dystopic dystopic

bussard ramjets, cryonic stasis, and exoplanetary colonization

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bussard ramjets, cryonic stasis, and exoplanetary colonization

what will it take?

from GalCiv2 Forums
hello everyone,

i'm a bit of a writer, and i can't help but feel drawn to science fiction. that shouldn't be surprising.

lately i've been reading up a great deal on theoretical physics, exobiological speculation, and all that. i was dismayed at first to learn that the chances of faster-than-light travel being physically possible are slim. it was also pretty discouraging when i sat down and looked at the actual speeds that'd be required to traverse sizable parts of the galaxy in a single conscious lifetime. it was a kick when i was down to learn about how difficult terraforming probably would be. but the more i've been learning, the more i've been excited about telling a different kind of science fiction story.

to draw an analogue to our world, the thing that made both the european colonial age and the modern process of globalization have been technology. it's not that we couldn't go to various places around the world before, it just cost too damn much to make anything worth it. i got my BA in sociology, and these sorts of things interest me.

if FTL travel isn't possible, then more than likely it'll be too damn costly to ever colonize beyond our own solar system as the way it's been envisioned in most of the celebrated scifi universes. But there are examples such as Arthur C. Clarke's Songs of a Distant Earth or Sid Meier's Alpha Centauri where humans colonize to escape destruction on earth.

recently i had the chance to meet both Kim Stanley Robinson and Geoff Ryman. Robinson is a hard scifi writer after my own heart; the Mars Trilogy is a really interesting look at our first attempts to colonize within our own star system. Ryman was actually more interesting to talk to, though. maybe because few people have ever heard of him (i was only there because i work at UCSD where he was being hosted). but i actually got to talk to him. he said he thinks we probably won't ever leave our galactic neighborhood.

i'm interested in writing a hard scifi story (or series) myself. i'm interested from a sociological point of view: what would drive us to colonize space? from a writer's point of view, i want to keep the earth around, so i'm not interested in a flight from disaster. what would societies be like after colonies were established? trade would be difficult, but not impossible. same goes for war.

while i'm certainly interested in contributions along those lines, i'm also interested in learning more about the hard science and engineering behind interstellar travel. i've got a lot of questions i haven't been able to answer through wikipedia and google alone. but i'm not about to list them all here.

it seems like a discussion about real ("real") colonization and space travel could use a place on these boards.

i'll kick it off. i've been reading up on propultion especially, and bussard ramjets seem like the most economically feasible option since they gather their fuel as they go - perhaps especially if it could be hybridized with another form such as antimatter-catalyzed fusion. the wikipedia article on bussard ramjets describe that they'd probably need what is essentially a magnetic funnel or ramscoop to gather interstellar hydrogen as propellant.

The mass of the ion ram scoop must be minimized on an interstellar ramjet. The size of the scoop is large enough that the scoop cannot be solid. This is best accomplished by using an electromagnetic field, or alternatively using an electrostatic field to build the ion ram scoop. Such an ion scoop will use electromagnetic funnels, or electrostatic fields to collect ionized hydrogen gas from space for use as propellant by ramjet propulsion systems (since much of the hydrogen is not ionized, some versions of a scoop propose ionizing the hydrogen, perhaps with a laser, ahead of the ship.) An electric field can electrostatically attract the positive ions, and thus draw them inside a ramjet engine. The electromagnetic funnel would bend the ions into helical spirals around the magnetic field lines to scoop up the ions via the starship's motion through space. Ionized particles moving in spirals produce an energy loss, and hence drag; the scoop must be designed to both minimize the circular motion of the particles and simultaneously maximize the collection. Likewise, if the hydrogen is heated during collection, thermal radiation will represent an energy loss, and hence also drag; so an effective scoop must collect and compress the hydrogen without significant heating.


talk about kick-butt imagery! spirals of heated gas careening towards a ship only to be fused and expelled in a jet plume? sweet.

anyway, i've written enough, and i hope it hasn't put anyone off. some of the the community here has proven to be very well read with regard to these kinds of science, so i thought it'd make a great topic for discussion: all things related to space exploration and colonization with reasonable extrapolations of current technology.

my biggest point of curiostiy was with respect to ramjets, so i'll take the kickoff: could the spiral motion of the inbound gas somehow be harnessed to artficially generate gravity by rotating the ship, instead of producing drag?

any volunteers?

final words: i hope no one minds my double-motive. i won't try to steer any dicussion, though if things quiet down i might pose more general questions to keep it going; i encourage anyone interested to pose your own!
off-topic
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Reply #826 from GalCiv2 Forums Top


Btw, no one may militarize space. International law.


