How would the sensor know if a car was parked or just stopped?
Typically, the difference between stopping and parking is defined by the time the car is standing at the place. So all the meters would need is a clock, but that's something they need anyway.
What about out-of-town visitors?
For those, there could be in addition traditional parking meters. If they don't like traditional parking meters, they could just buy a parking RFID, too.
Sounds like an invitation to phishing: Just change the number displayed to your own premium number charging more money, which just forwards the SMS to the original premium number. The people will not notice anything until they see their phone bill, and then they may not even remember how much they had to pay for their ticket.
According to the article, the dispute was settled with the city buying a new three-year license. If I understand correctly, that license should just have ended...
Well, they can just make a law that it's forbidden to drive during a power failure. Then there's no need to get your car out during a power failure, since you are not allowed to drive it anyway.
Type 1 diabetes is an autoimmune disease. Therefore I guess your immune system would destroy your replacement pancreas just as it did with the original one. However IANAMD.
Well, be assured that THEY do develop anti-robotic weapons. THEY just keep them secret so that normal humans like us won't have a chance. It's the preparation for the final... wait, why are there black helic... No Carrier
"Finally, the curvature is not "into another dimension"; space actually only has an inner curvature (basically, deformation along the space direction)."
This is something I find very difficult to grasp about Riemannian geometry.
If we have a 4D spacetime with 'inner curvature', why can't we just embed that 4D manifold in a 5D Eucledian manifold and make that inner curvature a real curvature?
Well, there are two things here.
First, embedding into an Euclidean manifold isn't even possible for a flat Minkovski space because the Euclidean space has a positive definite metric, while the spacetime metric is indefinite.
Other than that, embedding the curved space into a higher-dimensional flat space with indefinite metric is certainly possible (probably even in a higher-dimensional Minkowski space, but I'm not sure about it), although in general AFAIK 5 dimensions are not sufficient. But there are infinitely many such embeddings, and the physics doesn't depend in any way on them, because only the inner curvature enters the GR equations. Since the embedding doesn't give you anything but unnecessary complications, there's no point to do it. Indeed, Occams razor tells you to do without.
I'm not sure what this question aims at. If it aims directly at my post: It clarifies that, contrary to the claim of the post I replied to, GR doesn't do away with the concept of mass. However, your next question suggests that the question was more aimed at GR itself, in that case see my answer to that.
Does GR give any suggestion that we can create a gravitational field without mass?
Yes. A laser beam has no mass, but it does have a gravitational field. On a more general note, the same mass can generate different gravitational fields if it has different momentum. For example, if you have a gas (which I'll assume doesn't have a net movement), the gravitational field of that gas is not only affected by its energy (which, since the gas is at rest, can be directly translated to mass through E=mc^2), but also by its pressure (which clearly doesn't enter the mass).
The idea that scientific method is the ONLY true way of obtaining knowledge is a recent one.
The idea that electromagnetic waves can transmit information is also a recent one. On the other hand, the idea that earth is flat is very old.
The age of an idea doesn't tell you whether its true.
There are other valid ways such as direct expreince and mystic studies.
There's nothing wrong with direct experience. Indeed, any scientific knowledge ultimately comes from direct experience and reasoning about that experience. However, people tent to do invalid generalizations from their direct experience, and then claim those generalisations were their direct experience, which they weren't.
About mystic studies, well, can you tell me just one convincing reason why I should accept them as sources of truth?
There is overwhelming evidince that homeopathy saved millions during the spanish flue pandemic
{{citation needed}}
and I've seen accupancure perform what can only be deascribed as miracles by the westerners during my travels in China.
Such as?
Scientific method has it's uses but when it goes against ny commion sesne, well I go with common sense.
Well, that's your choice. How can you be so sure that your common sense is right?
Of course there's still mass in General Relativity. It's just that, unlike in Newtonian gravity, the mass isn't the source of the gravitational field (i.e. in GR, spacetime curvature), but energy and momentum are. But the mass still enters the equation through its energy content, and of course the inertial mass still governs the reaction of particles to non-gravitational forces like those coming from the electomagnetic field.
It's not mass that is replaced by (or rather identified with) spacetime curvature in GR, but the gravitational field.
Well, as I said, it's not just space which is curved, but spacetime. In this analogy, the north direction would be the time direction. You can't avoid moving in time, of course.
Actually according to GR gravity is a property of energy and momentum, and has a lot to do with movement. Which doesn't change the fact that a non-moving non-rotating mass still has a gravitational field (because it has still energy: E=mc^2)
Also, what does it mean if the bigger version of this test doesn't find gravitational waves? Does it poke a big fat hole in relativity?
From TFA: "If Advanced LIGO doesn't see gravitational waves I think people will be very surprised," Mandic told SPACE.com. "It is likely such a situation would require revision of General Relativity."
