tag:blogger.com,1999:blog-7494544263897150929.post3868874353045477073..comments2024-03-28T00:36:19.403-07:00Comments on Rocketpunk Manifesto: FTL Part II: Just Plain CheatingRickhttp://www.blogger.com/profile/16932015378213238346noreply@blogger.comBlogger329125tag:blogger.com,1999:blog-7494544263897150929.post-69444190335926506342022-03-13T08:08:58.313-07:002022-03-13T08:08:58.313-07:00All FTL is Just Plain Cheating. As someone who wri...All FTL is Just Plain Cheating. As someone who writes both Fantasy and SF, the usual rule is to just make your magic systems consistent and "relatable". Relatable meaning, your audience won't need a PhD in physics to understand what's happening in the story.<br /><br />FTL and Hard SF are a Venn diagram with no overlap.Saint Michaelnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-87390472789545117922011-04-24T23:16:17.527-07:002011-04-24T23:16:17.527-07:00Milo - "Ouch. Run on sentence."
It was...Milo - <i>"Ouch. Run on sentence."<br /></i><br /><br />It was late and I wasn't sure how to word it otherwise.<br /><br />As for Universal Frame, well I'm not even sure that's even possible with Special Relativity in the picture, let alone numerous extra-solar nations. Closest I could think of as a "Universal Time Frame" without resorting to an earth-centric view is by the lifetime of the Milky Way Galaxy and even then that's debatable.<br /><br /><i>"While most observers will agree that time travel took place at some point during the voyage (except for the observers on the ship itself), they will disagree on exactly when the first instance of time travel took place. And even in non-causality-violating FTL, you will still appear to travel back in time from some frames of reference."</i><br /><br />I was thinking that something like that would have happened if I choose the "FTL Time Travel equals death" that those on the destination end would know that someone accidentally went backwards through time, but they don't know when or by whom. Which would be useful in preserving some sense of Causality since if one knows not only when the "accident" would occur but by what ship then it would cause a kind of paradox.<br /><br />Of course, the whole "Time Travel is Relative" and all that is one reason why I didn't ask for a way to make my FTL idea Causality-safe. It's bad enough to know that, by Special Relativity, all FTL equates to time travel. Probably be (slightly) easier to just decree that one can't time travel via the Hyperspace Dive System, even though supporters of Special Realtivity and their mothers say that it can in theory.<br /><br /><i> "big trouble if it happens on the surface of an inhabited planet, not really a concern in deep space" </i><br /><br />Probably a good reason why to have such destination points be Stellar-massed objects rather than stars.<br /><br />Ferrel - <i>"Personally, I wouldn't want to be in the same star system as one of your ships that had an 'oopie!'"</i><br /><br />Unfortunately, the accident culminates in a Gamma Burst (not sure if "ray" would really be manifested) at the star system destination. That star's equatorial plane to be exact. Though then again, considering the mass swapping proposal to keep true the Conservation of Angular Momentum, the Gamma Explosion could occur at either end of the Dive. Though chances are I'm probably wrong on that one.<br /><br />- <a href="mailto:Sabersonic@hotmail.com" rel="nofollow">Hotmail Address</a> <br /><a href="mailto:jrposadas@gmail.com" rel="nofollow">Gmail Address</a>Sabersonicnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-42475424812210536772011-04-24T15:29:57.835-07:002011-04-24T15:29:57.835-07:00Sabersonic said:"Now that I think of it, I...Sabersonic said:"Now that I think of it, I'm not really sure if that flash of gamma rays is such a good idea to indicate an accidental passage through time. Though it's not anywhere near stellar-mass, I have a feeling that converting all of that matter into gamma rays would be some fraction of a Gamma Ray Burst."<br /><br />Personally, I wouldn't want to be in the same star system as one of your ships that had an 'oopie!' :0<br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-83868648260421439772011-04-24T13:50:09.067-07:002011-04-24T13:50:09.067-07:00Sabersonic:
