Thought Experiment: A Realistic/Hard SF Galactic Empire

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Magister Militum
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Magister Militum »

Somes J wrote: It also tends to underestimate how quickly the number of stars increases with a larger territory, probably because r^3 scaling just isn't very intuitive.
Somes J wrote:Want to guess how many stars you could reach with a lighthugger within a natural human lifespan? I calculate around seven thousand.
I'm curious as to how you came up with that number? Also, could you explain the first point some more?
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Destructionator »

r^3 is from the volume of a sphere.

The average density of stars in our local part of the galaxy is ~ 3.5 stars / 1000 cubic light years.

If we go 40 light years is the range of our empire. So the territory is a sphere with radius 40, figure its volume: 4/3 * pi * r^3

4/3 * pi * (40 light years)^3

= 270,000 cubic light years

Divide by 1000 then multiply by three to get a rough number of stars: ~ 800


Here's where the cubic scaling comes in - consider 100 light years radius. The volume is now over 4,000,000 cubic light years. Divide 1000 then times 3: in the ballpark of 12,000 stars available.


It looks like Somes J used 80 light years to get ~7000.


You can see here though how rather small increases in radius lead to pretty big increases in the number of stars available. 10x the range means 10*10*10 = 1000x the number of stars within reach.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Somes J »

Magister Militum wrote:I'm curious as to how you came up with that number?
Destructionator sort of beat me to it but:

Within the galactic plain expanding territory around a central point can be treated as a sphere. The volume of a sphere is 4/3TTradius^3. The number of stars within 100 light years is estimated to be 14,600 by NASA.gov. From this it's quite simple to calculate the number of stars within a given radius.
Also, could you explain the first point some more?
I may simply be projecting here, because exponents just aren't very intuitive to me, but I suspect most people tend to naturally think of things as linear.

To get right to a relevant example, let's say we have two interstellar empires. Empire 1 is a sphere with a radius of 50 light years around its central system, and Empire 2 is a sphere with a radius of 100 light years around its central system. How much bigger is Empire 2? My intuitive feeling is that it's around twice as big. But that's wrong - it's 8 times bigger than Empire 1.

Now the interesting thing about this is Empire 2 has twice as much difficulties relating to long communication and travel times, but in exchange it increases its size by a factor of 8. The same applies to the worldbuilding problem of creating a large setting - you get a much larger setting for relatively small increases in communication and travel time. But I suspect most people don't realize this, since they naturally tend to visualize things in terms of linear growth - hence they get a distorted sense of how hard it is to make a big setting that can be gotten around within timespans that don't completely make a modern human's head spin, and they think you need FTL for that.

I think another part of the problem might be that soft SF has its own informal rather arbitrary standards of scale that tend to influence people's conception of how big space is. Consider well-known examples of galactic empires in SF. Offhand I can think of the Star Wars Empire, the Warhammer 40K Imperium, and the GE from the Foundation series, and all of them are usually described as having single to double digit millions of planets. So it looks like we've got an operating informal idea of how big a galaxy-scale setting should be here. But, just going by number of stars, a million system empire could fit within a 500 light year sphere! Since these are heavily Earthlike planet centered polities let's say 1/10 stars has such a planet ... that still fits within a radius of 1000 light years - or .04% of the galaxy's disk! Even knock an order of magnitude off that, you're still looking at less than 1% of the galaxy's disk. I'm not sure about this, but I bet you'll find such arbitrary informal standards extent further down the scale, and in basically all cases the physical area needed for a setting of that size is greatly overestimated. But now I'm getting a bit off-topic.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Blackwing »

Keep in mind that the Star Wars Galaxy, for instance, has relatively few 'colonies' (or at least relatively few places that are inhabited now that weren't inhabited when they were discovered) and a good number of abandoned planets.

So most of the Empire's worlds are worlds that were inhabited (not always by intelligent life) beforehand.
Which goes somewhat more towards justifying it. (The Star Wars Galaxy is also specifically stated not to be our own).

Keep in mind also that while we can reach many stars with a near light-speed vessel the number of habitable planets is considerably less and the number of planets we can start living on the moment we get to them is approximately 0. This is because it took about 1-2 Billion years for earth to become habitable by us and while I fully support the idea that life may arise on other planets and that this life may even be recognisable to us as such, I doubt there's very many near enough to earth to reach and I doubt the ones closest to earth are going to be sufficiently earth-like to support earth life.

So even with fleet of very fast ships, you're still not going to build an 'empire' of habited worlds within the next few million years.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Destructionator »

Meh, if you handwave the habitable world thing I doubt most people would mind anyway, especially if you go with a relatively small percentage (like 1 in 10).
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Somes J »

Blackwing wrote:Keep in mind also that while we can reach many stars with a near light-speed vessel the number of habitable planets is considerably less and the number of planets we can start living on the moment we get to them is approximately 0. This is because it took about 1-2 Billion years for earth to become habitable by us and while I fully support the idea that life may arise on other planets and that this life may even be recognisable to us as such, I doubt there's very many near enough to earth to reach and I doubt the ones closest to earth are going to be sufficiently earth-like to support earth life.
Even if only 1 in every 100 stars has an Earthlike world there would be about 75 within a human lifetime's journey of Earth at near light speeds. 1 in every 100 stars being > 3-4 billion years old and having a world that's roughly Earthlike in mass, composition, conditions of light and heat, and optionally a large moon does not strike me as terribly unreasonable. If more Earthlike worlds than you think is plausible is desirable, you can always do what I did and write it up to terraforming by some long-dead alien race with conveniently human-like environmental needs.

