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Topic: Thoughts about the Ur-Quan... (Read 49809 times)
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Art
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I'm still a callow undergraduate, so nothing definite, but I'm interested in China as a region and in the 20th century as a time period, though interestingly not that much in 20th-century China. If I decide to specialize I'll probably be a buff of late imperial China; if I decide to be a pompous theorist it'll be the sort who spins interesting yarns about how the 20th century Fundamentally Changed the Course of the World and stuff.
We call it Medieval History too in the States -- well, most of us call it a waste of time when we talk about it, but that's Americans for you; if it doesn't get you a six-figure job it's not worth our attention. No wonder we consume so many boy-band CDs and romantic comedies. 
I do like reading about the hard sciences, though not enough to be a scientist and not enough to reliably talk about things I haven't read about in detail.
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Art
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Well, science fiction is different from science -- I read a whole lot more of the former than the latter, and if it were possible to major in science fiction at my school I might do it.
I would recommend taking a look at some layman-level science books, especially if you're into science fiction -- try a series like the Science of Star Trek books (starting with the Physics of Star Trek); Isaac Asimov was a great writer of science nonfiction in his day, as well as writing great sf, and anything that starts with Asimov's Guide is fun.
The site that I have to thank for most of my habit of trying to think about science fiction common-sensically and critically is http://www.stardestroyer.net, one of the major "Star Trek vs. Star Wars" sites. Silly as the concept sounds, it goes into detail about how to imagine an sf world as though it were real (and how to do this in such a way as to prove that the Empire could kick the Federation's ass). Worth a look.
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Death 999
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We did. You did. Yes we can. No.
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What would the Leyland whip manuveur look like around a black hole.
The Leyland whip maneuver as seen in Star Control does not exist in real life.
In SC, it appears that gravity is allowed to accelerate your ship above its maximum thrusting speed, and while you're in the gravity field the ship's engines will not slow it down from that point, so you can use the thrusters to help your ship maintain its new velocity while climbing out of the gravity well. Obviously, these principles do not apply to real life.
Real gravitational whips operate very differently.
Consider the case of a very light object approaching a very heavy object off to one side so it won't collide. The gravity of the heavier object will pull the lighter object into a parabola, and will not impart any energy to the lighter object... in the reference frame of the heavy object.
BUT, if you are considering things in a different reference frame, the heavy object can give energy to the ligher object or take it away. The simplest case is where you look at the same situation from the frame of reference where the light object is initially at rest: along comes this heavy object and hurls the light object off in some other direction!
So, a gravitational whip basically puts craft near the path of incoming planets and lets those planets add a portion of their orbital momentum to that of the craft. A braking gravity whip on the other hand lets the craft gradually catch up with the heavy orbiting object and whip around so it gives its energy to the heavier object (the reverse of the second example).
Just FYI.
I'm assuming the ship hits the axis at just the right angle to spin AWAY from the even horizen so as not to get trapped in the supposed time dilation.
I am not sure what you mean here... do you mean that the ship has a high enough impact parameter that it misses the event horizon? Basically, it would look like any other gravity whip but the attractive object will be very very small. BTW, there WILL be time dilation, that is one thing we've measured directly extensively (though not near black holes, we see no reason for this to be suspended).
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« Last Edit: August 12, 2004, 10:42:59 pm by Death_999 »
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Death 999
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We did. You did. Yes we can. No.
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Well, it all depends on the size of the black hole. You get a black hole with the mass of the Earth, and your only advantage is that you can get much closer. Which is a big advantage... but you'd have problems with tidal forces.
Also, it's not an 'active galaxy', it's an 'active galactic nucleus'.
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Chrispy
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Isn't a black hole a finite amount of mass in an infinitely small space? The size of a black whole is therefore always the same (infinitely small).
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Art
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Infinitely small space is a poor way to say it. Black holes just happen to have a volume very small compared to the gravity they exert. The equations tell us that when the ratio of volume to mass reaches a certain point things that get close to the stuff inside the black hole aren't able to escape the gravity again. So the black hole is "black", and the stuff inside it is invisible. What actually *happens* to the stuff inside, whether it's really crunched up into an infinitesimal point or has dropped through into another universe or whatever, is not knowable, because of the black hole being black. Hence the stuff inside a black hole is unique because it doesn't seem to affect or be affected by other stuff in the universe while the black hole lasts (it does eventually self-destruct, due to Hawking radiation, but that's another story). The laws of physics can't predict anything that happens in there; it's a single piece of the universe cut off from everything else, hence the name "singularity". (I know I'm butchering the explanation; someone else correct me if I'm wrong on any point.)
