The perceived order of events must always remain the same in every reference frame, or causality would be violated. This is one of the corner stones of Relativity. And you actually can sync clocks in different reference frames, if you have enough information of relative speed, relative position, and knowledge of gravitational field strength. That's what GPS satellites do all the time.
Interesting. Temperature and redshift of the CMBR just tell us the age of the universe as measured by clocks in our time frame. If we would put an astronaut in a spaceship and send him away at 99.99c or so, this person would slow down relative to our time frame. At the same time he would measure a different temperature and redshift of the CMBR because he would be moving relative to the photons that make up the CMBR (their speed remains c, but their frequency shifts). I think the result of all these would be that the astronaut measures a different age for the universe, but I'm not sure. Will be an interesting calculation when I have some time...
The point of relativity is not that you cannot sync clocks, it's that if you move a clock from one reference frame to a different one, it will move faster/slower than its twin in the original reference frame.
In general relativity time is relative. Only causality (the order of events) is absolute. While GR breaks down on a quantum scale, that doesn't mean it's not correct (i.e. experiments match theory to a very high degree) on a macro scale. Time Dilation is a real, measurable effect. A quantum theory of everything would have behave like GR on macro scales for it to match our observations of the universe.
If gravitational waves moved at instant speed, LIGO (our current detector) would indeed not be able to detect it, since it would instantaneously compress or expand space everywhere. This would also cause big problems. Energy would radiate out of the observable universe faster than the observable boundary expands (at light speed). Meaning conservation of energy would be violated big time. The first law is a cornerstone of physics, and has never been known to be violated. In cases where it seemed to be broken in some past experiments, some interesting phenomena were discovered that explained why it actually wasn't.
Also, I'm not at all certain that causality wouldn't be violated in this case. There might be some other way to detect a passing gravity wave (besides laser interferometry) that we just don't know about yet. Maybe some change in the rate of collisions between a particle beam and virtual particles from the fluctuating zero point energy. It wouldn't even have to be technically possible to measure it, so long as the effect would be physically real.
There can be several reasons why we didn't detect any yet. For one, gravitational effects are very weak and our sensors have limited sensitivity. Combined with this is the fact that gravitational radiation follows an inverse square law (its amplitude is inversely proportional to the square of the distance from the source). This means that only powerful sources like collapsing or colliding stars, or closely orbiting black holes or neutron stars can be detected if they're sufficiently close to us. The chances of measuring such an event with the current LIGO installation were estimated as only 1 in 6 by 2010, so it's quite possible such an event just didn't happen yet. LIGO2 will be 10 times more sensitive, and is expected to detect multiple events weekly. But we'll have to wait until 2014 for it to become operational.
It may turn out we don't detect anything, which may mean our detectors don't work, or our theories are wrong. The latter would actually be a very interesting result, since it would provide new insight into gravitation (whereas detection would just reaffirm our current theories). I'm still convinced that we will detect the waves eventually, and that they will be moving at light speed as GR predicts.
Gravitational waves emerge from the Einstein field equations, part of the mathematical formulation of General Relativity. Since we never measured any of them directly, we have no direct evidence of their existence, let alone their speed. But we do have good indirect evidence that they exist. All experiments/measurements we can come up with match GR to a very high degree.
If gravitational waves could go faster than the speed of light, that would break causality. This means that you could find some reference frame moving at a constant velocity (special relativity) or constant acceleration (general relativity) from/to the source of the gravitational wave, for which you would first detect the gravitational wave, and only later see the event that generated it. Which basically reverses the flow of time. Relativity forbids this (see here for SR: http://en.wikipedia.org/wiki/Relativity_of_simultaneity).
Stretching of space-time (metric expansion of space) is a non-local phenomenon, meaning it falls outside of the scope of SR, but in the domain of GR. It's a very very small effect, that can only be seen at galactic scales. It means space-time is created in between two connected points of space-time, which is not what is happening in your case. Even in expanding space, no signal goes faster than light, and causality is preserved. The light itself keeps moving at c, it only undergoes a red-shift because the space it travels through stretches.
So basically we just have a bunch of theories that tell us how the universe works, and those theories seem to hold up during experiments. They don't tell us why there is an upper speed limit, only that because the speed of light is constant and limited, no information can move faster, or causality would break, and the universe would be an even stranger place.
