I would never let my kid be alone with an adult -- ever. In a church I attend the pastor's kid was abused by a grandparent! These things happen, you have to be smart and be secure in advance. Why should I trust anyone, even a "good Christian."
It is a sad state of our society today: that one cannot send his child to borrow something from a neighbor, that one needs to be afraid of his husband's/wife's grandparents. And the worst thing is that, even if you do protect your kids, even if you do give them a proper education at home, still they can grow up and become bad persons. And I think there is no way to be "secure in advance". But one can be cautious!
The question is: What slows down? It is true that light is always moving at the speed of light (tautology), but not always along the same straight lines that an observer away from the gravitational influence of the black hole sees.
I think the issue is what happens with the matter. We expect to see all clocks on a spaceship approaching the event horizon slow down (provided we are located further away from the horizon than that spaceship is). As for the speed of light: if a spaceship is moving at the speed of light, than, for an external observer, the clock on that spaceship stands still. In other words, a photon has no internal clock, there is nothing that can "slow down" there.
He also assumes (from the abstract) that an eavesdropper can only eavesdrop by injecting current into the wire, which is blatantly false. One could easily tap the magnetic field generated by current in the wire, without drawing very much power from the wire at all.
Not so sure about that. In the paper he needs to inject a stohastic current in order to be able to compute TWO cross-correlations. If you passively measure the magnetic field, how do you extract the information bit without inducing the current change in the wires?
How about recording the signal after it has been transmitted through some output at the other end? This bugging would not interfere with the signal being transmitted but would still record the information for transmittal later? If you are transmitting the information through a computer, I think someone will figure out how to get it.
In the preprint he says that the encryption can be broken only if the eavesdropper injects a small current into the communications channel and measures cross-correlations between various quantities, thereby determining which resistor is at which end of a communication channel (that is where the security of the method lies, in the inability of the eavesdropper to determin it without interfering). Recording a signal after transmitting it does not help you to determine which resistor is at which end.
Actually I have heard a talk on astrophyisical N-body simualtions which run on 512 POWER4 processors. By using a combination of OpenMP on the nodes and MPI between the nodes you can do reasonably well (depending on how your problem changes with time). IBM's XL compilers are used.
Ah, well, you might also say that. However, there are some governments willing to fund proving of such speculations. I guess that these speculations have proven to be more succesful than some other.:)
No no, dark energy component percentage grows with time. Above redshift of about 2 (when the universe was a 1/4 of today's size I think) it was insignificant, i.e. the Universe was still deccelerating. When it will be twice today's size, dark energy will constitute even more of the whole energy density.
Well, doing realistic simulations of a galaxy even with "old" Newtonian physics is very expensive. I mean, imagine simulating 100 billion point masses all acting gravitationally on each other (not counting simulating the hydrodynamics of the gas clouds). So, in the best case you can reduce the number of operations to N log N, or about 2000 billion (per time step). Now simulate the whole galaxy, but also taking into account that your binary stars need a lot smaller time step then your simple stars... And then you have a huge discrepancy of time scales (years for binary stars, millions of years for a star like sun to orbit around the center ONCE).
And then add general relativity into this mess? Very hard with today's computers...
I wonder if some scientists might already be so invested in theories of dark matter that they will refuse to accept this position.
I would not worry too much about that... They will easily adapt, using their results as "boundary" cases of whatever currently popular new theory. Investing in theories is never futile...
...is going to become the major worry. Data from supernovae distance measurements indicate that the Universe has been expanding for some time already. That means that there has to exist a sort of anti-gravity (called dark energy by astrophysicists). Now, that is hard to explain by conventional means (although it is possible), and may involve either a "beyond Einstein" type of theory (e.g., an improved general relativity) or some exotic form of energy (or both). So, although general relativity alone might account for the rotational curves of galaxies, it does not account for the large-scale properties of the universe.
You are right, it is either sines and cosines or square roots and fractions (I am guessing here, it may be something else)...in any case a lot of algebraic computation is rather unpopular among pupils:(
A black hole is of a finite size (Schwarzschild radius in case of a non-rotating one). But you are right, inside all the matter is concentrated in a point, a singularity. But again, what appears to the outside observer as a black hole is of finite size. A black hole with the solar mass would have a radius of about 3km.