You're right that in a strictly realistic scenario you're probably not going to find any Earthlike worlds in the sense that planets in Star Trek are Earthlike - alien life is almost certainly going to be biochemically incompatible. But if you absolutely must have the classic soft SF conventions you can do what Larry Niven did and invoke panspermia.

There's another side of the coin to this too though - those conventions are both unnecessary and probably unrealistic. A civilization that instead used space habitats could colonize basically any kind of star system - just as long as the necessary raw materials were present.
So even with fleet of very fast ships, you're still not going to build an 'empire' of habited worlds within the next few million years.
With a fleet of very fast ships (.1 c) a million years is sufficient to send one to every star in the entire galaxy. The fleet will encounter many specimens of any planet type that isn't so rare as to be virtually nonexistant many times before it completes that mission; even if only one in a million stars has an Earthlike world it will be more like 5000 years before the first one is found.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Blackwing »

While I generally agree with that, in this case I'd say that if you handwave habitable planets, you might as well handwave FTL as well... And if you don't mind habitable planets getting handwaved, you really shouldn't mind FTL getting handwaved either.

Because the thing that people generally don't realize is that an 'earth-like' planet out there that is completely similar to what earth would be like without having had life on it would have: an unbreathable atmosphere (mostly Carbon-Dioxide, Water vapor, Carbon-Monoxide and Nitrogen), a barren soil (Earth's soil is 'fertile' due to a massive proliferation of microbial life which makes up the largest part of the Carbon- and Nitrogen cycles), no ozone layer (as there's little to no Oxygen to form an Ozone-Oxygen cycle) and toxic water (as large amounts of salts and dissolved Carbon-oxides make it undrinkable in it's natural state).

Getting a world to be habitable is not just a matter of 'instant oxygen, just add plants'. Land plants require fertile soil, which requires a carbon-cycle and a nitrogen-cycle, which requires microbial life which could not survive in 'lifeless earth' soil due to lethal amounts of UV light, radiation and toxic water, which needs water-based microbial life to filter those out first, etc... etc... Getting down to a process which started billions of years ago on earth which took millions of years to complete and for which most of the organisms that started it no longer exist on Earth. So yeah, without 'magic terraforming' or 'magic aliens', habitable planets can't exist.

Even orbital habitats would end up spending much more energy on getting materials from the planet and making them usable than they would ultimately get from then using them. (It might be able to distil and then salinate water to acceptable drinking levels on solar power alone, but getting it from a planet requires atmospheric flight in a dense atmosphere for which solar and even nuclear power are entirely unsuited).

If one's 'interstellar' empire is going to consist of orbital habitats. One is better off looking for asteroids and other low-gravity objects with sufficient resources. And in that case it's really better not to invite all the difficulties of going between the stars and simply concentrating on our own Asteroid Belt, eventually moving on to colonise the Trojans, Greeks and eventually the Kuijper Belt.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Destructionator »

Blackwing wrote:While I generally agree with that, in this case I'd say that if you handwave habitable planets, you might as well handwave FTL as well... And if you don't mind habitable planets getting handwaved, you really shouldn't mind FTL getting handwaved either.
Eh, not everyone is so black and white.
So yeah, without 'magic terraforming' or 'magic aliens', habitable planets can't exist.
Unless they are already there. Just have a kind God.
If one's 'interstellar' empire is going to consist of orbital habitats. One is better off looking for asteroids and other low-gravity objects with sufficient resources.
Indeed, I don't see much of a need to leave home at all.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Somes J »

Blackwing wrote:Because the thing that people generally don't realize is that an 'earth-like' planet out there that is completely similar to what earth would be like without having had life on it would have: <not be a friendly environment>
Yeah, but most of the stuff you talk about are fairly plausible developments once life exists. Photosynthesis is a nice way of getting energy, it releases oxygen as a waste product, stratospheric ozone production is a natural consequence of high atmospheric oxygen, life tends to spread to exploit new niches when they're available... So really the argument is over the plausibility of broadly (primordial)Earthlike starting conditions, life developing, and life following roughly the same developmental route it took on Earth. Which we don't really know.

Also, if you're assuming panspermia, that takes care of 2 and could easily at least partially take care of 3 (if the original seeded bacterium is photosynthetic). That leaves you with arguing over how common planets with broadly Earthlike starting conditions would be (I think it's reasonable to think the answer is actually fairly common - it just needs to be about the right size, composition, and surface temperature), and how likely simple life is to become complex life (we don't know).

Terraforming is obviously going to be hard, and from a pragmatic viewpoint I doubt it'd be worth it (much easier to just build space habitats). From a scientific plausibility standpoint it's still a lot better than FTL though - the problem is the scale the project has to operate at, rather than that the processes are inherently impossible.
Even orbital habitats would end up spending much more energy on getting materials from the planet and making them usable than they would ultimately get from then using them. (It might be able to distil and then salinate water to acceptable drinking levels on solar power alone, but getting it from a planet requires atmospheric flight in a dense atmosphere for which solar and even nuclear power are entirely unsuited).