International law is a paper tiger. The U.S. and other governments have looked into weapons based on Satelites, even if some or all of them dont have them. A pox on international law.



Looked into. When they actually do it. Tell us.
Reply #827 from GalCiv2 Forums Top

you don't by any small chance remember where you heard that, do you? i've been intrigued by this idea for years, but i've never been able to find anything much on it. i guess i should look again.


sorry this over 20 years ago.
WindowBlinds - Free yourself of the default settings, customize your desktop.
Reply #828 from GalCiv2 Forums Top



Btw, no one may militarize space. International law.


International law is a paper tiger. The U.S. and other governments have looked into weapons based on Satelites, even if some or all of them dont have them. A pox on international law.



Looked into. When they actually do it. Tell us.


HAHA! The thing is Firebender you sound like it CANNOT happen because International law says so... What I am saying isnt if they will arm space but if they can. There are other illegal things happening around the world as we sp.. er, type.

Lets see genocide is illegal by international law...hmmm many people are still dying through mass murder... Assasination is illegal by international law I believe Che what ever his name was killed when it was illegal INTERNATIONALLY.

So how is this international law going to be any diffrent?
Reply #829 from GalCiv2 Forums Top
Looked into. When they actually do it. Tell us.


china tested an anti satilite weapon last month, in orbit
Reply #830 from GalCiv2 Forums Top
Actually, part of my discussion relates to that. The people themselves will still be the same, to some degree. There will be things they simply don't understand about the technology around them. I wouldn't be surprised to see that humans end up even more specialized in the future.


ah, yes. i misunderstood part of the point of your post. yes, i agree. what's funny is the few people who do understand the technology probably wouldn't ever have much reason to explain it in most settings (not in a well-written book anyway, RPGs are another issue).


Denyasis,
totally random, i thought i'd suggest a book i think you'd like. right now i'm reading Imago, the 3rd book in Octavia Butler's Xenogenesis trilogy (Dawn, Adulthood Rites and Imago were also published in a single volume called Lilith's Brood). i read the first two books for a SF class in college, but i put the third down before i got very far into it.

i remember enjoying the first two, but i'm really liking this one. the basic premise of the series is that humanity is saved from near-extinction at the last moment by an alien race, the Oankali. they're a race of "life traders", hybrizing themselves with new life forms they meet as a means of basically expanding a genetic library for themselves, a repitoire of natural abilities if you will. they do this by forming families with 5 parents, a male and female human, a male and female Oankali, and an Ooloi, which is a kind of natural genetic engineer. they can innately manipulate genes, proteins and enzymes on a molucular level, and they're the means by which the Oankali mix with other species.

the books are developed with some very good ideas, but Butler doesn't get bogged down in technical jargon at all. the characters are rich, and the writing's very strong (Butler's easily one of the best writers working today in any genre, IMO). i'd highly recommend it if you haven't read it before. as it is, i might re-read the first two books (and i almost never re-read books).

actually, i'd recommend it to anyone in general, but given your background and some of what you've said about SF writing, i thought you might especially enjoy it Denyasis.
Reply #831 from GalCiv2 Forums Top
Thanks Dystopic! I'm definitely gonna have to check it out. It sounds pretty sweet.
Reply #832 from GalCiv2 Forums Top
ok new question. and yes i do know the answer.


watched part of x file episode


why can you not go back in time and kill your younger self.
Reply #833 from GalCiv2 Forums Top
why can you not go back in time and kill your younger self.


Depends. If you go back and time and kill yourself, you never existed, and therefore couldn't kill yourself, in which case you are still alive...paradox.

However, it is possible that you can kill yourself, provided that the "past" you visit isn't actually connected with your present, like visiting a parallel universe that is identical to a previous state or your native universe. Arguably, though, this isn't time travel.

But in any case, I believe that many scientists think that any device that was somehow capable of time travel would have the inconvenient side effect of generating a field that causes everything within it to rapidly decay at the quantum level. Now, I don't exactly know what "quantum decay" implies, but I'm gonna go out on a limb and say that it would render the machine inoperable.
Reply #834 from GalCiv2 Forums Top
why can you not go back in time and kill your younger self


Einstein said time travel isn't possible.

And as I said in the sorry but the game story has it wrong about Stargate's thread, FTL isn't possible either. Till so far in that thread the only credible piece of resistance offered in the subject was on the topic of light being not totally without mass because it is effected by black holes.
(I know I should post it in that thread but there is hardly any activity so...)
Light isn't effeced by the gravitational pull of the black hole but the distortion in Spacetime by the black hole's death grip. Inside a black hole there is no time. Time stops. Light is frozen in time in a black hole.