So yes, the singularity may or may not be infinitesimal. That's not what we care about, though; we define black holes by what we can observe of them, and what we *see* about the black hole is the simple fact that stuff that gets too close gets sucked in and never comes out again, and the size of the black hole defined by how close you can get before you never come out again -- the diameter of its event horizon. And the diameter of the event horizon is just determined by how strong, exactly, the gravity exerted by the singularity is at any point, and that's determined by the different finite masses that can go into making a black hole. Some black holes are made of really, really big masses crunched up small, like the black hole that might be at the center of the Galaxy holding it together, and in theory you could make a black hole of something very small, like the Earth, and the two black holes would be very different sizes. (The Earth's own gravity would never be able to crunch it up into a black hole normally, but it could be made into a black hole by some other force. Mini black holes may exist somewhere, formed by the pressures of inflation in the Big Bang, or so sf books say.)
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Art
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I'm assuming the ship hits the axis at just the right angle to spin AWAY from the even horizen so as not to get trapped in the supposed time dilation.
It's not supposed, it's very real. GPS systems have to have their clocks adjusted to take the very tiny gravitational time dilation caused by the difference in time's passage between the surface of the Earth and Earth orbit. It's not something that just starts and stops, though; little differences in time's passage occur everywhere because of slightly differently shaped space-time in areas with different gravity.
Black holes just create a very noticeable difference in a small area of space, but the effect (as does the gravity that causes it) slowly grows less pronounced as you move away from the black hole. Time dilation wouldn't be particularly serious if your passage near the black hole was not too long and stayed far enough away from the event horizon; maintain a distance from the black hole about twice as far from the center as the event horizon and you'll only lose 50% of the time you spend in there (i.e. if you come out after a week the place you return to will have experienced a week and a half).
Not that there aren't other problems with time dilation inherent in the situation of an interstellar civilization. The impossibility of truly synchronizing clocks between ships that are always popping into and out of TrueSpace at amazing apparent FTL velocities seems to make no difference in the SC2 universe, and one can only conclude that Hyperspace does a good job of keeping all ships synced to some universal Hyperspace time that, from the perspective of the TrueSpace universe, is as imaginary as the arrangement of Hyperspace constellations.
The game doesn't really work that way, but in theory one could imagine a world connected by a Hyperspace-like construct where, say, the Chenjesu civilization "actually" lives in a time thousands of years after humanity's "present" -- and, since they're thousands of light-years away, that's why they pick up human radio transmissions from our present in *their* present. This doesn't matter, of course, since communication between the Chenjesu and Humans in real space and real time is impossible, and the nature of Hyperspace means that ships and signals traveling through Hyperspace (or the Einstein-Rosen bridge or whatever it is) arrange themselves in a timeline that matches the shared timeline of those two ends of Hyperspace, or the wormhole, or whatever. (Two events separated on one side of the line by one year are separated on the other side of the line by one year, but the two sides of the line are separated by 10,000 years.) If you think about it it almost has to work this way -- simultaneity is not just unlikely but *meaningless* for two planets separated by a distance measurable in light-years -- but it's still a little disturbing to imagine.
Anyways, time dilation is only one of your problems concerning black holes. The bigger issue is that even if you don't tumble into the event horizon just being near black holes is unhealthy; very great mass in a very small volume will exert very strong tidal forces. That is, the force of gravity will increase very quickly as you get closer to the black hole because of its small size. Get too close to it, and the gravity on the side of your ship next to the black hole will be so much stronger than the gravity on the far side that your ship will rip in half. (This same idea is why oceans on the side of Earth facing the moon lift away from the Earth slightly toward the moon's gravity and cause tides. Hence the name.)
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Art
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"Pinhead"? The distance of a black hole's event horizon from its center in the case of stellar black holes (formed from a star collapsing, the most common kind) is measured in thousands of kilometers.
The size of the singularity inside the black hole is unmeasurable since the singularity cannot, by definition, be detected or interacted with from outside. You can say that a given mass *becomes* a singularity if it's squeezed into a spherical volume whose radius is less than a certain distance -- the Schwarzschild radius -- and that radius is often used to measure a black hole. That radius is very small, but is still measured in kilometers when dealing with stars -- the Sun's Schwarzschild radius is 3 kilometers, and that of a supergiant star that could become a black hole on its own would be several times that.
Light being trapped by a black hole is a consequence of the General Theory of Relativity, which (among other things) says that all matter and energy, including light, is affected by gravity. All gravity is in relativity is a curvature of space-time; things moving through curved space-time get their paths through space deflected. That includes photons. The General Theory was proven when Einstein showed that Mercury's orbit looked different from what we expected it to be because the light coming from Mercury was getting bent out of its path by the Sun's gravitational field.
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Bobucles
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The event horizon itself is huge, but thats just the outer limit of the inescapable gravitational pull, when it begins time dilation.
The singularity itself would be tiny.
At least, thats what i remember my 8th grade science teacher saying =p
Compared to how large matter is normally, a black hole is tiny. But we don't have the instruments to figure out just how tiny one is, yet. The singularity of the blackhole in the center of the galaxy could either be smaller than a pinhead, or larger than jupiter. I don't think anyone is sure how big it is. If we could figure out the exact size, that would be a very important thing indeed.
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