That's not possible, by information theory. In order to simulate a chaotic system, one needs perfect information (butterfly effect). Any system large enough to store info on the entire universe must have all the matter in the universe.
IANAP (yet, still studying) however there appears to be a great deal of evidence pointing towards our universe being nondeterministic. This means that chaos theory in the simplistic, naive sense isn't really valid. The butterfly effect assumes some level of determinism (it is based on the idea of cause and effect, and sensitivity to initial conditions). If you throw nondetermism (constantly random factors) into the equation, the "butterfly effect" can be drowned out. Even if you have *PERFECT* information on the current state of the system, it doesnt' help you much because its behavior is still the result of many stochastic processes.
Put another way, imagine a tree of all possible universes starting with the one we are in right now. This tree represents the set of all possible futures (nearly infinite, if quantum physics is indeed correct that our universe is nondeterministic). Now, if you make some change to the starting universe, if you go far enough into the future the two trees will end up looking identical (that is, in some universes the probabilities align to exactly cancel out the change, and this is of course symmetric).
So if you want to look at possible futures, you really have to look at it in a probabilistic fashion, and for that you don't need perfect information, because IT DOESN'T REALLY MATTER.
Chaos theory is great and all, but take it out of context and it can really mislead you.
I need to RTFA more often... apparently it *WAS* only a mass measurement. Heh. I suppose then what I said didn't make much sense, tehy were simply tracking the movement of the star very precisely (probably dopplar, there's no mention of a transit).
Ah, I need to RTFA more often... apparently it *WAS* only a mass measurement. Heh. I suppose then what I said didn't make much sense, tehy were simply tracking the movement of the star very precisely (probably dopplar, there's no mention of a transit).
Measuring the star's wobble via doppler shift can tell you the mass of the planet, and its period of revolution. The calculations pretty much treat the planet as a point mass, because it's roughly spherical. There's no information from dopplar shift that I'm aware of which can give you information on teh size of the planet.
They are talking about measuring the "tilt" of the light, presumedly polarization.
This is something that to my knowlege has never been done before, almost all extrasolar objects which are measured via astrometry are very large (with the notable exception of neutron stars, they are very small, but massive and bright). This is very cool and cutting-edge stuff, it's rather amazing IMHO.
Cheers,
Justin
The original article can be found here:
http://mcdonaldobservatory.org/news/releases/2002/ 1203.html
That particular article seems to be almost as light on details, but at least it's from the horse's mouth.
For another interesting read, try this article about a grad student there who believes they caught a black hole consuming an entire star. Pretty cool stuff.
I would assume the "tilt" of the light would be polarization. Diffraction doesn't really make much sense in this context (diffraction is really only measurable if the size of the object is within a few orders of magnitude of the size of the radiation, which is not the case here) Refraction doesnt' make sense, because that would be gravitational lensing which really doesn't tell you anything except the mass of the object. The planet's atmosphere wouldn't be big enough to cause a measurable refraction from our perspective, so I think we're pretty much left with the idea that it must be polarization. (Someone correct me if I'm wrong, I'm studying the theoretical aspects of astrophysics, not the observational aspects).
I think it was the emphasis on character that really made me fall in love with the concept of space opera. Do I want a book that makes me think? Yes. Do I want the book to be about amazing device X? No. I wnat it to be about how people deal with Amazing Device X, or how they use it to accomplish something, or how the nature of what it is to be human is revealed by some facet of Amazing Device X.
I guess I'm also a totally escapist reader. I'm an undergrad physics major, but i'd much rather be a 23rd century starship captain (born too early, alas) if I could. With a book, I can be there, having great adventures (without getting hurt, which is probably the b est part).
Bujold is really good... The other two main authors I like are David Weber (discussed at some length on this site previously, but you really have to read the whole series, and some of his other stuff is not good), and Timothy Zahn (probably still my all-time favorite, he has written some really amazing Sci-Fi because he *ALWAYS* gets his science right, yet his characters are totally believable).
Check them out if you get the chance. Thanks for the reply:)
Though often times in Sci-Fi, there's a great emphasis on technology or tricky plots, there's nothing more off-putting to me than a lack of interesting charactors. For instance, the book The Light of Other Days has an arguably good and interesting plot, and has technology that's both believable and very cool. But it lacks any sort of actually interesting charactors. The kind of character that makes you just want to go and meet them.