Well, if you RTFA you'll find that there are only a few non-established theories which predict gravitational waves that large that they could be detected with the current setup. Therefore all this experiment tells is that those theories are not true. Or, to quote from TFA:
Rather than be disappointed by the null findings, physicists say the results were expected, and in fact help them narrow down possibilities for what the universe was like just after it was born.
And later:
Most physicists think the models that would have produced gravitational waves above the threshold that could have been seen so far are unlikely, he said.
Well, it's easy to explain: It conveys the wrong message. While the curvature of space is indeed similar to the curvature of a rubber hose when a mass is on it, the image you get is wrong at quite a lot of counts:
To begin with, the mass is not lying on top of the space, it's inside space.
Next, while space is curved, that's not the main effect you see (indeed, the curvature of space near earth is so little that it's very hard to measure it). It's spacetime whose curvature is important.
The objects are not attracted downwards something "below space", and they don't just "roll down the hill" - indeed, the space curvature picture could equally well be depicted upwards without making a difference (except that the very intuitive, but wrong notion of objects rolling "down" wouldn't work any more). Indeed, the whole point of General Relativity is that the path of an object in spacetime is straight ahead (as long as no non-gravitative force modifies it, of course). However, since the spacetime is curved, their paths don't seem straight. An image for this would be two people on Earth, starting on slightly different places on the equator, and going North. Despite the fact that their ways start out parallel, and neither makes a turn to the left or the right, they'll come closer together until they meet at the north pole, where they meet at a non-zero angle.
Finally, the curvature is not "into another dimension"; space actually only has an inner curvature (basically, deformation along the space direction). However this is quite hard to visualize, therefore all pictures are a curved two-dimensional space embedded into three-dimensional space. However the outer curvature has no meaning at all. For example, you might depict flat space as a plain sheet of paper. However, you could depict the very same flat space also as convoluted piece of paper. It doesn't make any difference. It only makes a difference if you do something which would make the paper to get torn or to crumple (so you'd need a rubber sheet to maintain a continuous surface).
Well, there's simply no point outside of the black hole in the absolute future of any point inside the black hole. In other words: There's no way anything could go which leads outside the horizon. You'd need superluminal speed to escape, but gravitational waves only go at the speed of light (and everything else goes at most as far, too).
That's the "trick" of the event horizon: It's not exactly that a strong force keeps you from going out, it's just that there is no way out (at least no way you can follow).
Even if science were to come to the conclusion that some theologians were right all the time (it's completely impossible that all of them are right, because they contradict each other), it would still be a great achievement, because the theologians only have their faith, while the scientists would in that case have scientific proof. Or, to remain in the picture, while the theologists have been brought to the peak, and just had to believe it's the peak they were told it is, the scientists know the way to the peak and can therefore be completely certain of being on the right one. And BTW, even for the theologians sitting on that peak it would be great news, because they then would finally have a good argument that they got to the right peak, and the other theologians sitting on the other peaks were wrong.
However, it is more likely that when the scientists get over the final rock (assuming there is one), the'll find no theologian there, because those all sit on those lower peaks where it is much easier to get to.
and why do we think we can detect them this deep inside a Gravity well?
Because there's no reason why we shouldn't. Gravity waves should follow the same paths as light waves, and we get plenty of light waves in out gravity well. Gravity would have to have a repulsive effect to gravity waves to avoid them reaching us. Which I'm pretty sure is not the case in current theory.
Slashdot Mirror
Typically, the difference between stopping and parking is defined by the time the car is standing at the place. So all the meters would need is a clock, but that's something they need anyway.
For those, there could be in addition traditional parking meters. If they don't like traditional parking meters, they could just buy a parking RFID, too.
Sounds like an invitation to phishing: Just change the number displayed to your own premium number charging more money, which just forwards the SMS to the original premium number. The people will not notice anything until they see their phone bill, and then they may not even remember how much they had to pay for their ticket.
According to the article, the dispute was settled with the city buying a new three-year license. If I understand correctly, that license should just have ended ...
Well, they can just make a law that it's forbidden to drive during a power failure. Then there's no need to get your car out during a power failure, since you are not allowed to drive it anyway.
Well, think of the possibilities. A church wouldn't have to get an organ built, it could simply be grown.
Type 1 diabetes is an autoimmune disease. Therefore I guess your immune system would destroy your replacement pancreas just as it did with the original one. However IANAMD.
No, but it works with higher-order functions. Instead of having a function "bite this", it uses a function "give me something to bite with".
... until those grown third teeth are available for humans?
About your signature:
I guess you didn't know how to enceode 'y', 'o' and '\'', right? :-)
Well, be assured that THEY do develop anti-robotic weapons. THEY just keep them secret so that normal humans like us won't have a chance. It's the preparation for the final ... wait, why are there black helic... No Carrier
So they built a right-handed robot? I hope they'll follow-up with a left-handed one soon, in order to not be discriminating!
SCNR
"Finally, the curvature is not "into another dimension"; space actually only has an inner curvature (basically, deformation along the space direction)."
