Aside from increasing awareness of antibiotic resistant bacteria (ARB), and increasing intervention efforts, the big questions that should elicit the most worry are:
1.) whether intervention, by diminishing use of antibiotics will be _effective_?
2.) And what is the timescale in which we'll see our intervention efforts start to work?
Regarding 2., I mean to ask, how long will it take before the ARB begin to go away and be replaced by normal bacteria? If it's quick, then we should not be so worried. And that would be a silver lining for those who are thinking of tackling this problem. If it takes a very long time, then we should worry more.
And even more importantly, for the long-term planning people
3.) Once ARB have been reduced in bacterial populations, how easy is it for bacteria to acquire resistance again?
For answering 3., unfortunately, it's probably _not_ the same as bacteria acquiring resistance for the first time. From the molecular biology of antibiotics and bacteria, we know some antibiotic resistance genes are placed onto plasmids. Plasmids are separate from the bacteria. They are small, modular pieces of DNA that can encode resistance. Once you develop resistance, you can keep or pass these plasmids around until needed. Even if resistant bacteria die, the plasmids may still remain in existence. Thus the molecular biology of bacteria tells us we should consider these things to fully understand our intervention efforts.
We are uncertain, I believe, of the evolutionary time scales of all these events. (except for the one telling us how long it takes for antibiotic resistance to develop!)
Multiple anbitiotic resistance in bacteria is documented. I can refer you to a brief article which shows that the med community is aware of it.
* Tenover FC, Hughes JM. The challenges of emerging infectious diseases: development and spread of multiply-resistant bacterial pathogens. Journal of the American Medical Association 1996;275:300-304.
Also, we can consider this from two points of view and see why it's reasonable:
1.) bacteria can transfer genes from one to another by plasmid - a plasmid is a small circle of DNA that's not part of the bacterial genome. so one plasmid can code for resistance to antibiotic A, and another plasmid can code for resistance to antibiotic B. this modularity just from the molecular biology of bacteria makes bacteria well-equipped to deal with multiple assaults. a bacteria doesn't have to independently develop resistance, it can acquire it easily from another bacteria, mix and match etc.
2.) the nature of darwinian selection of the survivalists means that, while it is *unlikely* for any particular bacteria for develop resistance, *once* it does develop resistance, then it will likely survive and multiply under heavy antibiotic environments.
I bet most nonphysics/. readers will find the original Bogdanov papers quite difficult to read, and perhaps the theses even more so since they are in French. But I can show here some very simple things that will make nonphysics reader very suspicious about the Bogdanov twin's work.
As some/. readers have pointed out already, John Baez, the UCI physics prof, criticizes a very specific passage from one thesis, involving the Foucault pendulum part. You don't have to read everything, just see that Bogdanov mentions the pendulum and topology in one breath! here I quote from Baez's webpage:
"It goes on to discuss the supposed connection between N = 2 supergravity, Donaldson theory, KMS states and the Foucault pendulum experiment, which he claims "cannot be explained satisfactorily in either classical or relativistic mechanics". If you know some physics you'll find this statement slightly odd.
After several pages he concludes:
We draw from the above that whatever the orientation, the plane of oscillation of Foucault's pendulum is necessarily aligned with the initial singularity marking the origin of physical space S3, that of Euclidean space E4 (described by the family of instantons Ibeta of whatever radius beta), and, finally, that of Lorentzian space-time M4.
Zounds! He took that pendulum and rode it right off into hyperspace..."
And this Foucault pendulum quote you can obtain directly from one Bogdanov
thesis.
The Foucault pendulum bit is on page 49/162 of the thesis, in French. It's easy to read and probably will parse in babelfish.
So what's the big hoopla about Foucault's pendulum and the supergravity stuff? Well, Foucault's pendulum, contrary to the Bogdanov thesis that it's not understood in classical mechanics, is really well understood, at least the regular ole' Foucault pendulum. It's basically a free-swinging pendulum, that over time, rotates its plane of swinging because of the Coriolis force. You can check it out in any decent undergrad mechanics text, such as my dusty copy of Marion/Thornton classical dynamics, page 399, where the solution is quietly sitting. Or you can read this little web
tidbit.
That a PHD physics candidate would be trying to tell us there is some connection between the very earthly, understood Foucault pendulum, and the big bang (initial singularity) really stretches the imagination! But again, this just makes one suspicious, and doesn't prove anything.
