Its funny you say that, I did my undergrad in chemistry and organic was the one class that on the one had I felt I should like because its a bit like solving logic problems (i.e. the multistep synthesis) and on the other hand I really disliked because I felt it wouldn't really be that hard to write a simple computer program to solve any undergraduate text book problem so I didn't really see the point of me doing it. But, to be honest, at the end of the day I literally made it through that class w/ only that one piece of knowledge. And truth be told I actually did pretty horribly in the class. I'm not sure I ever really did learn anything but now i'm a physics professor where we encourage that sort of reductionist thinking so its all good in the end:)
BTW the quantization of angular momentum due to gravity only particles is pretty easy to do. Its the exact same problem from QM but you replace V(r) = 1/(4\pi \epsilion_0) Z e^2/r with V(r) = G m1m2/r). So the problem is exactly the same but instead of using the fine structure constant of e^2/(4\pi epsilon_0 \hbar c) aka 1/137 you define it to be G m^2/ (\hbar c) which means the new fine structure constant is 5.917*10^-39 for two neutron masses interacting only gravitationally. So anyway the modified bohr radius when you solve this problem w/ coulombs law is simply ((4\pi \epsilon_0) \hbar^2)/(\mu e^2) so for the two neutron gravity problem the modified bohr radius is equivalently (\hbar^2 / (\mu m1 m2 G) ) where \mu is the reduced mass.. which is 7.09^10^22 meters!!! Its smaller for larger masses. I am not sure what to make of that.
Sorry, I don't believe that story. Quote 1: "Despite making up only 10 percent of the population, Muslims account for most of the country's inmates and a growing percentage of the prison populations in many other European countries." - make up scary facts.
FYI the article I originally linked is actually a NYTimes article and it was just archived at the other site. Since you don't believe that post let me link a few more for you. This is an article I found from israel that states the actual number of muslim people in french jails at greater than 60%. This is a promuslim article that states the same thing. The israeli and pro muslim article averages to somewhere near the truth:). To be honest I didn't realize this was true at all until the nytimes article.
I'm originally from the UK and yes somewhat ironically given the circumstances, i think things are/were apparantly much better in the UK than in france. In the US if you are born here you can automatically be a US citizen. When I was born in england the same thing was true (I'm actually a US citizen). They changed it all now because of the whole EU thing.
Why is the majority of US prison inmates black and hispanic? Probably because poor people tend to end up in prison way more often than rich people.
I can't agree w/ this enough. This is exactly what the issue is. The issue is not that they are muslim, that they are immigrants and they won't assimilate it is because they are poor.
Somewhat oddly I just attended a talk by Frank Wilczek tonight. He actually had a slide on the current theory of distribution of "stuff" as 70% dark energy 25 % dark matter and 5 % normal matter. This is where I got the 25% dark matter from. Also apparantly there is a way of actually getting the dark matter/baryonic matter ratio from nucleosynthesis if you use super symmetry to extend SO so you are apparantly right about nucleosynthesis. I did not realize this but it makes me happy that there is a theoretical basis for having the slew of nonbaryonic matter that is apparantly out there. I already explained the differences: dark matter is present in far less density than you think (not 25% of the primordial protostellar disk mass, that's for sure), and it's also weakly interacting. As I said, some dark matter does end up getting trapped in the Sun, but it's not a substantial fraction of the Sun's mass.
The question is simple. If everything on a stellar scale interacts due to gravity why shouldn't dark matter coalesce in the same ratio as normal matter. The answer to that *I think* is equipartition, that is as normal matter coalesces the excess energy from walking down the gravitational well can irradiate off as EM waves that is the gravitational energy equipartitions equally to all other forms of energy available to the system (aka stat mech style). Dark matter deoesn't interact electrodynamically or much of any other way it is hypothesized therefore can't redistribute its energy into any other form such as radiation, so the dark matter won't coalesce because it can't irradiate the excess energy off.
The LHC will come up soon and apparantly some of the lower energy WIMPS have potential of showing up there.
Right, the baryonic matter is predicted by the nucleosynthesis cycle happens to match the luminosity profiles and spectral data. I am throwing out the possibility that if the if the nucleosynthesis profile is wrong and the luminosity profiles are wrong then we can have standard MACHO objects being the so called "dark matter". My objections to "dark matter" is it is a definition rather than a particle or even a theory.
BTW it is not obvious why the gravitational coalescence to star/planet formation won't affect the dark matter in the same way. The only thing I can think of is equipartitioning of energy. Is that right? (I.E. gravitational energy goes into electrostatic, strong, weak allowing coalescence?).
And you are absolutely right about gravititational waves not being large enough. You can estimate simply whats the maximum gravitational energy that can be carried off can be (i.e. fall into the well) and of course thats nowhere near the mass energy.
Right, read the commentary of the ruling. I will summarize it for you. The important implication is the "direct incitement" part. I am allowed to say "lets kill all [INSERT FAVORITE MINORITY GROUP/RELIGIOUS FIGURES/GOVERNMENTAL FIGURES HERE." (which is what the white supremacist did on television). I am not allowed to say go kill Mr Bob jobs. Thats why in America (except for perhaps due to the patriot act which likely will be overturned on these rulings) the blogs in france would be in fact legal. The french blogs are a written version of what the white supremacists said ("kill all black people") which is legal under our 1st amendment. Neither the white supremacist nor these blogs are advocating direct incitement but generally advocating violence against groups of people and completely analogous.
