Do you prefer real-world settings or "science fantasy"?

[Junghalli]

'A bit' meaning a factor of several ten thousand or so at the lower end. Sorry, a trip from one star to another taking several millenia does NOT fit my definition of actually 'roaming' the stars.

That would only be the case if we're restricted to more or less present technology. Thankfully, there are pretty plausible theoretical propulsion schemes that could do much better. Laser lightsails for instance.

None as advanced as we are. Otherwise we'd have heard of them by now, as per hard SciFi.

That depends, you could think up reasons why the galaxy might have advanced civilizations but they haven't completely colonized it billions of years ago. At any rate, you might as well say the same thing about most soft SF universes with aliens. Most of them basically just ignore the Fermi Paradox, and the Fermi Paradox is much worse in a universe with fast and easy FTL.

I seriously doubt there's 10,000 star systems PERIOD within 100 lightyears of our system leave alone 10,000 ones that actually have habitable planets. Or planets PERIOD.

The estimate is straight from from the Goddard Space Flight Center's website (14,600 stars within 100 light years).

A hard SciFi society that actually WOULD make use of all a system's resources wouldn't NEED to go interstellar.

Yeah. Because there's totally no adverse emotions among the public towards cloning that would prevent such a thing and where did you get the 1000 ton figure from?

I'll address these in reverse order. Second points: it does not matter in the long run. Even orders of magnitude greater resource commitments are a trifle before the resources of our solar system. The asteroid belt has an estimated mass of 3-3.6 X 10^18 tons (ref). Even if only .1% of that material is usable for construction that's enough that consuming a mere .1% of the resources of the asteroid belt (or .0001% its total material) would give you enough material to build 10,000 ships massing 300 million tons each. Next point is energy. The sun's total output is 3.86 X 10^26 watts (ref). A laser lightsail produces thrust on the order of 1 newton per 6.7 gigawatts of laser power (ref). A 1000 ton ship accelerating at 1 G therefore requires a laser power of 6.57 X 10^16 watts. 10,000 such ships require 6.57 X 10^20 watts. That is .00017% of the sun's energy. Even if the vessels massed 1 million tons each we're talking 1/5 of 1% of the sun's energy. The solar collector to collect this energy if stationed at .125 AU would require 7.5 X 10^13 tons of material to construct assuming each square meter of panel masses 10 kg. That is 2.5% of the resources of the asteroid belt using my initial estimate, and the facility can be re-used for more ships or re-tasked to generate power for other purposes afterward (granted, I ignored the mass of the actual lasers, mirror, and cooling systems, but on the other hand I used a ridiculously lowball estimate of how much of the asteroid belt's mass is actually usable and a rather highball estimate of the required mass for the panels). That is to send all 10,000 ships out simultaneously. With a 1 G acceleration you could reach high c-fractional speeds within a few years, so that sending them out in several smaller lots would be perfectly fine if we with to meet the target of 10,000 stars colonized within a century.

Whew, hope I didn't screw up any of that math!

Of course, this all assumes that for some reason we have the goal of colonizing 10,000 stars within a century. You don't need that kind of stupendous growth rate to be competitive with a typical soft SF star empire. The Federation in ST: TOS, for instance, had what, a few thousand settled systems after twice as long?

First point: a society that is vigorously exploiting the resources of its solar system does not need to have to send expeditions to other stars in order for that to happen. It only has to want to, for the same reason we want to send astronauts to the moon and Mars. As the above figures demonstrate, a tiny percentage of the resources of such a civilization would be enough for a very vigorous exploration program (I think most of us would consider even dozens of expeditions a year fairly vigorous, and that's small potatoes compared to the numbers above).

Which is why Africa is NOT an AIDS-ridden hellhole, the Middle East is NOT largely stuck in the Dark Ages other than where the technology they need to kill each other more efficiently is concerned, and there's totally nobody in the US trying to force Biblical law on anybody. Oh wait.

I never said a realistic universe couldn't have unpleasant aspects. That said, AI more efficient than the human brain is extremely plausible, and once you have it you don't really have an excuse for having any of your citizens living in poverty in the long term besides being strapped for resources (absurd for a civilization with access to the resources of a solar system on top of that unless they're ridiculously numerous), or being monumentally callous or actively sadistic.

Physically impossible if we accept the lightspeed limit.

Why?

[adam_grif]

They wouldn't KNOW that without spending a couple thousand years finding that out, if that. And without FTL, it isn't, at least not where threats from other species is concerned.

