Bzzzzt! No actual machine can ever be Turing complete, because theoretical Turing machines are capable of calculations which require an unbounded amount of space. That is, there exist algorithms which a Turing machine can execute which require more memory than any computer that you make.
Computer languages can be Turing complete, but physical computers cannot be.
He specifically said that nothing, including photons, was moving FTL in his example. His example is valid (BTW, IAAPhysicist, at CDF). However, it was perhaps not the most clear, mostly because he tried to demonstrate that a perceptual (ie, not physical) object such as a beamspot or a shadow can move infinitely fast. It is far easier and more clear to show that such a perceptual object can move faster than light if you keep its speed finite. In this post in this thread, I use such an example.
Moreover, in Quantum Mechanics, the collapse of the wavefunction is superluminal. See http://en.wikipedia.org/wiki/EPR_paradox. The key is that the collapse does not carry any information, and so it is really just as ephemeral as the bug's shadow or the pulsar's beam in my other post.
Two observers measuring the spin of EPR paradox entangled particles would notice a correlation between their measurements, just as observers on two of the "earths" in my pulsar example would notice a correlation between the times the beam struck their planets. However, in both cases, neither observer is able to affect the other's observations.
Ok, try this one on for size. A slightly different gedanken, but it still works.
Imagine a massively bright overhead projector, projecting onto a quite large screen which is a piece of sphere. This sphere has its center at the focal point of the projector's lens, and its radius is, say, 10 light years.
Ok, got that? Now a bug flies in front of the beam, quite close to the projector. Never mind that with the kind of luminosity necessary to have a visible beam 10 lyrs away, the bug would likely be incinerated... 10 years later, the signal reaches the screen, and the bug's shadow will slide across the screen at an arbitrary rate, possibly larger than c. Now, since the screen is a piece of a sphere, the distance from the source is constant. We'll assume that the bug's path lay on the surface of a much smaller sphere, also centered at the focal point. So, at any given instant while the bug is flying, exactly 10 years minus the distance of the bug from the focal point later, the bug's shadow will be at the corresponding position on the screen.
For another similar example, think of a pulsar, which has a beam that impacts the earth say once a second. Now, imagine a whole bunch of earths, all at the same distance from the pulsar (that is, the beam will take the same amount of time to travel from one to the next), strung out in a ring so that the beam touches each one in succession before returning to this earth. If we are 10 light years from the pulsar, then the beam spot is travelling 20*pi light years once each second!
Yes, the previous poster's argument was slightly flawed, in that the distance from the light source was increasing, which complicates the calculations incredibly. However, I think that my examples should be simple enough to cleanly demonstrate that "objects", if they are not physical objects, but only perceptual objects, can move faster than light.
For the previous argument, I guess you could imagine an arbitrarily high number of photons in the beam, but for any finite photon density, the time between photons still diverges as the "velocity" approaches infinity... But the spot would definitely appear to move faster than c before the "velocity" reached infinity, so for a high enough photon density, you could get apparent superluminal motion by this method.
Bull. If you are a-political, then stop ranting on and on about political matters! You might be against political parties, but any fool can see that you are not a-political. Of all the ludicrous things I have ever read on slashdot, this comes pretty close to the top.
Are you saying that GPL3 makes forbids using GNU tools to create non-GPL3 software?
In a work, no. I am saying that GPL3 forbids the use of GNU tools to create non-GPL3 software (or to do anything else whatsoever) on the type of platform described. Since GNU tools are the best unix tools out there, anyone wanting to sell any kind of unix on such a platform will either have to reconsider, or else use inferior tools, making it a good bit more difficult to sell their platform+unix combo. This is a pretty significant thing. I'm not saying whether I think this is a good significant thing or a bad significant thing, just that it is a significant thing.
distributing DRM functional code
Just so you know, the particular clause of the GPL3 which is primarily under discussion here says nothing about DRM functional code. It is about trusted computing hardware, a related beast, but of a different species. I never said that GPL3 would prevent GNU tools from being used to make any kind of software you want, provided you are working on an approved platform.
You obviously are having trouble understanding just what the GPL actually does. Think of this new clause like this: It is a promise that if you don't play the way we (meaning those who choose to use this license) like, we will take our ball and go home. You can get another ball and play without us if you like, but we will take ours and go home.