If one's 'interstellar' empire is going to consist of orbital habitats. One is better off looking for asteroids and other low-gravity objects with sufficient resources.
You won't get any argument from me there!
And in that case it's really better not to invite all the difficulties of going between the stars and simply concentrating on our own Asteroid Belt, eventually moving on to colonise the Trojans, Greeks and eventually the Kuijper Belt.
So your challenge is now to think of reasons people would leave the solar system besides resources and simple lebensraum. You have this problem in a planet-centered setting too. Even a perfectly Earthlike world around Alpha Centauri is in most senses really a much less attractive colonization target than the asteroid belt.

Alternately civilization might have totally filled up the Sol system. Which leaves you with a ridiculously vast setting before you start even considering other stars.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Blackwing »

So your challenge is now to think of reasons people would leave the solar system besides resources and simple lebensraum. You have this problem in a planet-centered setting too. Even a perfectly Earthlike world around Alpha Centauri is in most senses really a much less attractive colonization target than the asteroid belt.
That's why I like soft Sci-Fi. With 'easy' and 'cheap' FTL, mere wanderlust is enough to get people out in the galaxy and with 'magic terraforming' the logistic cost of settling other solar systems is no longer prohibitive.

Essentially with a softer science approach allows you to have the story take place, realistically, further in the galaxy than with hard science.

Especially since things like pan spermia or ancient aliens seeding life on various worlds are just as 'magical' as an FTL drive. Except that you're having the 'magic' done by something other than humans.
And Terraforming is no more scientifically feasible than Cryogenic Suspension or FTL propulsion. You cannot take a planet with earthlike parameters that is actually as old as earth is and make it livable by dropping a few germs.
This is because life on earth has affected it's weather patterns and soil cohesion. Without life on our planet, most of the mountains would have eroded to sand or gravel by now.

And you can't take a planet that is like Earth when life first appeared there either, since that would take a billion years to become habitable.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Somes J »

Blackwing wrote:That's why I like soft Sci-Fi. With 'easy' and 'cheap' FTL, mere wanderlust is enough to get people out in the galaxy
The same can be true without FTL if your civilization is just extremely wealthy.
and with 'magic terraforming' the logistic cost of settling other solar systems is no longer prohibitive.
It's not prohibitive with space habitats either.
Especially since things like pan spermia or ancient aliens seeding life on various worlds are just as 'magical' as an FTL drive.
Dropping a few bacteria on a lot of worlds similar to primordial Earth is easily feasible with scientifically plausible technology, and that's all you really need. Your main problem there is motivation. Perhaps it wasn't even deliberate; it could have just been some microbial spores that hitched a ride on robotic exploration craft.
And Terraforming is no more scientifically feasible than Cryogenic Suspension or FTL propulsion. You cannot take a planet with earthlike parameters that is actually as old as earth is and make it livable by dropping a few germs.
No, I have no problem believing it's a lot harder than that, but the main difficulty is the huge scale of the project (changing the atmosphere, possibly bringing in/removing volatiles, possibly changing landscape, possibly changing the rotation and obliquity etc., maybe even doing things to the crust if you want an Earthlike geology) rather than that any necessary process is physically impossible. It's not like FTL where there are literal physical laws that are violated by doing it. Somebody with sufficiently enormous resources or Von Neumann machines might be able to seriously contemplate it.

I think the real problem with terraforming is why anyone would do it. Anyone advanced enough to be able to do it probably shouldn't need to; instead of undertaking a thousand or million year project to make a lifeless rock Earthlike they could just build space habitats for a tiny fraction of the time and effort.

Maybe it was some God-AI's hobby?

Anyway, that whole tangent is all just to satisfy an unnecessary and unrealistic soft SF convention if you absolutely must follow it. Have people live in space habitats and all the problems associated with habitable worlds disappear.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Blackwing »

Except for the fact that you either need to carry the component parts or the tools required for making a space habitat with you to another solar system. Then you need a way to get people there.

Plus, FTL is not 'physically impossible'. An Alcubierre Drive may be out and even that is not as clear cut as you say, the Alcubierre metric is largely debated, but not even remotely conclusively falsified. For that matter while the Alcubierre metric is theoretical, but is based on General Relativity. The objections raised by Ford and Roman are based on THEIR Quantum inequality theories which, if proven, would have the whole 'amount of mass (not energy) one order larger than that of the universe. Problem is that those theories aren't falsifiable without the kind of tech required to build an Alcubierre drive which may itself be impossible. In other words the Alcubierre Drive is not proven to be physically impossible, it's just that we currently lack the technology to do falsifiable testing on the matter. The Alcubierre metric is, by the way, an exact solution to General Relativity. It's only used as a toy model for a 'warp drive', it's not expected to actually work that way.

But even if we throw the Alcubierre metric to the wayside there's still traversable Wormholes, Krasnikov tubes (and nuts to anyone who says that they violate causality. Anyone who thinks that needs to stop doing math and start looking at the real world) and anything else we might possibly discover in the gap between quantum mechanics and general relativity.

On the whole I don't take as dim a view as 'unnecessary and unrealistic' when thinking about soft science fiction.