Lolwut.

Relativistic Kill Vehicles, Berserkers.

The galaxy may well be a dangerous place.

[Junghalli]

The general point still has merit though. Interstellar war in a hard SF universe is probably MAD ... unless you assume one side is interstellar nomads who have no important fixed home bases for the other side to blow up. So Beserkers could be a definite worry.

[adam_grif]

They need not be going 0.99999999999999999 C in order to be dangerous. The .7c that the venture star gains still contains a tremendous amount of energy, and non-trivial to intercept. If the cargo primarily consisted of independent segments that separate and steer themselves into planets, orbitals and so on, they could probably still get a significant fraction of a solar population.

I'm not saying they're the be all end all interstellar weapon that people sometimes think they are, but calling them worthless because they're not totally effective smacks of hyperbole. I'll look up this thread though and give it a read.

[adam_grif]

Oh and just a tangentially (spellecheck insists that's a word, but I don't think it's the one I was trying to spell...) related thing:

If we can't feasibly get an RKV to near lightspeed and keep it there without investing the majority of the solar output of a star and mind boggling infrastructure, doesn't that also mean that interstellar travel at any interesting speed is also impossible, since they need to carry as much energy as it's launched with in order to slow down?

[Junghalli]

If we can't feasibly get an RKV to near lightspeed and keep it there without investing the majority of the solar output of a star and mind boggling infrastructure, doesn't that also mean that interstellar travel at any interesting speed is also impossible, since they need to carry as much energy as it's launched with in order to slow down?

You can slow down by braking against the interstellar medium with a magsail. Shove a big magnetic scoop in front of you while travelling at a significant fraction of c and it essentially becomes a rocket with the interstellar medium as propellant and an exhaust velocity equal to your forward velocity.

The Forward lightsail also had a system where one of the lightsails would be detached and used as a mirror to reflect the laser (fired from back home) back at the ship to slow it down.

[adam_grif]

A laser fired from earth used to brake the ship? Uhh, wouldn't the bloom on that make it useless at any real distance?

Also, braking at an interstellar medium will presumably only work when you're going at particularly high velocities. Won't braking become less and less effective the more you do it, eventually hitting some kind of inverse terminal velocity when braking is no longer effective by that means? If so, what is that?

[Junghalli]

A laser fired from earth used to brake the ship? Uhh, wouldn't the bloom on that make it useless at any real distance?

That's what the 1000 kilometer wide lens is for.

Also, braking at an interstellar medium will presumably only work when you're going at particularly high velocities. Won't braking become less and less effective the more you do it, eventually hitting some kind of inverse terminal velocity when braking is no longer effective by that means? If so, what is that?

Yes, it does become less effective as your speed reduces. I'm not sure what the function is. I'm not sure at what point it becomes totally ineffective. Assuming you were headed toward a star, I would guess the point at which the star's solar wind starts to move the ship in the opposite direction instead of just reducing its foreward velocity.

I imagine if it's a problem you could use a conventional rocket or maybe a solar sail for the final phase of decelleration.

[adam_grif]

I'm not entirely convinced you could brake on an interstellar medium for long enough to really make relativistic flight with high mass craft reasonable. If someone could do the calcs that'd be grand, but don't bussard scoops only start being able to scoop shit up at a good fraction of C (meaning braking on interstellar hydrogen via this wouldn't work below that speed either)? Are mag sails any better in this respect?

[Darth Hoth]

I see you aren't thinking with habitats.

A solar system can be a big place by itself to human sensibilities, but on any cosmic scale it is utterly insignificant. Scale is relative. It is also a matter of the audience's preconceptions and expectations. If they are fed up on interstellar alliances and galactic empires a realistic polity will inevitably look small.

The other edge of this sword is it prevents you from introducing technologies that may create problems down the line, thus saving you from being stuck between a rewrite and a gaping plot hole later on.

For example, Star Trek IV used time travel to kick off some fun antics, and was a great film. But now, we find ourselves wondering in the sequels why they can't just slingshot around the sun again to solve the new problem. There are no really satisfactory answers - we're left just saying "it was a fun film, but don't think too much about it".

Now, I like ST4 a great deal and would be sad if they decided against making it for this reason, but it is an inconsistency nonetheless.