Taking a look at the comments posted and moderated highly on/. on this thread is a bit horrifying. About 80% of the comments thus far are pointing to the fact that in spite of the fact that America gets so much flack for being a general world class jack ass the american's view of race/minority relations are so much better thought out than some of our european collegues. Let me point out some of the obvious issues here. There is a consensus forming that the "immigrants" have only themselves to blame as they have insulated themselves, refused to assimilate and are just leechers of a welfare state embracing multiculturalism and more over islam is "antidemocratic".
If you replaced "French Riots" w/ Watts Riots in Chicago and "north african/immigrant communities" w/ Black people, would you be so comfortable repeating your statements? Have we after all these years come nowhere? I am not justifying what is going on there but people are burning thousands of cars and rioting that is now spreading all over europe. To not be somewhat self-reflective enough to ask how did it come to this is woefully ignorant.
Might not the idea that the two immigrant hoodlums running from the police who accidentally killed "electrocuted" themselves, might have some what less credibility being that just a few months ago, the police stalked, chased down and gunned down a brazillian immigrant at a subway stop and initially covered it up and blamed the immigrant that allegedly was wearing a coat in summer and acting suspiciously and running away all of which turned out not to be true at all and in fact was a complete fabrication?
How did did it come to this? Tell me why enforced secular humanism seems to be targeted primarily at the muslim community? Tell me about job prospects> and what the french have to do fix this problem. Tell me why the majority of people in french jails are muslim.
And most of all tell me why europe is insisting on creating 2nd and 3rd generation second class non citizens "gast-werkers" who will never be allowed to truly be "french", "german" or more generally european because being born european doesn't make you european. To understand this more clearly I am linking a comparison of citizenship laws for countries around the world. The american so called "myth" is the nation of immigrants, we are all american one. But the europeans (somewhat ironically w/ their neoliberalism) makes you be european by blood or by an arbitrary bureaucracy leading to 2nd and 3rd generation foreigners (witness Germany and the Turks). If what is now going on in france happened here, we would not hear an end to the "shame of the nation" (aka la riots), and I find it mortifying that we collectively do not have enough reflexitivity to go beyond the "they are not us, they are them and they hate us, they are foreign" mentality. And it is shameful.
Did you even read the wiki article you linked to? They *reversed* the lower court conviction in an unanimous vote. Let me quote it for you :
The U.S. Supreme Court reversed Brandenburg's conviction, holding that government cannot constitutionally punish abstract advocacy of force or law violation. The unanimous majority opinion was per curiam ("signed" by the court as a whole rather than by individual justices): it was orginally drafted by Justice Abe Fortas before he had been forced to resign in the midst of an ethics scandal, and Justice William J. Brennan made only minor changes to the opinion before it was published. Justices Black and Douglas concurred separately.
For all the flack that the American's get, our view of freedom of religion and celebration of diversity rather than the forced secular humanism and assimilation of the french is much more palatable. What is going on in france is absolutely shameful.
What are you saying? That nucleosynthesis theories are wrong? Even if you have a reason to believe so, then why does the amount of dark matter predicted by them agree with the amount of dark matter predicted on the basis of galactic rotation curves, etc.? There are many independent lines of evidence that are all consistent with each other.
Dark matter is predicted by nucleosynthesis? I thought the nucleosynthesis theories predicted the ratio of the elements during the formation of our universe (given the lot of weirdness that goes on during the first few minutes). Anyway, I don't deny that neutralinos and other candidates may be out there.
One thing I dont understand is why the sun's mass isn't 25% or so off due to the dark matter halo that should be gravitationally attracted to the sun? When all the baryonic matter coalesced to a sun and a planet the original dust must have been a mixture of dust and dark matter, since gravity brings the dust together to form the sun and planets each planet and our sun should have brought w/it a proportional amount of dark matter that was also attracted gravitationally. Is star formation/planet formation only possible due to equipartitioning of gravitational energy to electrostatic interactions at short range? I'm not an astro guy but all right.
Anyway, I'll be *MUCH* happier when we find the WIMPS and find a plausible reason why there are so many of whatever WIMP candidate exists in that amount to actually exist in that amount. I dont like idea of finding a phenomonoligical discrepency and naming it a new form of matter w/out having the candidate particles show up in abundance in a laboratory or detector before hand. BTW why do astro people seem so defensive about this whole dark matter/emergy business? It seems that the number of naysayers are practically nonexistant!
btw I had no idea slashdot threads could last this long:)
I understand the experimental basis qualitatively enough but am still not really comfortable w/ it to be honest. I just think its "too weird" to have 95% of our universe be massless non-baryonic matter that gets defined as "dark matter". Its too phenomenological to me. (1) Estimating the baryonic matter by way of the nuclear cycle seems to me to leave room for misestimating the nuclear cycle and the initial conditions that lead to the eventual baryonic matter distribution. (2) The mass of galaxies are measured by examining the rotational velocity and comparing that to the mass measured by luminosity I would think still leaves room for errors in the luminosity measurements. I am sure there is are more dark matter estimates that I am missing. What bothers me about the whole thing is if 95% of our dark matter is stuff that has mass and hangs out in our universe, why can't we see this stuff *locally*? Shouldn't by gravitational attraction there be a lot of dark matter hanging out by our own sun, earth, moon? But, and perhaps I am wrong, the rotation of the moon around the earth and the earth around the moon can be explained completely by baryonic matter and newton's law. So why is our part of the solar system magically dark matter free? I agree though that energy of the gravitational field is likely to be negligable in comparison to the mass energy of the stars. As is obvious I am not a astrophysicist but have astro friends..
Thanks for the info, i'm sure I can find someone who's got the ohanian and ruffini book. I'd like to do this from the EM standpoint as I understand EM and special relativity reasonably well and know nothing about GR and friends.
