Of course a) and b) are strongly correlated. If I'm at home, I usually use my desktop computer; if I'm far away from home, I'll certainly not use that; I'll typically use my laptop. Now if I type differently on my laptop than on my desktop (not unlikely, since the keyboard is noticeably different), that means I would not be able to get into a Strongbox site when abroad.
Prestige may be part of it why the way it is, though I'm skeptical that this is the whole. But let's say it is.
It is, to a very large part.
Of course the fact that with Open Access journals you have to pay to publish doesn't help either. The subscription fee is paid by the library. It doesn't directly affect your research. The publication fee is usually paid from your own research money. That means you can spend less on your actual research.
However some places have a program where Open Access fees are paid for by the library as well; in such places Open Access publishing gets much more attractive.
Also note that the better availability causes Open Access journals to have on average a better impact factor. So their chances are good to win in the long term. OTOH, many non-OA journals allow you to also put your article online for free access, as long as it is not the version with the journal formatting. Therefore a large part of all articles is also found in places like arXiv.org. In that case, you can take the arXiv.org version as "the" article, and publication in the journal basically gives it the blessing of having passed peer review.
This method had been on the market at least since 2007: https://de.wikipedia.org/wiki/Psylock (German Wikipedia; there's apparently no English version of that page)
The convention is which one we call "North" and which one we call "South", but those are mere names anyways. The hemispheres as such are uniquely defined by the rotation of the earth. That is, there are two poles, and two hemispheres which reach from the corresponding pole to the equator. And thanks to the weak interaction (more exactly, its parity violation) you can even distinguish from the rotation which hemisphere is which using nothing but fundamental physical laws.
The Northern and Southern Hemisphere are defined by the physical characteristics of the planet (namely its rotation). There's nothing physically special about the Greenwich meridian or the International Date Line, they are just set by convention.
Or said differently, there's a Northern and a Southern Hemisphere because there's a North Pole and a South Pole. There's no West Pole, nor an East Pole.
Well, if the post explicitly says "in the Star Trek universe" it is a strong hint that it is about the Star Trek planet, not the Plutonian moon. And I didn't learn all arcana of the Star Trek universe either. I just learned how to do an internet search. However, the formulation was already clear enough without it; I only looked to make sure that the AC wasn't using knowledge of the Star Trek planet not being hot when making that statement (in which case he would have had a point). It did, however, confirm that the Star Trek planet is hot (and a desert planet), and thus the AC's comment is indeed as out of place as it seemed.
Well, in General Relativity time is continuous, and it is a dimension of spacetime. Spacetime is four-dimensional, with three space dimensions and one time dimension. Actually the time dimension only differs from the space dimensions by the sign in the metric (which basically means that as soon as time is involved, things are often reversed to what we are used in space, but the important part is that it makes it impossible to rotate the time dimension to a space dimension or vice versa; the metric is basically an onject which tells us how to measurte distances and angles). Also, while there are three space dimensions, there's only one time dimension (this makes it impossible to just turn around in time, as we can do in space). Note that this doesn't mean there's only one time direction; you can rotate the time axis in spacetime. That's known as boost; it's exactly what you do if you accelerate. Note that this is even true if you use a Newtonian spacetime, as one can easily convince oneself by simply drawing the world lines (i.e. the line describing at which place an object is at each point in time; to draw it, you certainly have to remove at least one spacial dimension). What's new in Special Relativity (which basically is a special case of General Relativity, namely the case of flat spacetime) is that also the space axis is turned on a boost, and in a way that the speed of light is the same in both systems. The time which elapses for you between two events is just the length of the world line (measured with the space time metric, with the different signs for space and time coordinates). Due to the different sign, the direct way is the one which takes the most time (unlike in space, where a detour makes the way longer). That's basically because if you detour in space, the change in the orthogonal direction adds to the distance, while for time, it gets subtracted (actually it's in the square of the distance where this addition/subtraction occurs, but the qualitative effect is the same: Moving in other dimensions at the same time adds to a length of a spacial path, but subtracts from the elapsed time, which is the length of the world line). This difference is generally known as twin paradox (the travelling twin makes the detour, and therefore he needs less time, and thus is younger than the waiting twin when he returns).