What is absolute zero is non-existant and therefore not a factor to begin with(10 points to who can figure this out).


Has no one figured this out yet? Similer to what was said above, its a paradox. Just a random thought in my mind.
Reply #835 from GalCiv2 Forums Top

Depends. If you go back and time and kill yourself, you never existed, and therefore couldn't kill yourself, in which case you are still alive...paradox.


very good.

However, it is possible that you can kill yourself, provided that the "past" you visit isn't actually connected with your present, like visiting a parallel universe that is identical to a previous state or your native universe.


in this case you are not really killing yourself.

FTL isn't possible either.


even if FTL was possible. it would not affect time on the planet. this is just a theory. but say in normal space it takes you 50 years one way to get to Alpha Centauri at the speed of light it only takes you 4 years. so that takes you 8 years to get there and back. the theory is that the earth has still aged 100 years. but the astronauts that went to the moon gained, i think it was 4 seconds on the rest of us, meaning that they were 4 seconds younger than we who stayed on the earth.
Reply #836 from GalCiv2 Forums Top
why can you not go back in time and kill your younger self.
Depends. If you go back and time and kill yourself, you never existed, and therefore couldn't kill yourself, in which case you are still alive...paradox.


FYI that basic connundrum is called the Grandfather Paradox. killing yourself specifically via time travel, i just learned, is called autoinfanticide.
Reply #837 from GalCiv2 Forums Top
from Firebender's post #832

forumid=346&aid=160212">sorry but the game story has it wrong about Stargate's thread, FTL isn't possible either. Till so far in that thread the only credible piece of resistance offered in the subject was on the topic of light being not totally without mass because it is effected by black holes.
(I know I should post it in that thread but there is hardly any activity so...)
Light isn't effeced by the gravitational pull of the black hole but the distortion in Spacetime by the black hole's death grip. Inside a black hole there is no time. Time stops. Light is frozen in time in a black hole.


and I posted

(Citizen)chadwbakerOctober 31, 2007 12:18:52Reply #76

and here is a bit more to add

Before he worked out the general theory of relativity, Einstein had already deduced that gravity must affect a light wave's frequency and wavelength. Light moving upwards from Earth's surface, for example, shifts to longer wavelength and lower frequency, as gravity saps it of some energy. But the effect is tiny in earth's modest gravity. In 1960 Robert Pound and Glen Rebka of Harvard University finally succeed in testing this crucial prediction, and they reported their results in PRL. Today the so-called gravitational redshift is essential for understanding the cosmos and operating the Global Positioning System (GPS).


I linked the site I found this at in the same post

what seems to be your personal idea about light and gravity is not a good theory. I like a good debate Firebender please show some proof if there is any.
Reply #838 from GalCiv2 Forums Top
I remember watching a special on National Geographic about the formation of the universe, where they explained how Gravity of a body, say a sun, is essentially a distortion of space time around it. This way it explained how objects would intereact with gravitational forces but not break any of Newtons laws.

That would acount for the redshift and the fact the light "bends" around large solar bodies, I would presume.
Reply #840 from GalCiv2 Forums Top
why can you not go back in time and kill your younger self.

Depends. If you go back and time and kill yourself, you never existed, and therefore couldn't kill yourself, in which case you are still alive...paradox.


FYI that basic connundrum is called the Grandfather Paradox. killing yourself specifically via time travel, i just learned, is called autoinfanticide.


as you may know... two perfectly same molocules can not occupy the same space, so if you go back in time, simply touching the other you will kill you both...

but first of all... who in their right mind would ever want to go back in time and kill themselves!?!?!?!?!?!?!??!

Reply #841 from GalCiv2 Forums Top
as you may know... two perfectly same molocules can not occupy the same space, so if you go back in time, simply touching the other you will kill you both


touching isn't occupying the same space. also, that sounds like the premise to Time Cop, which was a horrible movie.

but first of all... who in their right mind would ever want to go back in time and kill themselves


who said anything about having a right mind?
Reply #842 from GalCiv2 Forums Top
as you may know... two perfectly same molocules can not occupy the same space, so if you go back in time, simply touching the other you will kill you both



this wouldn't happen because your body is completely different every 5 years. at least your skin is.
Reply #843 from GalCiv2 Forums Top
I remember watching a special on National Geographic about the formation of the universe, where they explained how Gravity of a body, say a sun, is essentially a distortion of space time around it. This way it explained how objects would intereact with gravitational forces but not break any of Newtons laws.

That would acount for the redshift and the fact the light "bends" around large solar bodies, I would presume.