This does have the potential to have some power, because the GNU tools are far and away the best set of basic unix tools. Most of the unices have adopted them by now. It is possible that when trusted computing comes, that this clause will simply kill off the use of the gnu tools (back to the last version using gplv2), but I doubt it. Additionally, if we ever manage to write a good killer app that lots of windows users use, and license it under gplv3, then when trusted computing comes, it might make people actually realize that it is not all sweetness and light (which will no doubt be how it is advertised.).
Also, there is some reasoning behind this promise to take the ball and go home. Presumable foremost in FSF's collective mind is that in a real sense, the type of hardware described would restrict freedom number 1 [emphasis mine] "The freedom to study how the program works, and adapt it to your needs (freedom 1). Access to the source code is a precondition for this." [http://www.gnu.org/philosophy/free-sw.html]. Additionally, there is a security reason. If you cannot ever update to a newer version, then any security holes that exist are frozen. Once those holes are discovered, everyone who is on a platform like this becomes a sitting duck until such time as both their hardware vendor releases a new signature set and they upgrade the software. This is also a personal/professional pride reason, because everyone who thinks they understand security will blame the software for their box getting owned, which will only be half right. Such incidents could give free software an undeserved reputation for insecurity.
Yes, if they have not agreed to the GPL, they are not bound in any way to follow it. However, in not agreeing to the GPL, they are also preventing themselves from using the software. When installing something on windows, you get the little "here is your bend over and take it EULA" dialog, and if you don't click "accept", the installer (unless it is badly written) does not install the software.
I can decide I don't want to be bound by the doorframe, and thus I won't enter the door. But then how am I going to get into the room? I get arrested if I bust the window or make a hole in the wall. The door is just a door, not the law of the land. But use of anything else to get into the room is prohibited by the law of the land.
I think you may be confusing DRM with Trusted Computing. Of course, I might well just be confused about what actually counts as DRM.
Does any version of the GPL allow (technically, not legally) non-signed software to run on a DRM device?
Of course the GPL does not, in a technical sense, allow non-signed software to run on a device which is designed not to allow non-signed software to run. (I'm assuming that such a device is what you meant by a DRM device.) This would be flatly impossible except by workarounds and loopholes, which exist quite independently of the license of any computer program exploiting them. I think that this is a not very meaningful answer to a not very meaningful question. Which might just mean that I misunderstood the question.
Is that what you were wanting to know? As far as how slashcode actually handles the url tag, I have no idea, other than the input and the end result. It could very well have a hammer that hits a monkey on the head everytime you use a URL tag, and then the monkey writes out the URL on the back of a receipt, and mails it to Mars, where the top secret Chinese Mars base receives it, translates it into a string of digits in base 3 representing the EBCDIC encoding of the string, sends it back via pulses of plasma, which are detected by their interference with the cell phone satellite system, and then punched onto cards, which are used to build a large pyramid, which, when it inevitably falls, is designed to fall into a perfect stack in the correct order on a card reader, which generates the actual hyperlink in your final post. But I doubt it.
Lisp, particularly as McCarthy initially defined it (before it got into the hands of hackers, that is), is as much a mathematical structure (for finding the value of any computable function) as it is a programming language. In mathematics, when someone writes about a particular mathematical structure for the first time, particularly if they show it to have some interesting properties or applications, we say that they have discovered it. Thus, I say that John McCarthy discovered Lisp.
Additionally, as simple as (McCarthy's, not Common) Lisp is (only seven primitives), any structure which has (as primitives) atom, car, cdr, cons, cond, eq, and quote is in fact a dialect of Lisp, in a very mathematical sense. It might not have to look identical, but those seven mean that there is an isomorphism with Lisp, which in turn means that they are the same structure.
Lisp is not the only programming system like this. For instance, see the concept of a One Instruction Set Computer. Anything with the (equivalent of a) subtract and branch if negative instruction is isomorphic to this. So, the subleq OISC could be said to have been discovered as well.
You'll notice I said thousands or millions. Tens of thousands definitely falls within that range. It was a rough estimate (or BS if you want to call it that, although it was not an uneducated guess), because the precise details were not necessary, and so I didn't bother to look it up. Thanks for your correction.
Well, ZPE has yet to be proven to be anything but an idea.