Now General Relativity adds to the mix that the spacetime is curved (and the curvature depends on the energy and momentum of the matter inside). That works in principle the same way as for example the curvature or earth's surface. For example, imagine two people meet somewhere at the equator, and one goes 5000 km west, and then 5000 km north, while the other first goes 5000 km north, and then 3535.5 km west. Then they get (approximately) to the same place, although the second one has gone a shorter distance. Quite similarly, someone going closer to the black hole and then remaining there will need less time than someone first waiting far away from the black hole and only then going close to it to meet the other one.
Note that the analogy goes even further: After going first north and turning west, to keep going west you have to constantly turn right (i.e. to accelerate in the direction of the pole). If you just went straight on, you'd start moving southwards, as if the pole would push you away. The acceleration causes you to keep at fixed distance from the pole. Similarly, the observer going close to the black hole (assuming he does not orbit it) has to accelerate away from it to not fall in; again this is the effect of curvature (of spacetime in this case). However spacetime around a black hole is curved in a way to make unaccelerated motion go towards it instead of away from it, thus the acceleration has to go away from it (orbiting is another way to keep from falling in; this option is not available in the earth surface analogy).
I don't know the book (I hope I don't have to hand in my geek card because of this:-)), but if the Lifestone is a bit in the future, shouldn't you be a bit too early? If I arrive at the place where an event shall happen, and the event is ion the future, I'm too early. If I'm too late, the event is already in the past.
Anyway, in the Schwarzschild solution, the singularity being in the future means you will get to it, because you simply cannot avoid going to the future.
Actually there is a maximum angular momentum for a black hole (depending on its mass). However that's independent of how that hole was formed. If the angular momentum is larger than this maximum value, you'll get no hoizon, but a naked singularity (with closed timelike curves around it, allowing time travel).
However the bad news is that you cannot spin up a black hole beyond this value. Well, maybe it is good news, after all; who knows what sort of nasty stuff we'd get from there otherwise...;.)
For a non-rotating black hole in Schwarzschild coordinates, the radial vector inside the horizon gets timelike, that is, the singularity is not really "in the middle" but "in the future". This quite intuitively explains why you cannot go "outward": The "outward" direction is actually the past direction.
Now, Schwarzschild coordinates are not the full story, but neither are Eddington-Finkelstein coordinates (which obviously are what you had in mind). The complete structure of the Schwarzschild solution can only be seen in Kruskal coordinates, where you on one hand quite literally see that the singularity is in the future (for any world line starting outside the black hole and entering it), but you would still be able to evade it if you could travel faster than light (while in Schwarzschild coordinates it looks as if you'd have to travel backwards in time).
Anyway, light is not "bent towards the middle", that's only the result of non-ideal coordinates where the singularity appears spacelike while it is actually timelike.
For rotating black holes, things are more complicated (there are two horizons, the singularity is spacelike, but not a point, and inside the black hole there occur closed timelike curves).
Actually it is already a misconception that particles are sucked in. Particles can fall in, but they also can orbit the black hole (as long as nothing else is in the way), just as they can orbit earth. If they get too close they no longer can orbit the black hole for the simple reason that they would need to go faster than light to do so.
In some mediums, light moves faster than it does through a vacuum.
No, it doesn't. Not only does such a material not exist, it is proven beyond any reasonable doubt to be impossible.
That depends on what exactly you mean with the "speed in the medium".
You certainly can have a phase velocity larger than c, and AFAIK you also can have a group velocity larger than c. What you cannot have is a signal velocity larger than c.
That's the problem of non-interactive speaking. When explaining it to someone directly, you'd ask: "Do you know what a black hole is?" and if the other one says "yes" you'd skip the explanation (but keep in mind that you might have to do it anyway if it turns out that his understanding of black holes is wrong).
My thought has always been that black holes are black because the particles they are made from
Black holes are not made from particles. Black holes are vacuum. Curved vacuum, that is. Yes, that's hard to understand, because our brain was not made to deal with this. But that's what the mathematics says.
move faster than the speed of light, therefore don't give off light radiation
A charged particle does emit light radiation when going faster than light. This can be observed in a medium (e.g. water) where the speed of light is slower than in vacuum, so particles there can indeed go faster than light (but still not faster than the vacuum speed of light). That radiation is known as Cherenkov radiation. It is the optic analogue of the sonic boom. If the particles could go faster than light in vacuum, they'd emit that radiation also in vacuum.
Uncharged particles would not emit Cherenkov radiation, however uncharged particles don't emit light radiation no matter what their speed is.
No, time is the same everywhere, too. Only the length of timelike paths depends on how you move. But ultimately it is not too different from the fact that the length of spacelike paths depends on the way you take. Except that for spacelike paths, the direct path is the shortest, while for timelike paths, the direct path is the longest.
