Thermonuclear reaction in the sun can only produce electron neutrinos to conserve lepton number. To produce tau or muon neutrino, you must make muons or tau particles respectivly. As you know the thermonuclear reaction goes like:
P+P->deterium + positron + electron neutrino
deterium later merges with protons and other deterium nuclei to make He and heavier nuclei.
Each link of this reaction chain can be easily reproduced in particle accelerators. From these studies we know that electron neutrinos are the only kind to be produced. To produce other flavors, it is required to produce a particle of that flavor to conserve lepton number. However, the temperature, and thus the energy available, is not large enough to produce a significant number of muons and taus so only electron neutrinos are made.
The expense of the project is the engineering that goes into the design of the craft. The cost of the actual hardware is very small in comparison. The additional cost of designing a parachute system (one that could work for most failure modes) would probably be more expensive then mission failure.
Anyway with the pegasus booster itself costing around 10 million, not that much is going to be saved by recovering the aircraft. (see for example for cost of launch http://www.jsc.nasa.gov/bu2/ELV_US.html)
The interesting thing to do is of course stress analyses on the aircraft after its flight, but appernetly NASA dicided that was not important.
No, not quite. This implementation is not actually a quantum computer in the strict sense. If you read the article carefully you notice that the current experiment is unable to entangle states. So computationally speaking this is completly identical to a classical computer! The only benefit is that you can get some parallelism, in this case by using different frequencies. So the experiment is able to perform some (single-state) operations on all 50 states at once. Any normal computer can do the same. For example any 64 bit chip, like the Alpha, can perform a single operation on all 64 states at once (or at least with order 1).
The idea of quantum computation is to be able to perform complicated (multi-bit) computations using entangled states. For example finding prime factors of a number, can be solved in polynomial time. The proposed light approach as described in the article has no chance of achiving that. (I think)
So we should not be warried about proliferation of cheap quantum computers that can crack codes. We probably should not even worry about quantum computers that can crack codes at all for quite a while. (10-50 years depending on progress)
No, not aproximations. General relativity is a second order theory, just like Newton's theory. Here second order means that it involves second derivatives. The difference is that general relativity is a geometric theory while Newtonian physics is a classical field theory. Yes, if we do expand general relativity (for solar system dynamics) in factors of m/r, then the first power will give us Newton's theory, and next one Perhilion preccession. So one theory is not any more "exact" in field equation formulation. Ofcause it should be possible to construct field equations with more then more derivatives, or with more components, but general relativity is enough to have special relativity limit built in. We probably do not want an equation that is to complicated.
Also, shape of universe has almost no effect on solar system scale. We know that to extremly good approximation (by cosmic microwave background power spectrum and distribution) that universe is almost completly flat (Eucledian). The problem is that within experimental error it might be a very flat sphere or very flat hyperbola.
I think that the reason that probes are decelerating is of dark matter. No sane engineer would ever take it into account, but astronomers are not quite so sane.
Re:There is use for a table in zero-gravity ?
on
Home Improvement
·
· Score: 3
If I was designing such a table from scratch, I would consider making something like an air hockey table in reverse. However, th improvised version probably uses velcro for simplicity.
BTW acceleration is measure in m s^-2, and not m s^-1.
Assuming down means towards the wall it landed on, then absolutley yes. If the bread managed to land buttered side up, it will not stick to the wall and bounce off. However, if it lands buttered side down, it will surely stick to the wall.
Please note chances that the bread will end up buttered side down on certain portion of the space station is directly proportional to the cost of the landing site by Murphie's law.
Actually, in real life, if the buttered bread floats off the table unnoticed, it will almost certainly end up in one of the air filters. (probably with equal probability for buttered side towards the filter) If it is ejected from the table with high enough speed to hit space station walls then the previos theory of bouncing/sticking is more likely.
As a 3rd year physics students. Doing homework in gropus rocks for the smart students. I am not sure what it does for everyone else.
The physics department at Rice University encourages collabaration on homework. This really does help, because alone you can not solve everything. (Problem sets often do ask to solve everything, or at least a fair amount) If you get stuck because you do not understand a concept, it is much better to work through it with someone else, rather then being told the answer (and often given the look, go away, I want to get back to my research).
The only problem with groups (when doing physics problem sets), is that if the group gets stuck, it is really stuck. However, in that case you do not look as silly when asking the prof, since you came with most of the class.
On the other hand, doing exams in groups is plain silly when you get graded competativly (unless you are content with a B or a C).
Re:It's not just memories he's buying
on
Tito In Space
·
· Score: 3
Space missions have already become much less physically demanding then in the good old days. The space shuttle never experiences over 4G's. As compared to appolo's 6, and previous missions of up to 10G's (first soviet missions using voskhod were close to 10G's plus the bonus ejection at the end of mission probably at around 20G's)
International "guest" Astronauts and Cosmonauts have been flying since the eighties at least. Right now there is a Canadian, a Russian, and an Italian on Board the Shuttle. The Italian guy has never been in space, and is only there to "over see" unloading of Italian Rafaello module. It seems the only difference between Umberto Guidoni and Titto is ideological, they have about equal training, with the excpetion of the training that NASA refused to Mr. Titto.