To really know why this is so, and what exactly causes metric expansion of space, we need to find a working model of quantum gravity. GR doesn't seem to work very well at quantum scales. Several candidates exist, but they don't produce enough predictions to allow for conclusive testing. There are indications that the continuous space-time breaks down into a fractal pattern of small units of space-time (strings, loops, pentachoron depending on the theory) that form ever changing interconnections, a bit like water molecules in a drop moving around without the overall shape changing, but this in 4 or more dimensions. Since this all occurs at the Planck scale (about 10^20 times smaller that the diameter of a proton), and basically is the foundation of all space-time and thus reality, that makes it very hard to perform experiments that tell us anything more about it.
On the quantum level we have the same problem: we have complicated field theories (quantum chromodynamics) that tell us how particles interact, but they don't tell us why they do so, or why they even exist with the mass/charge/color they have.
One day we might find some unified theory that will answer all this, and from which everything will emerge naturally, but until then we'll have to do with what seems to work (SR/Newton for normal scales, GR for galactic scales and large masses, QM/QCD for quantum scales).
The problem is, there is no known mechanism for a mass of any significance just to appear somewhere (without disturbing space-time first). On a quantum scale virtual particles can pop in and out of existence, but that's just matter-energy conversion of the zero point energy (which is always there).
In case it would be possible, I think the effect would be like throwing a big rock in a pond. There would be an abrupt change in the space-time continuum, which would cause gravity waves to ripple out from that place at the speed of light. Since the presence of that new mass is information, the change in space-time will have to travel at light speed or less, or it would violate causality (special relativity).
Clojure is Lisp. It just runs on top of a Java VM instead of the usual Lisp VM.
I assume you meant EcmaScript/JavaScript instead of Java. Which by the way has many Lisp like features.
I expect the next step will be passing a law that makes circumvention of the filter illegal. And then p2p will be blocked country wide. Because this has nothing to do with protecting children, but everything with protecting profits for the media consortiums.
I still have a pentium 50 with the FDIV bug (with motherboard). Never bothered to exchange it, and never found myself in a situation where the bug surfaced (except while trying out some of the test calculations). It was the last main processor that I had that could operate with a simple heat sink (no fan). Great times...
I also stopped using antivirus software years ago. Firefox + NoScript + Adblock + common sense works much better.
I've seen Norton/Symantec installs on friends/relatives' computers that were bogging down the system more than most viruses would. And they still got viruses. Setting them up with Firefox + Avast (free home edition) fixed the performance issues and kept most viruses/malware out.
Took me a while to find, but this is the location.
And also the corresponding google maps location (point 23 on the other map). Too bad the satellite image doesn't show anything yet.
What we need is a bytecode-based platform like Java or.NET
The second all browsers support that, the web as we know it will cease to exist. Imagine each web page being like a flash applet. Great for the designers, but don't try to copy even a snippet of text, since they will have disabled it.
I don't know what you're smoking, but DirectX (or more precise its Direct3D component) is an API/library that exposes your GPU functionality to applications. Sure it can emulate some features in software if needed, but it is built to use hardware acceleration as much as possible. Using software to access/use the hardware acceleration of your GPU is not the same as software acceleration. That term is even meaningless, unless you mean using SIMD instructions on your main processor to accelerate things that would be slower using the normal instruction set.
Your statement was that XP doesn't have GPU support, which is plainly false, as even the later versions of Win95 supported direct access to GPU registers through DirectX (hence the name). The fact that some people may or may not have a GPU for their XP machine doesn't change the fact that you can use the GPU on an XP machine if there is one. Also, Vista doesn't require a GPU present to run. And when you play 3D games on Vista or Win7 they still use DirectX.
Never heard of DirectX, did you? XP doesn't have Windows Presentation Foundation (which uses DirectX for acceleration btw), but this is hardly the same as not having GPU support.
I'm fairly sure MS made the conscious decision to build IE9 on top of this new framework so it wouldn't be compatible with XP.
Understandably, because why would people upgrade to Vista/Win7 when they can get all the goodies for naught?
If they only wanted to do hardware acceleration, that was already possible with Windows 95 SR2 and DirectX 1.
Well, the Linux kernel comes to mind. The core is from the early '90s. Different parts would go into the public domain at different dates, since a lot was added to it later.
Whether this would be a good thing or a bad thing, I don't know. I'm more sympathetic to new-BSD styled licences, but I can see cases where the GPL would be preferrable.
I just wanted to remark that reducing copyright terms for commercial software is a knife that cuts both ways.
Slashdot Mirror
The perceived order of events must always remain the same in every reference frame, or causality would be violated. This is one of the corner stones of Relativity.
And you actually can sync clocks in different reference frames, if you have enough information of relative speed, relative position, and knowledge of gravitational field strength. That's what GPS satellites do all the time.
