Actually, it's a really, really big deal for experimental particle physics. Accelerator size is directly proportional to maximum energy for conventional acceleration. For a given energy, this thing halves the required size of the building (not to mention the cost). That's a big deal when you're talking about 100 km accelerators costing tens of billions of dollars. In fact, if SLAC were a little big bigger, they could reach the energies of CERN and scoop them on the Higgs boson.
I attended a talk from one of the primary investigators on this project a few months back. The system does indeed spread out the distribution, which can be bad for some circumstances. When all you care about is the peak energy, however, it's great. They call it a plasma afterburner.
One thing that isn't obvious is that you can't use two of these devices to double the energy twice. One doubling is all you got. Apparently there's some theorem in plasma physics that a Gaussian distributed pulse (as SLAC is) can only be energy-doubled by any method or methods once. I don't know the details of this, and I might be misrepresenting it, but there you go.
By the way, I think you have a misconception about temperature. It's true that a higher temperature gas has a wider energy spectrum, but the primary piece of information you're interested in is the average velocity. The statistical distribution is a function of only one variable -- you can't "spread out" the distribution to increase the temperature without simply dumping energy into the system. If you somehow separated the particles into low average energy and high average energy, you'd just have two classes of particles with two temperatures, not one cumulatively higher one.
But some people look at the cosmos and decide that despite not truly understanding the whole picture of physics at every scale yet, we can claim that dark matter exists and here's proof. Where in the Nine Hells does this stuff fit with the physics theories they alread promulgate as accepted science to be taught in universities?
More than just fitting in, dark matter is predicted by numerous very deep theories. Ask any theoretical particle physicist.
You can still "see" matter that's behind other matter. The other matter just radiates in the infrared. For example, we know there are stars behind big clouds of dust, even though we can't see any of the visible light.
I wonder if the power consumption of a low-end Pentium 2 is actually worth the computation capability it could contribute to a network. There's definitely a point at which it costs more to run a computer than you can get out of it -- where does that line fall?
The gravitational energy is negative, so it reduces the amount of available energy for the supernova
No, that's not right. If the dwarf collapses to, say, a neutron star, energy will be liberated when the radius of the star decreases. The change in gravitational potential is negative, so that extra energy has to go somewhere. This fuels Type 2 supernovas. I'm just not sure where that energy fits into the Type 1a.
I've heard that it might be that no neutron star is formed in 1a supernovas (the star is just blown apart), so there is no liberation of gravitational potential. That's probably the answer.
Something doesn't add up for me with that description of a 1a supernova. There's a hell of a lot of gravitational potential held in a white dwarf -- something like 10^44 joules. This is also incidentially approximately the same as the energy released in the fusion process, assuming 0.1% of rest mass is converted to energy. So either I'm missing something, or about half the energy of a 1a supernova comes from fusion, and the other half from gravitational collapse. It's not clear to me that one would dominate, in the way you describe.
Could things like this be part of the explanation for that "dark matter" that scientists are always talking about? Maybe there are more and we just haven't found them.
Well, yes, but only a small part. We can put a pretty good upper bound on the amount of dark matter that can be in black holes based on gravitational lensing data. Black holes most famously absorb light that is incident inside their event horizons, but they also cause light traveling outside to curve around it. (As does all matter.) Thus, a star that is behind a black hole looks to be in a different place than it should, or even at two different places at once (more info). We can measure how much light is bent and infer how much matter is contained in high-density regions.
Obviously, gravitational lensing only happens where matter is compact. Uniformly distributed stuff won't do it. Thus, we know about how much dark matter there is, and from this, roughly how much can be in black holes. The punch line is that only a small fraction of dark matter (I don't remember the statistic off hand) can come from black holes.