This is something I find very difficult to grasp about Riemannian geometry.
If we have a 4D spacetime with 'inner curvature', why can't we just embed that 4D manifold in a 5D Eucledian manifold and make that inner curvature a real curvature?
Well, there are two things here.
First, embedding into an Euclidean manifold isn't even possible for a flat Minkovski space because the Euclidean space has a positive definite metric, while the spacetime metric is indefinite.
Other than that, embedding the curved space into a higher-dimensional flat space with indefinite metric is certainly possible (probably even in a higher-dimensional Minkowski space, but I'm not sure about it), although in general AFAIK 5 dimensions are not sufficient. But there are infinitely many such embeddings, and the physics doesn't depend in any way on them, because only the inner curvature enters the GR equations. Since the embedding doesn't give you anything but unnecessary complications, there's no point to do it. Indeed, Occams razor tells you to do without.
I'm not sure what this question aims at. If it aims directly at my post: It clarifies that, contrary to the claim of the post I replied to, GR doesn't do away with the concept of mass. However, your next question suggests that the question was more aimed at GR itself, in that case see my answer to that.
Yes. A laser beam has no mass, but it does have a gravitational field. On a more general note, the same mass can generate different gravitational fields if it has different momentum. For example, if you have a gas (which I'll assume doesn't have a net movement), the gravitational field of that gas is not only affected by its energy (which, since the gas is at rest, can be directly translated to mass through E=mc^2), but also by its pressure (which clearly doesn't enter the mass).
The idea that electromagnetic waves can transmit information is also a recent one. On the other hand, the idea that earth is flat is very old.
The age of an idea doesn't tell you whether its true.
There's nothing wrong with direct experience. Indeed, any scientific knowledge ultimately comes from direct experience and reasoning about that experience. However, people tent to do invalid generalizations from their direct experience, and then claim those generalisations were their direct experience, which they weren't.
About mystic studies, well, can you tell me just one convincing reason why I should accept them as sources of truth?
{{citation needed}}
Such as?
Well, that's your choice. How can you be so sure that your common sense is right?
Of course there's still mass in General Relativity. It's just that, unlike in Newtonian gravity, the mass isn't the source of the gravitational field (i.e. in GR, spacetime curvature), but energy and momentum are. But the mass still enters the equation through its energy content, and of course the inertial mass still governs the reaction of particles to non-gravitational forces like those coming from the electomagnetic field.
It's not mass that is replaced by (or rather identified with) spacetime curvature in GR, but the gravitational field.
Well, as I said, it's not just space which is curved, but spacetime. In this analogy, the north direction would be the time direction. You can't avoid moving in time, of course.
Actually according to GR gravity is a property of energy and momentum, and has a lot to do with movement. Which doesn't change the fact that a non-moving non-rotating mass still has a gravitational field (because it has still energy: E=mc^2)
From TFA:
"If Advanced LIGO doesn't see gravitational waves I think people will be very surprised," Mandic told SPACE.com. "It is likely such a situation would require revision of General Relativity."
Maybe because it would cost much more to bring it to the Lagrange points?
And how does his model explain the deep inelastic scattering experiments? I cannot see how this could possibly work.
Well, if you RTFA you'll find that there are only a few non-established theories which predict gravitational waves that large that they could be detected with the current setup. Therefore all this experiment tells is that those theories are not true. Or, to quote from TFA:
And later:
Well, it's easy to explain: It conveys the wrong message. While the curvature of space is indeed similar to the curvature of a rubber hose when a mass is on it, the image you get is wrong at quite a lot of counts:
I hope those explanations did help a bit.
Well, there's simply no point outside of the black hole in the absolute future of any point inside the black hole. In other words: There's no way anything could go which leads outside the horizon. You'd need superluminal speed to escape, but gravitational waves only go at the speed of light (and everything else goes at most as far, too).
That's the "trick" of the event horizon: It's not exactly that a strong force keeps you from going out, it's just that there is no way out (at least no way you can follow).
Even if science were to come to the conclusion that some theologians were right all the time (it's completely impossible that all of them are right, because they contradict each other), it would still be a great achievement, because the theologians only have their faith, while the scientists would in that case have scientific proof. Or, to remain in the picture, while the theologists have been brought to the peak, and just had to believe it's the peak they were told it is, the scientists know the way to the peak and can therefore be completely certain of being on the right one. And BTW, even for the theologians sitting on that peak it would be great news, because they then would finally have a good argument that they got to the right peak, and the other theologians sitting on the other peaks were wrong.
However, it is more likely that when the scientists get over the final rock (assuming there is one), the'll find no theologian there, because those all sit on those lower peaks where it is much easier to get to.
Because there's no reason why we shouldn't. Gravity waves should follow the same paths as light waves, and we get plenty of light waves in out gravity well. Gravity would have to have a repulsive effect to gravity waves to avoid them reaching us. Which I'm pretty sure is not the case in current theory.