I think this is the first time someone has made careful measurements of a star that is very close to the galaxial center and its orbit around that galaxial center. This way, one can deduce properties of that galaxial center- that it's a blackhole is only a hypothesis! But the hard numbers, such as the mass of the supermassive center, and the upper limit on the radius, those are more real, barring experimental errors,(and metaphysical arguments about "real" etc.)
If we pointed our telescope at any old thing in the sky, like some random star, there's a good chance it's (a) not near the center so influenced by junk that's further from the center (b) or is under the influence of local masses and therefore not just circulating the supermassive center.
so these guys did something novel. but it's not a new theory or anything.
OOps, sorry. I just posted something like your post. Yeah, with all this posting, no one was bothering to check whether the numbers actually made sense. I got 1e10m, pretty close to your value. And I also posted Pluto's orbit, which was given on some shady website as 3e9 miles, or about 5e12m, definitely much bigger than 1e10m.
Turns out in the paper that the radius is the observed radius of a star orbiting supermassive center. The mass is correct, of course, but the radius is only an estimate.
Regarding discussions about whether the "volume" of the article implied the Event Horizon, that's what I thought it was at first also. But then I came up with some numbers that don't seem to correspond to those of the CNN article. I then checked out the original paper. The paper is formally on the observation of a star that seems to be orbiting the galaxial center, and this radius of orbiting is what they are pinning down as the a putative upper limit of the size of the supermassive object.
It would seem that the original poster's comment was correct in that this was the _Upper Limit_ of the radius of the supermassive object, and not the Event Horizon radius.
Let me clarify,
The Schwarzschild radius (Or Event Horizon) is given by
r_SCH = 2 G M / c^2
where G is gravitational constant, M is mass of object, and c is speed of light. If we use, as per CNN article (yeah, I know, good source)
M = 3 x 10 ^ 6 * mass of sun mass of sun = 2 x 10 ^ 30 kg s.t. M = 6 x 10 ^ 36 kg and G = 6.67 x 10^ -11 Nm^2/kg^2 and c = 3 x 10^8 m/s^2
then r_SCH = 12 x 10 ^ 36 * 6.67 x 10 ^-11/9 x 10^16
r_SCH ~ 1 x 10^10 meters.
I looked up some values of Pluto's radius, and got about 3000 million miles, or 5 x 10^9 km, or about 5 x 10^12 m.
So this galaxial blackhole seems to have a radius 100-1000 times less than the solar system radius.
And indeed, in the final page of the Schodel paper, there is a mention that the observed radius of the orbiting star is ~ 2000 times the Schwarzschild radius, and not the actual Schwarzschild of the star. i.e. the observed radius of orbit is much much larger than the putative Schwarzchild radius.
you're right in alluding to the fact that the investigators did get all their data by interviews. for instance, to establish that someone had 100 mgs average intake of caffeine for 20 years, they would ask for dietary history and extract information from that.
however, they didn't interview the alzheimer's patients (hm, wonder why?) they interviewed an "accompanying" person, probably a spouse or family member. for the control population, they interviewed the control participants directly. already there is some assymmetry in the data acquisition method.
very error prone, to do this kind of interviewing study! i don't know if they factored this kind of error into their p-value analysis, which they claimed was (p0.001) or 1/1000 chance that this correlation of reduction of alzheimer's risk was by coincidence only.
and as many have pointed out already, a study with 54 people is practically no study at all. esp. with this kind of post-analysis interviewing business.
Yes. No one will bother with whatever Zimbabwe does. Mugabe ruthlessly suppressed independent media and speech during the elections earlier this year. His govt is known for the gangs of vigilantes that roamed from house to house kicking the crap out of people who professed support for the opposition party.
Well, I should really say no one will bother except for other dictatorships that will seize upon this chance to enact similar laws against journalists. This is not really a precedent-setting case, as much as simply an unsurprising reflection of the ineptitude and corruption of Mugabe's government.
If you read the LA Times article, there's no reference to saying that the cyber-attacks are supposed to reduce military response time. The cyber-attacks are only what they sound like, attacks on the civilian and military infrastructures which depend on networked systems.
And as such, this has nothing to do with troop deployment, but rather just inflicting damage on your enemy without using missiles or bombs.
Don't forget genomes have "low" variations from person to person. i.e. my genome and your genome differ only by about 1%. I mean, that translates to 30 million bases still, but that's low compared to the whole genome.