So many people (a number of whom who should know better) get this totally wrong because you always here that a black hole has "such powerful gravity that not even light can escape!!!111!!!"
Which actually is correct (except for "here" instead of "hear":-)). What's wrong is the imagination that this is because the light is slowed down when going outwards (actually in some sense the light is slowed down, because the time as seen from outside is slowed down; but that's independent of the direction, and of course locally it is still going with c). The real reason is that the spacetime (not space, spacetime) is curved in a way that there's no way out when going at light speed or below. That is, the outward-going light is still going with light speed, but will not get out, but eventually reach the singularity. Yes, that seems paradox, since the singularity is "in the middle" (which isn't entirely accurate either; for a non-rotating black hole it is actually in the future), but that's because we are not very good in imagining curved four-dimensional spacetimes.
If you don't like it, then don't use it. It's a free country.
OK, do you have a comprehensive list of web sites using Google Analytics, Google AdSense or doubleclick, so I know which web sites to avoid? No? I thought so.
Since they have Javascript running on the page anyway,
Maybe on your browser. On my browser, I've got NoScript installed. I can't imagine that someone who is knowledgeable enough to edit his hosts file will not know about NoScript.
The AC is correct. Temperature has nothing to do with the definition of a desert. What matters is precipitation, or the lack of it.
But the Star Trek planet "Vulcan" is both hot and a desert planet. Thus it is a hot desert planet. Nowhere did the OP imply that "hot" was a defining characteristic of a desert. As I wrote, if "hot" were a defining characteristic of a desert, the "hot" in "hot desert planet" would be redundant; you could as well say "desert planet" in that case. Therefore if the explicit mention of "hot" suggests anything about the definition of a desert, it suggests that "hot" is not a part of that definition. Therefore while the AC's statement as such is correct, the implied message that the OP got it wrong is false.
Note that I also nowhere did claim that the AC's direct claim was wrong. Quite the opposite; if it were wrong, my reply would not have made any sense at all.
Workers cannot keep the fruits of their labour either. They get paid for their labour, but they don't get the fruit of it. If something they made turns out to be very successful, not the employees make the big money, but the employer. So from that logic, employment would be a direct antithesis of capitalism, too.
Slashdot Mirror
Did your brain have a power failure? It seems to be heavily corrupted.
Of course a) and b) are strongly correlated. If I'm at home, I usually use my desktop computer; if I'm far away from home, I'll certainly not use that; I'll typically use my laptop. Now if I type differently on my laptop than on my desktop (not unlikely, since the keyboard is noticeably different), that means I would not be able to get into a Strongbox site when abroad.
It is, to a very large part.
Of course the fact that with Open Access journals you have to pay to publish doesn't help either. The subscription fee is paid by the library. It doesn't directly affect your research. The publication fee is usually paid from your own research money. That means you can spend less on your actual research.
However some places have a program where Open Access fees are paid for by the library as well; in such places Open Access publishing gets much more attractive.
Also note that the better availability causes Open Access journals to have on average a better impact factor. So their chances are good to win in the long term. OTOH, many non-OA journals allow you to also put your article online for free access, as long as it is not the version with the journal formatting. Therefore a large part of all articles is also found in places like arXiv.org. In that case, you can take the arXiv.org version as "the" article, and publication in the journal basically gives it the blessing of having passed peer review.
This method had been on the market at least since 2007: https://de.wikipedia.org/wiki/Psylock (German Wikipedia; there's apparently no English version of that page)
The convention is which one we call "North" and which one we call "South", but those are mere names anyways. The hemispheres as such are uniquely defined by the rotation of the earth. That is, there are two poles, and two hemispheres which reach from the corresponding pole to the equator. And thanks to the weak interaction (more exactly, its parity violation) you can even distinguish from the rotation which hemisphere is which using nothing but fundamental physical laws.
The Northern and Southern Hemisphere are defined by the physical characteristics of the planet (namely its rotation). There's nothing physically special about the Greenwich meridian or the International Date Line, they are just set by convention.
Or said differently, there's a Northern and a Southern Hemisphere because there's a North Pole and a South Pole. There's no West Pole, nor an East Pole.