The real reason I'm asking the 2nd question is i've never been a big fan of either dark matter and/or energy and was wondering if any of the phenomonological effects of either (i'm not really sure what the consequence of gravitational energy waves are on matter) could be explained by having a lot of gravitational wave energy floating about.
There is an analogue of Maxwell's equations that you can recover using those arguments, which turns out to be the linearized approximation to general relativity. Constructing full GR requires more sophisticated argument
Do you happen to have a link or a paper (or book) where someone does this? I'm curious as to what it looks like. A somewhat simpler question is if energy is being "carried off" by these waves it should be easy to calculate a decay time that is how long will it take for two neutrons orbiting gravitationally to decay into each other (ignoring any quantum effects) and/or how long a binary star system will last before it collapses. Do you have a sense of what that timescale is? Actually that question can be generalized. If we have gravitons and "gravity-waves" floating around our universe which came from all the "acceleration" of all the stars of all our galaxies orbiting over the course of the lives of the stars and the galaxies, how much energy is emitted from a typical galaxy over the course of the life of a typical galaxy (ignoring reabsorption)? (in comparison to the EM radiation floating about)
Any accelerating charge (an electron for instance) will create an electromagnetic wave. A radio transmitter basically causes electrons in its antenna to oscillate at a particular frequency, and this produces radio waves at that frequency. Theoretically the same thing should hold for mass and gravity. If you cause a mass to accelerate (like the charge) then it should produce gravity waves (like the radio waves). Because gravity is so extraordinarily weaker than electromagnetism, the waves are correspondingly smaller, so very difficult to detect. Einstein says gravity causes space-time to curve, so passing gravity waves should stretch and squish space-time a little bit as they pass. Unfortunately you need to be able to measure distances really precisely.
I have a question for you, the obvious conclusion from what you say is that it seems to me you lose stable orbits now. That is all gravitational orbits should suffer from the same problem as classical electron-nucleus orbit decay. That is, since any 2 body orbiting system is accelerating its total angular momentum should decay, so I looked this up and in fact not only is this true, that is apparantly exactly what the 1993 nobel prize was given out for. Now I have two questions, if this is true, there should be "derivable" an equivalent of maxwell's equations for gravitational waves using the exact same argument that was used in electrodynamics (i.e. reference frame tricks). Also using the orbital decay analogy, w/ point masses shouldn't there also be a "quantization" due to the gravitational potential ala quantum mechanics. i.e. two hypothetical electroneutral point masses (say neutrons) gravitationally orbiting around each other have a "bohr" radius of ?? at the lowest allowed eigenstate? I'm curious what that number is. Is this below the strong/weak nuclear force length scale?
This isn't actually really that far from where the debate is actually. The ID argument is infact over whether "God could be directing evolution". The idea that this is actually possible and examining whether there is evidence w/in biology and paleontology that God, indeed "directed" evolution is what the ID people would like to bring up in biology classrooms at the high school level. This sort of "gut instinct" appeal to what God may have done is why I think ID is becoming an such a populist issue that needs to be addressed and debated.
I'm not sure where the catholics stand on this but there is also the vaguely deist idea of god being more of a blind clock maker, that is evolution itself is the method by which god "directs," which is somewhat weaker than god "directing" evolution.
Speaking as an atheist, the problem is I dont think the ID proponents are "radical" fundies/evangelical groups and while it would be easy to dismiss the movement as that its a debate that needs to be properly and completely w/out mischaracterizations on both sides.
They are reasonably binary compatible. That is the PPC instruction set is a subset of the PWR instruction set. Moreover with the default xl* compiler settings the same executable could be used on any of the of PWR and PPC chips. They are compatible in the sense that the intel chips themselves are compatible :
i.e. the entire line of Socket A,1,2,3,4,5,6,7,8,370,423,462,478,603,604,754,775, 939,940,M pin incompatible chips that may or may not have "extra" commands (like MMX, 3DNow, altivec or even hardware floating point) but otherwise reasonably compatible.
The difference is no longer an order of magnitude or two even for the SMP boxes that you are talking about. Googling a bit, I have found these reasonably priced Opteron boxes. These are variations of the same opteron v40z boxes that Sun sells. Quad Opteron boxes w/ hot swap power supplies and hot swap hard drives w/ ECC memory for reasonably cheap for the chassis.
I've never seen a terabyte of ram on a single domain but the very high end sun boxes will allow you to use either 576 or 288 gigs of ram on a single box, so I will use that as the base. The maximum in SMP mode for the opteron boxes you can homebrew is probably one based on the iwill motherboard which supports 64 gigs, which is now grabbing the midrange line of the sun server series.
In fact HP makes the ProLiant DL585 with opteron chips. They will sell you this machine w/ up to 128 gigabytes of ram, redundant roms, redundant power supplies, hot swappable hard drives, ECC memory.
Its not quite at the high end server sun range but the opteron chip and its use in machines built by traditional "big iron" builders is not really an order or magnitude off. Its really about a factor of 5 from the really high end (aka $1m+ sunfire installations).
And as the IWILL MB points out its not even that far away from home brew or at the very least a $100k officebrew given the amount of ram one has to buy.
Also its worth pointing out the processor supports up to a terabyte, the issue is the memory sticks/mb's are not available yet.
And here we are only talking about the SMP/redundancy style computing . For distributed style computing platforms (aka everything on the top 500 super computers), the 10th and 11th fastest computers in the world are Cray machines based on opterons currently running at Sandia National Labs and Oakridge National Labs respectively.