So even better is when you start adding genomes of other humans into your database. Since person-to-person variation of genomes is quite small, on the order of at most 1 per 100 bases, that means to store the *difference* from the 1st genome requires only about 10 MB.
So to store all human genetic material without compression, by storing it as *differences* to the first genome, assuming the human genome is uncorrelated and can't be compressed much, we would require only
6x10^9 x 10 MB + the first original 1 GB
~60000 TB.
That's only in the millions of dollars range.
Other gravity + QM experiments done before.
on
Quantum Gravity Observed
·
· Score: 5, Interesting
To reiterate previous posts, this is just standard quantum mechanics with gravity thrown in. Not quantum gravity! Something quantum gravity- related would involve observing gravitons or something sensational like that.
But there have been older experiments which involve quantum mechanics and gravity. For example, Colella + Overhauser + Werner wrote "Observation of Gravitationally Induced Quantum Interference," Phys. Rev. Lett. 34, 1472 (1975). For any budding physicist, you can check chapter 2 of Sakurai.
For non-physicists, the experiment involves the idea of Feynman path integrals, which is a beautiful, but normal quantum mechanics, idea. Roughly, it says that a quantum wave of particles (let's say, neutrons!) traveling through some potential (let's say, a gravity potential!) will acquire a phase. Now, to pick up this phase, we can combine it with another wave of particles which DIDN'T go through the same path and see if there's interference effects. The result was "yes it does." Thus establishing the applicability of quantum mechanics to regular old gravitational wells.
Now, in this recent Nesvizhevsky et al. paper in Nature, the results are exciting because the authors picked up bound states in a gravitational well, just as one would pick up bound states in a nucleon well (gives us atoms and orbitals and that stuff.)
I'm not a particle physicist, so I got this question. My question is what happens you a neutron makes a transition from one bound state to another? In the atom, you can spontaneously emit a photon and cause a transition, which sometimes comes out in the visible regime so you can see color. Like when you burn cobalt and it turns blue (well, I don't know whether it's really blue or not.) So if a neutron in the Nesvizhevsky experiment made a transition from one height to a lower height, it's gotta be emitting gravitons, right? Or should I wait till the development of Quantum Gravity for an answer?
Re:Very misleading, not "proof of quantum gravity"
on
Quantum Gravity Observed
·
· Score: 2, Informative
So I'm guessing the picture in your head is something like a big sun, and there's the earth going around the sun in circles. And then over time, you observe that the earth's orbit moves closer to the sun. Is there a loss of angular momentum here, or does the earth somehow speed up to compensate for it? Well, we can check it-
By some quick calculations, assuming circular orbits, you write L = m (r.x. v) for angular momentum. And noting that GM/r^2 = v^2/r, we can arrive at an expression for the angular momentum as a function of distance to the sun.
L(r) = m (GMr)^(1/2)
So you realize that as the earth moves closer in, it's orbital angular momentum is dropping as sqrt(r). Is this a loss in angular momentum? Sure, but it has to go somewhere.
I'm no planetary physicist, but I'll point to the example of the moon Io orbiting Jupiter. There is also a loss of orbital angular momentum, and that gets transferred into tidal forces that stretch and compress Io, which is thought to be the source of Io's volcanic activity. So we should have to account for the change in angular momentum by looking at the internal degrees of freedom in the massive objects, like axial rotation of Sun and Earth objects. In other words, the internal rotation of the massive objects will get bumped up if orbits start to decay... That is, if we only have Newtonian physics.
By perhaps you're thinking of something more exotic. Let's say that instead of massive objects, these are totally point-like objects, so that you can't transfer angular momentum to them. And then you also observe that orbits decay! So what would cause these orbits to decay? Well, I've forgotten most of my general relativity now, but I think accelerating masses generate gravitons, so angular momentum can be carried off by gravitons too! This, I think, is a very small effect that'll usually get washed out by the other mundane business I mention above.