On the other hand, one of my favorite SciFi writers, Lois McMaster Bujold, manages to incorporate amazing characters. The tech in her universe is fairly generic (in fact, it rarely calls attention to itself) and while it's mostly scientifically correct (that is, it doesnt' make any blatent errors) it doesn't seem to overly concern itself with mundane scientific details, but instead tells a very human story. And that, to me, is very important.
Yes, it's nice to have your action take place on a superintelligent space-ship, travelling through time to save the galaxy, but if your characters lack substance, I frankly don't care if they live or die. Good characters make people care.
Actually CDs which have been laminated make excellent coasters. My roommate's girlfriend printed up a bunch of Anime CD-Rs which we use around the appartment, they work very well.
It has it's moments...who can forget "Conan the Librarian" or "Gandi 2 - No More Mr Nice Pacifist Resistance Leader"?
Yeah that's true but "Raul's Kingdom" was probably the best of all... "Today we'll be teaching poodles how to fly!" Heh, too bad that actor guy died during the filming:(
It's still a terrible example of a movie, funny though it may be!
It's obvious that the story's poster didn't really look into FORTRAN much past the aging F77.
I currently use F77 to do research in magneto-hydrodynamics simulations of neutron stars on Cornell's Velocity Cluster (which has been featured on slashdot before). Fortran, due to its lack of things like pointers, etc, is rediculously efficient, and almost completely cross platform (because surprise surprise- it's very difficult to attempt to do anything remotely platform specific). The language is much simpler than something like C with pointers, etc, that must be messed with. Sure it's ugly as hell, but once again the newer versions of Fortran take care of most of these issues.
I would suggest that anyone interested in high performance computing should check out High Performance Fortran. It's a set of extensions to the F90 language to allow the seemless integration of large-scale parallelization in your code. It also has several other performance advancements.
I highly disagree with the poster of the story, Fortran 90 is much more modern than F77, including things like objects, safe pointers, better recursion, better array sharing, generic routines (a type of function overloading). The language syntax is also much more lenient than F77 (which was designed to work with punchcards). It also has some really great array operations (things like slices, etc) that are rediculously fast. While I absolutely hate F77, if I was going to write a computationally intensive simulation, I'd probably do so in F90 or HPF.
A lot of people still use Fortran, especially computational physicists and meteorologists... Many of these people don't have time to learn new programming languages, and Fortran works very well for what they need, better in most situations than almost any other language. It's something to consider.
The problem with that is if it was in fact a truely gravity-like force, it would not be limited to the surface.
It's odd, most of the forces we encounter in our daily life are contact forces, so we're not intuitively used to the idea of a permeating force (like gravity).
But just to be a smart ass, I'll show that jerk is once again not responsible for the damage, no matter if it's being pulled on the surface or what.
I want you to imagine a body in free space, no forces acting on it. Now, say you have a drag line or something connected to it, from which you can pull on the object. This drag line is connected to the surface of the object, so, your force only acts on the object.
Now, to make things more obvious, lets say the object is a long chain of various modules... you're only pulling on the first, and the chains holding them all together pull on the rest. In reality, any structure is a lot like that on a very small level, so it seems appropriate enough to me. Lets say that you use a rocket to apply a near-constant acceleration pulling this thing. I say near constant, because its thrust slowly increases.
As this thrust slowly increases, so does the force on the first module. And anyone that's done a bit of mechanics will know this also increases the force on the next module, and so on. Chains have a finite strength. Continue to keep upping the trust and you will reach a point at which the object breakds because the chains holding it together can no longer take this constant force.
Anyways... why isn't JERK the problem? Well, it comes from the fact that the thing that deforms an object is a force, not a change in force. If you took a can and suddenly applied 500+ lbs of force to the top of it, sure it'd crumple but the same thing gos if you slowly stacked up weights on top. There are exceptions to this rule (namely certain materials are affected by the shock waves created by large change in force at their surface) or that have structural properties that change over time (for instance, oobleck, that gooie cornstarch stuff that gets hard if you smack it). This is a valid point, however this is a specific phenomenon related to a specific set of materials, and is not a general physical principle. I suppose it could be argued that if you had a gravity weapon like that, that to save power, you'd pulse it such that the force wasn't enough to destroy the object but that it was quick enough to send a shockwave through the object to destroy delecate internals.
make me think that you are looking at this from a different perspective than many of us would. If you supply a uniform force to my body you will crush me if the force is directed towards my center. This is how I read your statement - that the force in question would be like atmospheric pressure.