The question is obviously, then, where's the rest of this matter? Some could be in other "normal" matter, like dwarf stars, but again, for various reasons that can't account for very much. Some could be in neutrinos (weakly interacting particles which are almost impossible to detect). This still leaves a whole lot of matter unaccounted for though. Maybe it's so-called WIMPs (weakly interacting massive particles) which theoretically could be very massive but interact with normal matter very little. Read more at Wikipedia.
With such a contentious issue like this, it's a good thing the title of the story isn't biased in any way. I really appreciate how Slashdot serves to be such a mediating influence.
My understanding is that while these stars are certainly more massive and probably just as dense (if not denser, contrary to what some posters have speculated) than our sun they are much, much hotter. A star can be thought of as a dynamic equilibrium between the force of gravity pulling the material together and the pressure produced by the heat of fusion pushing it apart. Therefore, the bigger a star is, the hotter it must be to equilibriate. This happens naturally, since the kinetics of the fusion reaction are related to the pressure. (That is, as the star collapses under its weight, the rate fusion increases -- that is, until it runs out of energy.) This has an interesting consequence regarding star lifetimes: contrary to what you might expect, the bigger a star is, the shorter its lifetime is, since it has to consume its fuel so much faster.
So to answer your question, the reason these stars don't become black holes is the same as the reason that any supermassive stars don't. The heat produced by fusion. The only difference with these is that they burn their fuel much faster than other stars, and correspondingly, can be expected to snuff it much sooner.
I might be wrong about some of this, but I'm pretty sure most of what I said is true, at least to a first approximation.
Filtering acid would do nothing
on
Hacking Vodka
·
· Score: 1
Even the best filters can only barely take out viruses -- considering that hydrogen ions (the thing that makes acid an acid) are five orders of magnitude (or so) smaller volume, the filter wouldn't do anything to the pH. I doubt it would even affect the molarity of the chlorine ions. I mean, come on. If a filter was fine enough to remove hydrogen, it would also stop water.
The 3 petabyte one is way inflated. 2 petabytes of that is 3.5M sound recordings. Doing a little math, they're assuming that each of those 3.5 million recordings takes up 600MB. I guess they consider each sound recording to be a full CD. First, most audio CDs don't fill up the entire 600 MB. Second, most of those recordings probably aren't entire CDs. Third, you can compress audio very well. Even losslessly, you can compress AIFF files at least 2x.
I'd say the upper bound on the Library of Congress is about 1 petabyte.
You say "legal," but clearly if free elections had been held Saddam would've been removed from power by a landslide. I call this tyranny, not legality.
A government doesn't have to be democratic to be legal. He was referring to the fact that the Hussein government was recognized as the legitimate government of Iraq.
I tend to think that dictators, especially unpopular and brutal ones, don't deserve the benefits of international law. If that makes me "imperialist", then go ahead and call me that.
Law is meaningless if you only apply it to the people you like. The vast majority of the world thinks the United States is unpopular and brutal -- should we be denied the benefits of international law?
"American safety" has no bearing on whether or not it's possible to properly reconstruct an invaded country.
Ummm... what? World War 2 started because we didn't properly reconstruct Germany after World War 1. I'd say "American safety" was affected a little bit by World War 2, wouldn't you?
One possible explanation is that Samsung wants to use bigger hard drives in the future, and are using this design as a 'proof of concept' sort of thing. Hard drive capacities scale much faster than flash memory (or at least they have), so its very likely that, using this now-perfected technology, Samsung will be able to have phones with several gigabytes of memory for much cheaper than they would be otherwise.
The physical minimum latency for a geosync sattelite (at an altitude of 22,300 miles) is 120ms, if anyone is interested. Of couse, you'd double that for an actual ping, since the signal has to go both up and back.
Europa is already under extreme radiation. The speculation is that if life existed, it would live under the hundreds of miles of ice which cover the planet. Water blocks electromagnetic radiation extremely well (for example, visible light can't penetrate more than a few hundred feet -- ask any SCUBA diver), so it seems like it would absorb electrons and alpha particles pretty well too. NASA does need to be careful, but not with regard to Europa. If this probe blew up on launch it would be bad.