Interesting. Temperature and redshift of the CMBR just tell us the age of the universe as measured by clocks in our time frame. If we would put an astronaut in a spaceship and send him away at 99.99c or so, this person would slow down relative to our time frame. At the same time he would measure a different temperature and redshift of the CMBR because he would be moving relative to the photons that make up the CMBR (their speed remains c, but their frequency shifts). I think the result of all these would be that the astronaut measures a different age for the universe, but I'm not sure. Will be an interesting calculation when I have some time...
The point of relativity is not that you cannot sync clocks, it's that if you move a clock from one reference frame to a different one, it will move faster/slower than its twin in the original reference frame.
In general relativity time is relative. Only causality (the order of events) is absolute. While GR breaks down on a quantum scale, that doesn't mean it's not correct (i.e. experiments match theory to a very high degree) on a macro scale. Time Dilation is a real, measurable effect. A quantum theory of everything would have behave like GR on macro scales for it to match our observations of the universe.
Well, you have to be drunk to enjoy that movie...
What you need already existed for many years: the DejaVu fonts (derived from the Bitstream Vera fonts, but with wider character range).
Why, they're Copernicus' remains, of course! It even says to in the story title. I know we don't read TFA or the summary around here, but the title!?
You're welcome.
If gravitational waves moved at instant speed, LIGO (our current detector) would indeed not be able to detect it, since it would instantaneously compress or expand space everywhere. This would also cause big problems. Energy would radiate out of the observable universe faster than the observable boundary expands (at light speed). Meaning conservation of energy would be violated big time. The first law is a cornerstone of physics, and has never been known to be violated. In cases where it seemed to be broken in some past experiments, some interesting phenomena were discovered that explained why it actually wasn't.
Also, I'm not at all certain that causality wouldn't be violated in this case. There might be some other way to detect a passing gravity wave (besides laser interferometry) that we just don't know about yet. Maybe some change in the rate of collisions between a particle beam and virtual particles from the fluctuating zero point energy. It wouldn't even have to be technically possible to measure it, so long as the effect would be physically real.
There can be several reasons why we didn't detect any yet. For one, gravitational effects are very weak and our sensors have limited sensitivity. Combined with this is the fact that gravitational radiation follows an inverse square law (its amplitude is inversely proportional to the square of the distance from the source). This means that only powerful sources like collapsing or colliding stars, or closely orbiting black holes or neutron stars can be detected if they're sufficiently close to us. The chances of measuring such an event with the current LIGO installation were estimated as only 1 in 6 by 2010, so it's quite possible such an event just didn't happen yet. LIGO2 will be 10 times more sensitive, and is expected to detect multiple events weekly. But we'll have to wait until 2014 for it to become operational.
It may turn out we don't detect anything, which may mean our detectors don't work, or our theories are wrong. The latter would actually be a very interesting result, since it would provide new insight into gravitation (whereas detection would just reaffirm our current theories). I'm still convinced that we will detect the waves eventually, and that they will be moving at light speed as GR predicts.
Regards.
Gravitational waves emerge from the Einstein field equations, part of the mathematical formulation of General Relativity. Since we never measured any of them directly, we have no direct evidence of their existence, let alone their speed. But we do have good indirect evidence that they exist. All experiments/measurements we can come up with match GR to a very high degree.
If gravitational waves could go faster than the speed of light, that would break causality. This means that you could find some reference frame moving at a constant velocity (special relativity) or constant acceleration (general relativity) from/to the source of the gravitational wave, for which you would first detect the gravitational wave, and only later see the event that generated it. Which basically reverses the flow of time. Relativity forbids this (see here for SR: http://en.wikipedia.org/wiki/Relativity_of_simultaneity).
Stretching of space-time (metric expansion of space) is a non-local phenomenon, meaning it falls outside of the scope of SR, but in the domain of GR. It's a very very small effect, that can only be seen at galactic scales. It means space-time is created in between two connected points of space-time, which is not what is happening in your case. Even in expanding space, no signal goes faster than light, and causality is preserved. The light itself keeps moving at c, it only undergoes a red-shift because the space it travels through stretches.
So basically we just have a bunch of theories that tell us how the universe works, and those theories seem to hold up during experiments. They don't tell us why there is an upper speed limit, only that because the speed of light is constant and limited, no information can move faster, or causality would break, and the universe would be an even stranger place.
To really know why this is so, and what exactly causes metric expansion of space, we need to find a working model of quantum gravity. GR doesn't seem to work very well at quantum scales. Several candidates exist, but they don't produce enough predictions to allow for conclusive testing. There are indications that the continuous space-time breaks down into a fractal pattern of small units of space-time (strings, loops, pentachoron depending on the theory) that form ever changing interconnections, a bit like water molecules in a drop moving around without the overall shape changing, but this in 4 or more dimensions. Since this all occurs at the Planck scale (about 10^20 times smaller that the diameter of a proton), and basically is the foundation of all space-time and thus reality, that makes it very hard to perform experiments that tell us anything more about it.
