The purpose of interstellar travel and consequences.

When considering the distances involved with interstellar travel, is it not safe to assume that the only worthwhile purpose is colonization, even when it involves inevitable conquest of alien civilizations?

Until some form of faster than light drive is developed (such as the famous doubletalk drives of science fiction), interstellar travel is strictly multi-generational and one-way.But there is no inherent requirement for us to conquer anybody.First, we don't know who is out there; maybe nobody.Second, any aliens out there may be interested in "serving" mankind (a theme also explored in SF); we may be the conqueree, not the conqueror.(This thread should be good for 400 posts easy.)

---

Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

Basically - except for the interstellar conquest bit. But even then, it's cheaper to use local solar-system resources to construct artificial habitats in space for extra living space (hollowed out asteroids or fully artificial constructs, either way). Conquest just makes the resource investment look even worse.Unless some game-changing surprise discovery is made that makes interstellar travel a lot easier than we think it is, it's really just not worth it from a practical standpoint. You could do it for exploration with probes instead of manned missions (delay is just as long, but cost goes down dramatically, and you don't risk lives).I suppose a legitimate reason to escape the solar system would be the Sun's natural aging. After all, eventually it's going to turn into a red giant and swallow the Earth...but that's so far in the distant future it's barely even worth considering.It would take an awfully long time for us to use all of the resources available to us here in our own solar system. The asteroid belt alone is a wealth of minerals, and a supply train would be difficult but not impossible. With extrasolar missions, you won't even hear progress reports or cries for help until years after the original broadcast, and it will take you even longer to respond with aid.

Hi Canis latrans,Should we take for granted that there is no faster than light travel? I think yes. I think we should also assume we would eventually find extra-terrestrial life forms. To a certain extent the foreign life could be an obstacle. I think an adversarial relationship at even a low level would exist if we encroached upon their world. We would be of the opinion that it was our new world. I think that is inevitable.Your multi-generational description of the trip is also inevitably true. What a sacrifice it would be then for the intermediate generations. Could the crew (community even) survive a trip like that?Edited by CosmicChimp, : word choiceEdited by CosmicChimp, : added greeting and fixed subtitle

Hi Rahvin,I can see that you are correct that staying in our own solar system is important to do for now. But, there will come a time when the great difficulties associated with the reasons for not venturing far will be overcome at the technical level. There is also a certain will, I see in the human spirit to take new territories; lay claim to our stake among the stars.Essentially, the solar system will not be enough to satisfy our wanderlust. I see this as taking place before humanity changes significantly enough to make those desires moot.Plus, is it not necessary that we "take our place" in this galaxy, so as to avoid the dangers associated with remaining in only one main planet and then some few nearby colonies? A supernova could explode nearby and wipe us out. Or conquest of us la The Chronicles of Riddick variety (did you see that flick?)Edited by CosmicChimp, : No reason given.

Is our best purpose to father another level of life, that I must assume is a robotic/android form, or is our best goal to remain human and reach new stars and solar systems. To a certain extent I think both are inevitable but maybe the second would be a better goal.