Yes, but if you read what they say in the article, it is the right kin of the perturbations what counts, not their magnitude. Because the system of partial differential equations (which is a good approximation to the temporal evolution of the atmosphere) is nonlinear, even a small perturbation can cause a major change in the future.
It would be nice to have more information about this. I wonder what China's plans are as to space, and whether their centralized government will be able to make better progress than the American system. Then again, beauracracy is beauracracy, so I don't have high hopes on China getting much further than developing extra-long range rockets.
Then again, if you pump enough money into the system, even with a considerable amount of bureaucratic friction you might get somewhere. They could also be sending interplanetary probes soon...
Exactly! Moreover, by spreading generators through the armor you can make the power supply more redundant, which is always good in combat.
Would this work for spacesuits during Mars exploration mission? I mean, OK, the joints are stiffer, but one would move also by jumping over large distances, due to less-then-normal gravity...
You may appreciate the sleek appearance of big lumps cluttering up key joints and generating minimal amounts of power.
Well, to be honest, I did not think about how big actually these things on joints would have to be, but perhaps not much bigger than the protection people on rollerblades use, especially if you are running (higher frequency)?
Well, on the other hand, if you would be running with a knee-mounted generator, perhaps it could make difference. Of course, you would not be running with a heavy backpack, but you might want to charge your batteries while jogging (which you might be doing anyway)?
why a backpack?
Well, I guess since your average generator-user willbe doing some field work, she would need to carry her basic equipment somewhere. Since she would need to carry it anyway...
I agree, wrist- or ankle-mounted generators are more elegant, but would there be such a demand as for backpacks? hmm...
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I would never let my kid be alone with an adult -- ever. In a church I attend the pastor's kid was abused by a grandparent! These things happen, you have to be smart and be secure in advance. Why should I trust anyone, even a "good Christian."
It is a sad state of our society today: that one cannot send his child to borrow something from a neighbor, that one needs to be afraid of his husband's/wife's grandparents. And the worst thing is that, even if you do protect your kids, even if you do give them a proper education at home, still they can grow up and become bad persons. And I think there is no way to be "secure in advance". But one can be cautious!
But that is another question: how fast is the (radiation) energy transferred. Of course it depends on the optical thickness of the material etc...
The question is: What slows down? It is true that light is always moving at the speed of light (tautology), but not always along the same straight lines that an observer away from the gravitational influence of the black hole sees.
I think the issue is what happens with the matter. We expect to see all clocks on a spaceship approaching the event horizon slow down (provided we are located further away from the horizon than that spaceship is). As for the speed of light: if a spaceship is moving at the speed of light, than, for an external observer, the clock on that spaceship stands still. In other words, a photon has no internal clock, there is nothing that can "slow down" there.
He also assumes (from the abstract) that an eavesdropper can only eavesdrop by injecting current into the wire, which is blatantly false. One could easily tap the magnetic field generated by current in the wire, without drawing very much power from the wire at all.
Not so sure about that. In the paper he needs to inject a stohastic current in order to be able to compute TWO cross-correlations. If you passively measure the magnetic field, how do you extract the information bit without inducing the current change in the wires?
How about recording the signal after it has been transmitted through some output at the other end? This bugging would not interfere with the signal being transmitted but would still record the information for transmittal later? If you are transmitting the information through a computer, I think someone will figure out how to get it.
In the preprint he says that the encryption can be broken only if the eavesdropper injects a small current into the communications channel and measures cross-correlations between various quantities, thereby determining which resistor is at which end of a communication channel (that is where the security of the method lies, in the inability of the eavesdropper to determin it without interfering). Recording a signal after transmitting it does not help you to determine which resistor is at which end.
Actually I have heard a talk on astrophyisical N-body simualtions which run on 512 POWER4 processors. By using a combination of OpenMP on the nodes and MPI between the nodes you can do reasonably well (depending on how your problem changes with time). IBM's XL compilers are used.
Corrupt politicians are only the ones you don't agree with :)
A good point
I wonder how does one reconcile unlimited campaign contributions with the incorruptibility of elected politicians...