Especially since half the shit we're told is impossible is based on the insane troll logic of the kind of mathematical physicists who think that Krasnikov Tubes violate causality and that travelling at relativistic speeds will somehow make time pass slower. This is the same kind of failure to understand the difference between toy model math and the real world that plagued Zeno when he argued that Achilles couldn't outrun a turtle (which is coincidentally exactly the kind of problem Relativity was thought up to explain).

We can't travel faster than c? Well if Relativity is to be believed then relative to some object in the universe somewhere, we already bloody well are.
Plus, if I've shown anything by switching to biology is that you people will accept any manner of scientific absurdity as long as it's not the field of science you've arbitrarily chosen as the one the fiction needs to be true to.

Terraforming a planet to be earth like ALSO, theoretically, requires an amount of energy larger than the amount of energy in the universe. Because when the lifeforms which first started off the process to making earth liveable for us first appeared Earth had a much different position in the solar system. Life which exists on modern day earth, even microbial life, would DIE on that earth and the life that lived on that earth has long since died on our own, we have no idea what it was like, other than what we can glean from the effect it had on our planet.
Humans and anything alive today would not survive on an earth like the ones the dinosaurs lived on, let alone a planet not having started a process to life under the exact same conditions our has.

Likewise, Space habitats: No. Not for more than a couple dozen people without putting whatever they're orbitting our of whack (plus: Where are they going to get their basic living needs? Earth has a gigantic, self-correcting life support system. Humans don't make up even 1% of that system and even so we're fucking that up to the point that it's starting to look like we might not be able to live here properly all that much longer).

Personally I applaud those who like to believe that Achilles can out run the tortoise and where Homer can take a bus. Even if their proposed solution for this is to put the tortoise on a leash and Homer on nuclear powered rollerskates. It's science FICTION and no matter what the nay-sayers claim, I don't want realism getting in the way of my imagination when I read fiction, I have newspapers for that shit.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Destructionator »

I think I lost 30 IQ points after reading your last post. You don't have the first clue what you're talking about.

btw give me a lever and a place to stand and I'll move the world.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Somes J »

Blackwing wrote:Except for the fact that you either need to carry the component parts or the tools required for making a space habitat with you to another solar system. Then you need a way to get people there.
Much the same is true for colonizing even a perfectly Earthlike world in another solar system, unless you plan to have the colony start out literally from the Stone Age; you have to bring all the materials to restart a technologically advanced industrial civilization.
Terraforming a planet to be earth like ALSO, theoretically, requires an amount of energy larger than the amount of energy in the universe. Because when the lifeforms which first started off the process to making earth liveable for us first appeared Earth had a much different position in the solar system.
It's not that Earth had a different position in the solar system, it's that the sun was about 30% dimmer, and this would not require more energy than exists in the universe to make up (this is rather trivially obvious as it represents a 30% difference in luminousity of a single middlingly large star of which the universe has many trillions). It would require 5.8 X 10^16 watts (going off Wikipedia, the total energy budget for modern Earth is 1.74 X 10^17 watts). If we wished to make up the difference with artificial fusion powered lamps, we would have to burn several hundred kilograms of hydrogen per second. Or we could focus more of the sunlight the sun is already producing on the planet with a huge mirror system. Or we could solve it the way real life Earth probably did with more greenhouse gasses (CO2 concentrations necessary to solve the faint sun paradox would be fatal to humans, but there are alternative greenhouse gases much more potent than CO2). Or if we really wanted to go all out we could move the planet to an orbit where sunlight would be at more Earthlike levels - even fully deorbiting the Earth (completely eliminating its orbital velocity) would only take the equivalent of 2.5 month's worth of energy production from a Dyson Sphere, and the necessary orbital adjustment to increase sunlight by 30% is much less. That's a crazy amount of energy by our standards, of course, but to a highly advanced interstellar society thousands or millions of years ahead of us ... maybe not so much.

I'm not even going to touch the stuff about relativity, that stuff's way over my head but I'm pretty skeptical of a claim that relativistic time dilation does not exist.
Humans and anything alive today would not survive on an earth like the ones the dinosaurs lived on
Why? The carbon dioxide was a bit high but well within OSHA limits for healthy adults - maybe children might have a problem with it but I kind of doubt it - there were already mammals around then and I doubt they were all that different from us physiologically.
Likewise, Space habitats: No. Not for more than a couple dozen people without putting whatever they're orbitting our of whack (plus: Where are they going to get their basic living needs? Earth has a gigantic, self-correcting life support system. Humans don't make up even 1% of that system and even so we're fucking that up to the point that it's starting to look like we might not be able to live here properly all that much longer).
I see no reason to think a self-sustaining habitat is anything but a matter of knowledge and practice. It doesn't have to look much like a natural ecosystem either; comparing it to Earth's present ecosystem strikes me a little as like calculating the amount of range a forager tribe would need and concluding supporting giant cities with agriculture would never work: one system is engineered specifically to support humans, the other isn't.
It's science FICTION and no matter what the nay-sayers claim, I don't want realism getting in the way of my imagination when I read fiction, I have newspapers for that shit.
I'm not completely without sympathy to this viewpoint, but one of my big problems is I find the opposite is often true ... the arbitrariness of a magic universe is often used to let people be unimaginative: to serve up the past or the present with the serial numbers filed off instead of the future. Take America or 19th century Britain or whatever, add lasers, put it IN SPACE, and use magic to handwave away the numerous square pegs for round holes that such a thing leaves you with. You can't do that if you're trying to keep things scientifically plausible, you have to actually face up to the ways in which you're dealing with a totally novel environment that will demand novel solutions and adaptations. And then I get to read something that actually feels like the future instead of the present or the past with the serial numbers filed off. I find such a lack of imagination a far bigger turn-off than any limitations hardness imposes; every time I see somebody doing a blatant file the serial numbers off allegory of 15th or 19th* century colonialism only instead of America it's Pandora I gag a little.