I assume you mean all that equal force would be acting in the same direction, not pressing on the outside of my body or can towards the middle.
Yes, alas, I'm a Physicist In Training, so I tend to use such terms rather litterally. When I speak of force, I speak of it as a vector quantity, thus a uniform force could really only be in one direction. When I say uniform, I mean applied to the entire body, not simply to the surface as one would apply a force with, say, an earth-like atmosphere.
You raise a good point, I should be more careful to specify what I mean by things... I talk to physics majors so often that I take it ofr granted that everyone knows a "uniform force upon a body" means throughout the body inside and out. Clearly you've shown that's not the standard way of perceiving it.
>
Certainly they can. Take a familiar object (say, an empty soda can) and put it in a uniform 20g field and it would crush.
It would only crush if it was being pushed by the gravitational field against something else. And, if that is true, then obviously the bottom of the can is not being accellerated at all (it is staying in the same place). From the can's perspective, part of it (the top part) is being accellerated, while the bottom is not. That's not a uniform accelleration. The reason that objects can be crushed is that you can accellerate part of the object without accellerating the rest of the object, thus changing the size of said object!
Be careful that you are not confusing uniform acceleration with uniform velocity. The first is not an inertial reference frame while the second is. Any simple accelerometer will tell you that you are accelerating; it is the special relativity constancy of physics that holds in the intertial reference frame. You might be thinking of Einstein's Equivalence Principle that says (colloquially) that you can't tell if you are standing on the surface of the Earth or in an elevator that accelerates in free space at 9.8 m/s2.
Once again, you are wrong. A simple accelerometer only tells you if you are applying a force on the sensor element in the accellerometer. Imagine that you are in free space with no forces acting on you. A properly calibrated accellerometer will read zero. Then imagine that you are moving with some velocity, and you encounter a planet. You begin to be pulled towards the planet, but your accellerometer reads zero. It will only register a gravitational pull on the sensor element if there is something to oppose it. In this case, you have nowhere to stand, so you cannot oppose the gravitational force; thus it reads nothing. It is physically impossible for the accelerometer to "know" you are falling down the gravity well. Another way of saying it is that accelerometers only work if you are feeling a force that the sensing element is not. (for instance, you're being pulled by a drag line to a spaceship)
So while it is true that there is a big difference here between constant acceleration and constant velocity, it doesn't change the validity of my previous post. And inertial reference frames have nothing to do with this, my discussion is entirely in newtonian mechanics, it need not require relativity.
I suppose I understand how my points could have been misunderstood, as I use my words in a very precise manner. They will not be true when interpreted imprecisely.
I know this sounds rediculously obvious (because it is), however I cannot think of any full-featured compter more efficient than a good laptop.
You could possibly run it directly off of your DC power, and you can take it anywhere you want. Laptop power consumption is typically less than 50 watts during peak usage, and during sleep it can use much less than that.
I know they aren't perfect, but sounds like it's what you need.
First of all, mad props for knowing the proper term for change in accelleration. Unfortunately you have a few incorrect physical ideas, perhaps based on some false assumptions.
I would like you to imagine a body in free space. Any accelleration of that body, or any change in that accelleration (and so on), provided the change was uniform throughout the body. This is the norm for graviational forces with extremely small gradients, like that a tthe surface of the earth). In fact, uniform accellerations cannot possibly inflict damage on an object. There is no truth to the idea that "jerk" is what causes damage.
What causes damage to any object is the application of differing amount of force to different parts of the object. For instance, if I was to hit you with a baseball bat, I'd be applying a lot of force to a small area of your body (that is, the outer layer of your skin at the point of impact). The rest of your body would not feel this force, and thus part of you would be compressed. If I was to, say, apply the same amount of force evenly over your body, it would do you no harm whatsoever (in fact, you could not possibly detect it, unless you noticed you were suddenly moving relative to everything nearby, that is, assuming things are in fact nearby).
"Jerk" has nothing to do with it. The only way a gravity weapon can be harmful to something is for it to have a very strong gradient, or for you to change the path of the body in such a way that it causes a high speed collision.
See my other post about possible ways the device could inflict damage on something else without inflicting damage on itself. It's quite possible to destroy an object without applying a *NET* force to it.
Of course, we do not even fully understand what gravity "is", so it's somewhat rediculous to think that they are developing gravity based weapons any time soon. They did say "gravity-like" though, so who knows what that means...