Ah, well, you might also say that. However, there are some governments willing to fund proving of such speculations. I guess that these speculations have proven to be more succesful than some other. :)
Again I err. I meant, the rate of expansion was decreasing, but now it is increasing.
Sorry. The acceleration was decreasing, not the size of the universe. You are right!
No no, dark energy component percentage grows with time. Above redshift of about 2 (when the universe was a 1/4 of today's size I think) it was insignificant, i.e. the Universe was still deccelerating. When it will be twice today's size, dark energy will constitute even more of the whole energy density.
Well, doing realistic simulations of a galaxy even with "old" Newtonian physics is very expensive. I mean, imagine simulating 100 billion point masses all acting gravitationally on each other (not counting simulating the hydrodynamics of the gas clouds). So, in the best case you can reduce the number of operations to N log N, or about 2000 billion (per time step). Now simulate the whole galaxy, but also taking into account that your binary stars need a lot smaller time step then your simple stars... And then you have a huge discrepancy of time scales (years for binary stars, millions of years for a star like sun to orbit around the center ONCE).
And then add general relativity into this mess? Very hard with today's computers...
I wonder if some scientists might already be so invested in theories of dark matter that they will refuse to accept this position.
I would not worry too much about that... They will easily adapt, using their results as "boundary" cases of whatever currently popular new theory. Investing in theories is never futile...
...is going to become the major worry. Data from supernovae distance measurements indicate that the Universe has been expanding for some time already. That means that there has to exist a sort of anti-gravity (called dark energy by astrophysicists). Now, that is hard to explain by conventional means (although it is possible), and may involve either a "beyond Einstein" type of theory (e.g., an improved general relativity) or some exotic form of energy (or both). So, although general relativity alone might account for the rotational curves of galaxies, it does not account for the large-scale properties of the universe.
You are right, it is either sines and cosines or square roots and fractions (I am guessing here, it may be something else)...in any case a lot of algebraic computation is rather unpopular among pupils :(
That's true, but the question is how long does it take for everything to get smashed into the same point. Maybe long enough to fool us? :)
A black hole is of a finite size (Schwarzschild radius in case of a non-rotating one). But you are right, inside all the matter is concentrated in a point, a singularity. But again, what appears to the outside observer as a black hole is of finite size. A black hole with the solar mass would have a radius of about 3km.
Yes, but if you read what they say in the article, it is the right kin of the perturbations what counts, not their magnitude. Because the system of partial differential equations (which is a good approximation to the temporal evolution of the atmosphere) is nonlinear, even a small perturbation can cause a major change in the future.
It would be nice to have more information about this. I wonder what China's plans are as to space, and whether their centralized government will be able to make better progress than the American system. Then again, beauracracy is beauracracy, so I don't have high hopes on China getting much further than developing extra-long range rockets.
Then again, if you pump enough money into the system, even with a considerable amount of bureaucratic friction you might get somewhere. They could also be sending interplanetary probes soon...
Exactly! Moreover, by spreading generators through the armor you can make the power supply more redundant, which is always good in combat.
Would this work for spacesuits during Mars exploration mission? I mean, OK, the joints are stiffer, but one would move also by jumping over large distances, due to less-then-normal gravity...
I guess you'd have to get up and go jogging every ten minutes to recharge the batteries!
That, or make your lightweight backpack-charged battery last long enough for the work you do at that particular site.
warning! humour alert: with generators on the wrist, a few minutes surfing for porn will probably store a few megajoules ready to power everything!!!
Yeah! You could power whole parts of the city that way, right?
You may appreciate the sleek appearance of big lumps cluttering up key joints and generating minimal amounts of power.
Well, to be honest, I did not think about how big actually these things on joints would have to be, but perhaps not much bigger than the protection people on rollerblades use, especially if you are running (higher frequency)?
Well, on the other hand, if you would be running with a knee-mounted generator, perhaps it could make difference. Of course, you would not be running with a heavy backpack, but you might want to charge your batteries while jogging (which you might be doing anyway)?
why a backpack?
Well, I guess since your average generator-user willbe doing some field work, she would need to carry her basic equipment somewhere. Since she would need to carry it anyway...
I agree, wrist- or ankle-mounted generators are more elegant, but would there be such a demand as for backpacks? hmm...