Now perhaps in your world the top 500 super computers are not considered big iron because they are distributed but i'm w/ the joe slashdotter crowd that considers "big iron" to include the top 500 fastest computers in the world.
There is a Cray XT3 that runs at 15 Teraflops at Sandia and made out of 2ghz opterons and is currently the 10th fastest computer in the world. There is a similar machine over at Oak Ridge National Labs that runs at 14 Teraflops and is the 11th fastest computer in the world.
In fact, those lowly AMD kids seem to also have their chips on the fastest machine at the Pittsburgh supercomputing center (ranked 33rd fastest computer in the world) and the US Army Research Laboratory (ranked 39th fastest) . The latter was actually being built by IBM for ARL, you know those guys who coined the term "big iron".
I looked into this a bit more. None of the X-FI card currently support it. The DIN connector on the elite pro is a volume control connector of some sort (whatever that means) but its not compatible w/ the DTT speakers. Creative labs apparantly is supposed to respond to users w/ digital speakers at some point. Currently people are modding the digital dtt 3500 speakers to give them selves an analog in. Ironically the X-FI series doesn't have the resampling problem that all the audigy cards do that you alluded to.
I think thats why I missed it. It mentions its a feature on the audigy 2-4 series but no longer does on the x-fi. I will look into it and see if it does. Ironically, the x-fi has a by-pass for the resampling problem while the audigy card seem not to!
I did not realize that (i'm on a mac). Thats exactly the way to go! Those mini 3.5 mm jacks can be spdif digital out? Or are the outputs all via the flexijack digital out? I've been looking around for something like this but the specs have always been a single toslink type digital output which I assume was the undecoded 5.1 signal out. I dont think any of the m-audio cards do this (but maybe i'm mistaken since I didn't notice that the sound blaster of all things does it). I got the idea really because I have a behringer 2496 (basically a $300 1U 2channel 31 band RTA/Equalizer/DAC) as my preamp for stereo use (w/ a pair of active mackies as speakers) and am a big fan of going that route but i'm routing through a computer I may as well equalize in the software as well. Its not hard to be cheaper than tact:) Thanks for the info., if you catch this message could you point me to a link for the sb cards where it says you can get a decoded spdif signal for all the channels separately? I can't seem to find it anywhere.
I dont think thats what he means.. most of the "high end" dvd players and receivers do upsampling so while you do want the pure digital out for video (which does exist via dvi/hdmi) what you also want is something that makes standard DVD look better than it does on your HDTV. I'd like to see how standard software upscalers fare against hardware upscalers. Given the processing power of most cpus I wouldn't be surprised if it could be done pretty easily in software.
I've been looking into going this route actually not for the sake of having a PC as a TVset-top box but because I think it offers more options than standard receivers, besides the obvious (Universal DVD-ROM drive can play all and new codecs unlike standard dvd players, simple instant digital access to any music libraries, cheap route to HDTV, cheap upgrade to new technologies as they come out).
The main issue I have been having is that currently all receivers except for the really high end ones (meridian, tata) offer only analogue out for the surround channels. That is the dvd is decoded either in the player or in the receiver and you get analogue out from their DAC. If you want to do anything to this signal you end up having to do another A->D->A swap. An obvious example of this is using pro-audio equipment for home theatre use to equalize out room anomalies. People spend tons of money on speakers and , but one of the largest factors in sound is simply the dynamics of the room which can cause peaks and dips depending on what and how your room is arranged. You can purchase an 8 channel 1/3 octave 31 band digital equalizers for pretty cheap (in the grand scheme of things for home theatre) from alesis which would be brilliant to fix these anomalies. Furthermore, you are no longer dependent on the DAC that you happen to get w/ your receiver, but you use whatever DAC you want (and these things aren't really that expensive but pro-audio dacs that are cheap are actually the same DACS that only come in >$3k receivers for instance). I haven't done this yet, but the idea is to use something like VLS (or maybe a hardware decoder solution but that would take a bit of coding) and output it to an ADAT card (basically a digital format that looks like toslink but w/ 8 channels) which then goes into a cheap Alesis equalizer which then goes into the amps. All in all a swanky upgradable preamp glued into a DVD player w/ HD upscaling and pure digital outs and room equalization on a level that simply doesn't exist in any level (even those $10k TATA preamps) all for hopefully about $800 or so. And you get for free everything else you expect for having a PC as your main home theatre box aka universal codec player, upgradable, music center, networkable etc etc.
I haven't actually done this yet I admit but its something I've been toying recently.
You're hanging out w/ the wrong people. Do you choose your friends on the basis of whether they like your wallet bulge? I dont know about you but i'd like my friends to hang out w/ me because of who I am not, not because of the number of rounds I buy. Correspondingly, if your SO likes your $$ more than you, howtf do you think thats going to turn out?
When I bought my 1.8 dual G5, they clocked our code at twice as fast as a standard PIV running at 2.6 ghz . A large chuck of this had to do w/ the fact that intel had a horrible bus architecture, especially for dual processors, while the G5's had two memory buses running at 1/2 clock speed. In practicality it mean 8 GBit/s bandwidth per CPU. I believe the opterons have a similar design and are probably as fast if not faster now (the spec ratings are crazy w/ the opterons), but the IBM G5 chip/architecture is really quite decent. The G4 chips on the other hand are basically like running on PIII, 800's.
Thats an awesome idea. Though what I would do is make it just as snappy (rather than crippled or w/out quartz) but have it run in a mode that doesn't allow the install of any apps and have the only thing that can run be safari and user setting adjustments etc etc i.e. just the os.