No but then the RIAA couldn't complain about stealing music, because they were getting their money. In fact, I'm sure they would just make all of their stuff available online, since people burining that music to CD would be paying them, even if its indirectly. Er... right?
It would also allow a better explanation for why Neo can get around the rules of physics than the handwaving "Agent's Have Special Ports!" one. If the Matrix is running in Neo's head, he has ultimate control over it.
Well, it is a anti-gravity device, but not a very good one. What happens is the cat and toast just hover there, spinning faster and faster; eventually, either the toast flies off or the cat dies and, as everyone knows, the cat must be alive to land on its feet. If you want a -practicle- anti-gravity device, just butter both sides of the toast!
I wish to express my support of California Representative Zoe Lofgren's Balance Act (H.R. 1066). It promises to fix the gross injustice imposed on consumers with the Digital Millennium Copyright Act (DMCA) that inhibits fair use and ultimately restrains trade. It makes illegal the circumvention of technological restrictions in any case, even that which involves fair use such as the compression of a copyright-protected CD for use in an MP3 player or the burning of a "mix" CD of licensed songs. When a consumer buys a CD, they do it not for the media that a song is recorded on, but rather the song itself. The DMCA unreasonably limits the consumer's rights over their own property and makes criminals out of those who attempt to regain them.
Furthermore, the DMCA fails in its original intention of addressing the very real problem of Internet piracy. Draconian restrictions do not fix the problem, but rather exacerbate it by alienating consumers by effectively requiring illegal activity for fair use. It places special and unreasonable restrictions on digital recordings; someone can sell a used book or lend it to a friend but cannot with a digital recording that is lawfully obtained.
Please vote for H.R. 1066 and encourage your fellow representatives to do likewise.
Slashdot Mirror
Actually, it's a really, really big deal for experimental particle physics. Accelerator size is directly proportional to maximum energy for conventional acceleration. For a given energy, this thing halves the required size of the building (not to mention the cost). That's a big deal when you're talking about 100 km accelerators costing tens of billions of dollars. In fact, if SLAC were a little big bigger, they could reach the energies of CERN and scoop them on the Higgs boson.
I attended a talk from one of the primary investigators on this project a few months back. The system does indeed spread out the distribution, which can be bad for some circumstances. When all you care about is the peak energy, however, it's great. They call it a plasma afterburner.
One thing that isn't obvious is that you can't use two of these devices to double the energy twice. One doubling is all you got. Apparently there's some theorem in plasma physics that a Gaussian distributed pulse (as SLAC is) can only be energy-doubled by any method or methods once. I don't know the details of this, and I might be misrepresenting it, but there you go.
By the way, I think you have a misconception about temperature. It's true that a higher temperature gas has a wider energy spectrum, but the primary piece of information you're interested in is the average velocity. The statistical distribution is a function of only one variable -- you can't "spread out" the distribution to increase the temperature without simply dumping energy into the system. If you somehow separated the particles into low average energy and high average energy, you'd just have two classes of particles with two temperatures, not one cumulatively higher one.
I laughed out loud. Nice job.
But some people look at the cosmos and decide that despite not truly understanding the whole picture of physics at every scale yet, we can claim that dark matter exists and here's proof. Where in the Nine Hells does this stuff fit with the physics theories they alread promulgate as accepted science to be taught in universities?
More than just fitting in, dark matter is predicted by numerous very deep theories. Ask any theoretical particle physicist.
You can still "see" matter that's behind other matter. The other matter just radiates in the infrared. For example, we know there are stars behind big clouds of dust, even though we can't see any of the visible light.
I wonder if the power consumption of a low-end Pentium 2 is actually worth the computation capability it could contribute to a network. There's definitely a point at which it costs more to run a computer than you can get out of it -- where does that line fall?