Warning: long reply, with math. I'm not sure about that."Technical levels" still have to work within the laws of physics. No matter how you cut it, extrasolar travel is an incredible investment in energy and materials. The energy cost to accellerate a vessel to a reasonable fraction of c is astronomical. The amount of space wasted by life support systems and the industrial/agricultural base to support a colony makes the problem worse by orders of magnitude.Our best bet would likely be to simply hollow out a large asteroid and set it up like an orbital space colony with an internal ecosystem...and then attach some engines and give it an internal fuel supply. Currently-known energy sources make fusion the most obvious choice (antimatter annihilation has all of teh problems of fusion multiplied tenfold, with the addition that the fuel itself is not inert and requires energized storage; if the containment fails, the whole ship will be lost. That's a pretty nasty consequence of a power outage). Make it a generational ship traveling relatively slowly but with a large supply of reaction mass and volatiles. You still run the significant risk of running out of resources before you arrive,or after you arrive but before you've set up a self-sufficient colony.Cryogenics makes eliminates need to take supplies for the trip itself, but an already-functioning mostly-self-sustaining ecosystem would be far more advantageous. You wouldn't even need to land on the alien planet - the ship is the colony, preventing the disadvantages of being caught in a planet's gravity well (it's awfully costly to go back and forth between space and a surface). Once you arrive, solar panels can supplement your power supply, you won't need to run the engines any more, and you can presumeably harvest more reaction mass from comets, which are a great source of water that's easily accessible once you're already in space.The problem, again, is that you'll get very little advantage from doing this. Using all of the available resources of even just our own solar system will take eons. Colonies will be far too distant to create a reasonable supply chain or trade; resources mined a dozen lightyears away will take almost certainly hundreds of years to get back to Earth, with a significant energy cost that will likely outweight the value of the resources being transported.What we'd need to make this work is FTL...which so far seems to be impossible. We need a relatively cheap way to make a wormhole, or a way to warp space without catastrophic side effects and again with a low energy cost. This goes beyond "scientific breakthrough" and truly enters the realm of science fiction, where we aren't even making educated guesses but rather are simply speculating about technology so vastly superior to what we understand to be possible that you may as well call it magic. Certainly. But the prohibitive energy cost of such an endeavor makes colonization for some absurd"manifest destiny" simply foolish. There has to be an advantage to be gained - new resources to be exploited. If transporting resources costs more resources than a given transport can carry, we're at a net loss for every trip. There's no profit in that, no reason to do it, and nobody will fund it.I would see humanity picking up and moving compeltely to a new solar system when our Sun enters its geriatric years rather than setting up colonies before then to simply extend the reach of human civilization. Our wanderlust has not allowed us to colonize Mars, or even the Moon. Hell, even the ISS barely qualifies as an orbital habitat. And these are relatively easy. It will still take us months for a capsule to reach Mars at current technology levels. Voyager 1 is travelling at 17km/s (0.0000567% of c), was launched back in the 70s, and still hasn't managed to leave the solar system. It will take tens of thousands of years to reach another solar system...and it had the advantage of gravity-assisted accelleration to get it moving so fast. It's taken almost 32 years to travel a distance of just 15 light-hours.Here's the deal. Relativity presents some very large problems for interstellar space travel. Let's say you want to accellerate to 10% of the speed of light. The nearest solar system to ours is roughly 4light years away, so it would take just 40 years to get there, right?Not really. You have to include the accelleration time, and an equal amount of time decellerating as you aproach your target.Let's say our spaceship is really small - we'll be insanely generous and say that we've managed to fit a fusion reactor, an industrial base, agricultural capability, living space, and everything else our colonists will need in a vessel of the same mass as an aircraft carrier. Let's say our aircraft carrier-sized vessel has a mass of about 24,000 tons. How much energy would it take to accellerate that vessel to 10% c?E=1/2M*V^2E=1/2 (24000000 kg) (29979245 m/s)^2E=1.0785e22 JoulesThat's an awful lot of energy.Let's say you were willing to spend 5 years accellerating.P=W/TP=1.0785e22 Joules / 157,784,630 seconds (in 5 years)P= 6.835e13 WattsYou would need to generate 68,350 gigawats of power constantly over those 5 years.And that assumes perfect efficiency, which is impossible.And you'd have to do the exact same thing just to slow back down before you get to your destination.The Sun, by the way, generates a grand total of roughly 4e26 Watts of power.The entire planet currently uses 1.585e13 Watts, meaning you'd need your spaceship to produce over 4 times the amount of power generated by every power plant on Earth.If we were to somehow miraculously find an efficient way to use antimatter (and create it - it's taken us decades to create even a few picograms of the stuff), I can tell you the amount of reaction mass you'll need:E=MC^21.0785e22=M*299792458^21.0785e22/299792458^2=M119,999.309=MAssuming perfect efficiency, you'd need about 120 metric tons of matter/antimatter...for the accelleration phase. You'd need another 120 metric tons of reaction mass to slow back down. Again, this assumes impossible perfect efficiency and doesn't leave anything left over for maneuvering. Once you get to your destination, you're out of gas and done.Nuclear fusion, the far safer and seemingly more practical means of energy generation, is nowhere near as efficient. You'd need a lot more reaction mass.Do you know what happens when a ship travelling at 10% c hits a small .5kg micrometeorite? Let's say the little rock was stationary. It will hit the ship with 2.237e14 Joules of energy. A one-kiloton nuclear device releases the equivalent of 4.184e12 Joules of energy...meaning our tiny half-kilogram rock just compeltely fucked up our starship. Moving at 10% c means there is absolutely no way to avoid small objects. You cannot maneuver. If it's in your path, you're going to hit it, unless you can see it 5 years in advance and expend your decelleration fuel to avoid it. Of course, then you're out of gas and nowhere near your destination.I also didn't calculate the effects of relativity - when tyou start travelling at significant fractions of c, your relative mass increases requiring more energy to continue accellerating. I simply don't know the formulae involved.Again - unless a scientific breakthrough of significance equalling the use of fire shows us a way to cheat relativity or thermodynamics, or to warp space itself, and do all of this cheaply, it's not going to happen at all. These problems are not going to be solved with "technology will make it all better" magic. It will take a fundamental paradigm shift in how we understand physics to even make this stuff possible. Which still says nothing about being feasible from an engineering perspective.You could try to take the timeelement out of the picture using cryonics. Who cares how long the trip takes, even if it's 100,000 years, if the ship can just cruise along and wake the crew when it arrives?The problem is you need to design a vessel that will last, reliably, for 100,000 years with only self-maintenance, and give it a power source that will keep its automated functions running for that long. Good luck with that. Any supernova that takes out the Earth will also affect any planets in reasonable reach. That's like trying to avoid a nuclear bomb by going to your neighbor's house. Okay action movie. Horrible science fiction - at least for my tastes. Melee combat? Giant statue-spaceships? Utterly bizarre. I watched it once and never again. Pitch Black was far better.Conquest of us faces new problems for our invaders. For one - why bother? It's no easier for them to get here than for us to get anywhere else. Why expend all that energy just to spend more energy wiping us out when there are plenty of uninhabited systems available? Habitable planets don't matter - artificial orbitals make far better habitats anyway because you don't have to worry about expending energy gettng into and out of a gravity well. Why bother, when you can achieve the same goals without the risks of war and retaliation?