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Its funny you say that, I did my undergrad in chemistry and organic was the one class that on the one had I felt I should like because its a bit like solving logic problems (i.e. the multistep synthesis) and on the other hand I really disliked because I felt it wouldn't really be that hard to write a simple computer program to solve any undergraduate text book problem so I didn't really see the point of me doing it. But, to be honest, at the end of the day I literally made it through that class w/ only that one piece of knowledge. And truth be told I actually did pretty horribly in the class. I'm not sure I ever really did learn anything but now i'm a physics professor where we encourage that sort of reductionist thinking so its all good in the end :)
BTW the quantization of angular momentum due to gravity only particles is pretty easy to do. Its the exact same problem from QM but you replace V(r) = 1/(4\pi \epsilion_0) Z e^2/r with V(r) = G m1m2 /r). So the problem is exactly the same but instead of using the fine structure constant of e^2/(4\pi epsilon_0 \hbar c) aka 1/137 you define it to be G m^2/ (\hbar c) which means the new fine structure constant is 5.917*10^-39
for two neutron masses interacting only gravitationally. So anyway the modified bohr radius when you solve this problem w/ coulombs law is simply ((4\pi \epsilon_0) \hbar^2)/(\mu e^2) so for the two neutron gravity problem the modified bohr radius is equivalently (\hbar^2 / (\mu m1 m2 G) ) where \mu is the reduced mass.. which is 7.09^10^22 meters!!! Its smaller for larger masses. I am not sure what to make of that.
Sorry, I don't believe that story. Quote 1: "Despite making up only 10 percent of the population, Muslims account for most of the country's inmates and a growing percentage of the prison populations in many other European countries." - make up scary facts.
FYI the article I originally linked is actually a NYTimes article and it was just archived at the other site. Since you don't believe that post let me link a few more for you.
This is an article I found from israel that states the actual number of muslim people in french jails at greater than 60%. This is a promuslim article that states the same thing. The israeli and pro muslim article averages to somewhere near the truth
I'm originally from the UK and yes somewhat ironically given the circumstances, i think things are/were apparantly much better in the UK than in france. In the US if you are born here you can automatically be a US citizen. When I was born in england the same thing was true (I'm actually a US citizen). They changed it all now because of the whole EU thing.
Why is the majority of US prison inmates black and hispanic? Probably because poor people tend to end up in prison way more often than rich people.
I can't agree w/ this enough. This is exactly what the issue is. The issue is not that they are muslim, that they are immigrants and they won't assimilate it is because they are poor.
Somewhat oddly I just attended a talk by Frank Wilczek tonight. He actually had a slide on the current theory of distribution of "stuff" as 70% dark energy 25 % dark matter and 5 % normal matter. This is where I got the 25% dark matter from. Also apparantly there is a way of actually getting the dark matter /baryonic matter ratio from nucleosynthesis if you use super symmetry to extend SO so you are apparantly right about nucleosynthesis. I did not realize this but it makes me happy that there is a theoretical basis for having the slew of nonbaryonic matter that is apparantly out there.
I already explained the differences: dark matter is present in far less density than you think (not 25% of the primordial protostellar disk mass, that's for sure), and it's also weakly interacting. As I said, some dark matter does end up getting trapped in the Sun, but it's not a substantial fraction of the Sun's mass.
The question is simple. If everything on a stellar scale interacts due to gravity why shouldn't dark matter coalesce in the same ratio as normal matter. The answer to that *I think* is equipartition, that is as normal matter coalesces the excess energy from walking down the gravitational well can irradiate off as EM waves that is the gravitational energy equipartitions equally to all other forms of energy available to the system (aka stat mech style). Dark matter deoesn't interact electrodynamically or much of any other way it is hypothesized therefore can't redistribute its energy into any other form such as radiation, so the dark matter won't coalesce because it can't irradiate the excess energy off.
The LHC will come up soon and apparantly some of the lower energy WIMPS have potential of showing up there.
Right, the baryonic matter is predicted by the nucleosynthesis cycle happens to match the luminosity profiles and spectral data. I am throwing out the possibility that if the if the nucleosynthesis profile is wrong and the luminosity profiles are wrong then we can have standard MACHO objects being the so called "dark matter". My objections to "dark matter" is it is a definition rather than a particle or even a theory.
BTW it is not obvious why the gravitational coalescence to star/planet formation won't affect the dark matter in the same way. The only thing I can think of is equipartitioning of energy. Is that right? (I.E. gravitational energy goes into electrostatic, strong, weak allowing coalescence?).
And you are absolutely right about gravititational waves not being large enough. You can estimate simply whats the maximum gravitational energy that can be carried off can be (i.e. fall into the well) and of course thats nowhere near the mass energy.
-avi
Right, read the commentary of the ruling. I will summarize it for you. The important implication is the "direct incitement" part. I am allowed to say "lets kill all [INSERT FAVORITE MINORITY GROUP/RELIGIOUS FIGURES/GOVERNMENTAL FIGURES HERE." (which is what the white supremacist did on television). I am not allowed to say go kill Mr Bob jobs. Thats why in America (except for perhaps due to the patriot act which likely will be overturned on these rulings) the blogs in france would be in fact legal. The french blogs are a written version of what the white supremacists said ("kill all black people") which is legal under our 1st amendment. Neither the white supremacist nor these blogs are advocating direct incitement but generally advocating violence against groups of people and completely analogous.