ZPE as a power source is fiction, unless quantum field theory is quite wrong. A quantum mechanical harmonic oscillator, in its ground state (lowest energy that it can reach) still retains some energy. Field theory supposes a harmonic oscillator at every point in space (now, I'm getting a bit out of my league here. I haven't studied field theory, but I have studied vanilla QM). So, every point in space, even in the purest vacuum, retains some energy. This is the fabled Zero Point Energy. However, it is not a useful power source, because in order to get that energy, the QM harmonic oscillators would have to be left with less energy than they have in their ground state. This contradicts the theory that predicts ZPE in the first place!
Now, it is worth pointing out that ZPE is experimentally verified. So, if QFT is drastically wrong, which it could be, then perhaps there is a way to reduce the vacuum below the QM ground state, and thus extract the energy. However, things are currently looking pretty good for QFT.
The reality is that the only reproducable, controlled, fusion reactions mankind has managed to generate in a reproducable manner consume much more power than they generate, and are many, many years before becoming a source of power.
Only half true. Magnetic confinement fusion has definitely passed breakeven. The amount by which the output power exceeds input power is still sufficiently low (ratio around 1.2), however, that it is not yet a source of power, and probably will not be for several years yet.
Regarding fusion by-products, the fact is that most fusion reactions produce deadly forms of radiation, weather "cold" or "hot", and the fuels required for a-neutronic reactions are not in infinite supply.
Which fusion byproducts were you thinking of? Helium? Not particularly deadly or radioactive. Shielding from the radiation produced during the fusion reaction itself is trivial, and as I said, you don't really get much in the way of dangerous byproducts. d+t fusion gives Helium-4 (perfectly safe), and d+d fusion either gives Helium-3 (again, safe), or tritium. The tritium is radioactive, true. Most of it will likely be consumed in d+t reactions, and whatever is left over (if any) is enormously less problematic that fission byproducts. The halflife is ~12 years, compared to halflives in the thousands or millions of years for fission byproducts. Aneutronic fusion is not necessary. Desirable, perhaps. The aneutronic reactions produce significantly less energy than d+t, but on the other hand, it is much easier to capture and use. But certainly not necessary. And the fuels for neutronic reactions are available in enormously abundant supply. FUD.
You would think that the fusion reactions are not dangerous, do not pollute, and the fuels involved are of infinite supply.
Yes. Yes you would think that. For a very good reason. It is very nearly true. The danger is nearly zero (in an accident, the machinery necessary to sustain the plasma would be destroyed very quickly, and the remaining plasma would not last long enough to do nearly any damage at all.), the pollution is nearly zero (see what I said about byproducts and radiation shielding above), and the fuel is nearly inexhaustible (The sun is likely to go nova (thus ending the possiblity of, say, solar power...) before we use up the fusion fuel available in our oceans).
Excuse me sir, but I must protest. I am a high energy physicist currently working at Fermilab (CDF). High energy physics today has nothing to do with fusion, except in that it might occasionally occur as a side effect of our collisions. Ah wait, there is one other regard in which we would be concerned with fusion, and it is the same as for everyone else: cheap, clean power. The electric bill here is in excess of 1 million USD a month. If cheap fusion power were available, that might well be significantly reduced, leading to greater ease in acquiring funding for our research. It matters not to us whether cheap power comes from cold fusion, tokamaks, bubble fusion, inertial confinement, or hamster wheels. If cold fusion is possible, then I (and probably most of my colleagues) are all for it. Please refrain, sir, from smearing the name of those you do not know.
About the rest of your post: You seem to be confused about Popper's statements. An assertion of the form "If A, then (every time) B" cannot be proven true by experiment. However, a single experiment in which A is known to have occurred, but B is known not to have occurred, proves that the assertion is false. This is the sort of thing Popper is talking about. Of course, experiment always introduces some error, so we must bring in the ideas of statistics, uncertainty, etc. If a hypothesis says "Under conditions A and B, C will occur D percent of the time", and sufficient experiments are done that the occurence of C is established with a high confidence not to occur D percent of the time, then the hypothesis will be generally rejected by the scientific community. For instance, if C occurs, under conditions A and B, 10% of the time, with a standard deviation of 1%, and theory predicts that it will occur 30% of the time, then it is extremely unlikely that said hypothesis is true. Fleishmann and Pons' explanation for their experimental results boils down to "If you follow our experimental procedures, then cold fusion will occur". AFAIK, they did not assert any rate of occurence, so presumably the rate is close to 100% (if their explanation is true).