DISCLAIMER: I am not a physicist, but I am studying to become one at Cornell.
It was good of you to notice this rather important issue, however you are only partially correct... Imagine a situation where this gravity-like force is not evenly distributed, in fact the force vectors are such that they have a high magnitude, but are pointing in different directions in different places so that when summed up together, they add to zero (or near zero). This is a very common occurance in situations where forces between two objects are applied via waves (and different areas of the object may be at different phases of the wave, and thus have different vectors).
Don't be so quick to assume that this weapon is simply a pushing or pulling effect... it could be a symmetrical sheering force (part of the target is, say, pulled up, and part is pulled down, ripping it apart) or something similar.
How the hell they generate a gravity-like force, however, is completely beyond me. No problem with Newton though. Perhaps it's electromagnetic yet affects nonconductors?
(Also, if you did have a "poking" type weapon, it may be possible to couple the gravitational force to a plasma inside the weapon that will be accellerated out of the back, absorbing whatever momentum the attack generated).
DISCLAIMER: I am not a physicist (yet) but I'm studying to become one.
I most definately second that about Vorkosigan, there's a few of the books that aren't easy to get ahold of that I'd really like to read, and I'm definitely going to buy the next one.
Granted their code-morphing and use of VLIW had some interesting concepts, and their power consumption was perfect for laptops, but there just wasn't much of a market for what they developed. Had some of the bigger players (Dell, etc) actively pushed transmeta chips on the market, perhaps they might have made some money.
I for one am not sad this happen... they had some good ideas, but nothing insanely great. br.
Slashdot Mirror
That's not possible, by information theory. In order to simulate a chaotic system, one needs perfect information (butterfly effect). Any system large enough to store info on the entire universe must have all the matter in the universe.
IANAP (yet, still studying) however there appears to be a great deal of evidence pointing towards our universe being nondeterministic. This means that chaos theory in the simplistic, naive sense isn't really valid. The butterfly effect assumes some level of determinism (it is based on the idea of cause and effect, and sensitivity to initial conditions). If you throw nondetermism (constantly random factors) into the equation, the "butterfly effect" can be drowned out. Even if you have *PERFECT* information on the current state of the system, it doesnt' help you much because its behavior is still the result of many stochastic processes.
Put another way, imagine a tree of all possible universes starting with the one we are in right now. This tree represents the set of all possible futures (nearly infinite, if quantum physics is indeed correct that our universe is nondeterministic). Now, if you make some change to the starting universe, if you go far enough into the future the two trees will end up looking identical (that is, in some universes the probabilities align to exactly cancel out the change, and this is of course symmetric).
So if you want to look at possible futures, you really have to look at it in a probabilistic fashion, and for that you don't need perfect information, because IT DOESN'T REALLY MATTER.
Chaos theory is great and all, but take it out of context and it can really mislead you.
Did anyone else read "European Life in Doubt"?
:)
I guess I should probably get some sleep
This is a dupe.... Maybe cowboyneal is now stealing stories from chrisd? ;)
I need to RTFA more often... apparently it *WAS* only a mass measurement. Heh. I suppose then what I said didn't make much sense, tehy were simply tracking the movement of the star very precisely (probably dopplar, there's no mention of a transit).
:)
Sorry about that
Ah, I need to RTFA more often... apparently it *WAS* only a mass measurement. Heh. I suppose then what I said didn't make much sense, tehy were simply tracking the movement of the star very precisely (probably dopplar, there's no mention of a transit).
:)
Sorry about that
Measuring the star's wobble via doppler shift can tell you the mass of the planet, and its period of revolution. The calculations pretty much treat the planet as a point mass, because it's roughly spherical. There's no information from dopplar shift that I'm aware of which can give you information on teh size of the planet.
They are talking about measuring the "tilt" of the light, presumedly polarization.
This is something that to my knowlege has never been done before, almost all extrasolar objects which are measured via astrometry are very large (with the notable exception of neutron stars, they are very small, but massive and bright). This is very cool and cutting-edge stuff, it's rather amazing IMHO.
Cheers,
Justin
The original article can be found here:/ 1203.html
http://mcdonaldobservatory.org/news/releases/2002
That particular article seems to be almost as light on details, but at least it's from the horse's mouth.
For another interesting read, try this article about a grad student there who believes they caught a black hole consuming an entire star. Pretty cool stuff.