Taking a look at the comments posted and moderated highly on /. on this thread is a bit horrifying. About 80% of the comments thus far are pointing to the fact that in spite of the fact that America gets so much flack for being a general world class jack ass the american's view of race/minority relations are so much better thought out than some of our european collegues. Let me point out some of the obvious issues here. There is a consensus forming that the "immigrants" have only themselves to blame as they have insulated themselves, refused to assimilate and are just leechers of a welfare state embracing multiculturalism and more over islam is "antidemocratic".
If you replaced "French Riots" w/ Watts Riots in Chicago and "north african/immigrant communities" w/ Black people, would you be so comfortable repeating your statements? Have we after all these years come nowhere? I am not justifying what is going on there but people are burning thousands of cars and rioting that is now spreading all over europe. To not be somewhat self-reflective enough to ask how did it come to this is woefully ignorant.
Might not the idea that the two immigrant hoodlums running from the police who accidentally killed "electrocuted" themselves, might have some what less credibility being that just a few months ago, the police stalked, chased down and gunned down a brazillian immigrant at a subway stop and initially covered it up and blamed the immigrant that allegedly was wearing a coat in summer and acting suspiciously and running away all of which turned out not to be true at all and in fact was a complete fabrication?
How did did it come to this? Tell me why enforced secular humanism seems to be targeted primarily at the muslim community? Tell me about job prospects> and what the french have to do fix this problem. Tell me why the majority of people in french jails are muslim.
And most of all tell me why europe is insisting on creating 2nd and 3rd generation second class non citizens "gast-werkers" who will never be allowed to truly be "french", "german" or more generally european because being born european doesn't make you european. To understand this more clearly I am linking a comparison of citizenship laws for countries around the world. The american so called "myth" is the nation of immigrants, we are all american one. But the europeans (somewhat ironically w/ their neoliberalism) makes you be european by blood or by an arbitrary bureaucracy leading to 2nd and 3rd generation foreigners (witness Germany and the Turks). If what is now going on in france happened here, we would not hear an end to the "shame of the nation" (aka la riots), and I find it mortifying that we collectively do not have enough reflexitivity to go beyond the "they are not us, they are them and they hate us, they are foreign" mentality. And it is shameful.
Did you even read the wiki article you linked to? They *reversed* the lower court conviction in an unanimous vote. Let me quote it for you :
The U.S. Supreme Court reversed Brandenburg's conviction, holding that government cannot constitutionally punish abstract advocacy of force or law violation. The unanimous majority opinion was per curiam ("signed" by the court as a whole rather than by individual justices): it was orginally drafted by Justice Abe Fortas before he had been forced to resign in the midst of an ethics scandal, and Justice William J. Brennan made only minor changes to the opinion before it was published. Justices Black and Douglas concurred separately.
For all the flack that the American's get, our view of freedom of religion and celebration of diversity rather than the forced secular humanism and assimilation of the french is much more palatable. What is going on in france is absolutely shameful.
What are you saying? That nucleosynthesis theories are wrong? Even if you have a reason to believe so, then why does the amount of dark matter predicted by them agree with the amount of dark matter predicted on the basis of galactic rotation curves, etc.? There are many independent lines of evidence that are all consistent with each other.
Dark matter is predicted by nucleosynthesis? I thought the nucleosynthesis theories predicted the ratio of the elements during the formation of our universe (given the lot of weirdness that goes on during the first few minutes). Anyway, I don't deny that neutralinos and other candidates may be out there.
One thing I dont understand is why the sun's mass isn't 25% or so off due to the dark matter halo that should be gravitationally attracted to the sun? When all the baryonic matter coalesced to a sun and a planet the original dust must have been a mixture of dust and dark matter, since gravity brings the dust together to form the sun and planets each planet and our sun should have brought w/it a proportional amount of dark matter that was also attracted gravitationally. Is star formation/planet formation only possible due to equipartitioning of gravitational energy to electrostatic interactions at short range? I'm not an astro guy but all right.
Anyway, I'll be *MUCH* happier when we find the WIMPS and find a plausible reason why there are so many of whatever WIMP candidate exists in that amount to actually exist in that amount. I dont like idea of finding a phenomonoligical discrepency and naming it a new form of matter w/out having the candidate particles show up in abundance in a laboratory or detector before hand. BTW why do astro people seem so defensive about this whole dark matter/emergy business? It seems that the number of naysayers are practically nonexistant!
btw I had no idea slashdot threads could last this long
I understand the experimental basis qualitatively enough but am still not really comfortable w/ it to be honest. I just think its "too weird" to have 95% of our universe be massless non-baryonic matter that gets defined as "dark matter". Its too phenomenological to me. (1) Estimating the baryonic matter by way of the nuclear cycle seems to me to leave room for misestimating the nuclear cycle and the initial conditions that lead to the eventual baryonic matter distribution. (2) The mass of galaxies are measured by examining the rotational velocity and comparing that to the mass measured by luminosity I would think still leaves room for errors in the luminosity measurements. I am sure there is are more dark matter estimates that I am missing. What bothers me about the whole thing is if 95% of our dark matter is stuff that has mass and hangs out in our universe, why can't we see this stuff *locally*? Shouldn't by gravitational attraction there be a lot of dark matter hanging out by our own sun, earth, moon? But, and perhaps I am wrong, the rotation of the moon around the earth and the earth around the moon can be explained completely by baryonic matter and newton's law. So why is our part of the solar system magically dark matter free? I agree though that energy of the gravitational field is likely to be negligable in comparison to the mass energy of the stars. As is obvious I am not a astrophysicist but have astro friends..
Thanks for the info, i'm sure I can find someone who's got the ohanian and ruffini book. I'd like to do this from the EM standpoint as I understand EM and special relativity reasonably well and know nothing about GR and friends.