The GR gravitational wave decay was thought to be observed in some binary neutron star system. Sorry, I don't have a reference for it.
yes, pictures aren't random. in fact, natural images exhibit a power law decay in the intensity autocorrelation function, over frequency. a random image would have a flat autocorrelation function.
i don't have a reference handy for this. i came across the topic in a neuro/vision class once. so maybe check psychology or neurology journals and textbooks.
it's hoped that the study of statistics of natural images can lend insight into how the optic nerve compresses visual information. and this is thought to occur, err, not for a good reason that i remember. but i think it's because the resolution of images are much higher than can be passed through the neurons of the optic nerve without compression.
let me point out that this article claims the study advises at the end says that one should switch to decaffeinated coffee- so is it the caffeine in the coffee that's causing the artery hardening, etc?
to establish that it's the caffeine, then a control study should have been done with decaffeinated coffee. even better, another study should be conducted in which the effects of no-doz or other purified caffeine pills are measured relative to placebo pills.
and if it is *just* the caffeine, then clearly the advisory should be applied toward all caffeinated drinks. just such jolt, or cola, or tea.
in short, i think that either the reporting of this science or the science itself is a bit sloppy. this must have been funded by some anti-coffee foundation.
first, alpha has a dependence on c, which is the most important constant in special relativity. so yes, alpha may be important for relativity- but in this tortured way. in the limit c --> infinity, then we recover galilean invariance. if we change c, then predictions such as SR redshifts or GR redshifts will also change.
second, alpha doesn't change with energy. it's a ratio of constants, and none of those constants change with the energy regime. your very own definition shows that it has nothing to do with the energy regime: not hbar, not c, and not the basic charge.
and thirdly, i have to add my own thoughts... although the random errors are known to be small enough such that the prediction is within four sigma (4 standard deviation, >99.8% that it did *not* occur by chance,) there is a possibility of systematic errors. the difference observed was so small, 10^-5, or 0.001% difference, that any very small, almost undetectable systematic error could cause it. the experiment should be repeated in another lab and set-up, and the same prediction verified before we leap to conclusions.
Oh Shatner did get paid in Priceline stock. But he sold his shares before they dropped. He made a few million. At that time, his actions made it clear to a lot of business analysts and lay people like me that he had little faith in the business.
i first came across shannon in a basic semiconductor class when designing my first digital circuit. then i came across him in a bioinformatics class when talking about information entropy in genomic DNAs. and then again while reading recreational computer books, and then in statistical field theory, and then again... and again... i always thought he was one of the giants of modern science, whose work, though seemingly confined to the field of information theory, actually reached across disciplines and influenced them all in subtle but notable ways. i pay tribute here.
Slashdot Mirror
Aside from increasing awareness of antibiotic resistant bacteria (ARB), and increasing intervention efforts, the big questions that should elicit the most worry are:
1.) whether intervention, by diminishing use of antibiotics will be _effective_?
2.) And what is the timescale in which we'll see our intervention efforts start to work?
Regarding 2., I mean to ask, how long will it take before the ARB begin to go away and be replaced by normal bacteria? If it's quick, then we should not be so worried. And that would be a silver lining for those who are thinking of tackling this problem. If it takes a very long time, then we should worry more.
And even more importantly, for the long-term planning people
3.) Once ARB have been reduced in bacterial populations, how easy is it for bacteria to acquire resistance again?
For answering 3., unfortunately, it's probably _not_ the same as bacteria acquiring resistance for the first time. From the molecular biology of antibiotics and bacteria, we know some antibiotic resistance genes are placed onto plasmids. Plasmids are separate from the bacteria. They are small, modular pieces of DNA that can encode resistance. Once you develop resistance, you can keep or pass these plasmids around until needed. Even if resistant bacteria die, the plasmids may still remain in existence. Thus the molecular biology of bacteria tells us we should consider these things to fully understand our intervention efforts.
We are uncertain, I believe, of the evolutionary time scales of all these events. (except for the one telling us how long it takes for antibiotic resistance to develop!)
Multiple anbitiotic resistance in bacteria is documented. I can refer you to a brief article which shows that the med community is aware of it.
* Tenover FC, Hughes JM. The challenges of emerging infectious diseases: development and spread of multiply-resistant bacterial pathogens. Journal of the American Medical Association 1996;275:300-304.
Also, we can consider this from two points of view and see why it's reasonable:
1.) bacteria can transfer genes from one to another by plasmid - a plasmid is a small circle of DNA that's not part of the bacterial genome. so one plasmid can code for resistance to antibiotic A, and another plasmid can code for resistance to antibiotic B. this modularity just from the molecular biology of bacteria makes bacteria well-equipped to deal with multiple assaults. a bacteria doesn't have to independently develop resistance, it can acquire it easily from another bacteria, mix and match etc.