The time travel example was deliberate, since there are such clear examples of it working both of these ways. On the one hand, it can create extremely interesting stories and concepts; on the other, as it is usually used, it is generally tacked onto existing universes and abused as a cop-out/reset button (Star Trek and Stargate are both particularly egregious offenders, here). Any technology or plot device a writer chooses to introduce should naturally be thought through, with its implications considered beforehand. A lot of soft sci-fi fails at this, but then a lot of purportedly hard stuff also does. It is more a symptom of writer laziness than the impossible technologies themselves; you can include magic and call it such in a setting and still not have it suffer much for it, as long as you do it logically with a consistent set of rules. It just means more work for you to elaborate on the pseudophysics of Technobabblium Item X.

Not really. Like I said, you can easily have interstellar war, politics, what have you in a no-FTL universe. You just need to drop the assumption that future people have the same mayfly planning horizons as ourselves. Two hard SF civilizations that control substantial portions of the galaxy clashing could give you scale and scope to make universes like Star Wars and WH40K look small, for instance. Quintillion-strong fleets of robot and upload crewed warships tearing through the galaxy, executing strategems and manuevers that may take thousands of years, consuming the resources of entire solar systems to swell their numbers, the entire war dragging on for hundreds of thousands of years as the tides of battle flow over the spiral arms - you want epic, you can have it.

I generally avoid writing nonhuman viewpoint characters, for the simple reason that their mindset will logically be completely alien from that of humans like myself. First, because I do not have confidence in myself as being able to write such characters in a convincing manner (it is hard enough to think in the way someone from a radically divergent culture here on Earth would - how much more so, then, something that does not even share my kingdom?). Second, because even if I am successful, a genuinely alien character will be very difficult for (most of?) my audience to empathise with, thereby running a huge risk of making my story unappealing. Overall I would say that in most cases I find it vastly easier (and less prone to screw-ups) to change the physics of a setting than the species/mindset of the protagonists.

Yes, but on the other hand it may lead you to interesting things that you wouldn't have gotten with soft SF because the issues that create them can be just handwaved away. Like the "follow two upload copies of one person and watch their personalities diverge as they have different experiences" idea, which would probably never have occurred to me in the context of a soft SF setting because it's easier just to postulate mile-long FTL ships crewed by meatbags and handwave away all the difficulties, whereas with hard SF you start thinking a lot harder about "how can I shave down mass on my lighthugger so the energy requirements are less obscene, oh yeah, I can probably reduce it by a couple of orders of magnitude if it carries uploads instead of living humans".

I can see the point you are making, but in the end that is not really a limitation on soft sci-fi, merely on writer imagination. You can have every kind of uploading, "super intelligence", nano-gizmos or other AI-wankery in a soft setting as well (say, the Culture or OA as examples) and explore the realistic consequences of those things in such environs. The breaking point is really that in a soft story you can have any realistic story element and any unrealistic one, while in a "hard" such you are restricted to the realistic ones only. Therefore by definition it is more restricted; soft sci-fi only grants more options, but removes none.

Yeah, but unless the fact that these things are similar is vital to your setting I don't think that's necessarily a bad thing. I mean, if you're dead set on writing the modern world with starships and lasers I guess that's cool, but I question how many authors really write that way because they couldn't do it any other way and how many do it just because it's easier to follow in the path everyone else has already trodden. Maybe as an author it wouldn't be a bad idea to try to think of the ways in which the future might logically be different as opportunities to be embraced rather than problems to be desperately handwaved away, and see if that approach really does totally break your vision or if that's just fear and laziness speaking. I know my personal work became much less of a generic unremarkable setting after I started doing that.

Certainly - if that is the story you want to tell. But it may not be, and all stories do not fit into a given format (say, if you wanted to write an epic althist global war on Earth that lasted for years you would need to set it before nuclear weapons became commonplace). Building up a science-fiction universe it is usually necessary to adapt the technology so as not to make the plot impossible. (People do this with soft sci-fi as well, obviously.)

[Darth Hoth]

Scale and scope, for one thing, are severely hampered by a realistic treatment of space travel, which more or less requires that the story take place inside Sol System.

You're only saying this because you have no actual sense of scale. Why does a science fiction universe need a million star systems in order to feel large? Given how lightly detailed the great majority of these systems or planets will be, what makes it any different to offhand mentions of millions of orbital habitats around Jupiter? It's true that a solar system is smaller than a galaxy, but a solar system is so wildly divorced fromt he human scale that it's basically totally irrelevant.