I'll have to do some searching, but if I remember correctly, then the latest observations about gravity effectively negate that notion.

I think it was a quaser being observed from long distance. I'll try to find the story for my next post. But, anyway, what was observed is that gravity from the quaser was blocked by a planetary body. They ran the data and determined that gravity was acting like a radiation in how it was blocked. Which, if proven, would possibly disprove relativity as being accurate as well as accounting for a lot of what is currently being blamed on dark matter.
Reply #844 from GalCiv2 Forums Top
I think it was a quaser being observed from long distance. I'll try to find the story for my next post. But, anyway, what was observed is that gravity from the quaser was blocked by a planetary body. They ran the data and determined that gravity was acting like a radiation in how it was blocked. Which, if proven, would possibly disprove relativity as being accurate as well as accounting for a lot of what is currently being blamed on dark matter.


even einstein accepted that gravity might have a communicative medium (the graviton). but prooving this wouldn't necessarily disprove general/special relativity; it'd simply prove that these theories are incomplete. that's not going to be a shocking statement to any modern physicist, especially since quantum dynamics has already proven the incompleteness of einstein's work.

mass, via gravity, distorts spacetime. this we know through experimental verification. we don't understand how it does this, AFAIK. gravitons may or may not exist; we haven't ever isolated one.

physics can be seen as a series of approximations. no theory as of yet is complete, and if you go back to my post #812, i talked about Godel's incompleteness theorem--which asserts essentially that no model can be complete. E=Mc^2 is a model, not the universe itself. just because mathematics is, hands-down, the best tool we have to describe physical reality, and a pretty good one in itself, doesn't mean it's perfect or complete. a perfect and complete mathematical representation of the universe would need at least one variable for every particle in the universe to be complete, but writing such a formula in the universe would be impossible because we'd need some sort of particle or medium to keep track of all those variables - i.e., at best the universe is its own grand unified theory, experssed not in symbols but in real particles, and we're merely part of the theory  

that's an absurd statement, i know. but to an extent, so is thinking that our "laws of phsyics" are inherent traits of the universe we've had the intllectual power to discover. they are theories, models, approximations of the inherent traits of the universe. we use them pragmatically, because they work (or at least, they work well to satisfy our other goals). when they don't work, we try to figure out what's wrong, and either fix them or invent new theories. this is how scientific knowledge advances. for the sake of our minds, i kind of hope we never achieve complete understanding. we'd be bored.

just to be clear, many modern phsyicists don't see a problem with incomplete theories. they simply think it's best to examine a problem and apply the most accurate theory or theories they have, and they don't necessarily feel a need to integrate these theories. we're still taught newtonian phsyics, after all. why? phsyics isn't a history class, after all. it's still taught it because it still works in enough situations to remain useful. i think relativity is going to remain useful enough that it'll never be thrown out, even if we do come up with better theories to describe things relativity only describes poorly (such as the acceleration of the galaxies away from each other).

BTW Amensotep, welcome to our discussion  i saw your post about hydrogen fuel cell cars and replied. it was both interesting and well-written.
Reply #845 from GalCiv2 Forums Top
what seems to be your personal idea about light and gravity is not a good theory. I like a good debate Firebender please show some proof if there is any.


Here's your proof:

Quote from wikipedia:

There are several ways of describing the situation that causes escape to be impossible. The difference between these descriptions is how space and time coordinates are drawn on spacetime (the choice of coordinates depends on the choice of observation point and on additional definitions used). One common description, based on the Schwarzschild description of black holes, is to consider the time axis in spacetime to point inwards towards the center of the black hole once the horizon is crossed.[8] Under these conditions, falling further into the hole is as inevitable as moving forward in time. A related description is to consider the future light cone of a test object near the hole (all possible paths the object or anything emitted by it could take, limited by the speed of light). As the object approaches the event horizon at the boundary of the black hole, the future light cone tilts inwards towards the horizon. When the test object passes the horizon, the cone tilts completely inward, and all possible paths lead into the hole.[9]



Reply #846 from GalCiv2 Forums Top

There are several ways of describing the situation that causes escape to be impossible. The difference between these descriptions is how space and time coordinates are drawn on spacetime (the choice of coordinates depends on the choice of observation point and on additional definitions used). One common description, based on the Schwarzschild description of black holes, is to consider the time axis in spacetime to point inwards towards the center of the black hole once the horizon is crossed.[8] Under these conditions, falling further into the hole is as inevitable as moving forward in time. A related description is to consider the future light cone of a test object near the hole (all possible paths the object or anything emitted by it could take, limited by the speed of light). As the object approaches the event horizon at the boundary of the black hole, the future light cone tilts inwards towards the horizon. When the test object passes the horizon, the cone tilts completely inward, and all possible paths lead into the hole.[9]


But your not explaining why earth's gravity is effecting the light.. when its going to a gravity You have said light is immune to gravity.


