to pull it off, you have to have a fairly high precision machine working to rather close tolerances for extended periods of time, without any possibility of maintenance. I'm sure they'll get it right eventually, but I would bet that Comrade Murphy will get a couple of good rounds in before they do ... :-)
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I'm pretty sure that I already said that I was *assuming* that the created universes do in fact have the same, or similar physical laws as the parent universe. If this is the case, then yes, the number of universes in which life can exist should vastly outnumber the ones in which life cannot.
Now, is this a valid assumption? Who knows. There is probably no way to know yet. This whole idea depends on so many assumptions and unknowns that it is very unlikely to be true. But I think it's a fun possibility to consider.
You did indeed say that "the new universe inherits the same basic physical constants as the parent universe, but with perhaps a few minor tweaks here and there." However, this does not solve the problem. If you assume that the initial universe was life bearing, then it's reasonable to assume that most of its descendants might also be life bearing, but that begs the question of how the first universe managed to be life bearing. If on the other hand you assume that the first universe was not life bearing, then there is enough flexibility in the evolutionary process for a descendant to reach the sweet spot. However, that in turn means there's enough flexibility for *that* universe's descendants to *leave* the sweet spot, and most of them will. Either way, you're not solving the problem ...
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There's a rather decent SF novel by Stephen Baxter that explores similar issues ... http://en.wikipedia.org/wiki/The_Light_of_Other_Days
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Time passes more slowly at high speeds and in strong gravity, so you could certainly travel forward in time. IIRC there are solutions to the relativity equations which imply the possibility of traveling backwards in time as well, but the conditions for realizing them IRL are sufficiently ... tricky ... that nobody has (yet) demonstrated them.
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To my knowledge, most cosmologists believe that the process that created the Big Bang most likely still continues, and has produced countless other universes- at least, that is certainly the case with the eternal inflation model. Basically, while universes are finite in age, the multiverse that gives rise to them may not be. You only need ONE of those countless universes to be life bearing to get the ball rolling, if we assume that laboratory-created universes actually inherit the characteristics of the parent universe.
Sorry, I guess I wasn't clear. My objection is not that life bearing universes wouldn't happen, merely that, even ignoring any considerations of eternal inflation, they will be a tiny minority, since there is no reason to expect that a universe spawned from a life bearing universe will itself be life bearing. (A few probably will be, most probably won't.) Throw in eternal inflation, and it just gets worse. Unless the boys and girls in the lab have the ability to control which laws of physics get selected in the child universe, your theory, although quite interesting, does not appear to solve the problem.
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But anyway, I was thinking of his idea, and then I remembered how many theoretical physicists had discussed the possibility of making a universe in a lab. It truly might be possible to design a particle physics experiment that creates a new universe. This possibility has been discussed for decades. From my memory of the last time I had read of this idea, the new baby universe would only, for the briefest fraction of a second, be connected with the universe of its creators through a small wormhole. The wormhole would quickly pinch off, and the new baby universe would undergo inflation, expansion, and in general, very likely end up resembling our own universe- but the creator universe would never again be able to interact with the created universe after the wormhole had closed (otherwise, they wouldn't be separate universes, would they?).
Don't ask me how exactly you could do this, that's above my pay grade. Maybe create a higher false vacuum state and then collapse it back down? I donno. Anyway, I realized that if it truly WAS possible to create a universe in a lab, then the number of universes in which the physical constants were fine-tuned for life could vastly outnumber the number of universes in which life could not exist. All you need is the first, original universe in which intelligent civilizations could arise. This universe might naturally arise through the "eternal inflation" concept or other multiverse theories. Anyway, this original life-bearing universe gives birth (through those civilization's particle physics experiments) to millions or billions of new universes, which inherit the same or similar properties of the parent universe, whether by design or by accident (if you were creating a baby universe in a lab, wouldn't you want your creation to have the possibility of one day hosting life?). Those children universes then give birth to billions of universes of their own, and so on, until the number of universes in which life is, or was, possible outnumber the lifeless universes by a ratio of infinity to one (as the lifeless universes produce no progeny). So it ends up infinitely (or nearly so) more likely for you to find yourself in a universe in which life is possible than in a universe in which life cannot exist.
Maybe life really does have a huge impact on the evolution of the multiverse. Maybe the universe really IS fine-tuned for life, and maybe we are not so insignificant after all. Just a thought.
Hmmm ... I think there's a snag to this theory. If we accept that the laws of physics are fine tuned to produce a life-bearing universe, then that means that most of the possible combinations *won't* give you a life-bearing universe. That in turn means that most likely, the original universe was non-life-bearing, and its children gradually evolved to the point where at least one of them reached a state where life was possible. But, if there was enough variability possible between generations to get from non-life-bearing to life-bearing, there has to be enough variability for the reverse to occur as well, and the finer the tuning needs to be to produce life, the more likely it is that any changes take you out of the sweet spot. Thus, most of the experimentally produced universes should still be sterile ...