The gravitational energy is negative, so it reduces the amount of available energy for the supernova
No, that's not right. If the dwarf collapses to, say, a neutron star, energy will be liberated when the radius of the star decreases. The change in gravitational potential is negative, so that extra energy has to go somewhere. This fuels Type 2 supernovas. I'm just not sure where that energy fits into the Type 1a.
I've heard that it might be that no neutron star is formed in 1a supernovas (the star is just blown apart), so there is no liberation of gravitational potential. That's probably the answer.
Something doesn't add up for me with that description of a 1a supernova. There's a hell of a lot of gravitational potential held in a white dwarf -- something like 10^44 joules. This is also incidentially approximately the same as the energy released in the fusion process, assuming 0.1% of rest mass is converted to energy. So either I'm missing something, or about half the energy of a 1a supernova comes from fusion, and the other half from gravitational collapse. It's not clear to me that one would dominate, in the way you describe.
They're right.
Could things like this be part of the explanation for that "dark matter" that scientists are always talking about? Maybe there are more and we just haven't found them.
Well, yes, but only a small part. We can put a pretty good upper bound on the amount of dark matter that can be in black holes based on gravitational lensing data. Black holes most famously absorb light that is incident inside their event horizons, but they also cause light traveling outside to curve around it. (As does all matter.) Thus, a star that is behind a black hole looks to be in a different place than it should, or even at two different places at once (more info). We can measure how much light is bent and infer how much matter is contained in high-density regions.
Obviously, gravitational lensing only happens where matter is compact. Uniformly distributed stuff won't do it. Thus, we know about how much dark matter there is, and from this, roughly how much can be in black holes. The punch line is that only a small fraction of dark matter (I don't remember the statistic off hand) can come from black holes.
The question is obviously, then, where's the rest of this matter? Some could be in other "normal" matter, like dwarf stars, but again, for various reasons that can't account for very much. Some could be in neutrinos (weakly interacting particles which are almost impossible to detect). This still leaves a whole lot of matter unaccounted for though. Maybe it's so-called WIMPs (weakly interacting massive particles) which theoretically could be very massive but interact with normal matter very little. Read more at Wikipedia.
Good question, though.
With such a contentious issue like this, it's a good thing the title of the story isn't biased in any way. I really appreciate how Slashdot serves to be such a mediating influence.
If you're wondering, here is a feature plan for 4.0.
My understanding is that while these stars are certainly more massive and probably just as dense (if not denser, contrary to what some posters have speculated) than our sun they are much, much hotter. A star can be thought of as a dynamic equilibrium between the force of gravity pulling the material together and the pressure produced by the heat of fusion pushing it apart. Therefore, the bigger a star is, the hotter it must be to equilibriate. This happens naturally, since the kinetics of the fusion reaction are related to the pressure. (That is, as the star collapses under its weight, the rate fusion increases -- that is, until it runs out of energy.) This has an interesting consequence regarding star lifetimes: contrary to what you might expect, the bigger a star is, the shorter its lifetime is, since it has to consume its fuel so much faster.
So to answer your question, the reason these stars don't become black holes is the same as the reason that any supermassive stars don't. The heat produced by fusion. The only difference with these is that they burn their fuel much faster than other stars, and correspondingly, can be expected to snuff it much sooner.
I might be wrong about some of this, but I'm pretty sure most of what I said is true, at least to a first approximation.
Even the best filters can only barely take out viruses -- considering that hydrogen ions (the thing that makes acid an acid) are five orders of magnitude (or so) smaller volume, the filter wouldn't do anything to the pH. I doubt it would even affect the molarity of the chlorine ions. I mean, come on. If a filter was fine enough to remove hydrogen, it would also stop water.