If it is OK to fly political "guests" why not bussiness "guests"?
Todays event, is an event we will remeber. (Maybe not quite as well as Gagarin flight, but that was first for man, not bussinesman.)
You are confusing fission with fusion.
So some general remarks are in order:
Fission is the reaction which powers nuclear bombs and power plants. The energy comes from spliting of Plutonium or Uranium nuclei into lighter nuclei. Fission can work in a chain reaction because usually spliting of heavy nucleous produces neutrons which in turn can split other nuclei.
On the other hand fusion is the reaction which powers H bombs and stars. In fusion 2 lighter nuclei combine to form a havier nucleous. Unlike fission, there is no fusion chain reaction (more or less). Further, using current technology, fusion is to be produced in tokamak, which is a self stabilizing system! In the sense that reaction will never run away. Tokamaks work by confining high temperature plasma with magnetic field. The nuclei in plasma fuse because of collisions due to high temperature in the said plasma. If reaction is going too well, the plasma temperature gets too high, and magnetic field becomes too weak to confine the plasma, causing the plasma to leak out and reaction to stop.
Unfortunatly fusion has major drawback: there are no working reactors!
Also fusion is not as clean as claimed, and you are right to be worried. The easiest way to fusion is the Deuterium-Tritium reaction, unfortunatly it produces a large number of neutrons. The neutrons are ofcause the major problem with all nuclear power and are very harmfull to humans. The neutrons cause formation of unstable isotopes in everything surrounding the reactor making it neccessary to dispose of core and shielding not just the spent fuel.
So fusion will not solve any problems here on Earth. Hopefully, controlled fusion will be allowed into space since the reactor and fuel are "clean" until turned on, where it will be a very useful power source. The only thing better would be antimatter, but that is even harder to get to work.
The interesting property of holagram is that if there is a small flaw in the coating, instead of making one bit unreadable, it will cause all bits to be slightly less readable, since the information for each bit is encoded in the whole cube! So accidental scratches will not cause errors, untill there is enough damage to cause the whole cube to fail.
In one dimention, the data stored in the hologram, is basically the Fourier transform of data that you actually see, in three dimmentions, the equations are a bit more complicated, but same idea holds, damage results mostly in overall degradation, not loss of any particular spot.
Slashdot Mirror
Thermonuclear reaction in the sun can only produce electron neutrinos to conserve lepton number. To produce tau or muon neutrino, you must make muons or tau particles respectivly. As you know the thermonuclear reaction goes like:
P+P->deterium + positron + electron neutrino
deterium later merges with protons and other deterium nuclei to make He and heavier nuclei.
Each link of this reaction chain can be easily reproduced in particle accelerators. From these studies we know that electron neutrinos are the only kind to be produced. To produce other flavors, it is required to produce a particle of that flavor to conserve lepton number. However, the temperature, and thus the energy available, is not large enough to produce a significant number of muons and taus so only electron neutrinos are made.
The expense of the project is the engineering that goes into the design of the craft. The cost of the actual hardware is very small in comparison. The additional cost of designing a parachute system (one that could work for most failure modes) would probably be more expensive then mission failure.
Anyway with the pegasus booster itself costing around 10 million, not that much is going to be saved by recovering the aircraft. (see for example for cost of launch http://www.jsc.nasa.gov/bu2/ELV_US.html)
The interesting thing to do is of course stress analyses on the aircraft after its flight, but appernetly NASA dicided that was not important.
Sorry can not resist.
Soyuz paperwork must consists of the following:
Recipt for 20 Million USD
Insurrence policy
Promise not to touch any american equipment
No, not quite. This implementation is not actually a quantum computer in the strict sense. If you read the article carefully you notice that the current experiment is unable to entangle states. So computationally speaking this is completly identical to a classical computer! The only benefit is that you can get some parallelism, in this case by using different frequencies. So the experiment is able to perform some (single-state) operations on all 50 states at once. Any normal computer can do the same. For example any 64 bit chip, like the Alpha, can perform a single operation on all 64 states at once (or at least with order 1).
The idea of quantum computation is to be able to perform complicated (multi-bit) computations using entangled states. For example finding prime factors of a number, can be solved in polynomial time. The proposed light approach as described in the article has no chance of achiving that. (I think)
So we should not be warried about proliferation of cheap quantum computers that can crack codes. We probably should not even worry about quantum computers that can crack codes at all for quite a while. (10-50 years depending on progress)
No, not aproximations. General relativity is a second order theory, just like Newton's theory. Here second order means that it involves second derivatives. The difference is that general relativity is a geometric theory while Newtonian physics is a classical field theory. Yes, if we do expand general relativity (for solar system dynamics) in factors of m/r, then the first power will give us Newton's theory, and next one Perhilion preccession. So one theory is not any more "exact" in field equation formulation. Ofcause it should be possible to construct field equations with more then more derivatives, or with more components, but general relativity is enough to have special relativity limit built in. We probably do not want an equation that is to complicated.