"All I could think of without re...Sabersonic:<br /><br /><i>"All I could think of without resorting to Special Frames is [...] that any possible time travel through the Dive System could only conclude with said starcraft converted into a flash of gamma rays."</i><br /><br />Ouch. Run on sentence.<br /><br />But it doesn't work, because there is no exact moment at which time travel takes place. While most observers will agree that time travel took place at some point during the voyage (except for the observers on the ship itself), they will disagree on exactly when the first instance of time travel took place. And even in non-causality-violating FTL, you will still appear to travel back in time from some frames of reference. To be able to say which time travel is acceptable and which isn't, you need some sort of universal frame of reference - so you will only explode if you try to travel back in time according to the universal frame. But once you have a universal frame, it's easier to just not have any means of even getting close to time travel, rather than merely blowing up people who try.<br /><br /><br /><i>"Though it's not anywhere near stellar-mass, I have a feeling that converting all of that matter into gamma rays would be some fraction of a Gamma Ray Burst."</i><br /><br />A gamma ray burst produces about the same amount of energy as a supernova, 10^44 joules or 1 foe, only beamed in a more narrow direction so it appears to be more intense if you happen to be in the path of the beam. This equates 11 yottatons of matter-energy, which is in the range of a brown dwarf - 6 Jupiter masses, but only 0.0056 (1/179) of a Solar mass.<br /><br />A WWII-in-SPACE! spaceship-sized mass-energy explosion would be 0.1 to 10 yottajoules (20 to 2000 teratons of TNT), which is in the range of a dino-killer (0.5 yottajoules) - big trouble if it happens on the surface of an inhabited planet, not really a concern in deep space.Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-54561359063697880132011-04-23T23:29:09.526-07:002011-04-23T23:29:09.526-07:00Raymond - I am (unfortunately) familiar enough wit...Raymond - I am (unfortunately) familiar enough with the "FTL Travel equals Time Travel" problem to the point that the best idea's I've come up with to avoid such causality violating dives is probably just as full of holes as the "Jump Anywhere" Drive commonly seen nowadays. <br /><br />All I could think of without resorting to Special Frames is, beyond making the transit time through the reference of "normal" space-time measured in days at the very least as opposed to the seemingly instant attenuated time of Hyper Space-Time such as a thousand parsec dive takes over a century to complete in "real" space-time as oppose to the hour long duration as experienced by the starcraft through Hyper space-time, that any possible time travel through the Dive System could only conclude with said starcraft converted into a flash of gamma rays. The only form of Time Travel that should have occured is the time dialation towards the future with no hope of traveling back into the past.<br /><br />Now that I think of it, I'm not really sure if that flash of gamma rays is such a good idea to indicate an accidental passage through time. Though it's not anywhere near stellar-mass, I have a feeling that converting all of that matter into gamma rays would be some fraction of a Gamma Ray Burst.<br /><br />- <a href="mailto:Sabersonic@hotmail.com" rel="nofollow">Hotmail Address</a> <br /><a href="mailto:jrposadas@gmail.com" rel="nofollow">Gmail Address</a>Sabersonicnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-15748990554076743352011-04-23T19:16:14.862-07:002011-04-23T19:16:14.862-07:00Sabersonic:
It's not so much the duration of ...Sabersonic:<br /><br />It's not so much the duration of travel as the frame of reference you take when you jump. If you make it so that, say, you have to be stationary with reference to the star you're using as your jump point, that'll get rid of most of the problem. Then you just have to deal with the (relatively slight) difference in reference frames between stars - if the destination is moving away from the origin, theoretically you could jump, take on the new frame, then jump back, and end up earlier than you started. Just make sure the travel time is long enough that jumping there and back takes longer than the difference in coordinates.Raymondhttps://www.blogger.com/profile/18103471451043461302noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-4962476307324479802011-04-23T15:22:53.174-07:002011-04-23T15:22:53.174-07:00So long as I keep the attenuated transit time of t...So long as I keep the attenuated transit time of the IP Warp Drive away from anything near the minute range, I should be able to not suffer the "FTL is Time Travel" conundrum. Though to be honest, I think I feel safer if said transit is measured in days rather then hours. Not exactly fast enough to deal with emergencies, but certainly fast enough to keep the equilibrium of realistic plausability and onboard passenger boredome limits.