* Actually market colonialism would be somewhat novel and therefore cool, and for a bonus actually makes some small amount of sense in a halfway realistic interstellar setting (think some politician on Alpha Centauri deciding create jobs by dumping horrendously overpriced cheap goods on Earth, thus creating demand and keeping the factories open). But no, it's always resource colonialism, which makes no sense whatsoever in such a setting, with magic used to ram the square peg into the round hole.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Dakarne »

A few things about this 'magic' environment you keep going on about;
  1. To disregard things which are 'magic', would disregard, oh... say... the entire fantasy genre. Yes, the whole lot of it. Everything ranging from Malazan Book of the Fallen, through to Discworld, passing by Tolkien, dotting off at everything Neil Gaiman has ever written, checking off Narnia, and swinging on back to annihilate the Harry Potter novels specifically because they all involve magic because they're works of fantasy. They're also all pretty damn good.
  2. To disregard things which are allegory because they make you gag a little is completely unrelated to the idea of hard science fiction, and to be honest? Most of Avatar was pretty much hard science fiction in many places, nothing which disregarded the laws of physics, though there were certainly many things that were implausible such as the whole neural network thing on Pandora. The simple fact of the matter is that this seems to be a tangent against allegorical works and your assumption is that hard science fiction would change that, which simply is not true.
  3. In addition to the above, the simple fact of the matter is that allegorical works aren't necessarily bad. The Star Wars trilogy was specifically built to be a story of mythological orientation, about a hero's journey from simple, headstrong youth to becoming a great and noble warrior-mage who battles evil. This is highly allegorical of a great number of hero myths, with mythic individuals such as Heracles and Perseus often fulfilling the same roles.
  4. The idea that working from the perspective of hard science forces the writer to be original only really works a certain number of times, because you start to run out of things to do with hard science. After a while, everyone starts just using the same solutions within hard science and then someone has the original idea of disregarding reality (which, for fiction, is often kind of the point) and then going on to write something featuring a thief who's caught up by a wizard but ultimately becomes the wizard's apprentice. Though a story that has been done before in its premise, the originality of the characters, elements of the plot, and extremely brilliant storytelling nets it dozens of awards and acclaim.
Because at the end of the line, that's what writing ought to come down to. It's not whether you're strictly using hard science or strictly using magic as to rule out either one would be an act of equal stupidity, but it's about whether your characters, storytelling, and plot are decent. They don't even have to be wholly original, and to be quite honest; they won't be. You will insert elements of things you know from your life experiences, characterisation traits from people you know, little occasional joking references to other works, and maybe the plot would be inspired by two different ideas you'd seen beforehand and you thought 'maybe it'd be cool to combine them'.

The simple fact of the matter is that using hard science for the reasons you describe it is both inaccurate and unnecessary. You certainly can use it, but the simple fact of the matter is that it's not the automatic fix-all-problems-with-fiction deus ex machina you claim it to be.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Destructionator »

Blackwing wrote:For that matter while the Alcubierre metric is theoretical, but is based on General Relativity.
This is where my Archimedes quote comes in. You can do the math, but good luck finding a suitable stick and place to stand to actually do it.
and nuts to anyone who says that they violate causality. Anyone who thinks that needs to stop doing math and start looking at the real world
Damn those physicists and their pesky physics! :argh:

btw, this is another example of your double standard. When the math says what you want to hear, you stick to it and ignore everything else. If it doesn't, it's just stupid math with no connection to the real world.
Especially since half the shit we're told is impossible is based on the insane troll logic of the kind of mathematical physicists who think that Krasnikov Tubes violate causality and that travelling at relativistic speeds will somehow make time pass slower.
Time dilation has been experimentally proven; it has been directly observed on several occasions.
We can't travel faster than c? Well if Relativity is to be believed then relative to some object in the universe somewhere, we already bloody well are.
It says nothing of the sort.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Somes J »

Dakarne wrote:<snip>
I don't have a problem with fantasy or allegorical fiction. I don't even have a big problem with a lot of the sci fi I complain about in isolation. My problem is with the lack of imagination and originality I percieve in the genre. You want to make it soft as oatmeal, fine, but I read SF because I want my imagination stimulated by novel ideas and worlds, and Generic Corporate Badguys and Space Blackwater going to Pandora to shoot up blue Native-American stereotypes and steal their gold oil magic space rocks really doesn't hit the spot for me.

No, MOAR SCIENCE doesn't necessarily make this any better, but... eh, I'll admit I'm probably generalizing a bit from personal experience. My own sci fi became less generic the harder I made it, because I was forced to deal with the fact that the assumptions I'd picked up from other SF by osmosis didn't make sense in a realistic universe. It's not necessary, but I found having a pre-existing consistent rule-set that would give the finger to standard conventions in lots of places to be a useful crutch.