The planet Earth is so wildly divorced from the human scale that it is basically totally irrelevant that it is smaller than the Inner System. Why do we need habitats, or to set it in space at all, when we can just have the story play out in Nevada and mention offhand that there are thousands of cities in the US and hundreds of ocean-going ships in its merchant marine? These are huge numbers; no one human being can comprehend the totality of the unimaginable vastness that is the United States of America!

My apologies if that sounded snarky, but scale is also a matter of expectations. All the above is very much true; the US is huge, and a much larger country than many people living only a couple of hundred years ago could ever dream of crossing in their lifetime. Hell, there are primitives in distant corners of the Earth today who would look upon American scale and technology, or what little of it that they could at all comprehend, as basically God-like. But we are used to it, so it does not really feel very great to us. For the same reason, sci-fi readers are used to huge scales much larger than a single system, having read about them in fiction ever since E. E. Smith invented multi-system polities in his proto-space opera. Hence, it feels small by comparison, even though a single planet (and arguably a single large city) is something you could inhabit for a lifetime, travelling far and wide within its boundaries without ever meeting more than a fraction of its population.

[Coyote]

...not even asking for transhumanism and shit, how about instead of WWII or 1800s in space you take the "go anywhere jump drive = MAD" and make a political order based on the Cold War with the Great Powers sweating under the threat of mutual annihilation and fighting through proxy wars on Third Galaxy planets. I can't offhand remember a single setting that does something like that, even though MAD scenarios are really not hard to achieve with an interstellar setting with multiple roughly equal power blocs. Yeah, I get that MAD won't let you have them awesome dramatic between roughly equal opponents (unless you're willing to really go balls-out and show your entire setting turned into a charnel house), but come on, would it really hurt so much to challenge yourself a bit there?

I need to get off my ass and start doing my comics and stories again. That is exactly what I have. A tense political standoff between two galactic superpowers that are constantly in rivalry for smaller, nearby factions to ally with them, brushfire wars, propaganda being tossed back and forth, the occassional tension-filled joint operation... yeah, I grew up in that shit, during the 1980's.

A lot of the earlier, sci-fi great stories were shaped by authors who lived through or at least were alive during the time of the Big Wars, so their fiction reflected that, and the Vietnam-era authors were more interested (IMO) in the escapism aspects. Those who directly confronted Vietnam tended to use it as a backdrop for military sci-fi with a conveniently more "clean" (ethically speaking) conflict.

But from my earliest years putting together my funky 'verse, one of my early ideas was "how about telling a story from the Empire's point of view, where the Stormtroopers are the armor-clad defenders of society and their under attack from a bunch of Commie-pinko terrorist rebel types?" It then led me to asking, "well, who is funding and supporting the commie pinko rebel terrorists? It has to be a big nation, maybe a bigger one, to keep the Empire from just running in and smashing shit. There has to be a reason why they can't escalate."

I actually have the first chapter in a new story already fleshed out, I just need to finish it and post it. Hmmm, maybe AM&P...

[Nyrath]

I seriously doubt there's 10,000 star systems PERIOD within 100 lightyears of our system leave alone 10,000 ones that actually have habitable planets. Or planets PERIOD.

According to the best figures I have available, a sphere with a radius of 100 light years centered on Sol should contain roughly 10,000 stars. With a large error bar, of course. (between 8.33x10^-2 and 8.67x10^-2 stars per cubic parsec)

If you accept Dr. Jill Tarter's paper on stars likely to host a planet that some conceivable form of life could survive on, there would be very very roughly about 2000 such stars.

[Nyrath]

Getting back on topic, I recently found this little quote:

Copernicus’ Law of Science Fiction: Bending the laws of physics out of service to the story is fine, doing it out of ignorance is unconscionable.

[Junghalli]

I'm not entirely convinced you could brake on an interstellar medium for long enough to really make relativistic flight with high mass craft reasonable. If someone could do the calcs that'd be grand, but don't bussard scoops only start being able to scoop shit up at a good fraction of C (meaning braking on interstellar hydrogen via this wouldn't work below that speed either)? Are mag sails any better in this respect?

Estimates for how fast a Bussard ramjet would need to be going for the scoop to work vary between .01-.06 c according to Atomic Rocket. A magsail brake that shaved off the need for external fuel above the last .06 c of decelleration would still be enormously useful. If your starting velocity is .9 c, for instance, I calculate you would need to carry more than 700 times as much fuel to decellerate without a magsail as you would need with it, and that's just based on kinetic energy, without factoring in the mass ratio death spiral problem (past a certain point you end up using up most of your fuel to accelerate the rest of your fuel instead of your ship).