So, if your "object floats in the air" hypothesis fails to include the requirements of being structured as a kite, and being sustained by an air current, it is an incorrect hypothesis. Furthermore, if you release the most accurate and detailed accounting that you can of the conditions under which your object floated, and many others recreate the same conditions in their laboratories, but fail to observe the levitation, then your explanation of the phenomenon (presumably based on those conditions) will be called into severe question.
Similarly, the debate was not primarily whether or not room-temperature fusion could happen (it can), but on whether or not Fleischmann and Pons had in fact acheived it. That is, given that their experimental results were correct (which is and has been in quite a bit of doubt, given their unnecessary secrecy in the matter), it is still not demonstrated that their explanation is correct, particularly given the extremely high rate of failure of attempts at verification. Or would you suggest that the large number of experimenters who failed to reproduce F&P's results were under a mass hallucination?
Slashdot Mirror
0*0
00*
***
Didn't you mean a glider?
0**
0*0
00*
Yep. Funny only to you.
In my experience at an American high school and then college in the south, bellbottoms didn't make a comeback, but flare-leg jeans did.......
Computer languages can be Turing complete, but physical computers cannot be.
He specifically said that nothing, including photons, was moving FTL in his example. His example is valid (BTW, IAAPhysicist, at CDF). However, it was perhaps not the most clear, mostly because he tried to demonstrate that a perceptual (ie, not physical) object such as a beamspot or a shadow can move infinitely fast. It is far easier and more clear to show that such a perceptual object can move faster than light if you keep its speed finite. In this post in this thread, I use such an example.
Moreover, in Quantum Mechanics, the collapse of the wavefunction is superluminal. See http://en.wikipedia.org/wiki/EPR_paradox. The key is that the collapse does not carry any information, and so it is really just as ephemeral as the bug's shadow or the pulsar's beam in my other post.
Two observers measuring the spin of EPR paradox entangled particles would notice a correlation between their measurements, just as observers on two of the "earths" in my pulsar example would notice a correlation between the times the beam struck their planets. However, in both cases, neither observer is able to affect the other's observations.
Ok, try this one on for size. A slightly different gedanken, but it still works.
Imagine a massively bright overhead projector, projecting onto a quite large screen which is a piece of sphere. This sphere has its center at the focal point of the projector's lens, and its radius is, say, 10 light years.
Ok, got that? Now a bug flies in front of the beam, quite close to the projector. Never mind that with the kind of luminosity necessary to have a visible beam 10 lyrs away, the bug would likely be incinerated... 10 years later, the signal reaches the screen, and the bug's shadow will slide across the screen at an arbitrary rate, possibly larger than c. Now, since the screen is a piece of a sphere, the distance from the source is constant. We'll assume that the bug's path lay on the surface of a much smaller sphere, also centered at the focal point. So, at any given instant while the bug is flying, exactly 10 years minus the distance of the bug from the focal point later, the bug's shadow will be at the corresponding position on the screen.
For another similar example, think of a pulsar, which has a beam that impacts the earth say once a second. Now, imagine a whole bunch of earths, all at the same distance from the pulsar (that is, the beam will take the same amount of time to travel from one to the next), strung out in a ring so that the beam touches each one in succession before returning to this earth. If we are 10 light years from the pulsar, then the beam spot is travelling 20*pi light years once each second!
Yes, the previous poster's argument was slightly flawed, in that the distance from the light source was increasing, which complicates the calculations incredibly. However, I think that my examples should be simple enough to cleanly demonstrate that "objects", if they are not physical objects, but only perceptual objects, can move faster than light.
For the previous argument, I guess you could imagine an arbitrarily high number of photons in the beam, but for any finite photon density, the time between photons still diverges as the "velocity" approaches infinity... But the spot would definitely appear to move faster than c before the "velocity" reached infinity, so for a high enough photon density, you could get apparent superluminal motion by this method.
This sounds good. But you still have to ask yourself "Sed quis custodiet ipsos custodes?". ("Who watches the watchers?")