Yes, I suppose if everybody started doing it pretty soon we'd be back where we started, with one set of tired tropes replacing another. That's just human nature; we're lazy imitative creatures.

Honestly though, it's really something that springs to my mind when people start talking about how hard SF is so restrictive and unimaginative. As a defense of a genre that I find to often have serious tunnel vision on FTL starships and BFGs while everything else in society stays exactly the same I find "stop trying to destroy my dreams with your small-minded realism!" rather ironic.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Somes J »

Destructionator wrote:btw, this is another example of your double standard. When the math says what you want to hear, you stick to it and ignore everything else. If it doesn't, it's just stupid math with no connection to the real world.
It also sounds like he's fallen into a classic example of the Middle World Problem. The idea that a heavy concrete block and a feather would fall at the same rate, or that it takes just as much energy to slow down as to speed up, also sound intuitively crazy. We evolved in an environment where those things weren't issues, so they aren't intuitive. Ditto for relativity.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Siege »

If I may be so bold as to inject something -- I don't think you folks are actually disagreeing (much). More like you're talking past each other.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Blackwing »

Somes J wrote: It also sounds like he's fallen into a classic example of the Middle World Problem. The idea that a heavy concrete block and a feather would fall at the same rate
Except that in the real world they don't, on every day earth, a heavy concrete block and a feather don't. Because a feather has a specific shape that makes it fall slower, this is due to the fact that they are affected by atmospheric conditions and buoyancy.

In vacuum, they do, but people get confused because they've SEEN feathers and bricks (or other heavy objects) fall, outside of a vacuum, at different rates.
This is why on earth two objects of different weights but the same shape (when showing this to schoolchildren they use spheres to ensure that one of the objects does not spin in a way that increases drag and muck up the 'experiment') tend to fall at the same rate, but two objects with vastly different shapes and the same weight (like a parachutist without and with his chute deployed) do not.

Which is why we never say 'a heavy concrete block and a father fall at the same rate'. We add 'in a vacuum' before or after that because otherwise we're liars. It's not a complete lie to say that they fall at the same rate, because under the right circumstances, they do. But it's a better example for my case than yours, because some physicist claiming they fall at the same rate without adding the vacuum part is confusing the theoretical math (which ignores buoyancy because it's not part of the basic formula) with observable evidence in a real-world situation (in which buoyancy will not let itself be ignored).
or that it takes just as much energy to slow down as to speed up
This one is a better example. People get intuitive dissonance on this because of things they experience in real life. In order to stop a moving car (or bicycle) you stop putting energy in it, so you get the impression that slowing down doesn't take energy. But it does. The only difference between speeding up and slowing down on earth and in space being where the energy comes from (a spacecraft in a vacuum needs to provide it's own energy to stop, while a racecar on earth stops due to energy provided by the earth).

That said observationally it currently does take less energy to stop in space than it does to speed up. This is because we use reaction mass for propulsion in spacecraft and thus the more you speed up, the lower the weight of your craft will be and so you will need to use less energy over all to slow down than you did to speed up (the amount of energy per unit of weight stays the same though).
btw, this is another example of your double standard. When the math says what you want to hear, you stick to it and ignore everything else. If it doesn't, it's just stupid math with no connection to the real world.
You're confusing my rebuttal to your point based on your beliefs with my own point based on my beliefs. The reason why I know that the Alcubierre metric probably can't be used for FTL has little to do with some convoluted calculation which is just as 'not even wrong' as the Alcubierre metric itself and more to do with the fact that an 'engine' based on the principle would require MATERIALS that do not, currently, seem to exist. I never said, after all, that an Alcubierre metric will produce an FTL drive, I only said that it's not as prohibitted by physics as you seem to think it is.

The bias also goes both ways, except in this case I am functionally more reasonable than you are. The Alcubierre metric and it's opposition are both based on purely mathematical thinking along the line of 'if these assumptions are true, this conclusion is also true'. The difference between our biasses then is that I say 'well if this metric and turns out to be true, FTL is not impossible' and you say 'but I don't want FTL to be possible and this theory says it isn't, so FTL is impossible'. Based on theoretical mathematics I'm giving the matter a 'maybe', based on equally theoretical mathematics you're giving it a solid 'no'.
Time dilation has been experimentally proven; it has been directly observed on several occasions.
Well yes. Time dilation is an OBSERVATIONAL PHENOMENON. A very basic experiment: A lightning bolt hits. You are an undetermined distance away, I am half that distance away. At what time is there light and at which time is there sound? In reality, both originate the instant the bolt hits, but observationally, both events occur after twice as much time for you as it does for me. Does that mean that I am twice as far ahead in time than you are? No.

Because Time Dilation is an observational thing and while the light and sound are moving at different speeds relative to each other, despite originating at the same point. Assuming that Time Dilation is a physical thing (i.e. Because we observe events occurring at different times, we must therefore be moving through time at different rates) is wrong.