Well, if the post explicitly says "in the Star Trek universe" it is a strong hint that it is about the Star Trek planet, not the Plutonian moon. And I didn't learn all arcana of the Star Trek universe either. I just learned how to do an internet search. However, the formulation was already clear enough without it; I only looked to make sure that the AC wasn't using knowledge of the Star Trek planet not being hot when making that statement (in which case he would have had a point). It did, however, confirm that the Star Trek planet is hot (and a desert planet), and thus the AC's comment is indeed as out of place as it seemed.
Well, in General Relativity time is continuous, and it is a dimension of spacetime. Spacetime is four-dimensional, with three space dimensions and one time dimension. Actually the time dimension only differs from the space dimensions by the sign in the metric (which basically means that as soon as time is involved, things are often reversed to what we are used in space, but the important part is that it makes it impossible to rotate the time dimension to a space dimension or vice versa; the metric is basically an onject which tells us how to measurte distances and angles). Also, while there are three space dimensions, there's only one time dimension (this makes it impossible to just turn around in time, as we can do in space). Note that this doesn't mean there's only one time direction; you can rotate the time axis in spacetime. That's known as boost; it's exactly what you do if you accelerate. Note that this is even true if you use a Newtonian spacetime, as one can easily convince oneself by simply drawing the world lines (i.e. the line describing at which place an object is at each point in time; to draw it, you certainly have to remove at least one spacial dimension). What's new in Special Relativity (which basically is a special case of General Relativity, namely the case of flat spacetime) is that also the space axis is turned on a boost, and in a way that the speed of light is the same in both systems. The time which elapses for you between two events is just the length of the world line (measured with the space time metric, with the different signs for space and time coordinates). Due to the different sign, the direct way is the one which takes the most time (unlike in space, where a detour makes the way longer). That's basically because if you detour in space, the change in the orthogonal direction adds to the distance, while for time, it gets subtracted (actually it's in the square of the distance where this addition/subtraction occurs, but the qualitative effect is the same: Moving in other dimensions at the same time adds to a length of a spacial path, but subtracts from the elapsed time, which is the length of the world line). This difference is generally known as twin paradox (the travelling twin makes the detour, and therefore he needs less time, and thus is younger than the waiting twin when he returns).
Now General Relativity adds to the mix that the spacetime is curved (and the curvature depends on the energy and momentum of the matter inside). That works in principle the same way as for example the curvature or earth's surface. For example, imagine two people meet somewhere at the equator, and one goes 5000 km west, and then 5000 km north, while the other first goes 5000 km north, and then 3535.5 km west. Then they get (approximately) to the same place, although the second one has gone a shorter distance. Quite similarly, someone going closer to the black hole and then remaining there will need less time than someone first waiting far away from the black hole and only then going close to it to meet the other one.
Note that the analogy goes even further: After going first north and turning west, to keep going west you have to constantly turn right (i.e. to accelerate in the direction of the pole). If you just went straight on, you'd start moving southwards, as if the pole would push you away. The acceleration causes you to keep at fixed distance from the pole. Similarly, the observer going close to the black hole (assuming he does not orbit it) has to accelerate away from it to not fall in; again this is the effect of curvature (of spacetime in this case). However spacetime around a black hole is curved in a way to make unaccelerated motion go towards it instead of away from it, thus the acceleration has to go away from it (orbiting is another way to keep from falling in; this option is not available in the earth surface analogy).
I don't know the book (I hope I don't have to hand in my geek card because of this :-)), but if the Lifestone is a bit in the future, shouldn't you be a bit too early? If I arrive at the place where an event shall happen, and the event is ion the future, I'm too early. If I'm too late, the event is already in the past.
Anyway, in the Schwarzschild solution, the singularity being in the future means you will get to it, because you simply cannot avoid going to the future.
Actually there is a maximum angular momentum for a black hole (depending on its mass). However that's independent of how that hole was formed. If the angular momentum is larger than this maximum value, you'll get no hoizon, but a naked singularity (with closed timelike curves around it, allowing time travel).
However the bad news is that you cannot spin up a black hole beyond this value. Well, maybe it is good news, after all; who knows what sort of nasty stuff we'd get from there otherwise ... ;.)
Well, at the big bang, it was extremely hot everywhere in the universe. So how could that have happened except by global warming? :-)
For a non-rotating black hole in Schwarzschild coordinates, the radial vector inside the horizon gets timelike, that is, the singularity is not really "in the middle" but "in the future". This quite intuitively explains why you cannot go "outward": The "outward" direction is actually the past direction.