I would assume the "tilt" of the light would be polarization. Diffraction doesn't really make much sense in this context (diffraction is really only measurable if the size of the object is within a few orders of magnitude of the size of the radiation, which is not the case here) Refraction doesnt' make sense, because that would be gravitational lensing which really doesn't tell you anything except the mass of the object. The planet's atmosphere wouldn't be big enough to cause a measurable refraction from our perspective, so I think we're pretty much left with the idea that it must be polarization. (Someone correct me if I'm wrong, I'm studying the theoretical aspects of astrophysics, not the observational aspects).
Cheers,
Justin
I think it was the emphasis on character that really made me fall in love with the concept of space opera. Do I want a book that makes me think? Yes. Do I want the book to be about amazing device X? No. I wnat it to be about how people deal with Amazing Device X, or how they use it to accomplish something, or how the nature of what it is to be human is revealed by some facet of Amazing Device X.
:)
I guess I'm also a totally escapist reader. I'm an undergrad physics major, but i'd much rather be a 23rd century starship captain (born too early, alas) if I could. With a book, I can be there, having great adventures (without getting hurt, which is probably the b est part).
Bujold is really good... The other two main authors I like are David Weber (discussed at some length on this site previously, but you really have to read the whole series, and some of his other stuff is not good), and Timothy Zahn (probably still my all-time favorite, he has written some really amazing Sci-Fi because he *ALWAYS* gets his science right, yet his characters are totally believable).
Check them out if you get the chance. Thanks for the reply
Though often times in Sci-Fi, there's a great emphasis on technology or tricky plots, there's nothing more off-putting to me than a lack of interesting charactors. For instance, the book The Light of Other Days has an arguably good and interesting plot, and has technology that's both believable and very cool. But it lacks any sort of actually interesting charactors. The kind of character that makes you just want to go and meet them.
On the other hand, one of my favorite SciFi writers, Lois McMaster Bujold, manages to incorporate amazing characters. The tech in her universe is fairly generic (in fact, it rarely calls attention to itself) and while it's mostly scientifically correct (that is, it doesnt' make any blatent errors) it doesn't seem to overly concern itself with mundane scientific details, but instead tells a very human story. And that, to me, is very important.
Yes, it's nice to have your action take place on a superintelligent space-ship, travelling through time to save the galaxy, but if your characters lack substance, I frankly don't care if they live or die. Good characters make people care.
Actually CDs which have been laminated make excellent coasters. My roommate's girlfriend printed up a bunch of Anime CD-Rs which we use around the appartment, they work very well.
I heartily agree... /.ers seem to love google, and it's definately save a lot of typing.
:)
Maybe comments might even be more insightful on average?
Or maybe that's not saying much
It has it's moments...who can forget "Conan the Librarian" or "Gandi 2 - No More Mr Nice Pacifist Resistance Leader"?
:(
Yeah that's true but "Raul's Kingdom" was probably the best of all... "Today we'll be teaching poodles how to fly!" Heh, too bad that actor guy died during the filming
It's still a terrible example of a movie, funny though it may be!
I feel so bad for anyone who actually *GETS* a reference to that terrible movie!
(Still funny though)
Only 17 comments so far and the server's melted. I happenned to get a few picts myself, but that's about it.
We really need a slashdot cache! Come on commander taco, surely you can program that!
Netscape 7.0 will suck. Film at 11.
It's obvious that the story's poster didn't really look into FORTRAN much past the aging F77.
I currently use F77 to do research in magneto-hydrodynamics simulations of neutron stars on Cornell's Velocity Cluster (which has been featured on slashdot before). Fortran, due to its lack of things like pointers, etc, is rediculously efficient, and almost completely cross platform (because surprise surprise- it's very difficult to attempt to do anything remotely platform specific). The language is much simpler than something like C with pointers, etc, that must be messed with. Sure it's ugly as hell, but once again the newer versions of Fortran take care of most of these issues.
I would suggest that anyone interested in high performance computing should check out High Performance Fortran. It's a set of extensions to the F90 language to allow the seemless integration of large-scale parallelization in your code. It also has several other performance advancements.
I highly disagree with the poster of the story, Fortran 90 is much more modern than F77, including things like objects, safe pointers, better recursion, better array sharing, generic routines (a type of function overloading). The language syntax is also much more lenient than F77 (which was designed to work with punchcards). It also has some really great array operations (things like slices, etc) that are rediculously fast. While I absolutely hate F77, if I was going to write a computationally intensive simulation, I'd probably do so in F90 or HPF.