<br /><br />Still, there's just something strangely romantic about Cycler Stations being akin to a Cruise Ship. I know, I know, space is NOT an ocean, but I can't help it.<br /><br />As for the Mass/Energy/Momentum Swap for the Dive System, I had originally envisioned the destination point to be a strange swirling "vortex" for lack of a better word of strange energies that indicates an incomming Hyperspace Dive equipped starcraft. Granted, it'll probably now look like a mini-black hole that's drawing in stellar matter into it but it's a big enough indicator that something's comming. Not sure how to work it out with my Stargate Off-Ramp idea or just hand wave it as usual.<br /><br />Though I gotta wonder, considering the minimum size of the Starcrafts I envisioned (big MFs), wouldn't the Dive resemble a more explosive version of a Coronal Mass Ejection?<br /><br />- <a href="mailto:Sabersonic@hotmail.com" rel="nofollow">Hotmail Address</a> <br /><a href="mailto:jrposadas@gmail.com" rel="nofollow">Gmail Address</a>Sabersonicnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-75227659539597550752011-04-23T11:29:07.269-07:002011-04-23T11:29:07.269-07:00Sabersonic: so long as your IP warp just compresse...Sabersonic: so long as your IP warp just compresses or 'attenuates' time, so that time flow for your starships never goes negative, then it should be fine. As for Conservation of Angular Motion, do what Luke suggessted and have an amount of matter equal to the ship's mass swap positions and speed/tragectory. Because you already use stellar poles for interstellar jump-off points, there should be lots of solar wind for the mass/energy/momentum swap. <br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-85129018417111465452011-04-22T22:57:13.738-07:002011-04-22T22:57:13.738-07:00Ferrel - Oh, it's my IP Warp drive that you me...Ferrel - Oh, it's my IP Warp drive that you mentioned. Well considering that I initially envisioned it as a compliment to reaction drives both conventional and magi-tech torch types, though I'm not sure if the IP Warp Drive would improve either deltaV budget or transit time. Didn't really envisioned the IP Warp Drive to have the transit time measured in hours, more like days at best to half of what VASIMIR promised.<br /><br />I'm more concerned with how I solve the Conservation of Angular Momentum on my Hyperspace Warp Dive System. Sure, I've tinkered with the idea so that the seemingly near instanantious transit time through Hyperspace via the drive is measured in days at the very least in "real" space-time, having said starcraft accelerate to the orbital velocity of the superior stellar-massed object before the jump, and even surrendered to the idea that Lagrange Points up to Gas Giants could be used as subsituted for stellar-mass gravity points if enough energy is pumped into the drive at the expense of an exponentially greater time dialation that is measured in decades rather than days via stellar-mass dives, but the way Luke explained the problem with such a drive system has me rather worried on my idea.<br /><br />Not sure if decreased transit time would help solve my little magi-tech issue, but whatever would help make it not beat up physics as we know them to a pulp.<br /><br />- <a href="mailto:Sabersonic@hotmail.com" rel="nofollow">Hotmail Address</a> <br /><a href="mailto:jrposadas@gmail.com" rel="nofollow">Gmail Address</a>Sabersonicnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-87623268543612000152011-04-22T22:26:06.697-07:002011-04-22T22:26:06.697-07:00Sabersonic; yes, (I should refrain from posting be...Sabersonic; yes, (I should refrain from posting before coffee or when nodding off), I meant an FTL system that reduced the amount of time needed to go from point A to point B, instead of somehow increasing your delta-V without increasing your remass. You already said that you wanted sub-stellar range warp drive, so different 'grades' of your drive seemed the way to go; a small ship that can deploy from Earth orbit to Jupiter orbit and back again in a matter of hours would be very useful, even if it couldn't get from Sol to Alpha Centuri in a lifetime.<br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-65613824582006971622011-04-22T21:20:21.191-07:002011-04-22T21:20:21.191-07:00Ferrel - I'm not really sure what you meant by...Ferrel - I'm not really sure what you meant by "Reducing Time of Transit", but I do get the idea of different Dive System grades for various "operational ranges" though I wasn't sure if that was really neccesssary since I envisioned star-to-star travel. Though then again, transit time ratio between Hyper spacetime and "normal" spacetime could also be a grade factor. Was that what you meant?