2.) the nature of darwinian selection of the survivalists means that, while it is *unlikely* for any particular bacteria for develop resistance, *once* it does develop resistance, then it will likely survive and multiply under heavy antibiotic environments.
I bet most nonphysics /. readers will find the original Bogdanov papers quite difficult to read, and perhaps the theses even more so since they are in French. But I can show here some very simple things that will make nonphysics reader very suspicious about the Bogdanov twin's work.
As some /. readers have pointed out already, John Baez, the UCI physics prof, criticizes a very specific passage from one thesis, involving the Foucault pendulum part. You don't have to read everything, just see that Bogdanov mentions the pendulum and topology in one breath! here I quote from Baez's webpage:
"It goes on to discuss the supposed connection between N = 2 supergravity, Donaldson theory, KMS states and the Foucault pendulum experiment, which he claims "cannot be explained satisfactorily in either classical or relativistic mechanics". If you know some physics you'll find this statement slightly odd.
After several pages he concludes: We draw from the above that whatever the orientation, the plane of oscillation of Foucault's pendulum is necessarily aligned with the initial singularity marking the origin of physical space S3, that of Euclidean space E4 (described by the family of instantons Ibeta of whatever radius beta), and, finally, that of Lorentzian space-time M4.
Zounds! He took that pendulum and rode it right off into hyperspace..."
And this Foucault pendulum quote you can obtain directly from one Bogdanov thesis.
The Foucault pendulum bit is on page 49/162 of the thesis, in French. It's easy to read and probably will parse in babelfish.
So what's the big hoopla about Foucault's pendulum and the supergravity stuff? Well, Foucault's pendulum, contrary to the Bogdanov thesis that it's not understood in classical mechanics, is really well understood, at least the regular ole' Foucault pendulum. It's basically a free-swinging pendulum, that over time, rotates its plane of swinging because of the Coriolis force. You can check it out in any decent undergrad mechanics text, such as my dusty copy of Marion/Thornton classical dynamics, page 399, where the solution is quietly sitting. Or you can read this little web tidbit.
That a PHD physics candidate would be trying to tell us there is some connection between the very earthly, understood Foucault pendulum, and the big bang (initial singularity) really stretches the imagination! But again, this just makes one suspicious, and doesn't prove anything.
I think this is the first time someone has made careful measurements of a star that is very close to the galaxial center and its orbit around that galaxial center. This way, one can deduce properties of that galaxial center- that it's a blackhole is only a hypothesis! But the hard numbers, such as the mass of the supermassive center, and the upper limit on the radius, those are more real, barring experimental errors,(and metaphysical arguments about "real" etc.)
If we pointed our telescope at any old thing in the sky, like some random star, there's a good chance it's (a) not near the center so influenced by junk that's further from the center (b) or is under the influence of local masses and therefore not just circulating the supermassive center.
so these guys did something novel. but it's not a new theory or anything.
OOps, sorry. I just posted something like your post. Yeah, with all this posting, no one was bothering to check whether the numbers actually made sense. I got 1e10m, pretty close to your value. And I also posted Pluto's orbit, which was given on some shady website as 3e9 miles, or about 5e12m, definitely much bigger than 1e10m.
Turns out in the paper that the radius is the observed radius of a star orbiting supermassive center. The mass is correct, of course, but the radius is only an estimate.
Regarding discussions about whether the "volume" of the article implied the Event Horizon, that's what I thought it was at first also. But then I came up with some numbers that don't seem to correspond to those of the CNN article. I then checked out the original paper. The paper is formally on the observation of a star that seems to be orbiting the galaxial center, and this radius of orbiting is what they are pinning down as the a putative upper limit of the size of the supermassive object.
It would seem that the original poster's comment was correct in that this was the _Upper Limit_ of the radius of the supermassive object, and not the Event Horizon radius.
Let me clarify,
The Schwarzschild radius (Or Event Horizon) is given by
r_SCH = 2 G M / c^2
where G is gravitational constant, M is mass of object, and c is speed of light. If we use, as per CNN article (yeah, I know, good source)
M = 3 x 10 ^ 6 * mass of sun
mass of sun = 2 x 10 ^ 30 kg
s.t. M = 6 x 10 ^ 36 kg
and G = 6.67 x 10^ -11 Nm^2/kg^2
and c = 3 x 10^8 m/s^2
then r_SCH = 12 x 10 ^ 36 * 6.67 x 10 ^-11/9 x 10^16
r_SCH ~ 1 x 10^10 meters.