The 3 petabyte one is way inflated. 2 petabytes of that is 3.5M sound recordings. Doing a little math, they're assuming that each of those 3.5 million recordings takes up 600MB. I guess they consider each sound recording to be a full CD. First, most audio CDs don't fill up the entire 600 MB. Second, most of those recordings probably aren't entire CDs. Third, you can compress audio very well. Even losslessly, you can compress AIFF files at least 2x.
I'd say the upper bound on the Library of Congress is about 1 petabyte.
You say "legal," but clearly if free elections had been held Saddam would've been removed from power by a landslide. I call this tyranny, not legality.
A government doesn't have to be democratic to be legal. He was referring to the fact that the Hussein government was recognized as the legitimate government of Iraq.
I tend to think that dictators, especially unpopular and brutal ones, don't deserve the benefits of international law. If that makes me "imperialist", then go ahead and call me that.
Law is meaningless if you only apply it to the people you like. The vast majority of the world thinks the United States is unpopular and brutal -- should we be denied the benefits of international law?
"American safety" has no bearing on whether or not it's possible to properly reconstruct an invaded country.
Ummm... what? World War 2 started because we didn't properly reconstruct Germany after World War 1. I'd say "American safety" was affected a little bit by World War 2, wouldn't you?
One possible explanation is that Samsung wants to use bigger hard drives in the future, and are using this design as a 'proof of concept' sort of thing. Hard drive capacities scale much faster than flash memory (or at least they have), so its very likely that, using this now-perfected technology, Samsung will be able to have phones with several gigabytes of memory for much cheaper than they would be otherwise.
The physical minimum latency for a geosync sattelite (at an altitude of 22,300 miles) is 120ms, if anyone is interested. Of couse, you'd double that for an actual ping, since the signal has to go both up and back.
Europa is already under extreme radiation. The speculation is that if life existed, it would live under the hundreds of miles of ice which cover the planet. Water blocks electromagnetic radiation extremely well (for example, visible light can't penetrate more than a few hundred feet -- ask any SCUBA diver), so it seems like it would absorb electrons and alpha particles pretty well too. NASA does need to be careful, but not with regard to Europa. If this probe blew up on launch it would be bad.
No but then the RIAA couldn't complain about stealing music, because they were getting their money. In fact, I'm sure they would just make all of their stuff available online, since people burining that music to CD would be paying them, even if its indirectly. Er... right?
It would also allow a better explanation for why Neo can get around the rules of physics than the handwaving "Agent's Have Special Ports!" one. If the Matrix is running in Neo's head, he has ultimate control over it.
Unfortunately, no one can be told what the Matrix is. You have to see it for yourself.
Well, it is a anti-gravity device, but not a very good one. What happens is the cat and toast just hover there, spinning faster and faster; eventually, either the toast flies off or the cat dies and, as everyone knows, the cat must be alive to land on its feet. If you want a -practicle- anti-gravity device, just butter both sides of the toast!
Hey, it's not like there's anyone on Slashdot that would like to hurt Microsoft.
Representative McDermott,
I wish to express my support of California Representative Zoe Lofgren's Balance Act (H.R. 1066). It promises to fix the gross injustice imposed on consumers with the Digital Millennium Copyright Act (DMCA) that inhibits fair use and ultimately restrains trade. It makes illegal the circumvention of technological restrictions in any case, even that which involves fair use such as the compression of a copyright-protected CD for use in an MP3 player or the burning of a "mix" CD of licensed songs. When a consumer buys a CD, they do it not for the media that a song is recorded on, but rather the song itself. The DMCA unreasonably limits the consumer's rights over their own property and makes criminals out of those who attempt to regain them.
Furthermore, the DMCA fails in its original intention of addressing the very real problem of Internet piracy. Draconian restrictions do not fix the problem, but rather exacerbate it by alienating consumers by effectively requiring illegal activity for fair use. It places special and unreasonable restrictions on digital recordings; someone can sell a used book or lend it to a friend but cannot with a digital recording that is lawfully obtained.
Please vote for H.R. 1066 and encourage your fellow representatives to do likewise.