<br /><br />- <a href="mailto:Sabersonic@hotmail.com" rel="nofollow">Hotmail Address</a> <br /><a href="mailto:jrposadas@gmail.com" rel="nofollow">Gmail Address</a>Sabersonicnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-46796083897773113522011-04-22T11:05:26.813-07:002011-04-22T11:05:26.813-07:00Sabersonic: I'd go with the 'reducing time...Sabersonic: I'd go with the 'reducing time of transit' type of warp drive; have different 'grades' of drive (reduction of time in transit by 5, by 10, by 100, etc). That should help, I hope.<br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-38391091015639313902011-04-21T22:45:18.236-07:002011-04-21T22:45:18.236-07:00Well, since we're somewhat on the subject, mig...Well, since we're somewhat on the subject, might as well throw in a question of my own.<br /><br />It isn't the Conservation of Causality (paygrade isn't nearly high enough to even think up the correctly worded question), but rather the Conservation of Angular Momentum as mentioned by <a href="http://www.rocketpunk-manifesto.com/2011/03/ftl-part-ii-just-plain-cheating.html?showComment=1300232077536#c8144114989175829857" rel="nofollow">Luke</a>.<br /><br />Basically, how do I plausibly keep that particular law intact with the FTL Drive I described in my responces in the <a href="http://www.rocketpunk-manifesto.com/2010/04/good-shepherd.html?showComment=1270497276716#c6212745491389089436" rel="nofollow">Good Sheperd</a> blog entry?<br /><br />As for Stevo Darkly's scenario, well I don't see a violation of causality as far as I know it. It's one thing to see the past as if it happened before you, it's another to change past events either passively or actively.<br /><br />Then again, I'm not even sure if the scenario that was described would even work in practice.<br /><br />- <a href="mailto:Sabersonic@hotmail.com" rel="nofollow">Hotmail Address</a> <br /><a href="mailto:jrposadas@gmail.com" rel="nofollow">Gmail Address</a>Sabersonicnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-39656593389482562252011-04-21T12:05:06.625-07:002011-04-21T12:05:06.625-07:00Stevo Darkly:
"(Although I sorta presume the...Stevo Darkly:<br /><br /><i>"(Although I sorta presume the unsigned "Anonymous" immediately preceding Milo's comment is from Milo also.)"</i><br /><br />Yeah. Forgot to enter my name, sorry.<br /><br /><br /><i>"However, I'm working out some economic and political background that generally makes large ships too valuable to throw away as super-missiles, and weapons of mass-destruction too much overkill to be militarily effective."</i><br /><br />Using passenger jets as missiles is not militarily cost-effective either. This can be neatly circumvented if you stole your jets rather than building them yourself. There's also simple accidents to worry about.<br /><br />Anyway, it's okay - I found (to my surprise) that numbers were less extreme than I was expecting.<br /><br /><br /><i>"Arguably, this highly decentralized society was only "metastable"."</i><br /><br />The problem is that if you're in a position of sufficient strength, you're going to try getting rid of any enemies that it is within your power to, and particularly ones which pose a threat due to their proximity to your own home.<br /><br />You will end up with something like a Go board - as one chieftain's forces start dominating a part of the island, they will envelope and eliminate other chieftains' retainers.<br /><br />To prevent this, you need strong incentives for different factions to live peacefully with each other even when they're within easy reach of each others' weapons. If the only combat is highly ritualized (probably favoring one-on-one duels between chosen champions, for example - to move away from the Iceland example - ones called "lawyers"), with the rules enforced by a higher authority or by mutual agreement (break the treaty and every other chieftain will gang up on you), then that would permit people to live next-door to their enemies without fearing assassination.<br /><br /><br /><i>"Actually, on such a planet, even if otherwise Earthlike, there may only be a few limited areas habitable to human beings due to temperatures and weather patterns."</i><br /><br />Temperature I'll buy. Although humans (like Eskimos) can live even in subzero temperatures, which are an obvious lower bound for any water-based life, if a planet has a much higher temperature than Earth (perfectly feasible, since Earth is at the lower end of the scale where water remains liquid), then only the poles and very high altitude peaks will be cool enough for humans.