On the quantum level we have the same problem: we have complicated field theories (quantum chromodynamics) that tell us how particles interact, but they don't tell us why they do so, or why they even exist with the mass/charge/color they have.
One day we might find some unified theory that will answer all this, and from which everything will emerge naturally, but until then we'll have to do with what seems to work (SR/Newton for normal scales, GR for galactic scales and large masses, QM/QCD for quantum scales).
You didn't pay enough attention to the fucking diary: fucking booms work when done fucking properly.
I meant gravitational waves, of course. Gravity waves are a fluid boundary phenomenon.
The problem is, there is no known mechanism for a mass of any significance just to appear somewhere (without disturbing space-time first). On a quantum scale virtual particles can pop in and out of existence, but that's just matter-energy conversion of the zero point energy (which is always there).
In case it would be possible, I think the effect would be like throwing a big rock in a pond. There would be an abrupt change in the space-time continuum, which would cause gravity waves to ripple out from that place at the speed of light. Since the presence of that new mass is information, the change in space-time will have to travel at light speed or less, or it would violate causality (special relativity).
Clojure is Lisp. It just runs on top of a Java VM instead of the usual Lisp VM.
I assume you meant EcmaScript/JavaScript instead of Java. Which by the way has many Lisp like features.
That would be CSI Miami (the yeeeah is from the theme song): http://www.youtube.com/watch?v=GeeyWvo1rNg
html5 is just a version of html which supports a video tag just like an image tag
Among many, many other things...
I expect the next step will be passing a law that makes circumvention of the filter illegal. And then p2p will be blocked country wide. Because this has nothing to do with protecting children, but everything with protecting profits for the media consortiums.
I still have a pentium 50 with the FDIV bug (with motherboard). Never bothered to exchange it, and never found myself in a situation where the bug surfaced (except while trying out some of the test calculations). It was the last main processor that I had that could operate with a simple heat sink (no fan). Great times...
I also stopped using antivirus software years ago. Firefox + NoScript + Adblock + common sense works much better.
I've seen Norton/Symantec installs on friends/relatives' computers that were bogging down the system more than most viruses would. And they still got viruses. Setting them up with Firefox + Avast (free home edition) fixed the performance issues and kept most viruses/malware out.
What quality control system?
Took me a while to find, but this is the location.
And also the corresponding google maps location (point 23 on the other map). Too bad the satellite image doesn't show anything yet.
The second all browsers support that, the web as we know it will cease to exist.
Imagine each web page being like a flash applet. Great for the designers, but don't try to copy even a snippet of text, since they will have disabled it.
I don't know what you're smoking, but DirectX (or more precise its Direct3D component) is an API/library that exposes your GPU functionality to applications. Sure it can emulate some features in software if needed, but it is built to use hardware acceleration as much as possible. Using software to access/use the hardware acceleration of your GPU is not the same as software acceleration. That term is even meaningless, unless you mean using SIMD instructions on your main processor to accelerate things that would be slower using the normal instruction set.
Your statement was that XP doesn't have GPU support, which is plainly false, as even the later versions of Win95 supported direct access to GPU registers through DirectX (hence the name). The fact that some people may or may not have a GPU for their XP machine doesn't change the fact that you can use the GPU on an XP machine if there is one. Also, Vista doesn't require a GPU present to run. And when you play 3D games on Vista or Win7 they still use DirectX.
So get your facts straight.
Never heard of DirectX, did you? XP doesn't have Windows Presentation Foundation (which uses DirectX for acceleration btw), but this is hardly the same as not having GPU support.
I'm fairly sure MS made the conscious decision to build IE9 on top of this new framework so it wouldn't be compatible with XP.
Understandably, because why would people upgrade to Vista/Win7 when they can get all the goodies for naught?
If they only wanted to do hardware acceleration, that was already possible with Windows 95 SR2 and DirectX 1.
Well, the Linux kernel comes to mind. The core is from the early '90s. Different parts would go into the public domain at different dates, since a lot was added to it later.
Whether this would be a good thing or a bad thing, I don't know. I'm more sympathetic to new-BSD styled licences, but I can see cases where the GPL would be preferrable.
I just wanted to remark that reducing copyright terms for commercial software is a knife that cuts both ways.
You do realize that copyright is what makes the GPL work?