The real reason I'm asking the 2nd question is i've never been a big fan of either dark matter and/or energy and was wondering if any of the phenomonological effects of either (i'm not really sure what the consequence of gravitational energy waves are on matter) could be explained by having a lot of gravitational wave energy floating about.
There is an analogue of Maxwell's equations that you can recover using those arguments, which turns out to be the linearized approximation to general relativity. Constructing full GR requires more sophisticated argument
Do you happen to have a link or a paper (or book) where someone does this? I'm curious as to what it looks like. A somewhat simpler question is if energy is being "carried off" by these waves it should be easy to calculate a decay time that is how long will it take for two neutrons orbiting gravitationally to decay into each other (ignoring any quantum effects) and/or how long a binary star system will last before it collapses. Do you have a sense of what that timescale is? Actually that question can be generalized. If we have gravitons and "gravity-waves" floating around our universe which came from all the "acceleration" of all the stars of all our galaxies orbiting over the course of the lives of the stars and the galaxies, how much energy is emitted from a typical galaxy over the course of the life of a typical galaxy (ignoring reabsorption)? (in comparison to the EM radiation floating about)
Any accelerating charge (an electron for instance) will create an electromagnetic wave. A radio transmitter basically causes electrons in its antenna to oscillate at a particular frequency, and this produces radio waves at that frequency. Theoretically the same thing should hold for mass and gravity. If you cause a mass to accelerate (like the charge) then it should produce gravity waves (like the radio waves). Because gravity is so extraordinarily weaker than electromagnetism, the waves are correspondingly smaller, so very difficult to detect. Einstein says gravity causes space-time to curve, so passing gravity waves should stretch and squish space-time a little bit as they pass. Unfortunately you need to be able to measure distances really precisely.
I have a question for you, the obvious conclusion from what you say is that it seems to me you lose stable orbits now. That is all gravitational orbits should suffer from the same problem as classical electron-nucleus orbit decay. That is, since any 2 body orbiting system is accelerating its total angular momentum should decay, so I looked this up and in fact not only is this true, that is apparantly exactly what the 1993 nobel prize was given out for. Now I have two questions, if this is true, there should be "derivable" an equivalent of maxwell's equations for gravitational waves using the exact same argument that was used in electrodynamics (i.e. reference frame tricks). Also using the orbital decay analogy, w/ point masses shouldn't there also be a "quantization" due to the gravitational potential ala quantum mechanics. i.e. two hypothetical electroneutral point masses (say neutrons) gravitationally orbiting around each other have a "bohr" radius of ?? at the lowest allowed eigenstate? I'm curious what that number is. Is this below the strong/weak nuclear force length scale?
God could be directing evolution
This isn't actually really that far from where the debate is actually. The ID argument is infact over whether "God could be directing evolution". The idea that this is actually possible and examining whether there is evidence w/in biology and paleontology that God, indeed "directed" evolution is what the ID people would like to bring up in biology classrooms at the high school level. This sort of "gut instinct" appeal to what God may have done is why I think ID is becoming an such a populist issue that needs to be addressed and debated.
I'm not sure where the catholics stand on this but there is also the vaguely deist idea of god being more of a blind clock maker, that is evolution itself is the method by which god "directs," which is somewhat weaker than god "directing" evolution.
Speaking as an atheist, the problem is I dont think the ID proponents are "radical" fundies/evangelical groups and while it would be easy to dismiss the movement as that its a debate that needs to be properly and completely w/out mischaracterizations on both sides.
They are reasonably binary compatible. That is the PPC instruction set is a subset of the PWR instruction set. Moreover with the default xl* compiler settings the same executable could be used on any of the of PWR and PPC chips. They are compatible in the sense that the intel chips themselves are compatible :
, 939,940,M pin incompatible chips that may or may not have "extra" commands (like MMX, 3DNow, altivec or even hardware floating point) but otherwise reasonably compatible.
i.e. the entire line of Socket A,1,2,3,4,5,6,7,8,370,423,462,478,603,604,754,775
The difference is no longer an order of magnitude or two even for the SMP boxes that you are talking about. Googling a bit, I have found these reasonably priced Opteron boxes. These are variations of the same opteron v40z boxes that Sun sells. Quad Opteron boxes w/ hot swap power supplies and hot swap hard drives w/ ECC memory for reasonably cheap for the chassis.
I've never seen a terabyte of ram on a single domain but the
very high end sun boxes will allow you to use either 576 or 288 gigs of ram on a single box, so I will use that as the base. The maximum in SMP mode for the opteron boxes you can homebrew is probably one based on the iwill motherboard which supports 64 gigs, which is now grabbing the midrange line of the sun server series.
In fact HP makes the ProLiant DL585 with opteron chips. They will sell you this machine w/ up to 128 gigabytes of ram, redundant roms, redundant power supplies, hot swappable hard drives, ECC memory.
Its not quite at the high end server sun range but the opteron chip and its use in machines built by traditional "big iron" builders is not really an order or magnitude off. Its really about a factor of 5 from the really high end (aka $1m+ sunfire installations).
And as the IWILL MB points out its not even that far away from home brew or at the very least a $100k officebrew given the amount of ram one has to buy.
Also its worth pointing out the processor supports up to a terabyte, the issue is the memory sticks/mb's are not available yet.
And here we are only talking about the SMP/redundancy style computing . For distributed style computing platforms (aka everything on the top 500 super computers), the 10th and 11th fastest computers in the world are Cray machines based on opterons currently running at Sandia National Labs and Oakridge National Labs respectively.