<br /><br />I don't think weather is a good excuse. What weather patterns, short of giant years-long hurricanes or relentless Atacama-level drought, would prevent humans from entering? And both of those would hurt native life as well.<br /><br /><br /><i>"For a long time many doubted that such a tidally locked world could harbor life at all, but more recent studies and simulations of water and air current circulation are painting a more optimistic view. Even so, the "back" of the planet would likely be entirely frozen over, and the center of the sunward side would be a blazing hot desert."</i><br /><br />Would not. Simulations show that wind patterns will blow towards the hot pole, meaning that it will be a tropical rainforest, not a desert.<br /><br />Anyway, if it were a blazing hot desert, than I'll classify that back under the "will hurt humans no more than it hurts native life" category.<br /><br />A tidally locked planet would indeed have large areas uninhabitable to humans (the entire dark side, as you said) - but so does Earth (most of the planet is ocean). I don't think this justifies a description of "only a few small regions".Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-85151403479221130582011-04-21T04:25:11.218-07:002011-04-21T04:25:11.218-07:00"Some clues indicate very approximately when ...<i>"Some clues indicate very approximately when the attack occurred, but there are no witnesses or records to identify who did it."</i><br /><br /><i>Oh come on. There's plenty of technology. Just boot up anything too cheap for the pirates to bother ransacking and check logs to see when errors started mounting.</i><br /><br /><i>Besides, someone is bound to have left records, though probably not in an obvious location.</i><br /><br />Yeah, even as I wrote it I knew this was the weakest thing in the whole scenario. Even today we have near-ubiquitious video recording devices in our little phones. Somewhere in the colony would be a camera or phone or personal computing device with a record of the attack, and the pirates would be unable to find and grab/smash them all.Stevo Darklynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-76726200826017862932011-04-21T04:19:23.536-07:002011-04-21T04:19:23.536-07:00"A primary activity of the outpost is investi...<i>"A primary activity of the outpost is investigating the local biota and cataloguing biochemicals that may be potentially useful for [Lord knows what]."</i><br /><br /><i>I expect that applications of some biochemical will only be discovered after the fact, after someone looked at it and went "Hey wait, I can use this for something...", rather than specifically setting out to find a biochemical with a certain application (this can more sensibly be done in a chemistry lab rather than by examining wildlife).</i><br /><br />Yep, that's actually what I'm thinking. If there is life on other worlds, this might be one of the few things that could justify interstellar trade (if FTL travel is relatively cheap). Evolution can produce some odd things that human designers would never deliberately dream up, and some of these may be seredipitiously useful. A major "industry" of a colony world might be for the settlers to catalogue and describe the local biochemistry, and maybe send samples, for chemical and pharmaceutical labs back on Earth. "Hey, this plant sap has an unusual make-up and some weird properties -- maybe it would be useful as a solvent or a cancer cure or an improved glue for Post-It Notes or something. Why don't you use your sophisticated research facilities back home to investigate further?"Stevo Darklynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-49353741891453876812011-04-21T04:02:57.183-07:002011-04-21T04:02:57.183-07:00"Orbiting a red dwarf star HD-[string of numb...<i>"Orbiting a red dwarf star HD-[string of numbers] is the planet Podunk. Local life has evolved there, but only a few small regions are habitable to human beings."</i><br /><br /><i>I take it that is because these regions have been built of with pressurized dome infrastructure, rather than because a few spots on the planet naturally have an entirely different atmosphere or something?</i><br /><br />Actually, on such a planet, even if otherwise Earthlike, there may only be a few limited areas habitable to human beings due to temperatures and weather patterns.<br /><br />An Earth-sized planet of a red dwarf star, if it were close enough and warm enough to have liquid water, would be tidally locked so that only one side of the planet faced the star. <br /><br />For a long time many doubted that such a tidally locked world could harbor life at all, but more recent studies and simulations of water and air current circulation are painting a more optimistic view. Even so, the "back" of the planet would likely be entirely frozen over, and the center of the sunward side would be a blazing hot desert.