Now, Schwarzschild coordinates are not the full story, but neither are Eddington-Finkelstein coordinates (which obviously are what you had in mind). The complete structure of the Schwarzschild solution can only be seen in Kruskal coordinates, where you on one hand quite literally see that the singularity is in the future (for any world line starting outside the black hole and entering it), but you would still be able to evade it if you could travel faster than light (while in Schwarzschild coordinates it looks as if you'd have to travel backwards in time).
Anyway, light is not "bent towards the middle", that's only the result of non-ideal coordinates where the singularity appears spacelike while it is actually timelike.
For rotating black holes, things are more complicated (there are two horizons, the singularity is spacelike, but not a point, and inside the black hole there occur closed timelike curves).
Actually it is already a misconception that particles are sucked in. Particles can fall in, but they also can orbit the black hole (as long as nothing else is in the way), just as they can orbit earth. If they get too close they no longer can orbit the black hole for the simple reason that they would need to go faster than light to do so.
In some mediums, light moves faster than it does through a vacuum.
No, it doesn't. Not only does such a material not exist, it is proven beyond any reasonable doubt to be impossible.
That depends on what exactly you mean with the "speed in the medium".
You certainly can have a phase velocity larger than c, and AFAIK you also can have a group velocity larger than c. What you cannot have is a signal velocity larger than c.
That's the problem of non-interactive speaking. When explaining it to someone directly, you'd ask: "Do you know what a black hole is?" and if the other one says "yes" you'd skip the explanation (but keep in mind that you might have to do it anyway if it turns out that his understanding of black holes is wrong).
No no, a mass is what happens in a Church you heathen.
Ah, now I understand why the Higgs particle is the god particle: It is causing what happens in a Church!
Black holes are not made from particles. Black holes are vacuum. Curved vacuum, that is. Yes, that's hard to understand, because our brain was not made to deal with this. But that's what the mathematics says.
A charged particle does emit light radiation when going faster than light. This can be observed in a medium (e.g. water) where the speed of light is slower than in vacuum, so particles there can indeed go faster than light (but still not faster than the vacuum speed of light). That radiation is known as Cherenkov radiation. It is the optic analogue of the sonic boom. If the particles could go faster than light in vacuum, they'd emit that radiation also in vacuum.
Uncharged particles would not emit Cherenkov radiation, however uncharged particles don't emit light radiation no matter what their speed is.
No, time is the same everywhere, too. Only the length of timelike paths depends on how you move. But ultimately it is not too different from the fact that the length of spacelike paths depends on the way you take. Except that for spacelike paths, the direct path is the shortest, while for timelike paths, the direct path is the longest.
Which actually is correct (except for "here" instead of "hear" :-)). What's wrong is the imagination that this is because the light is slowed down when going outwards (actually in some sense the light is slowed down, because the time as seen from outside is slowed down; but that's independent of the direction, and of course locally it is still going with c). The real reason is that the spacetime (not space, spacetime) is curved in a way that there's no way out when going at light speed or below. That is, the outward-going light is still going with light speed, but will not get out, but eventually reach the singularity. Yes, that seems paradox, since the singularity is "in the middle" (which isn't entirely accurate either; for a non-rotating black hole it is actually in the future), but that's because we are not very good in imagining curved four-dimensional spacetimes.
If you don't like it, then don't use it. It's a free country.
OK, do you have a comprehensive list of web sites using Google Analytics, Google AdSense or doubleclick, so I know which web sites to avoid? No? I thought so.
And ad networks don't track you, they track your web usage.
Maybe on your browser. On my browser, I've got NoScript installed. I can't imagine that someone who is knowledgeable enough to edit his hosts file will not know about NoScript.
But the Star Trek planet "Vulcan" is both hot and a desert planet. Thus it is a hot desert planet. Nowhere did the OP imply that "hot" was a defining characteristic of a desert. As I wrote, if "hot" were a defining characteristic of a desert, the "hot" in "hot desert planet" would be redundant; you could as well say "desert planet" in that case. Therefore if the explicit mention of "hot" suggests anything about the definition of a desert, it suggests that "hot" is not a part of that definition. Therefore while the AC's statement as such is correct, the implied message that the OP got it wrong is false.
Note that I also nowhere did claim that the AC's direct claim was wrong. Quite the opposite; if it were wrong, my reply would not have made any sense at all.
What would those £3 be today after adjusting for inflation?
Workers cannot keep the fruits of their labour either. They get paid for their labour, but they don't get the fruit of it. If something they made turns out to be very successful, not the employees make the big money, but the employer. So from that logic, employment would be a direct antithesis of capitalism, too.