Now perhaps in your world the top 500 super computers are not considered big iron because they are distributed but i'm w/ the joe slashdotter crowd that considers "big iron" to include the top 500 fastest computers in the world.
There is a Cray XT3 that runs at 15 Teraflops at Sandia and made out of 2ghz opterons and is currently the 10th fastest computer in the world. There is a similar machine over at Oak Ridge National Labs that runs at 14 Teraflops and is the 11th fastest computer in the world.
In fact, those lowly AMD kids seem to also have their chips on the fastest machine at the Pittsburgh supercomputing center (ranked 33rd fastest computer in the world) and the US Army Research Laboratory (ranked 39th fastest) . The latter was actually being built by IBM for ARL, you know those guys who coined the term "big iron".
I looked into this a bit more. None of the X-FI card currently support it. The DIN connector on the elite pro is a volume control connector of some sort (whatever that means) but its not compatible w/ the DTT speakers. Creative labs apparantly is supposed to respond to users w/ digital speakers at some point. Currently people are modding the digital dtt 3500 speakers to give them selves an analog in. Ironically the X-FI series doesn't have the resampling problem that all the audigy cards do that you alluded to.
I think thats why I missed it. It mentions its a feature on the audigy 2-4 series but no longer does on the x-fi. I will look into it and see if it does. Ironically, the x-fi has a by-pass for the resampling problem while the audigy card seem not to!
thanks again for the info.
I did not realize that (i'm on a mac). Thats exactly the way to go! Those mini 3.5 mm jacks can be spdif digital out? Or are the outputs all via the flexijack digital out? I've been looking around for something like this but the specs have always been a single toslink type digital output which I assume was the undecoded 5.1 signal out. I dont think any of the m-audio cards do this (but maybe i'm mistaken since I didn't notice that the sound blaster of all things does it). I got the idea really because I have a behringer 2496 (basically a $300 1U 2channel 31 band RTA/Equalizer/DAC) as my preamp for stereo use (w/ a pair of active mackies as speakers) and am a big fan of going that route but i'm routing through a computer I may as well equalize in the software as well. Its not hard to be cheaper than tact :) Thanks for the info., if you catch this message could you point me to a link for the sb cards where it says you can get a decoded spdif signal for all the channels separately? I can't seem to find it anywhere.
thanks again!
I dont think thats what he means.. most of the "high end" dvd players and receivers do upsampling so while you do want the pure digital out for video (which does exist via dvi/hdmi) what you also want is something that makes standard DVD look better than it does on your HDTV. I'd like to see how standard software upscalers fare against hardware upscalers. Given the processing power of most cpus I wouldn't be surprised if it could be done pretty easily in software.
I've been looking into going this route actually not for the sake of having a PC as a TVset-top box but because I think it offers more options than standard receivers, besides the obvious (Universal DVD-ROM drive can play all and new codecs unlike standard dvd players, simple instant digital access to any music libraries, cheap route to HDTV, cheap upgrade to new technologies as they come out).
The main issue I have been having is that currently all receivers except for the really high end ones (meridian, tata) offer only analogue out for the surround channels. That is the dvd is decoded either in the player or in the receiver and you get analogue out from their DAC. If you want to do anything to this signal you end up having to do another A->D->A swap. An obvious example of this is using pro-audio equipment for home theatre use to equalize out room anomalies. People spend tons of money on speakers and , but one of the largest factors in sound is simply the dynamics of the room which can cause peaks and dips depending on what and how your room is arranged. You can purchase an 8 channel 1/3 octave 31 band digital equalizers for pretty cheap (in the grand scheme of things for home theatre) from alesis which would be brilliant to fix these anomalies. Furthermore, you are no longer dependent on the DAC that you happen to get w/ your receiver, but you use whatever DAC you want (and these things aren't really that expensive but pro-audio dacs that are cheap are actually the same DACS that only come in >$3k receivers for instance). I haven't done this yet, but the idea is to use something like VLS (or maybe a hardware decoder solution but that would take a bit of coding) and output it to an ADAT card (basically a digital format that looks like toslink but w/ 8 channels) which then goes into a cheap Alesis equalizer which then goes into the amps. All in all a swanky upgradable preamp glued into a DVD player w/ HD upscaling and pure digital outs and room equalization on a level that simply doesn't exist in any level (even those $10k TATA preamps) all for hopefully about $800 or so. And you get for free everything else you expect for having a PC as your main home theatre box aka universal codec player, upgradable, music center, networkable etc etc.
I haven't actually done this yet I admit but its something I've been toying recently.
You're hanging out w/ the wrong people. Do you choose your friends on the basis of whether they like your wallet bulge? I dont know about you but i'd like my friends to hang out w/ me because of who I am not, not because of the number of rounds I buy. Correspondingly, if your SO likes your $$ more than you, howtf do you think thats going to turn out?
When I bought my 1.8 dual G5, they clocked our code at twice as fast as a standard PIV running at 2.6 ghz . A large chuck of this had to do w/ the fact that intel had a horrible bus architecture, especially for dual processors, while the G5's had two memory buses running at 1/2 clock speed. In practicality it mean 8 GBit/s bandwidth per CPU. I believe the opterons have a similar design and are probably as fast if not faster now (the spec ratings are crazy w/ the opterons), but the IBM G5 chip/architecture is really quite decent. The G4 chips on the other hand are basically like running on PIII, 800's.
Thats an awesome idea. Though what I would do is make it just as snappy (rather than crippled or w/out quartz) but have it run in a mode that doesn't allow the install of any apps and have the only thing that can run be safari and user setting adjustments etc etc i.e. just the os.