At any rate, you can find good information about magsails here. The section where they discuss braking starts on page 26. They calculate 30 years for a 1 ton (+968 kg for the magsail brake loop) probe to decellerate from .1 c to ~300 km/s using a magsail with a radius of 28 km, so apparently it works down to at least that speed. That's rather slow decelleration, but reasonable for a voyage lasting hundreds of years anyway. Decellerating from 300 km/s would be easy with a number of plausible secondary propulsion systems. Performance increases sharply with speed, so decellerating from higher fractions of c would not add much decelleration time. They also give the magsail drag formula:

A MagSail field will also deflect ionized material in the interstellar medium (ISM), and will therefore
produce drag when active. The magnitude of this drag can be estimated by treating the MagSail as a
dipole, which will form a magnetosphere whose size is set by equilibrium between the dynamic pressure of
the ISM and the magnetic field pressure. The drag force is calculated to be:
Fdrag = 1.175 π (Ni mi μ1/2 I r2 V2)2/3
where Ni and mi are the number density and mass of ISM ions, and V is the vehicle velocity through
the ISM, nominally 0.1c = 3 x 107 m/s.
For the baseline 100 meter loop, and with an assumed density of the ISM of 105 ions/m3, the drag is
33.6 N.

The paper is also a good introduction to the sailbeam concept, which is basically like a laser lightsail only instead of shining a laser directly on the ship you use the laser to send a bunch of tiny sails flying at the ship, and the ship uses an onboard laser to turn them into ionized gas which hits the magsail and pushes it forward. It saves you the engineering difficulties of having to build a laser capable of pushing a ship at light year distances.

-------

It is also a matter of the audience's preconceptions and expectations. If they are fed up on interstellar alliances and galactic empires a realistic polity will inevitably look small.

One good way to counteract this would be to show the great scale and diversity that you could fit into a single solar system. You could easily support more people in a single system than many "galactic empires" probably do in all their vast dominions. Of course, as I said, if you drop the idea that everything has to happen on the scale of natural human lifetimes then you can easily have vibrant interstellar settings.

I generally avoid writing nonhuman viewpoint characters, for the simple reason that their mindset will logically be completely alien from that of humans like myself.

Uploads could still be quite human mentally. They would only become inhuman mentally if they deliberately modified the brain simulator program to make them so. It's pretty plausible that most of them would choose not to do that - I imagine people with no attachment to their mental humanity would be considerably rarer than people with no attachment to their physical humanity.

Of course for the kind of setting I was talking about there are other options, like showing the war from the perspective of some third party caught in the middle of it.

I can see the point you are making, but in the end that is not really a limitation on soft sci-fi, merely on writer imagination. You can have every kind of uploading, "super intelligence", nano-gizmos or other AI-wankery in a soft setting as well (say, the Culture or OA as examples) and explore the realistic consequences of those things in such environs. The breaking point is really that in a soft story you can have any realistic story element and any unrealistic one, while in a "hard" such you are restricted to the realistic ones only. Therefore by definition it is more restricted; soft sci-fi only grants more options, but removes none.

That is true. I don't dispute that it is more limited, I dispute that it's some kind of creative straightjacket that severely limits what the author can do. There's still lots of things you can do within the limits of hard science.

[Junghalli]

Correction in my reply to Batman: a laser lightsail has thrust of 6.7 newtons per gigawatt, not 1 newton per 6.7 gigawatts. The required energy and area for the solar panel should therefore be divided by 6.7 from my estimates.

reference.

[adam_grif]

Had no idea the Bussard scoop could operate at such low velocities. For some reason I had it in my head you had to be something like 20% of C to get it running.

So if we can get down to <1% C with the mag-sail drag, that makes stationary positions providing acceleration then ships slowing down under their own power much more reasonable over interstellar distances.

The other day I got all depressed because I read somewhere that an objects KE exceeds it's rest mass converted to energy at .94 C (or somewhere around there), meaning to accelerate a mass of X up to that speed you need X/2 matter combined with X/2 antimatter, not counting the excess you need to accelerate the fuel up with it, and assuming magical 100% conversion efficiency.

If you had to slow down under power the whole way you'd thus need to carry >X antimatter and >X matter to ship X cargo. Which is a ridiculous amount. Otherwise you're forced to go between fixed positions with some kind of beam powered acceleration and deceleration, meaning you'll only ever be boldly going where many men have been before.