Protocol Transmission:I think your comment about sci-fi becomes increasingly more correct the further one delves into the matter. To that end, may I submit a further idea. Remember in that film Species, an advanced intelligent alien race broadcast protocols for creating evidently some sort of their "basic essence." Earth scientists decoded the message and then went about following the protocol. Voil! An intelligent race has traversed the gulf between stars (albeit only one individual). Maybe that's not such a bad idea. Humanity might land amidst another race of intelligent beings, and all that that might entail.Panspermia:In any of this it must be almost a kind of accepted premise to assume that there would be no further contact with whoever or whatever was sent off. Going with the idea that we humans would never have a profitable contact with what we sent off; we could simply seed nearby stars with any number of earth organisms capable of surviving the journey. In a sterile world this at least seeds another complex chain of events, perhaps even similar to what we have had on earth. The fruits of this sort of work may or may not be what we would have expected. But at the very least a complex molecule like DNA would gain a foothold, hopefully.Further Realization:My earlier idea had as a goal to secure the survival of humanity, but it is at least as easy to recognize that we could be sending off our future enemies, (i.e. if they come back, which is quite possibly a likely scenario; possibly even the demise of humanity).

If we simply wanted to propagate humanity we could send out a vessel complete with human embryos which could be raised to full age later on. It might take an extremely long time to reach its destination, but would be moreviable than sending full grown humans.