<br /><br />There might be a habitable belt on the sunward side, but there would also likely be severe winds and strange things like permanent shadows of mountains and stuff resulting in some weird and unpleasant weather. And who knows how much liquid water would be available on the sunward side, with so much frozen on the back. So that's why I'm assuming that even in the "habitable belt," there might just be a few "oases" where humans would be reasonably comfortable.<br /><br />Gotta run -- more later.Stevo Darklynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-73669157511521486202011-04-21T03:44:26.932-07:002011-04-21T03:44:26.932-07:00Thanks for the reminder that any spaceship with to...Thanks for the reminder that any spaceship with torch-drive-like performance would make a helluva missile. Actually, it's even worse than that -- the magi-tech drive that my ships use is propellentless too. (Look up "induction sail" for info.) Basically, I decided that having to deal with rapid propellent consumption and attendant mass ratios was too constraining for the kinds of stories I'd like to tell.<br /><br />However, I'm working out some economic and political background that generally makes large ships too valuable to throw away as super-missiles, and weapons of mass-destruction too much overkill to be militarily effective. Unlike most of you guys, I'm not envisioning large political organizations capable of fielding large military space fleets. <br /><br />The world I'm building is a post-Westphalian, post-nation-state world where geographic location is less important. Instead of large contiguous nation-states, people of different political/cultural affiliations are more geographically mingled than they are today. It would be hard to lob a WMD against a concentrated population of your political enemies without killing a lot of friends and neutrals as well. (Imagine a war between geographically dispersed and intermingled groups such as, say, the Coca-Cola Company and the Mormons. They won't be throwing nukes at each other.)<br /><br />This is inspired in part by medieval Iceland. Any free man of Iceland could choose to be a follower of any of the island's various "chieftains" (not a good translation, but it will do for now) regardless of where that freeman lived. That meant any chieftain could have followers anywhere on Iceland, and the farms of the followers of different chieftains were all intermingled among each other. And there was no one political authority over all the chieftains, either -- the island was "anarchic" in the technical sense of lacking a single overall head.<br /><br />Arguably, this highly decentralized society was only "metastable." It eventually collapsed due to machinations by the king of Norway, some unwitting undermining by the Christian church, and some internal political weaknesses. But it did last for 350 years, which ain't bad. (How long do democratic republics last?)<br /><br />I'm also assuming that tax-evasion technologies such as encrypted anonymous e-cash are both effective and in wide use. So government spending, including military spending, is highly constrained (arguably, perhaps, to a short-sighted degree). The private sector is correspondingly more powerful. There are lots of private security forces but no massive national space fleets with super-weapons. Violence is organized differently: there is very little war between massed state militaries but lots of fighting on the scale of gang warfare, plus some opportunistic piracy. The density of military force is low, and predatory types are more interested in stealing than destroying.Stevo Darklynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-34820951018165158542011-04-21T02:59:50.225-07:002011-04-21T02:59:50.225-07:00Thanks, Milo! And Anonymous! (Although I sorta pre...Thanks, Milo! And Anonymous! (Although I sorta presume the unsigned "Anonymous" immediately preceding Milo's comment is from Milo also.)<br /><br />I put together that scenario mostly just to test whether the combination of "looking into the past" (which, as you pointed out, astronomers already do, just not in such fine resolution) + "spaceships capable of traveling from one star system to another FTL" might somehow screw with the causality of the scenario. I couldn't see how it could -- but I wasn't sure whether I might have overlooked something subtle. I really don't have a good intuitive grasp of relativity at all. That's why I wanted to bounce the scenario off youse guys.