But this is good news, yes.

[Shinova]

Prefer soft sci-fi because of the bigger variety of possible settings, and because big honkin space guns and wonked psychic powers of doom are AWESOME.

[bz249]

I prefer stories where characters/groups have beleivable (hard) motivations and goals instead of doing unreasonable (soft) things. That's where most so-called hard sci-fis fail, by keeping the physics "hard" (by the way from late eighteenth century point of view steampunk is hard sci-fi while yesterdays BBC World News are soft sci-fi) they just make setting which are nonsense from economical point of view.

[RedImperator]

they just make setting which are nonsense from economical point of view.

Wait, what? Soft sci-fi more often than not transplants 21st century Earth economics (or the Gilded Age, or the high middle ages, or the Roman Empire) into a setting full of magi-tech and an entire galaxy's worth of natural resources, and you're bitching about hard sci-fi not having realistic economics?

[bz249]

they just make setting which are nonsense from economical point of view.

Wait, what? Soft sci-fi more often than not transplants 21st century Earth economics (or the Gilded Age, or the high middle ages, or the Roman Empire) into a setting full of magi-tech and an entire galaxy's worth of natural resources, and you're bitching about hard sci-fi not having realistic economics?

For example interstellar travel is really stupid thing, or doing anything in space other than tying yourself to a certain dustball. Moving things in space are tremendously costly (or it take millions of years), that's why moving anything is a really bad idea. There is hardly anything out there worth the cost of transportation with any plausible drive we could have since it requires more resources than the amount of resource it can offer. One must really think hard why to do anything in space under those settings (apart from one way trips to build a colony somewhere).

[Junghalli]

For example interstellar travel is really stupid thing, or doing anything in space other than tying yourself to a certain dustball. Moving things in space are tremendously costly (or it take millions of years), that's why moving anything is a really bad idea. There is hardly anything out there worth the cost of transportation with any plausible drive we could have since it requires more resources than the amount of resource it can offer. One must really think hard why to do anything in space under those settings (apart from one way trips to build a colony somewhere).

Same reason we send space probes to Mars. We want to see what's there, and it's a trivial expenditure compared to the resources a civilization that exploits even 1% of the resources of our solar system would have access to. And once you have visited a system travel there need not be expensive if you ditch the really kind of silly concept that you must transport living humans. Upload their mind states and send them on a comm laser.

[bz249]

Same reason we send space probes to Mars. We want to see what's there, and it's a trivial expenditure compared to the resources a civilization that exploits even 1% of the resources of our solar system would have access to. And once you have visited a system travel there need not be expensive if you ditch the really kind of silly concept that you must transport living humans. Upload their mind states and send them on a comm laser.

Yes since we've never been on the Mars what is out there might be interesting. Now imagine if we had sent probes to one houndred systems.. and we find exactly nothing there. You should not, the physical laws are the same, the elements are the same. Star systems would be well... the same. Would one send a probe for the next one? Or how many people going yearly to Bumbfuck, Idaho on touristic purposes (a trivial expenditure at our current technological level)?

Also it is interesting how to exploit 1% of the resources of the Solar System based on our knowledge. Since space travel is a very energy inefficient (simply because of conservation of momentum and energy), digging here on Earth would always be the economical solution. Unless we have:
- a way different method of propulsion (some whacky reactionless drive)
- energy would be costless (and even than, digging here on Earth would be the better option)
it is rather difficult to imagine some self-sustained colonization of the Solar System.

[Junghalli]

Yes since we've never been on the Mars what is out there might be interesting. Now imagine if we had sent probes to one houndred systems.. and we find exactly nothing there. You should not, the physical laws are the same, the elements are the same. Star systems would be well... the same. Would one send a probe for the next one? Or how many people going yearly to Bumbfuck, Idaho on touristic purposes (a trivial expenditure at our current technological level)?

There can't be anything interesting in other solar systems? Different planetary configurations can't be scientifically interesting (most of the exoplanets we've found do not look like planets in the solar system)? Alien ecologies can't be interesting? Intelligent aliens can't be interesting? You must be easily bored.

Also it is interesting how to exploit 1% of the resources of the Solar System based on our knowledge. Since space travel is a very energy inefficient (simply because of conservation of momentum and energy), digging here on Earth would always be the economical solution. Unless we have:
- a way different method of propulsion (some whacky reactionless drive)
- energy would be costless (and even than, digging here on Earth would be the better option)
it is rather difficult to imagine some self-sustained colonization of the Solar System.