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Heh ... there's a line I read once, I think it was in a Larry Niven novel, to the effect that trying to change one law of physics is like trying to eat one peanut: it's theoretically possible, but it just doesn't happen IRL ...
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This is not a weapon of immediate action, rather it is a defense system that is deployed in orbit a large amount of time before the orbit is threatened.
So what? It still relies on your opponent being improbably dumb. And there are still cheaper and easier ways to achieve the same effect.
How about the computer would automatically recognize which polarity the targeted part of the ship has?The point is, the target is not even going to be made of magnetic materials, never mind radiating a magnetic field of whatever polarity.
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Well, if your enemy obligingly passes within a few inches of your bomblets, at no more than a few fps speed difference, then I suppose it might possibly have some effect. Of course, if you can manage something like that, it would be a whole lot easier and cheaper just to use a warhead that generates regular high-speed dumb shrapnel. Spacecraft are fragile ...
PS --- Magnets do not have a 'negative mode'. The will repel other magnets of similar polarity, but not random objects. Also, weight being at a premium in spacecraft, they are frequently made of light, non-magnetic materials such as aluminum, titanium, or composites.
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Yup, and then the defending side has twice as much fuel as you to maneuver, and just going to start doing things you either can't match, or you will match, but end up running of fuel and give them easy target practice.
This, of course, presumes that the defender survives the attack and is able to maneuver afterwards. Which is not a given, especially since the attacker, assuming identical ships, will be more maneuverable during the interface due to lower mass ...
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When we actually have political entities on separate planetary bodies at war, we may have space battles. Until then, why bother when you can just invade their land? Well, I guess it would look cool, and I would like to see what the world superpowers could come up with if they all somehow agreed to make all wars be fought in space.
What, you've never heard the expression "Nuke 'em from orbit, it's the only way to be sure" ??? There will be battles in space, because control of space conveys *HUGE* advantages in C4ISR and early strikes. Which is to say, if you try to launch an invasion without at least denying space (and air!) to your opponent, your invasion forces will get zapped before they can leave your own soil!
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If you launch your asat weapon, say, a few dozen bricks with orbital manouvering capabilities, AGAINST the rotation of the earth. When the satelites connect with your orbital wall, could the loss of velocity be enough to make a satelite re enter? How far up, if anywhere, could you do this? What posibilities are there to forcibly decomission geostationary satelites without the debris staying in orbit?
One of the quiet nightmares for NATO planners during the cold war was the realization that just about all the satellites in GEO belonged to the western powers --- the Soviets tended not to use that orbit, since much of the USSR is too far north to be seen from GEO. It was posited that the Soviets could launch an ASAT mission atop a large booster, and use a lunar swing-by maneuver to place it in a retrograde orbit at geosych altitude. Detonating the warhead would then create a cloud of debris moving in the opposite direction to most of NATO's commsats, thereby taking out a dismayingly large portion of their communications in one fell swoop ... :-(
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Naval reactors aren't really suitable for spaceflight, as they all weigh at least hundreds of tons. The last I heard, the biggest reactor anyone had flown was rated for a couple of hundred KILOwatts, on late Cold War era Soviet radar ocean recon satellites. The infamous Kosmos 954 was such a beast.
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I believe you miss my meaning, KerikBalm - probably because I haven't elaborated as much as I should have.
I'm not stating that species do not expand. I am saying that such expansion will be slower, and not sustainable over the billenia required to colonize the galaxy.
The essential assumption being made by "rapid expansion" theories is that a species - let's cleverly call them X - once it starts seeding neighboring stars will not stop. Ever. I don't think so. Let's look at how rapid expansionists see X's expansion throughout the galaxy:
1. Species X arises on a planet. Over time, thousands of years mostly, it soon occupies all niches on that planet.
2. Species X looks to the planets and the stars, declares a "Manifest Destiny", and starts a grand campaign, lasting millions of years, to colonize. We are assuming that Species X does not develop any form of faster-than-light travel or communication.
3. ??? Somehow, Species X is able to maintain its focus over a timeframe of millions of years, and over a scope of hundreds or even thousands of light-years in diameter. Each colony, once established, spends only a short time ensuring its survival and then begins working on the next phase of interstellar expansion. No colony falters or changes its mind - or at least, not enough colonies do so to matter.
4. Profit! Species X fills up the galaxy.
This is the model I question. Specifically, steps 2 and 3.
Life - and civilization - tends to move along the path of least resistance, on the paths that expend the smallest amount of energy needed to accomplish the goal. We expend more energy than "necessary" only when it becomes tied to our survival. To use one of the examples I used in my last post: once Europeans started colonizing North America, they filled up North America. The American colonists did not start looking for another continent to colonize in the name of European civilization. This is because there were plenty of resources and living space on the continent they found, that searching for a new continent made no sense. Meanwhile, Europe gradually lost interest in expansion.
(I am aware, of course, that the Europeans dislodged a number of native cultures already living on North America. Let us hope our future descendants are more ethical).