<br /><br />The economical, technological and planetary details of the scenario are peripheral to that, but I appreciate your feedback about that stuff anyway. I'll respond via a few other comments to follow.Stevo Darklynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-28721369599787661582011-04-20T16:20:41.821-07:002011-04-20T16:20:41.821-07:00"Orbiting a red dwarf star HD-[string of numb...<i>"Orbiting a red dwarf star HD-[string of numbers] is the planet Podunk. Local life has evolved there, but only a few small regions are habitable to human beings."</i><br /><br />I take it that is because these regions have been built of with pressurized dome infrastructure, rather than because a few spots on the planet naturally have an entirely different atmosphere or something?<br /><br /><br /><i>"A primary activity of the outpost is investigating the local biota and cataloguing biochemicals that may be potentially useful for [Lord knows what]."</i><br /><br />I expect that applications of some biochemical will only be discovered after the fact, after someone looked at it and went "Hey wait, I can use this for something...", rather than specifically setting out to find a biochemical with a certain application (this can more sensibly be done in a chemistry lab rather than by examining wildlife).<br /><br />I mean, I doubt that when Alexander Fleming first discovered Penicillium mould growing in his petri dishes, he immediately knew that its uses would be combating disease and making really tasty cheese.<br /><br />(Okay, so it seems the cheeses actually existed before the antibiotics. Whatever.)<br /><br /><br /><i>"Some clues indicate very approximately when the attack occurred, but there are no witnesses or records to identify who did it."</i><br /><br />Oh come on. There's plenty of technology. Just boot up anything too cheap for the pirates to bother ransacking and check logs to see when errors started mounting.<br /><br />Besides, <i>someone</i> is bound to have left records, though probably not in an obvious location.<br /><br /><br /><i>"One problem I can see is knowing exactly when to watch the Podunk system. I can see how it would be difficult to synchronize calendars, let alone clocks, between stars."</i><br /><br />Anyone capable of performing interstellar travel should be capable of doing the math to compensate for temporal anomalies.<br /><br />Anyway, since you're watching over a wide span of time (the entire period that the attack conceivably could have taken place in), it doesn't matter that much if you're off by a day or two.<br /><br /><br /><i>"Is this likely to result in any causality problems? I don’t see how. For example, I can’t see any way that Captain Tiberius could use this information to travel back to the Podunk system and stop the attack before it happened."</i><br /><br />Nope. As long as your FTL travel is constrained by a special frame of reference, there's no causality problems. Looking into the past like this might be unintuitive, but we can already see the Andromeda of 2.5 million years ago today! The farther you're trying to look into a past, the better a telescope you need to have - resolving a picture with such a small angular size has got to be difficult, even with gravitational lensing unobtainium.<br /><br />It also means, though, that you'll have to wait at least 4 years before bringing the pirates to justice. But then again, if your detectives manage to find them by some other means before that time, then you can send a courier to Van Maanen's star and tell them to call off the plan.Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-75132523710223472552011-04-20T16:19:57.329-07:002011-04-20T16:19:57.329-07:00Stevo Darkly:
"The spaceships have a magitec...Stevo Darkly:<br /><br /><i>"The spaceships have a magitech drive that lets them accelerate at about 1 gee."</i><br /><br />Indefinitely?<br /><br />Obligatory Rick Robinson's First Law of Space Combat test:<br /><br />That would reach 1 Rick in 5 minutes (do damage equal to your mass in TNT), and 86 kiloRicks in 1 day (a 1 kiloton ship leaves a crater just over the size of the Tsar Bomba), but even a 10 kiloton ship after 1 year of acceleration you would "only" have around the energy of a dino-killer.<br /><br />It takes 600 days (coordinate time) to gain kinetic energy equal to your mass energy, and 1000 days (coordinate time) to gain kinetic energy equal to twice you mass energy, which means that you cause antimatter levels of damage.