Actually it's a real diff. geom. theorem (2nd-year math undergraduate stuff) which is indeed applicable to tokamaks, since ionized particles stay (up to diffusion) "stuck" in magnetic field lines.
The Wikipedia article is indeed accurate, although very terse.
-- and yes, I AM a plasma physicist (or at least, was one for 4 years)
But there's also a theory that the real mathematician behind his work was Mileva.
interesting. any evidence for this ?
The main argument is that his seminal papers were written during the years that they were together, and after they split up, he never again produced anything of such importance.
What work of academic merit did Mileva Maric produce ? If she was that seminal an academic, wouldn't there have been a major publication, before or after (or during) their marriage ?
The culture back then was not very interested in recording the details of a mere wife's contributions.
True. That did not stop historians from acknowledging works by other great women of the age: Noether and, eventually, Meitner. This Mileva rumor ("theory" is realy something else, BTW) looks quite fictional, I think.
The crossection is SO small, the needed target so rare, the needed deltaV so large, thats there not much chance of something like this happening in a galaxy ever...
You are forgetting the super-massive black hole in the center of the galaxy, and any black-holes (or neutron-stars) which may very probably be in orbit around it. (lookup AGN - active-galactic nuclei)
In fact, I'm not sure that the slingshot option isn't rather more probable than the fast-supernova-remnant hypothesis. Remember that the star-density at the core is rather high. A "collision" every 10^5 years may not be that rare.
It's pretty much the death knell for any scheme that isn't magnetic confinement of D-T fusion
DT I agree, the cross sections are too low otherwise, but what about indirect-drive ICF ? It seemed (in my Plasma-physics days) to me a rather more promising avenue than MCF. The reaosn being that the hohlraum's (and fusion pellet's) spherical symmetry and the high X-ray power obtained from a wire-array Z-pinch are supposed to considerably reduce instabilities.
(And no, I have not read the thsis you've linked to - I have my own research to do...)
2.5 thousand years ago, you might have said the same for urban-garbage collection:
I mean, who will pay ? Suppose the governing clan did ? Then the rest of the clans get a nice clean polis without contributing a single loaf of bread ?
I'm not trying to mock you, just give a reasonable counter-example by analogy: by which I mean that under a certain population density, there was no need for garbage-collectors. Once the technical capabilities and common need arose, so did the financial mechanisms.
This is especially the case among the borderline-Asperger's-Syndrome types that like to frequent Slashdot
Wow, I looked it up on wikipedia and found a description of myself - thanks for the info.
Because of ionic energy levels
on
19 million Amps
·
· Score: 1
The material material explodes and ionizes at pulse begining, so that it's initial resistivity does not matter anyway.
What does matter is the inner-shell ionization potential, so that at stagnation (highest pressure and heat) the ions have a few energy-levels at the expected energy.
For this, Helium-like ions are the simplest, and are widely used.
Silver has way too many electrons, and will not ionize sufficiently.
(In my MSc we've used He-like Neon for a much weaker Z-Pinch, ~0.3 MA current)
-- and yes, I WAS a plasma physicist.
Resistence drops sharply on ionization
on
19 million Amps
·
· Score: 1
Because the material explodes and ionizes already at pulse start. The Plasma resistivity is many orders of magnitudes lower than the Al.
(In fact, partly-ionized Plasma can have negative resistivity)
However, the shell implodes, so that R drops sharply - at some point resistance sharply rises as well.
Is there a fundamental limit to our ability to extract virtual particles from vacuum,
First, there's the uncertainty principle.
Second, although I've studied QFT ~4 yrs ago, and so I may very well be mistaken about this, AFAIK Casimir effect does NOT violate energy-conservation, and so the maximum one can reach is a vacuum-energy based energy-storage, rather than a "generator"
I did study it for several years. Note that people invested whole decades in it and still have things to know, though...
From what I know, the ways that we get power (electricity mostly?) from nuclear reactions is to extract the heat produced. If your hot, fusing plasma is contained in a magnetic field, how do you extract the heat from it?
Only partly correct. There are two kinds of nuclear reactions, neutronic (those that produce neutrons) and non-neutronic. Those involving only hydrogen-isotopes are neutronic. These fast neutrons, being electrically neutral, immediately escape the magnetic field and hit the container surrounding the vacuum-chamber. They heat this container, and this heat can be used in the usual fashion.