At this point I could start bringing up hypothetical scenarios by which space colonization would be profitable, but that actually isn't necessary. All you need is AI + Von Neumann machines + people who have any interest in exploiting the solar system for any reason. AI and Von Neumanns are pretty hard SF and the combination is Kryptonite to a lot of our assumptions about how economics works* (since it has the potential to easily give every human basically a giant army of perfectly obedient robots).

* Well, not exactly. Technically, it doesn't fundamentally change anything. But it does have the potential to turn every human into the equivalent of a billionaire, provided sufficient raw resources are available.

[bz249]

For example interstellar travel is really stupid thing, or doing anything in space other than tying yourself to a certain dustball.

Another person not thinking with habitats!

Why should I, materials have to be moved there, so better start with an already existing asteroid (a dustball). It is way cheaper to construct anything where the resources are, than to mine the resources and move to somewhere else. Unless of course cost is of no importance.

Moving things in space are tremendously costly (or it take millions of years), that's why moving anything is a really bad idea.

Two errors:

Poor logic: just because something is costly doesn't mean it is a bad idea. The benefit may outweigh the cost.

Ok let us start from the very principles: the conservation of momentum and energy. If we have a spaceship, the following equations will hold for a burst (in center of mass system).

m(fuel)*u(fuel)=M(ship)*v(ship)

from that v(ship)=m(fuel)/M(ship)*u(fuel)

The kinetic energy you gave to the fuel (lets calculate in a classical way, because it is easier)

0.5*m(fuel)*u(fuel)^2

The kinetic energy of the ship

0.5*M(ship)*v(ship)^2=0.5*m(fuel)*u(fuel)^2*[m(fuel)/M(ship)]

So a burst of rocket drive have an energy efficiency of m(fuel)/[M(ship)+m(fuel)]

For any normal spaceship design, the mass of the ship outweight the mass of the fuel by orders of magnitude, (unless you have a gun-like system... but then stopping at the destination would still be an issue). Thus you can expect a very poor energy efficiency.

Incorrect premise: moving things in space are not in fact tremendously costly, nor does it take millions of years. Consider that we have landed men on the moon and brought them back - alive - in the real world.

Cost of course matters nothing when we think about exploration, going to the Moon would have worth any price that time, since the thing was about going there. In the meantime, the astronaut brought back 381 kgs of lunar stone, for a mere 145.000.000.000$ (current value).

Okay they have to maneuver in and out of Earth gravity well, but using plausible scientific principles there is no way that you can apply enough delta v on anything for a reasonable cost, for the simple reason that most of the energy is wasted on accelerating the fuel.

There is hardly anything out there worth the cost of transportation with any plausible drive we could have since it requires more resources than the amount of resource it can offer.

Circular logic. Let me reword it: Since it costs more than the benefit can be, there is no benefit out there worth the cost.

What is out there which is unavailable in Earth for less of an investment? If there are no unknown elements* (there aren't), alloys (there aren't) and molecules (there aren't). Then all you have to compare the cost of transportation, and it is high and it would remain high if you want reasonable timescales**. Reasonable timescales means: the material would still needed by the time it arrives; and the group which launched it would still exists.

*you may say He3 isotope, but it is such an abysmal quantity, that even it is worth collecting, it is better used where it is.

**by applying a very small delta v the cost could be reduced, but the price is the package will arrive very late

One must really think hard why to do anything in space under those settings (apart from one way trips to build a colony somewhere).

Science (doing this today), tourism (doing this today, though it isn't profitable yet), living space (habitats), energy (solar power satellites - a company is planning to do this today, and the only reason we aren't doing it now is coal remains so cheap).

Raw materials from space could be used to support the other goals; mining the moon to build habitats, capturing asteroids to build solar power satellites, etc.

Science: can be done, sure it is not cost sensitive.
Tourism: can be done for sure it is for the rich people it should not be cost sensitive.
Colonization: possible, but only as one way trips, go there, live there and be forgotten.
Space mining: cheaper to use wherever it is, then you don't have to add an inefficient transportation system
Power satellites: that will never happen, unless we will have too much energy to lob something there (that case there is no need for those satellites) or we have too little energy to put something up there. If you would like to replace just one large nuclear reactor you need something of 4x4 km2.