I looked up some values of Pluto's radius, and got about 3000 million miles, or 5 x 10^9 km, or about 5 x 10^12 m.
So this galaxial blackhole seems to have a radius 100-1000 times less than the solar system radius.
And indeed, in the final page of the Schodel paper, there is a mention that the observed radius of the orbiting star is ~ 2000 times the Schwarzschild radius, and not the actual Schwarzschild of the star. i.e. the observed radius of orbit is much much larger than the putative Schwarzchild radius.
you're right in alluding to the fact that the investigators did get all their data by interviews. for instance, to establish that someone had 100 mgs average intake of caffeine for 20 years, they would ask for dietary history and extract information from that.
however, they didn't interview the alzheimer's patients (hm, wonder why?) they interviewed an "accompanying" person, probably a spouse or family member. for the control population, they interviewed the control participants directly. already there is some assymmetry in the data acquisition method.
very error prone, to do this kind of interviewing study! i don't know if they factored this kind of error into their p-value analysis, which they claimed was (p0.001) or 1/1000 chance that this correlation of reduction of alzheimer's risk was by coincidence only.
and as many have pointed out already, a study with 54 people is practically no study at all. esp. with this kind of post-analysis interviewing business.
Yes. No one will bother with whatever Zimbabwe does. Mugabe ruthlessly suppressed independent media and speech during the elections earlier this year. His govt is known for the gangs of vigilantes that roamed from house to house kicking the crap out of people who professed support for the opposition party.
Well, I should really say no one will bother except for other dictatorships that will seize upon this chance to enact similar laws against journalists. This is not really a precedent-setting case, as much as simply an unsurprising reflection of the ineptitude and corruption of Mugabe's government.
If you read the LA Times article, there's no reference to saying that the cyber-attacks are supposed to reduce military response time. The cyber-attacks are only what they sound like, attacks on the civilian and military infrastructures which depend on networked systems.
And as such, this has nothing to do with troop deployment, but rather just inflicting damage on your enemy without using missiles or bombs.
Don't forget genomes have "low" variations from person to person. i.e. my genome and your genome differ only by about 1%. I mean, that translates to 30 million bases still, but that's low compared to the whole genome.
So even better is when you start adding genomes of other humans into your database. Since person-to-person variation of genomes is quite small, on the order of at most 1 per 100 bases, that means to store the *difference* from the 1st genome requires only about 10 MB.
So to store all human genetic material without compression, by storing it as *differences* to the first genome, assuming the human genome is uncorrelated and can't be compressed much, we would require only
6x10^9 x 10 MB + the first original 1 GB
~60000 TB.
That's only in the millions of dollars range.
To reiterate previous posts, this is just standard quantum mechanics with gravity thrown in. Not quantum gravity! Something quantum gravity- related would involve observing gravitons or something sensational like that.
But there have been older experiments which involve quantum mechanics and gravity. For example, Colella + Overhauser + Werner wrote "Observation of Gravitationally Induced Quantum Interference," Phys. Rev. Lett. 34, 1472 (1975). For any budding physicist, you can check chapter 2 of Sakurai.
For non-physicists, the experiment involves the idea of Feynman path integrals, which is a beautiful, but normal quantum mechanics, idea. Roughly, it says that a quantum wave of particles (let's say, neutrons!) traveling through some potential (let's say, a gravity potential!) will acquire a phase. Now, to pick up this phase, we can combine it with another wave of particles which DIDN'T go through the same path and see if there's interference effects. The result was "yes it does." Thus establishing the applicability of quantum mechanics to regular old gravitational wells.
Now, in this recent Nesvizhevsky et al. paper in Nature, the results are exciting because the authors picked up bound states in a gravitational well, just as one would pick up bound states in a nucleon well (gives us atoms and orbitals and that stuff.)
I'm not a particle physicist, so I got this question. My question is what happens you a neutron makes a transition from one bound state to another? In the atom, you can spontaneously emit a photon and cause a transition, which sometimes comes out in the visible regime so you can see color. Like when you burn cobalt and it turns blue (well, I don't know whether it's really blue or not.) So if a neutron in the Nesvizhevsky experiment made a transition from one height to a lower height, it's gotta be emitting gravitons, right? Or should I wait till the development of Quantum Gravity for an answer?