<br /><br />This isn't extremely unreasonable, though it warrants caution. Even if your ships are fuel-efficient enough to accelerate continuously for this duration, someone will probably notice what you're doing and interfere by the time you're able to build up super-destructive speeds. Also, you could cap propellant supplies at one month or so.<br /><br />Formulas... (Note: Accuracy not guaranteed.)<br /><br />E = m*c^2 * (cosh(tau*g/c)-1) = m*c^2 * 2*sinh(tau*g/c/2)^2<br />E = m*c^2 * (sqrt(c^2+(g*t)^2) / c - 1)<br /><br />(E = kinetic energy. g = Earth gravity, or whatever you're accelerating at. c = speed of light. m = mass. tau = proper time. t = coordinate time. Coordinate time is measured from Earth, proper time is measured in the spacecraft's frame of reference.)<br /><br /><br /><i>"travel from settled planets to the outer reaches of the local star system (circa Neptune’s orbit) where space is flat enough to enter the corridors"</i><br /><br />At 1 gee brachistochrone (pretending we're in flat space), reaching Neptune's orbit takes some 11 days, assuming you don't care about coming to a stop when you get there. By this point you would have built up 10 megaRicks (compare to maybe 1 megaRick from a really efficient atomic bomb), meaning that a kiloton ship would deal several times the impact of Krakatoa (likely to cause major inconvenience but not the immediate termination of civilization). This means speeds of some 10000 km/s or 3% c.<br /><br /><br /><i>"However, to use our Sun as a gravitational lens, our telescope would have to be in a focal region at least 550 AU from the Sun. That’s hella far out."</i><br /><br />Just to be clear, the radius of the solar system can be interpreted as 110 AU (if you measure to the heliopause) or 230 AU (if you measure to the size of the bow shock). So 550 AU is well outside the solar system. It's also over 3 lightdays, but still very little compared to the distance to Proxima Centauri (270000 AU).<br /><br />At 1 gee brachistochrone (again, flat space approximation, but this time taking into account the need to stop on the other end), 550 AU takes 67 days to reach.<br /><br /><br /><i>"Among other things, it makes moving the telescope around the Sun to see different parts of the sky problematic."</i><br /><br />I'll say!<br /><br />And you can't wait for natural orbit - an observatory orbiting at 550 AU would take 12900 Earth years to complete one revolution. If it's even still strongly enough affected by the sun's gravity to not be perturbed out of its orbit by other effects.<br /><br />(Note, 12900 = 550^1.5, rounded. Simple.)<br /><br /><br /><i>"However, a white dwarf star such as Van Maanen’s star could be useful as a gravitational lens from closer distances, starting as close as 0.13 AU. Assuming we could travel to the Van Maanen system (14 light years from Sol), and build or transport our telescope there, this is easier to work with."</i><br /><br />That depends on whether Van Maanen's star has a planet capable of being used as a base of operations for supplying the telescope.<br /><br />(Oh, and white dwarfs aren't exactly "stars" since they're no longer undergoing fusion. Rather, they're stellar remnants, like neutron "stars" and black holes. Granted, astronomers are pretty fuzzy on their terminology too...)Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-54659161973958717132011-04-20T11:53:41.078-07:002011-04-20T11:53:41.078-07:00Thanks, Rick! And Ferrell!
(Would still love it i...Thanks, Rick! And Ferrell!<br /><br />(Would still love it if, say, Luke could pronounce on this as well, in case there are any non-obvious ramifications.)Stevo Darklynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-43722047617633554042011-04-20T10:36:40.149-07:002011-04-20T10:36:40.149-07:00I belatedly let the original posts out of spam jai...I belatedly let the original posts out of spam jail!<br /><br />I agree with Ferrell - so far as I can tell, there are no causality issues here. 'Seeing into the past' is odd in terms of our experience, but no violation of causality is implied, because no one is going back to change what happened; they are only recording it.Rickhttps://www.blogger.com/profile/16932015378213238346noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-78971955541347063972011-04-20T10:29:17.424-07:002011-04-20T10:29:17.424-07:00Stevo Darkly: I don't see anything in your sce...Stevo Darkly: I don't see anything in your scenario that violates causalty; no information from the future, nothing happening before the cause, so no violations.<br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-87711444048190983502011-04-20T09:49:12.680-07:002011-04-20T09:49:12.680-07:00Thanks, KraKon! That's all of it -- dupes and ...Thanks, KraKon! That's all of it -- dupes and all.(How do you do that?)Stevo Darklynoreply@blogger.com