The problem is that this only has a chance of working with another intelligent species who is advanced enough to follow such instructions, and has the resources available to persue such an endeavor at little benefit for themselves. Further, any genetically enginered human will almost certainly be merely the subject of experimentation - we aren't talking about a meeting of cultures here, since any genetically engineered human will have absolutely no idea what's going on.What's the advantage for us? Humans exist outside of our solar system...as guinea pigs for an alien species to probe our interesting biology. In the very best case, we'd have a human being raised in an alien culture with absolutely no ties to us.Species is no better than Riddick - hot chick, bad scifi. What's the point? Preservation of life? Frankly, if we're not among the life preserved, there's no reason to engage in panspermia. There's no objective reason to prefer life over non-life - it only has subjective value to us because we ourselves are alive. Making some algea grow in the oceans of a distant world doesn't do anything for us. We don't get to increase our knowledge or understanding of life or the Universe, we don't preserve our species or cultures, we don't acquire new resources...there's just no reason beyond idle amusement, which will hardly justify expending resources for an interstellar probe.There is a tie-in to this, however. Ever heard of a von Neuman Probe?A von Neuman probe is a machine capable of self-replication and interstellar travel. Theoretically it would arrive in a targeted star system, find suitable sources of raw materials (asteroids, comets, etc), and begin processing those materials into a copy of itself, which then targets a new star system and continues the cycle.Eventually this would result in probes filling every system in teh galaxy at an exponential rate, for only the resource cost of a single probe.Now, imagine that we also program the probe to search for human-habitable worlds. Hell, we could even stick with searching for Sun-like stars with ample resources in an asteroid belt. Self-replciation could build up a construction fleet capable of building an orbital habitat. Theoretically it could also be possible to construct a human embryo from raw materials - meaning we could have probes that find habitable regions of space, build habitats and an industrial base, and then begin manufacturing life.It's the least resource-intensive process I can imagine to spread humanity to the stars, without overt physics-breaking nonsense like FTL. It still requires some magic-tech, though - we don't have anywhere near the capability to build a machine capable of harvesting and processing raw materials from an asteroid and using the resources to manufacture a copy of itself. We also don't have nearly the capability to assemble life at the molecular level from raw materials. The logistics involved in equipping an interstellar probe with full mining,refining, and manufacturing capability with multiple design patterns (ie, the capability to build not only replicas but other items as well) are astronomically difficult. Modern factories have to be retooled completely at enormous cost to change the product they manufacture - that's a luxury a space probe won't have. Landing on an asteroid for mining is risky and difficult, and the probe will need the computational capacity to intelligently assess potential targets and maneuver safely to intercept. It will need to be able to re-launch and find comets for new Hydrogen fuel. We aren't breaking physics this time, but we might be making some engineers cry.And again, what's the purpose? The distances involved (not to mention construction time) still preclude any useful resourcing missions, though at least with superscience probes like these we wouldn;t strictly speaking need to involve human beings at all. Creating human beings with recorded education programs on-site could prevent extinction and spread us around the galaxy...but to what purpose? It could make for a very interesting setting for a scifi movie (hmmm...), but practically speaking there's still little reason to bother. It would take eons to spread humanity to the point where we're effectively immune from a nearby supernova, but the small colonies we manufacture would evolve (socially and genetically) isolated from any other human populations. Given a few dozen generations, we wouldn't be preserving "us" so much as spreading new somewhat-human-related species around who have no cultural ties to us beyond what we can program into the first generation with automated education programs (which are themselves again pure fiction - teaching children requires an authority figure to keep them focused, meaning the level of interactivity required would necessitate a general AI of => human capabilities). Unlikely, for the same reasons that others are unlikely to come conquer us and we're unlikely to try to conquer other species. Resources are pretty plentiful in the Universe. Only ideological wars are really plausible. I suppose I can't discount that possibility over resources - human beigns right now expend innumerable resources fighting wars for no practical benefit over ideological concerns, so it's certainly a possibility even given space. Of course, given the timescales we could all calm down and go through multiple cultural revolutions between the time an assault is launched and when it reaches its destination...Picture this: through magic super-telescopes, an alien species watches us during the Holocaust and decides we're really dangerous. They want to blow us up to keep us out of space.But they're 50 light-years away. They just saw those images in the 90's. Let's say it took ehtem 10 years (conservative) to assemble an attack. At 10% c, it will take them another 500 years to get here. We could blow ourselves up long before then. We already have completely changed our cultural makeup several times over in the intervening 60 years - the amount of change possible over the next 500 years is unimagineable. Further, we could leave Earth long before that attack ever gets here, making their strike impotent. If we look in the right direction, we'll even see the attack coming, potentially decades or centuries in advance (and engine capable of accellerating to 10% c will have quite a heat signature compared to the background and shouldn;t look anything like a star, meaning we could notice it).Space-based attacks are easy, too. They don't even need to be manned. Remember our 20,000 ton 10% c colony ship? All it needs to do is be targeted correctly and then not slow down. A 20,000 ton object hitting the Earth at 10% c would be a mass-extinction-level event. Which of course means that, given a few decades or centuries of notice, we can potentially not only escape (or maybe even intercept and divert the attack), but launch an assault of our own and wreck their homeworld...in 500 years.Yet another reason orbital habitats are superior to being trapped in a gravity well.Basically what this whole discussion boils down to is that, given what we currently understand of the Unvierse, interstellar travel is impractical at best. That doesn't stop us, but it makes it far less likely.