Actually, this is a real engineering problem, since, first, it is inefficient, and second, these neutrons transmute the atoms of container in much the same fashion a neutron bomb affects one's body, causing both reactor degradation and turning it into dangerous radioactive waste.
There is a much more elegant way to extract energy directly from the plasma motion (MHD-generators), however, it requires that some of the nuclear reactions would be non-neutronic. Sadly, it means they envolve Boron-He3 or even heavier particles, and are therefore orders of magnitude harder to produce.
Obviously our first step is to make a self-sustaining fusion reaction, but I hope (and know, really) that SOMEONE is thinking about how to make it commercially viable.
Yes, someone is;-)...
I just want to know what those people are thinking.:-)
Although physics is by no means always easy, it's not voodoo either... You can study it for yourself. If you have some undergraduate physics background, Goldstone & Rutherford's book is a nice, easy introduction. Chen's introduction to plasma-physics is also nice.
The only limiting power about fusion reactors is size:
Wrong. The limiting factor are plasma instabilities, which limit the time that the plasma can be contained (lookup Lawson Criterion)). This is true for both ICF and MCF.
Commercially (and eneregtically) viable controlled fusion is not just a technological problem, it turned out to be an extremely hard scientific one. In fact, I've heard from several Plasma-physics profs that the ITER approach is considered by many professionals as LESS likely to succeed than ICF (google for fusion, indirect-drive, and Z-Pinch).
-- and yes, I was a Plasma-physics student. I did my Masters on a Z-Pinch machine, not on a Tokamak, though.
Destroying an asset... is a bad idea. If you were to generalize that thinking...
But he was not. Applying a principle, or a model, outside the original context (i.e. for different axioms) , although interesting intelectually, does not make a valid rebuttal.
In fact, it is ones of the main arguments of the "IP"-related political debate, that the "IP" kinds of "asset" (as you call it) , are not property and should be treated differently than other government-created monopolies.
PP's (in this regard, "sloppy") generalization ignores this completely.
I stop by that passage in Leviticus on how to do slavery up right in the eyes of the Lord.
Are you kidding ? The slavery laws were way advanced for the age. An age when slavery was as common economical practice as being an employer today.
The ancient israelites insistence on freeing slaves every 50 years ensured that whole FAMILIES will not have to stay in slavery, and lack of freedom was so frowned on that a slave choosing to REMAIN a slave would be branded in shame. Again, this is the old world - compare this to the neighbours, even to the later, relatively tolerant, Romans, where slavery was practially the only game in town.
(though I doubt it was really king solomon as most of the church claims)
AFAIK this claim predates the church, it is a part of the jewish bible.
Also, IIRC from my highschool days (12yrs ago), there were text-analysis which found that the language and style of ecclesiastes are inconsistent with those in K. Solomon's time (circa 950 BC).
In a similar manner, "Job" (which I,IMHO, found to be more interesting and relevant then Ecc.) is suspected to be an earlier work than the rest of the bible, perhaps not jewish at all.
Even if Orion wouldn't have worked (we won't know), the show-stopper is the low energy density and specific impulse to be obtained by chemical rockets.
The trade-off is F(money, performance, power, safety). If the energy-density were ~10^6 higher (==nuke) the engineers could design a craft with simpler systems and include several of these 4each purpose w/o going into complicated hacks to save every gram.
This would result in much safer and much cheaper crafts.
what your basicly saying is that the blame for cracking the system is on the crackers (ip-speculators)
This is, of course, true, but irrelevant. The point is that the system can be so easily exploited, and so should be reformed or rebuilt. It's a bit more realistic, IMHO, than trying to remove human greed...
Slashdot Mirror
Actually it's a real diff. geom. theorem (2nd-year math undergraduate stuff) which is indeed applicable to tokamaks, since ionized particles stay (up to diffusion) "stuck" in magnetic field lines.
The Wikipedia article is indeed accurate, although very terse.
-- and yes, I AM a plasma physicist (or at least, was one for 4 years)
But there's also a theory that the real mathematician behind his work was Mileva.
interesting. any evidence for this ?
The main argument is that his seminal papers were written during the years that they were together, and after they split up, he never again produced anything of such importance.
What work of academic merit did Mileva Maric produce ?
If she was that seminal an academic, wouldn't there have been a major publication, before or after (or during) their marriage ?
The culture back then was not very interested in recording the details of a mere wife's contributions.