Whether a species colonizes a continent, a planet, or a solar system, you have only so much living space and resources to go around. Unless our species is a race-mind, you will also likely have a variety of cultures within that species, with new cultures splintering off the parent culture. This means we get competing spheres of influence.
Eventually, within a given region, all available living space and all available resources are claimed by one culture or another. Their spheres of influence are now set. If a new culture arises, it now cannot establish itself, because the existing cultures are not likely to divide up their finite resources to support it. The result is that the new culture must do one of the following: take resources by force, assimilate into one or more of the cultures already existing, or leave to find unclaimed territory elsewhere.
That last option is the one for expansion, but its the highest energy expenditure of the lot. First you have to find a place where you might be able to live. Then you have to travel there, carrying all the basics so you can survive and start building a new civilization there. Then you have to survive long enough to build that civilization. It happens because there are times where migration is still lower energy - or at least lower negative outcome - than warfare.
Once that high energy expenditure is made, however, the splinter culture goes back to low energy use. Let's look at Species X now from this perspective.
Steps 1 and 2 remain the same as in our original scenario, but something happens to the colonies when they arrive at their destinations:
3(a): The colonists find a whole new planet or solar system full of resources and living space they can expand into. Species X's central government (the one with "Manifest Destiny" on the brain) is now too far away to rap knuckles. Why waste time and resources expanding to yet another star system when the colonists have all they need here and nobody to force them to do otherwise?
4(a): The colonists build their own culture, separate from Species X - let's call them X'. X' eventually develops splinter cultures, just as X did on its home world. These splinter cultures take the low-energy way out, migrating to other planets or asteroids in the same system as X'. This process continues until nobody can safely migrate without grabbing already claimed territory and sparking wars. Given the vast amount of resources within a given system, this process will take many thousands of years to run its course.
5. Back in the home system, Species X's "manifest destiny" ideology burns out. The rebellion of the colonies, once news filters back home, sparks disillusionment in the fiction of continuing a species' existence by seeding it elsewhere. After all children never want what their parents want. Meanwhile, other - presumably more ethical - ways of dealing with cultural disputes are found, Species X integrates into a system-wide culture which leaves colonization behind. Missions of exploration may be launched, and trade with the former colonies may occur, but new interstellar colonies are no longer seeded by Species X.
6. Species X's expansion in the galaxy grinds to a halt. The daughter cultures may repeat the cycle, expanding to neighboring star systems once they've occupied all available living space in their system, but by that time, they have evolved into something different from the culture or species that seeded them.
So eventually intelligent life can spread through the galaxy, but the rate of expansion will likely be much, much slower. And each wave of expansion brings with it different cultural evolution. The final result is that no one species can or will fill up the entire galaxy.
I hope this makes my point clearer.
This is a likely path for species X to follow, IMO, if and only if X chooses to expand by actually moving population around directly. If X expands by using von Neumann probes to create population in situ, the expansion will proceed much more swiftly, and there's no real reason to assume it will run out of steam, absent programmed limits. Since the latter method is orders of magnitude cheaper than the former, it is, IMO, rather more likely to be used ...
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One comes with the download, for the more extreme one search for attosecond on spaceport.
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I think that as long as we are limited to chemical propulsion, expendables are the only thing that makes sense. There's no point in hauling a lot of empty tankage any further than you have to, chemical rockets just don't have enough power. Once we graduate to something better (nuclear? ion? solar sail?) the answer will depend a lot on how reliable the engines are, and how much maintenance they require.
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It's also not uncommon for the rating of an engine to really mean "maximum sustained output without risk of failure", which rating the engine can exceed for brief periods, though that is apparently not the case here.
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I think landing anything on Europa may be dangerous with or without spikes. How.. active is Europa? All that ice floating on a massive ocean. I imagine the ground constantly shifting and breaking appart with earth quakes ( Europa quakes ? ) Same with Io.. but many times more hellish.
Well, the ice is 100 km thick. It's not stable on a scale of millennia the way Earth's surface is, but it's certainly stable enough for anything short of a permanent colony. Scientific estimates typically place the average age of the surface in the range of 20 - 180 million years.
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How hot was the rocket exhaust for the landing stage of Apollo 11?
I don't think you'd want to do that, ice that is suddenly heated can shatter rather violently ...
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But .. but ... ZOMG! NOOKYOOLUR! MUSHROOM CLOUDS! RADIOACTIVE WASTE! AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA!!!!!111!!
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Blue Super-Giant Stars!
in Science & Spaceflight
Posted
There is some question as to whether planets can actually form around blue supergiant stars, as the radiation from them is so intense that it tends to vaporize anything that gets remotely close to them. There is also the issue that these stars only live for a few tens of millions of years, and stars tend to get brighter as they age, so the life zone, and indeed the zone where planets can survive, shifts rather rapidly. Assuming that you can get around all of that, the life zone for these sorts of stars is centred more than 200 AU out (which means the star, as seen from there, is probably little more than a point). Even at that distance, UV is going to be a MAJOR issue, because these stars are 25000 to 30000 times brighter than the sun, and far more of their output is above the visual range.