Since earth's gravity is effecting light its not just blackholes. You need to show why Einstein was wrong.

So here again is why you need to prove wrong:

Before he worked out the general theory of relativity, Einstein had already deduced that gravity must affect a light wave's frequency and wavelength. Light moving upwards from Earth's surface, for example, shifts to longer wavelength and lower frequency, as gravity saps it of some energy. But the effect is tiny in earth's modest gravity.


why does earth's gravity the frequency and wavelenght if light is IMMUNE to gravity.
Reply #847 from GalCiv2 Forums Top
why does earth's gravity the frequency and wavelenght if light is IMMUNE to gravity.


i think this explanation might be what you're looking for...

gravity acts directly on objects with mass. since light has no mass, it isn't affected by gravity directly. gravity also distorts spacetime, causing it to expand or contract relative to other observers. since light does move through space, it's affected indirectly by gravitational spacetime distortion relative to obeservers in another spacetime metric.

specifically related to gravity changing the wavelength of light, AFAIK it's actually not that gravity saps energy from light. what's really going on is similar to the red/blue shift phenomenon (that is, if light is emitted from a body moving away from an observer, the light will appear be shifted to the red/low energy side of the spectrum compared to an observer would see who's stationary to the light-emittid body, and the opposite is true for an object moving toward the observer).

when light leaves a gravity well, it travels through "extra" (dialated) space. because nothing adds or removes energy, and because the speed of light is constant, to an outside observer the light appears to be at a lower frequency/ higher wavelength/ less energetic. to put it more simply, when spacetime is stretched, so is the wavelenth of a photon.

this is because the speed of light is constant no matter what your frame of reference is: it's always observed to be (roughly) the constant c. the light doesn't look slower to us, and we can't really "see" spacetime distortion (we envision it with a 2-D planar grid, and where spacetime is distorted we move the grid into the negative or positive Z axis - but it's hard for us to envision 4-dimensional spacetime, let alone distortions in it). the only other possible effect we can observe is that the light looks less energetic.

the reason light doesn't escape the gravity well of a black hole (a singularity) is a bit different. spacetime is 'broken' in a manner of speaking. it becomes tangental: that is, if you imagine the graph of y=tan(x), there are various values for X where the value of Y approaches infinity. from what i understand, spacetime distortion at a singularity is infinite. from the light's perspective, it's travelling on a straight line at constant speed, but from our perspective, it seems like the light disappears. the event horizon of a black hole is actually the point where spacetime curvature becomes infinite. when light crosses an event horizon, it will never come out on the other side because there's infinite spacetime inside the event horizon that it must travel through before it could emerge.

if you're interested in black holes, the work of Stephen Hawking is really the best place to turn, even more so than Einstein.
Reply #848 from GalCiv2 Forums Top
i think this explanation might be what you're looking for...

Stephen Hawking is really the best place to turn, even more so than Einstein.


So this is wrong then or am I just not understanding it...


However in a book that he revised in 1952, Relativity: the special and general theory [20] on page 76 he makes his important statement - that in General relativity, the law of the constancy of the velocity of light in vacuo, which was a fundamental assumption in Special relativity, cannot claim any unlimited validity. And that Special relativity can only hold when there is no gravity affecting light paths. On page 93 he clarifies it further by saying that in General relativity the velocity of light depends on the coordinates of when a gravitational field is present. And that gravity defines the coordinates.

So, light speed is not constant !

from
WWW Link

and I will take back the personal theory Firebender.
Reply #849 from GalCiv2 Forums Top
I think its just two different ways of explaining the same thing, friend. Though the speed of light is constant. The red shift experiments demonstrated that. I think

You see if I were moving forward and I throw a ball forward, the ball will have my original speed plus its own speed, relative to a stationary person. To me, the ball will just appear to have its own speed. However with turned on a flashlight, the speed of the light would we the same, whether its measured by me (I'm moving remember) or by someone who is stationary. That's why its considered a constant.

I hope that helps a bit, the whole light thing really messes with me too.
Reply #850 from GalCiv2 Forums Top
However with turned on a flashlight, the speed of the light would we the same, whether its measured by me (I'm moving remember) or by someone who is stationary. That's why its considered a constant.



this is the part i disagree with. light may be traveling so fast that you can't see the difference but it is there.