$ vi
bash: syntax error near unexpected token `newline'
In a work, no. I am saying that GPL3 forbids the use of GNU tools to create non-GPL3 software (or to do anything else whatsoever) on the type of platform described. Since GNU tools are the best unix tools out there, anyone wanting to sell any kind of unix on such a platform will either have to reconsider, or else use inferior tools, making it a good bit more difficult to sell their platform+unix combo. This is a pretty significant thing. I'm not saying whether I think this is a good significant thing or a bad significant thing, just that it is a significant thing.
Just so you know, the particular clause of the GPL3 which is primarily under discussion here says nothing about DRM functional code. It is about trusted computing hardware, a related beast, but of a different species. I never said that GPL3 would prevent GNU tools from being used to make any kind of software you want, provided you are working on an approved platform.
You obviously are having trouble understanding just what the GPL actually does. Think of this new clause like this: It is a promise that if you don't play the way we (meaning those who choose to use this license) like, we will take our ball and go home. You can get another ball and play without us if you like, but we will take ours and go home.
This does have the potential to have some power, because the GNU tools are far and away the best set of basic unix tools. Most of the unices have adopted them by now. It is possible that when trusted computing comes, that this clause will simply kill off the use of the gnu tools (back to the last version using gplv2), but I doubt it. Additionally, if we ever manage to write a good killer app that lots of windows users use, and license it under gplv3, then when trusted computing comes, it might make people actually realize that it is not all sweetness and light (which will no doubt be how it is advertised.).
Also, there is some reasoning behind this promise to take the ball and go home. Presumable foremost in FSF's collective mind is that in a real sense, the type of hardware described would restrict freedom number 1 [emphasis mine] "The freedom to study how the program works, and adapt it to your needs (freedom 1). Access to the source code is a precondition for this." [http://www.gnu.org/philosophy/free-sw.html]. Additionally, there is a security reason. If you cannot ever update to a newer version, then any security holes that exist are frozen. Once those holes are discovered, everyone who is on a platform like this becomes a sitting duck until such time as both their hardware vendor releases a new signature set and they upgrade the software. This is also a personal/professional pride reason, because everyone who thinks they understand security will blame the software for their box getting owned, which will only be half right. Such incidents could give free software an undeserved reputation for insecurity.
Yes, if they have not agreed to the GPL, they are not bound in any way to follow it. However, in not agreeing to the GPL, they are also preventing themselves from using the software. When installing something on windows, you get the little "here is your bend over and take it EULA" dialog, and if you don't click "accept", the installer (unless it is badly written) does not install the software.
I can decide I don't want to be bound by the doorframe, and thus I won't enter the door. But then how am I going to get into the room? I get arrested if I bust the window or make a hole in the wall. The door is just a door, not the law of the land. But use of anything else to get into the room is prohibited by the law of the land.
Of course the GPL does not, in a technical sense, allow non-signed software to run on a device which is designed not to allow non-signed software to run. (I'm assuming that such a device is what you meant by a DRM device.) This would be flatly impossible except by workarounds and loopholes, which exist quite independently of the license of any computer program exploiting them. I think that this is a not very meaningful answer to a not very meaningful question. Which might just mean that I misunderstood the question.
Like this: slashdot.org
What I typed looks like <URL:slashdot.org>
Is that what you were wanting to know? As far as how slashcode actually handles the url tag, I have no idea, other than the input and the end result. It could very well have a hammer that hits a monkey on the head everytime you use a URL tag, and then the monkey writes out the URL on the back of a receipt, and mails it to Mars, where the top secret Chinese Mars base receives it, translates it into a string of digits in base 3 representing the EBCDIC encoding of the string, sends it back via pulses of plasma, which are detected by their interference with the cell phone satellite system, and then punched onto cards, which are used to build a large pyramid, which, when it inevitably falls, is designed to fall into a perfect stack in the correct order on a card reader, which generates the actual hyperlink in your final post. But I doubt it.
Lisp, particularly as McCarthy initially defined it (before it got into the hands of hackers, that is), is as much a mathematical structure (for finding the value of any computable function) as it is a programming language. In mathematics, when someone writes about a particular mathematical structure for the first time, particularly if they show it to have some interesting properties or applications, we say that they have discovered it. Thus, I say that John McCarthy discovered Lisp.