True. That did not stop historians from acknowledging works by other great women of the age: Noether and, eventually, Meitner. This Mileva rumor ("theory" is realy something else, BTW) looks quite fictional, I think.
At $100k per infection, which in Texas alone would amount to something in the $50+ billion
what happens if sony decides just not to pay ? what, legally, can the state of Texas do ?
WYSIWYM ?
The Japanese were preparing to surrender but where going to set terms
Which is practically equivalent to "... were considering surrender, but not at that point in time". Setting terms can take as long as one wants.
To prevent the soviets from moving in the Americans dropped the bombs
Now that can be seen as even MORE controversial. I'm not saying your interpretation of the events is wrong, but an interpretation it is.
The crossection is SO small, the needed target so rare, the needed deltaV so large, thats there not much chance of something like this happening in a galaxy ever...
You are forgetting the super-massive black hole in the center of the galaxy, and any black-holes (or neutron-stars) which may very probably be in orbit around it. (lookup AGN - active-galactic nuclei)
In fact, I'm not sure that the slingshot option isn't rather more probable than the fast-supernova-remnant hypothesis. Remember that the star-density at the core is rather high. A "collision" every 10^5 years may not be that rare.
It's pretty much the death knell for any scheme that isn't magnetic confinement of D-T fusion
...)
DT I agree, the cross sections are too low otherwise, but what about indirect-drive ICF ? It seemed (in my Plasma-physics days) to me a rather more promising avenue than MCF.
The reaosn being that the hohlraum's (and fusion pellet's) spherical symmetry and the high X-ray power obtained from a wire-array Z-pinch are supposed to considerably reduce instabilities.
(And no, I have not read the thsis you've linked to - I have my own research to do
I mean, who would pay for such a service?
2.5 thousand years ago, you might have said the same for urban-garbage collection:
I mean, who will pay ? Suppose the governing clan did ? Then the rest of the clans get a nice clean polis without contributing a single loaf of bread ?
I'm not trying to mock you, just give a reasonable counter-example by analogy: by which I mean that under a certain population density, there was no need for garbage-collectors. Once the technical capabilities and common need arose, so did the financial mechanisms.
I believe it may not be different for LEO g.c.
This is especially the case among the borderline-Asperger's-Syndrome types that like to frequent Slashdot
Wow, I looked it up on wikipedia and found a description of myself - thanks for the info.
The material material explodes and ionizes at pulse begining, so that it's initial resistivity does not matter anyway.
What does matter is the inner-shell ionization potential, so that at stagnation (highest pressure and heat) the ions have a few energy-levels at the expected energy.
For this, Helium-like ions are the simplest, and are widely used.
Silver has way too many electrons, and will not ionize sufficiently.
(In my MSc we've used He-like Neon for a much weaker Z-Pinch, ~0.3 MA current)
-- and yes, I WAS a plasma physicist.
Because the material explodes and ionizes already at pulse start. The Plasma resistivity is many orders of magnitudes lower than the Al.
(In fact, partly-ionized Plasma can have negative resistivity)
However, the shell implodes, so that R drops sharply - at some point resistance sharply rises as well.
Is there a fundamental limit to our ability to extract virtual particles from vacuum,
First, there's the uncertainty principle.
Second, although I've studied QFT ~4 yrs ago, and so I may very well be mistaken about this, AFAIK Casimir effect does NOT violate energy-conservation, and so the maximum one can reach is a vacuum-energy based energy-storage, rather than a "generator"
since you claim to know about plasma-physics
...
;-) ...
:-)
... You can study it for yourself. If you have some undergraduate physics background, Goldstone & Rutherford's book is a nice, easy introduction. Chen's introduction to plasma-physics is also nice.
I did study it for several years. Note that people invested whole decades in it and still have things to know, though
From what I know, the ways that we get power (electricity mostly?) from nuclear reactions is to extract the heat produced. If your hot, fusing plasma is contained in a magnetic field, how do you extract the heat from it?
Only partly correct. There are two kinds of nuclear reactions, neutronic (those that produce neutrons) and non-neutronic. Those involving only hydrogen-isotopes are neutronic. These fast neutrons, being electrically neutral, immediately escape the magnetic field and hit the container surrounding the vacuum-chamber. They heat this container, and this heat can be used in the usual fashion.
Actually, this is a real engineering problem, since, first, it is inefficient, and second, these neutrons transmute the atoms of container in much the same fashion a neutron bomb affects one's body, causing both reactor degradation and turning it into dangerous radioactive waste.