You have some good posts Rahvin, But is the "problem" of a greater magnitude than those problems (impossibilities, really) you had outlined above in your previous posts; those associated with traveling via starship? It would be an immense benefit for those intelligent beings. Curiosity is surely the spark for intelligence. The advantage for us is that we would have been able to spread complexity in the universe. We as a living complex organism would have been furthered in the universe. I can only assume that goal is a worthy one, not ever having seen anything as complex and remarkable as the human mind.I'm not sure yet how to respond to your Von Neuman probe scenario and raised issues. It's good stuff. I will say however that you seem a bit pessimistic.Let me sum up my general idea. I see that as carbon based life in the form that we or any life on this planet has taken, as being a sort of middle of the road most common solution given the most common circumstances prevalent in the universe. This would put DNA at the forefront for promoting complexity in the universe; which I see as a worthy goal for works of any kind. I have also considered an even more basic approach, having to do with speeding up life cycles of the stars so as to enrich the cosmos with heavier elements but that's not really under discussion, so far.{ABE}
You did touch upon conflicts of interest in the last section. I do think it is a very real consideration. We have seen how precious solar systems are. You have even effectively stated we get only one, for all practicality. So, if we could have two, I still think we would take the second at almost any cost. I see the motivation being the same for aliens.Edited by CosmicChimp, : punctuationEdited by CosmicChimp, : last bit of the subject added and subtitle

I'm something of a scifi geek. Discussions of how it really works have come up before. Unfortunately, really "hard" science fiction is not nearly as entertaining as Star Trek and the like. Oh it's certainly easier. You don't have to break the laws of physics, which is quite a bit less challenging for the engineers.That doesn't mean it's practical, though. It offers them no new resources. It offers them no greater understanding of life than they already possess (assuming they are capable of cloning). It would be a better idea to simply broadcast a message containing details about or culture, some pictures, and a great big "Hi, let's be penpals, I'll expect your response in a few decades." At least ehn we could provide useful information.And what benefit is there for us? Why would the aliens make more than one subject? Why would they keep it alive? What benefit is there in trying to get small populations of human beings isolated from Earth in alein cultures with no idea who they are or where they came from, possibly to be dissected and discarded by the aliens? If we're sending a message to other intelligent societies, "complexity" already exists wherever our message will arrive. TO paraphrase Colbert, "reality has a well-known pessimistic bias."I'm not a pessimist, I'm a realist. I don't artificially inflate human capabilities or willfully ignore the laws of physics in "serious" debates. As I said, unless we have a major paradigm-breaking shift in our understanding of physics on the level with figuring out that the Earth is not flat, interstellar travel just isn't going to be much of a practical reality.Don't get me wrong - we'll get off this rock and explore our own solar system. We'll send interstellar probes eventually (technically, Voyager 1 and 2 are interstellar, though it'll take thousands of years for them to actually reach the closest star). Given we don't blow ourselves up first, we'll even leave this solar system before our Sun turns into a red giant and consumes the Earth.But the imminent survival of teh species is about the only motive that justifies the resource expenditure given technology we can reasonably predict to exist. All other problems for the forseeable future have far more simple and less resource-intensive solutions. Interstellar travel at the moment is rather like planning to mine Jupiter for Hydrogen: it costs more than you'll get in return, and it's an insanely difficult engineering problem even by itself. It's easier to crack water to get the Hydrogen than to go to another planet. The Universe already has plenty of heavy elements - it's had a few billion years of supernovae to build up a hefty supply, and it increases constantly. There's no need to speed up the process - again, you'd spend more resources in your solution than you'd get in return. When you're low on gas, you don't plan a trip to Saudi Arabia to get more.There are very few circumstances I see that could lead to humanity leaving the solar system. One is the aging of our star. Another is a religious or political dispute - a polity inhabiting a relatively self-sufficient orbital habitat decide to turn their home into a generation ship and leave the rest of humanity behind. This may or may not succeed.But there are no scientific missions that could not be solved more easily with robotic probes, and no resource missions that would provide a net resource gain. And the resource expenditure involved is too significant for any motive that does not involve practical results.Here's hoping for that paradigm-shifting discovery in physics. A practical way to cheat the c limit with reasonable energy expenditure would have me jumping with excitement like a kid who jsut watched Star Wars for the first time.

Even then all is not lost. There's a good chance that Mother Earth will have been towed away & placed in the ultimate Nature Preserve, if the cards are well-played out.Now there's an engineering project.

---

- xongsmith

Of course, one thing we know from looking at the behavior of other war-proned creatures is that the decision to go to war or not is rarely based on logic, reason, or reality. Besides a few billion extra slaves could really make the building of all those luxurious habitats a luxury in itself.

---

[O]ur tiny half-kilogram rock just compeltely fucked up our starship. - Rahvin