Additionally, as simple as (McCarthy's, not Common) Lisp is (only seven primitives), any structure which has (as primitives) atom, car, cdr, cons, cond, eq, and quote is in fact a dialect of Lisp, in a very mathematical sense. It might not have to look identical, but those seven mean that there is an isomorphism with Lisp, which in turn means that they are the same structure.
Lisp is not the only programming system like this. For instance, see the concept of a One Instruction Set Computer. Anything with the (equivalent of a) subtract and branch if negative instruction is isomorphic to this. So, the subleq OISC could be said to have been discovered as well.
You'll notice I said thousands or millions. Tens of thousands definitely falls within that range. It was a rough estimate (or BS if you want to call it that, although it was not an uneducated guess), because the precise details were not necessary, and so I didn't bother to look it up. Thanks for your correction.
The fact that they cannot come up with a description of how to do it suggests that their explanation is flawed.
Now, it is worth pointing out that ZPE is experimentally verified. So, if QFT is drastically wrong, which it could be, then perhaps there is a way to reduce the vacuum below the QM ground state, and thus extract the energy. However, things are currently looking pretty good for QFT.
Which fusion byproducts were you thinking of? Helium? Not particularly deadly or radioactive. Shielding from the radiation produced during the fusion reaction itself is trivial, and as I said, you don't really get much in the way of dangerous byproducts. d+t fusion gives Helium-4 (perfectly safe), and d+d fusion either gives Helium-3 (again, safe), or tritium. The tritium is radioactive, true. Most of it will likely be consumed in d+t reactions, and whatever is left over (if any) is enormously less problematic that fission byproducts. The halflife is ~12 years, compared to halflives in the thousands or millions of years for fission byproducts. Aneutronic fusion is not necessary. Desirable, perhaps. The aneutronic reactions produce significantly less energy than d+t, but on the other hand, it is much easier to capture and use. But certainly not necessary. And the fuels for neutronic reactions are available in enormously abundant supply. FUD.
Yes. Yes you would think that. For a very good reason. It is very nearly true. The danger is nearly zero (in an accident, the machinery necessary to sustain the plasma would be destroyed very quickly, and the remaining plasma would not last long enough to do nearly any damage at all.), the pollution is nearly zero (see what I said about byproducts and radiation shielding above), and the fuel is nearly inexhaustible (The sun is likely to go nova (thus ending the possiblity of, say, solar power...) before we use up the fusion fuel available in our oceans).
Ah. Good point. Thank you for the correction, sir.
About the rest of your post: You seem to be confused about Popper's statements. An assertion of the form "If A, then (every time) B" cannot be proven true by experiment. However, a single experiment in which A is known to have occurred, but B is known not to have occurred, proves that the assertion is false. This is the sort of thing Popper is talking about. Of course, experiment always introduces some error, so we must bring in the ideas of statistics, uncertainty, etc. If a hypothesis says "Under conditions A and B, C will occur D percent of the time", and sufficient experiments are done that the occurence of C is established with a high confidence not to occur D percent of the time, then the hypothesis will be generally rejected by the scientific community. For instance, if C occurs, under conditions A and B, 10% of the time, with a standard deviation of 1%, and theory predicts that it will occur 30% of the time, then it is extremely unlikely that said hypothesis is true. Fleishmann and Pons' explanation for their experimental results boils down to "If you follow our experimental procedures, then cold fusion will occur". AFAIK, they did not assert any rate of occurence, so presumably the rate is close to 100% (if their explanation is true).
So, if your "object floats in the air" hypothesis fails to include the requirements of being structured as a kite, and being sustained by an air current, it is an incorrect hypothesis. Furthermore, if you release the most accurate and detailed accounting that you can of the conditions under which your object floated, and many others recreate the same conditions in their laboratories, but fail to observe the levitation, then your explanation of the phenomenon (presumably based on those conditions) will be called into severe question.
Similarly, the debate was not primarily whether or not room-temperature fusion could happen (it can), but on whether or not Fleischmann and Pons had in fact acheived it. That is, given that their experimental results were correct (which is and has been in quite a bit of doubt, given their unnecessary secrecy in the matter), it is still not demonstrated that their explanation is correct, particularly given the extremely high rate of failure of attempts at verification. Or would you suggest that the large number of experimenters who failed to reproduce F&P's results were under a mass hallucination?
I'm curious as to your field, sir.