There is a much more elegant way to extract energy directly from the plasma motion (MHD-generators), however, it requires that some of the nuclear reactions would be non-neutronic. Sadly, it means they envolve Boron-He3 or even heavier particles, and are therefore orders of magnitude harder to produce.
Obviously our first step is to make a self-sustaining fusion reaction, but I hope (and know, really) that SOMEONE is thinking about how to make it commercially viable.
Yes, someone is
I just want to know what those people are thinking.
Although physics is by no means always easy, it's not voodoo either
The only limiting power about fusion reactors is size:
Wrong. The limiting factor are plasma instabilities, which limit the time that the plasma can be contained (lookup Lawson Criterion)). This is true for both ICF and MCF.
Commercially (and eneregtically) viable controlled fusion is not just a technological problem, it turned out to be an extremely hard scientific one. In fact, I've heard from several Plasma-physics profs that the ITER approach is considered by many professionals as LESS likely to succeed than ICF (google for fusion, indirect-drive, and Z-Pinch).
-- and yes, I was a Plasma-physics student. I did my Masters on a Z-Pinch machine, not on a Tokamak, though.
Sloppy ( Horrible nickname, BTW ) wrote :
... is a bad idea. If you were to generalize that thinking ...
Destroying an asset
But he was not. Applying a principle, or a model, outside the original context (i.e. for different axioms) , although interesting intelectually, does not make a valid rebuttal.
In fact, it is ones of the main arguments of the "IP"-related political debate, that the "IP" kinds of "asset" (as you call it) , are not property and should be treated differently than other government-created monopolies.
PP's (in this regard, "sloppy") generalization ignores this completely.
A mathematical proof is nothing but a manner of convincing someone (other mathematicians) that what you assert is indeed correct
More correctly, I would say:
A mathematical proof is the method of convincing mathematicians (the first one being yourself) that what you assert is indeed correct.
This, of course, only strenghthens your concluding sentence...
I stop by that passage in Leviticus on how to do slavery up right in the eyes of the Lord.
Are you kidding ? The slavery laws were way advanced for the age. An age when slavery was as common economical practice as being an employer today.
The ancient israelites insistence on freeing slaves every 50 years ensured that whole FAMILIES will not have to stay in slavery, and lack of freedom was so frowned on that a slave choosing to REMAIN a slave would be branded in shame. Again, this is the old world - compare this to the neighbours, even to the later, relatively tolerant, Romans, where slavery was practially the only game in town.
(though I doubt it was really king solomon as most of the church claims)
AFAIK this claim predates the church, it is a part of the jewish bible.
Also, IIRC from my highschool days (12yrs ago), there were text-analysis which found that the language and style of ecclesiastes are inconsistent with those in K. Solomon's time (circa 950 BC)
In a similar manner, "Job" (which I
A camel is a horse that was designed by committee
This is doubly funny, as camels are much tougher, stronger workers than horses
That's the real show-stopper.
Even if Orion wouldn't have worked (we won't know), the show-stopper is the low energy density and specific impulse to be obtained by chemical rockets.
The trade-off is F(money, performance, power, safety). If the energy-density were ~10^6 higher (==nuke) the engineers could design a craft with simpler systems and include several of these 4each purpose w/o going into complicated hacks to save every gram.
This would result in much safer and much cheaper crafts.
I see it with my kid's friends: whenever the "dumbox" is turned on, the kids are magnetized.
So when an overworked, underslept parent hears the screams of boardom they just turn the TV on just to get some rest.
IANAP[arent], so it's easy for me to comment, but it does seem to me like selling (a bit of) the kid's future for some instant gratification.
an icon with Uri-Geller's face will do fine.
So what happens when someone converts an old microwave to an EMP blaster and shorts out the joystick, then sends thier own signal to the bot?
If the EMP works It will disable control for both operator and malicious signals
I reckon economics is, like theology, euclidean geometry and the propositional calculus, a formal system, which doesn't really apply to the real world
Are you kidding ? Except for the really large (think much larger than earth) and really small (lookup planck scale) euclidean geometry is king.
I dare you measure a deviation from euclidean geometry in, say, a month.
what your basicly saying is that the blame for cracking the system is on the crackers (ip-speculators)
This is, of course, true, but irrelevant. The point is that the system can be so easily exploited, and so should be reformed or rebuilt. It's a bit more realistic, IMHO, than trying to remove human greed