A lot of people still use Fortran, especially computational physicists and meteorologists... Many of these people don't have time to learn new programming languages, and Fortran works very well for what they need, better in most situations than almost any other language. It's something to consider.
Cheers
Justin
The problem with that is if it was in fact a truely gravity-like force, it would not be limited to the surface.
It's odd, most of the forces we encounter in our daily life are contact forces, so we're not intuitively used to the idea of a permeating force (like gravity).
But just to be a smart ass, I'll show that jerk is once again not responsible for the damage, no matter if it's being pulled on the surface or what.
I want you to imagine a body in free space, no forces acting on it. Now, say you have a drag line or something connected to it, from which you can pull on the object. This drag line is connected to the surface of the object, so, your force only acts on the object.
Now, to make things more obvious, lets say the object is a long chain of various modules... you're only pulling on the first, and the chains holding them all together pull on the rest. In reality, any structure is a lot like that on a very small level, so it seems appropriate enough to me. Lets say that you use a rocket to apply a near-constant acceleration pulling this thing. I say near constant, because its thrust slowly increases.
As this thrust slowly increases, so does the force on the first module. And anyone that's done a bit of mechanics will know this also increases the force on the next module, and so on. Chains have a finite strength. Continue to keep upping the trust and you will reach a point at which the object breakds because the chains holding it together can no longer take this constant force.
Anyways... why isn't JERK the problem? Well, it comes from the fact that the thing that deforms an object is a force, not a change in force. If you took a can and suddenly applied 500+ lbs of force to the top of it, sure it'd crumple but the same thing gos if you slowly stacked up weights on top. There are exceptions to this rule (namely certain materials are affected by the shock waves created by large change in force at their surface) or that have structural properties that change over time (for instance, oobleck, that gooie cornstarch stuff that gets hard if you smack it). This is a valid point, however this is a specific phenomenon related to a specific set of materials, and is not a general physical principle. I suppose it could be argued that if you had a gravity weapon like that, that to save power, you'd pulse it such that the force wasn't enough to destroy the object but that it was quick enough to send a shockwave through the object to destroy delecate internals.
Is that what you meant?
The robots will race from Los Angeles to Las Vegas completely without human intervention. This could prove useful in the battlefield someday.
Yes, when our battle robots stumble upon Canada's massive Mecha army in World War Three, they will have to be able to run away very fast!
make me think that you are looking at this from a different perspective than many of us would. If you supply a uniform force to my body you will crush me if the force is directed towards my center. This is how I read your statement - that the force in question would be like atmospheric pressure. I assume you mean all that equal force would be acting in the same direction, not pressing on the outside of my body or can towards the middle.
Yes, alas, I'm a Physicist In Training, so I tend to use such terms rather litterally. When I speak of force, I speak of it as a vector quantity, thus a uniform force could really only be in one direction. When I say uniform, I mean applied to the entire body, not simply to the surface as one would apply a force with, say, an earth-like atmosphere.
You raise a good point, I should be more careful to specify what I mean by things... I talk to physics majors so often that I take it ofr granted that everyone knows a "uniform force upon a body" means throughout the body inside and out. Clearly you've shown that's not the standard way of perceiving it.
Cheers,
Justin
I'm sorry man, but you're completely wrong.
> Certainly they can. Take a familiar object (say, an empty soda can) and put it in a uniform 20g field and it would crush.
It would only crush if it was being pushed by the gravitational field against something else. And, if that is true, then obviously the bottom of the can is not being accellerated at all (it is staying in the same place). From the can's perspective, part of it (the top part) is being accellerated, while the bottom is not. That's not a uniform accelleration. The reason that objects can be crushed is that you can accellerate part of the object without accellerating the rest of the object, thus changing the size of said object!
Be careful that you are not confusing uniform acceleration with uniform velocity. The first is not an inertial reference frame while the second is. Any simple accelerometer will tell you that you are accelerating; it is the special relativity constancy of physics that holds in the intertial reference frame. You might be thinking of Einstein's Equivalence Principle that says (colloquially) that you can't tell if you are standing on the surface of the Earth or in an elevator that accelerates in free space at 9.8 m/s2.