Similarly the Hafele-Keating experiment and successive verifications haven't proven, despite this being the accepted conclusion, that time itself moves differently, only that measuring devices measure time differently, when under the influence of altered gravity and relative velocity. In order to verify Time Dilation as actually affecting time itself you'd need a clock that is not affected by gravitational or kinematic forces at all. Which requires Exotic Matter, which makes the whole thing academical any way.
It says nothing of the sort.
Yes it does. (if you can do it, so can I. Now accept my saying 'yes it does' as true without arguments, the same way you expect me to accept you saying 'No it doesn't' without argument.)
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Destructionator »

Blackwing wrote:This is why on earth two objects of different weights but the same shape (when showing this to schoolchildren they use spheres to ensure that one of the objects does not spin in a way that increases drag and muck up the 'experiment') tend to fall at the same rate
Not actually true. The heavier one will push air aside more easily and thus fall faster. Contrast a paper ball with a rubber ball.
People get intuitive dissonance on this because of things they experience in real life. In order to stop a moving car (or bicycle) you stop putting energy in it,
To stop it, you actively take energy out of it - by hitting the brakes.
Well yes. Time dilation is an OBSERVATIONAL PHENOMENON. A very basic experiment: A lightning bolt hits. You are an undetermined distance away, I am half that distance away. At what time is there light and at which time is there sound?
That has nothing whatsoever to do with time dilation, that's just plain old speed.
Similarly the Hafele-Keating experiment and successive verifications haven't proven, despite this being the accepted conclusion, that time itself moves differently, only that measuring devices measure time differently, when under the influence of altered gravity and relative velocity.
Everything that's dependent on time was measured differently, to the same degree, from speed of vibrations to the time it takes radioactive stuff to decay. That means time changed by any useful definition.



We don't even disagree all that much on a few of the main thrusts, but you keep making these confident statements that are just horribly wrong. Soon enough I'll have to stop posting to keep you from digging even deeper.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Blackwing »

Nah.

Destructionator, in your last few posts at least, you keep telling me I'm wrong, you keep failing to say why I'm wrong.

Either your grasp of physics is so far beyond mine that I am indeed dead wrong to such an extent to where it's no longer possible to correct my mistakes or you've stopped being able to actually find fault in what I say and are just disagreeing on principle.

For instance:
The heavier one will push air aside more easily and thus fall faster. Contrast a paper ball with a rubber ball.
Is functionally wrong itself. I mentioned showing it to school children because schools can't afford vacuum tubes. The point being that they usually use metal balls both of which are heavy enough to ignore most side-ways air currents and pockets of rising hot air and such (but still of different weights). A paper ball is porous to the core (also, I've sorta just started suspecting here that you just tried this for yourself by crumpling a sheet of paper into a ball or something, which isn't a perfect sphere to say the least), while a rubber ball is malleable. They do not have the same shape while falling.
To stop it, you actively take energy out of it - by hitting the brakes.
Or you don't. In which case friction will still cause it to stop eventually. Point being that 'we' ('we' being the average non-physicist) don't usually associate braking with 'putting in energy'. Even if it is.
That has nothing whatsoever to do with time dilation, that's just plain old speed.
Functionally it does have something to do with it. We measure time by observing events. I see the light twice as fast as you do, but I also hear the sound twice as fast as you do. This despite the fact that the light and the sound are moving at different velocities relative to us. Time dilation dictates that since light moves at the speed of light and sound moves at a good number of orders of magnitude slower than that, the sound should move through time slower. So if I 'observe' the sound twice as fast as you do, I'm moving twice as fast through time than you are, relative to both of them.

It was a clumsy attempt at re-framing the Triplet/Quadruplet variation of the Twin paradox.
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Somes J »

Siege wrote:If I may be so bold as to inject something -- I don't think you folks are actually disagreeing (much). More like you're talking past each other.
I think you're right. When I was reading Dakarne's post, for instance, I didn't actually strongly disagree with anything.
Blackwing wrote:Except that in the real world they don't, on every day earth, a heavy concrete block and a feather don't. Because a feather has a specific shape that makes it fall slower, this is due to the fact that they are affected by atmospheric conditions and buoyancy.
That's sort of my point: our intuitive assumptions are all based on living in a strong gravity field and an ocean of gas, because that's the environment we evolved in. Take us out of that environment - into a freefall vacuum - and our intuitive assumptions are all wrong; a description of reality intuitively sounds like crazy talk.

Same thing with time. The idea of time as relative intuitively sounds like crazy talk, but that doesn't actually tell you anything except that your brain is wired for an environment where time does not act that way on a perceptable level.

I say this because your objections to things like time dilation and wormholes causing casualty violations sound very much like an appeal to personal intuitive incredulity. It must be just silly math because it's just so obvious the world doesn't actually work that way ... just like it's obvious that if I throw a ball it will lose speed and fall, not continue moving away in a straight line at the same speed indefinitely!
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Destructionator »

Blackwing wrote:Destructionator, in your last few posts at least, you keep telling me I'm wrong, you keep failing to say why I'm wrong.
You're just that far away from reality. Most the definitions you claim are just factually wrong. You can't just make stuff up and expect me to do into great detail for every little thing.
The heavier one will push air aside more easily and thus fall faster. Contrast a paper ball with a rubber ball.
Is functionally wrong itself.
What the hell does that even mean? It's a simple fact that heavier things fly through air better than lighter things, all other things being equal. It's just inertia, and seen quite often in every day life. Even been on a bike ride with someone bigger than you? Ever notice how you have to pedal to keep up with him downhill? (assume you both have roughly equal bikes and posture)

It is ultimately caused by the same reasons that things fall equally in vacuum, regardless of weight. Gravity puts in a force per mass. An equal force is required to overcome air regardless of mass given a particular shape. The heavier object gets more force, thus pushes through air better.
Or you don't. In which case friction will still cause it to stop eventually. Point being that 'we' ('we' being the average non-physicist) don't usually associate braking with 'putting in energy'. Even if it is.
Actually, you are not putting in energy to slow down. You are taking energy out. (What Somes J is saying is the energy out will be equal to energy in, which anyone with half the knowledge you pretend to have would have easily recognized.)