Also, shape of universe has almost no effect on solar system scale. We know that to extremly good approximation (by cosmic microwave background power spectrum and distribution) that universe is almost completly flat (Eucledian). The problem is that within experimental error it might be a very flat sphere or very flat hyperbola.
I think that the reason that probes are decelerating is of dark matter. No sane engineer would ever take it into account, but astronomers are not quite so sane.
If I was designing such a table from scratch, I would consider making something like an air hockey table in reverse. However, th improvised version probably uses velcro for simplicity. BTW acceleration is measure in m s^-2, and not m s^-1.
Assuming down means towards the wall it landed on, then absolutley yes. If the bread managed to land buttered side up, it will not stick to the wall and bounce off. However, if it lands buttered side down, it will surely stick to the wall.
Please note chances that the bread will end up buttered side down on certain portion of the space station is directly proportional to the cost of the landing site by Murphie's law.
Actually, in real life, if the buttered bread floats off the table unnoticed, it will almost certainly end up in one of the air filters. (probably with equal probability for buttered side towards the filter) If it is ejected from the table with high enough speed to hit space station walls then the previos theory of bouncing/sticking is more likely.
As a 3rd year physics students. Doing homework in gropus rocks for the smart students. I am not sure what it does for everyone else.
The physics department at Rice University encourages collabaration on homework. This really does help, because alone you can not solve everything. (Problem sets often do ask to solve everything, or at least a fair amount) If you get stuck because you do not understand a concept, it is much better to work through it with someone else, rather then being told the answer (and often given the look, go away, I want to get back to my research).
The only problem with groups (when doing physics problem sets), is that if the group gets stuck, it is really stuck. However, in that case you do not look as silly when asking the prof, since you came with most of the class.
On the other hand, doing exams in groups is plain silly when you get graded competativly (unless you are content with a B or a C).
Space missions have already become much less physically demanding then in the good old days. The space shuttle never experiences over 4G's. As compared to appolo's 6, and previous missions of up to 10G's (first soviet missions using voskhod were close to 10G's plus the bonus ejection at the end of mission probably at around 20G's)
International "guest" Astronauts and Cosmonauts have been flying since the eighties at least. Right now there is a Canadian, a Russian, and an Italian on Board the Shuttle. The Italian guy has never been in space, and is only there to "over see" unloading of Italian Rafaello module. It seems the only difference between Umberto Guidoni and Titto is ideological, they have about equal training, with the excpetion of the training that NASA refused to Mr. Titto.
If it is OK to fly political "guests" why not bussiness "guests"?
Todays event, is an event we will remeber. (Maybe not quite as well as Gagarin flight, but that was first for man, not bussinesman.)
You are confusing fission with fusion.
So some general remarks are in order:
Fission is the reaction which powers nuclear bombs and power plants. The energy comes from spliting of Plutonium or Uranium nuclei into lighter nuclei. Fission can work in a chain reaction because usually spliting of heavy nucleous produces neutrons which in turn can split other nuclei.
On the other hand fusion is the reaction which powers H bombs and stars. In fusion 2 lighter nuclei combine to form a havier nucleous. Unlike fission, there is no fusion chain reaction (more or less). Further, using current technology, fusion is to be produced in tokamak, which is a self stabilizing system! In the sense that reaction will never run away. Tokamaks work by confining high temperature plasma with magnetic field. The nuclei in plasma fuse because of collisions due to high temperature in the said plasma. If reaction is going too well, the plasma temperature gets too high, and magnetic field becomes too weak to confine the plasma, causing the plasma to leak out and reaction to stop.
Unfortunatly fusion has major drawback: there are no working reactors!
Also fusion is not as clean as claimed, and you are right to be worried. The easiest way to fusion is the Deuterium-Tritium reaction, unfortunatly it produces a large number of neutrons. The neutrons are ofcause the major problem with all nuclear power and are very harmfull to humans. The neutrons cause formation of unstable isotopes in everything surrounding the reactor making it neccessary to dispose of core and shielding not just the spent fuel.
So fusion will not solve any problems here on Earth. Hopefully, controlled fusion will be allowed into space since the reactor and fuel are "clean" until turned on, where it will be a very useful power source. The only thing better would be antimatter, but that is even harder to get to work.
David
The interesting property of holagram is that if there is a small flaw in the coating, instead of making one bit unreadable, it will cause all bits to be slightly less readable, since the information for each bit is encoded in the whole cube! So accidental scratches will not cause errors, untill there is enough damage to cause the whole cube to fail. In one dimention, the data stored in the hologram, is basically the Fourier transform of data that you actually see, in three dimmentions, the equations are a bit more complicated, but same idea holds, damage results mostly in overall degradation, not loss of any particular spot.
This is exactly why apple made G# towers and iMacs. One for proffesionals one for consumers!