Once again, you are wrong. A simple accelerometer only tells you if you are applying a force on the sensor element in the accellerometer. Imagine that you are in free space with no forces acting on you. A properly calibrated accellerometer will read zero. Then imagine that you are moving with some velocity, and you encounter a planet. You begin to be pulled towards the planet, but your accellerometer reads zero. It will only register a gravitational pull on the sensor element if there is something to oppose it. In this case, you have nowhere to stand, so you cannot oppose the gravitational force; thus it reads nothing. It is physically impossible for the accelerometer to "know" you are falling down the gravity well. Another way of saying it is that accelerometers only work if you are feeling a force that the sensing element is not. (for instance, you're being pulled by a drag line to a spaceship)
So while it is true that there is a big difference here between constant acceleration and constant velocity, it doesn't change the validity of my previous post. And inertial reference frames have nothing to do with this, my discussion is entirely in newtonian mechanics, it need not require relativity.
I suppose I understand how my points could have been misunderstood, as I use my words in a very precise manner. They will not be true when interpreted imprecisely.
I know this sounds rediculously obvious (because it is), however I cannot think of any full-featured compter more efficient than a good laptop.
You could possibly run it directly off of your DC power, and you can take it anywhere you want. Laptop power consumption is typically less than 50 watts during peak usage, and during sleep it can use much less than that.
I know they aren't perfect, but sounds like it's what you need.
Just my two cents.
First of all, mad props for knowing the proper term for change in accelleration. Unfortunately you have a few incorrect physical ideas, perhaps based on some false assumptions.
I would like you to imagine a body in free space. Any accelleration of that body, or any change in that accelleration (and so on), provided the change was uniform throughout the body. This is the norm for graviational forces with extremely small gradients, like that a tthe surface of the earth). In fact, uniform accellerations cannot possibly inflict damage on an object. There is no truth to the idea that "jerk" is what causes damage.
What causes damage to any object is the application of differing amount of force to different parts of the object. For instance, if I was to hit you with a baseball bat, I'd be applying a lot of force to a small area of your body (that is, the outer layer of your skin at the point of impact). The rest of your body would not feel this force, and thus part of you would be compressed. If I was to, say, apply the same amount of force evenly over your body, it would do you no harm whatsoever (in fact, you could not possibly detect it, unless you noticed you were suddenly moving relative to everything nearby, that is, assuming things are in fact nearby).
"Jerk" has nothing to do with it. The only way a gravity weapon can be harmful to something is for it to have a very strong gradient, or for you to change the path of the body in such a way that it causes a high speed collision.
See my other post about possible ways the device could inflict damage on something else without inflicting damage on itself. It's quite possible to destroy an object without applying a *NET* force to it.
Of course, we do not even fully understand what gravity "is", so it's somewhat rediculous to think that they are developing gravity based weapons any time soon. They did say "gravity-like" though, so who knows what that means...
DISCLAIMER: I am not a physicist, but I am studying to become one at Cornell.
It was good of you to notice this rather important issue, however you are only partially correct... Imagine a situation where this gravity-like force is not evenly distributed, in fact the force vectors are such that they have a high magnitude, but are pointing in different directions in different places so that when summed up together, they add to zero (or near zero). This is a very common occurance in situations where forces between two objects are applied via waves (and different areas of the object may be at different phases of the wave, and thus have different vectors).
Don't be so quick to assume that this weapon is simply a pushing or pulling effect... it could be a symmetrical sheering force (part of the target is, say, pulled up, and part is pulled down, ripping it apart) or something similar.
How the hell they generate a gravity-like force, however, is completely beyond me. No problem with Newton though. Perhaps it's electromagnetic yet affects nonconductors?
(Also, if you did have a "poking" type weapon, it may be possible to couple the gravitational force to a plasma inside the weapon that will be accellerated out of the back, absorbing whatever momentum the attack generated).
DISCLAIMER: I am not a physicist (yet) but I'm studying to become one.
I most definately second that about Vorkosigan, there's a few of the books that aren't easy to get ahold of that I'd really like to read, and I'm definitely going to buy the next one.
:)
Also, cool to see a chick post on slashdot
Cheers,
Justin
Granted their code-morphing and use of VLIW had some interesting concepts, and their power consumption was perfect for laptops, but there just wasn't much of a market for what they developed. Had some of the bigger players (Dell, etc) actively pushed transmeta chips on the market, perhaps they might have made some money.
I for one am not sad this happen... they had some good ideas, but nothing insanely great.
br.