This is common knowledge too. Something comes to a stop and the brakes get hot. Eventually they have to be replaced due to the wear involved.
Time dilation dictates that since light moves at the speed of light and sound moves at a good number of orders of magnitude slower than that, the sound should move through time slower.
No it doesn't. From Wikipedia, this one sentence explains it reasonably well: "It can be illustrated by supposing that two observers are in motion relative to each other, or differently situated with regard to nearby gravitational masses. They each carry a clock of identical construction and function. Then, the point of view of each observer will generally be that the other observer's clock is in error (has changed its rate)."

Note the very important thing in the first sentence two observers are in motion relative to each other. Not that the thing they saw was in motion, that the observers are moving.

They weren't in your situation, so it doesn't apply there. Your situation is trivial: omfg it takes double the time to cross double the distance at the same speed SAY IT AIN'T SO
It was a clumsy attempt at re-framing the Triplet/Quadruplet variation of the Twin paradox.
It's really unfortunate that it's called a "paradox", since it isn't one at all; it makes perfect sense if you consider the whole picture from each twin's perspective.

In the classic setup, the twin away from home comes home younger than the one who stayed home. But if it is all relative, can't we just flip the situation and expect the same result from the away person's perspective?

Well, yes you can. It only looks like you can't because you made an error when flipping the situation. Time isn't the only thing that changes when you're moving. Wikipedia explains: http://en.wikipedia.org/wiki/Twin_paradox

An interesting fact about the length contraction is it means you can actually cross the universe in your lifetime, if you can get up to enough speed: http://www.strange-loops.com/scilightspeedtravel.html
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Re: Thought Experiment: A Realistic/Hard SF Galactic Empire

Post by Blackwing »

No it doesn't. From Wikipedia, this one sentence explains it reasonably well: "It can be illustrated by supposing that two observers are in motion relative to each other, or differently situated with regard to nearby gravitational masses. They each carry a clock of identical construction and function. Then, the point of view of each observer will generally be that the other observer's clock is in error (has changed its rate)."

Note the very important thing in the first sentence two observers are in motion relative to each other. Not that the thing they saw was in motion, that the observers are moving.

They weren't in your situation, so it doesn't apply there. Your situation is trivial: omfg it takes double the time to cross double the distance at the same speed SAY IT AIN'T SO
This was actually my point: Time Dilation has to do with observers. When two observers aren't moving relative to each other and they observe two seperate events through media that travels at different speeds (relativistic for light and non-relativistic for sound) time dilation does not occur. Because the observers are not in motion relative to each other, despite moving at different speeds relative to the two media.

It was supposed to be a Toy Model analogy for a solution to the Twin 'Paradox' that I came up with a while back. But I misremembered a few steps:

There should be a third observer where I am, who's looking in your direction. It should be pitch black so that the only light in this experiment is that from the lightning. The sound doesn't matter. And we're all wearing blinds so we can only see light when it hits our eyes directly. And there are two flashes.

Now when the flash happens, I see it at time '1'. You see it at '2'. And the last observer sees it at '3', when you reflect the light back into his eyes. And the second flash, which occurs at '2', is seen by me at '3', by you at '4' and but the last observer at '5'.

Despite standing in the same spot as me, the other observer sees the Events after three times as much times passes compared to me. I'm the 'staying' twin. The other observer is the 'travelling' twin. Just because I observe the flases three times as fast as the person standing next to me, that doesn't mean that I'm moving faster through time. It just means that the light needs to travel less far to get to me. The same is true for time dilation, in that if you substitute 'time' for the light in that the light doesn't travel any faster for me than it does for the third observer, as 'you' in the experiment can attest (you see us illuminated by the light at the same time) But because the light takes longer to reach the third observer, he will claim the flashes happened three times later than I do.
If we were all moving (at the same speed relative to each other), there would be no difference in when each of us sees the flash.
But if only you are moving and you're moving away from us at a speed where, when the first flash reaches me, you're twice as far away from it as I am, the third observer sees the second flash even later, thus he assumes the first flash happens at '3', but the second flash, for him might happen as late as '7'. He's still not moving at a different rate through time than I am though.

But that may be flawed, I dunno.

Personally, I hold the theory that the results of the Hafele-Keating experiment (and subsequent verifications) does prove conclusively that everything by which we measure the passage of time is affected by 'Time Dilation'. But that means that the number of 'instances observed' is lower. Essentially Time Dilation doesn't mean you're moving through time at a different rate, it means that you're experiencing time at a different rate. Outward observers can still see you existing in their time at their rate of time, after all.
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