So I'm guessing the picture in your head is something like a big sun, and there's the earth going around the sun in circles. And then over time, you observe that the earth's orbit moves closer to the sun. Is there a loss of angular momentum here, or does the earth somehow speed up to compensate for it? Well, we can check it-
.x. v) for angular momentum. And noting that GM/r^2 = v^2/r, we can arrive at an expression for the angular momentum as a function of distance to the sun.
By some quick calculations, assuming circular orbits, you write L = m (r
L(r) = m (GMr)^(1/2)
So you realize that as the earth moves closer in, it's orbital angular momentum is dropping as sqrt(r). Is this a loss in angular momentum? Sure, but it has to go somewhere.
I'm no planetary physicist, but I'll point to the example of the moon Io orbiting Jupiter. There is also a loss of orbital angular momentum, and that gets transferred into tidal forces that stretch and compress Io, which is thought to be the source of Io's volcanic activity. So we should have to account for the change in angular momentum by looking at the internal degrees of freedom in the massive objects, like axial rotation of Sun and Earth objects. In other words, the internal rotation of the massive objects will get bumped up if orbits start to decay... That is, if we only have Newtonian physics.
By perhaps you're thinking of something more exotic. Let's say that instead of massive objects, these are totally point-like objects, so that you can't transfer angular momentum to them. And then you also observe that orbits decay! So what would cause these orbits to decay? Well, I've forgotten most of my general relativity now, but I think accelerating masses generate gravitons, so angular momentum can be carried off by gravitons too! This, I think, is a very small effect that'll usually get washed out by the other mundane business I mention above.
The GR gravitational wave decay was thought to be observed in some binary neutron star system. Sorry, I don't have a reference for it.
yes, pictures aren't random. in fact, natural images exhibit a power law decay in the intensity autocorrelation function, over frequency. a random image would have a flat autocorrelation function.
i don't have a reference handy for this. i came across the topic in a neuro/vision class once. so maybe check psychology or neurology journals and textbooks.
it's hoped that the study of statistics of natural images can lend insight into how the optic nerve compresses visual information. and this is thought to occur, err, not for a good reason that i remember. but i think it's because the resolution of images are much higher than can be passed through the neurons of the optic nerve without compression.
let me point out that this article claims the study advises at the end says that one should switch to decaffeinated coffee- so is it the caffeine in the coffee that's causing the artery hardening, etc?
to establish that it's the caffeine, then a control study should have been done with decaffeinated coffee. even better, another study should be conducted in which the effects of no-doz or other purified caffeine pills are measured relative to placebo pills.
and if it is *just* the caffeine, then clearly the advisory should be applied toward all caffeinated drinks. just such jolt, or cola, or tea.
in short, i think that either the reporting of this science or the science itself is a bit sloppy. this must have been funded by some anti-coffee foundation.
first, alpha has a dependence on c, which is the most important constant in special relativity. so yes, alpha may be important for relativity- but in this tortured way. in the limit c --> infinity, then we recover galilean invariance. if we change c, then predictions such as SR redshifts or GR redshifts will also change.
second, alpha doesn't change with energy. it's a ratio of constants, and none of those constants change with the energy regime. your very own definition shows that it has nothing to do with the energy regime: not hbar, not c, and not the basic charge.
and thirdly, i have to add my own thoughts... although the random errors are known to be small enough such that the prediction is within four sigma (4 standard deviation, >99.8% that it did *not* occur by chance,) there is a possibility of systematic errors. the difference observed was so small, 10^-5, or 0.001% difference, that any very small, almost undetectable systematic error could cause it. the experiment should be repeated in another lab and set-up, and the same prediction verified before we leap to conclusions.
he's 29. on the site he was 19 in 1990.
Oh Shatner did get paid in Priceline stock. But he sold his shares before they dropped. He made a few million. At that time, his actions made it clear to a lot of business analysts and lay people like me that he had little faith in the business.
i first came across shannon in a basic semiconductor class when designing my first digital circuit. then i came across him in a bioinformatics class when talking about information entropy in genomic DNAs. and then again while reading recreational computer books, and then in statistical field theory, and then again... and again... i always thought he was one of the giants of modern science, whose work, though seemingly confined to the field of information theory, actually reached across disciplines and influenced them all in subtle but notable ways. i pay tribute here.