The cooling of a neutron star via neutrinos occurs via the Urca process named because the process removes heat as effectively as the Urca casino removes money.
The Urca process is p+e->n+v->p+e+v+vbar.
The neutrinos are from both electron capture and neutron decay.
Yes, neutrinos are not the dark matter that they're suggesting. But it's not like they're suggesting a ludicrous kind of matter the likes of which we've never seen. Pauli's proposal of the neutrino is in fact almost a direct analog of dark matter: proposing a new particle to explain the failure of classical physics in a regime where it should be accurate.
Because that's what the evidence indicates. The CMBR evidence strongly hints that it's non-baryonic dark matter. The only non-luminous non-baryonic particles that we know about are neutrinos. Plus neutrinos, with mass, will make up a large portion of the "non-baryonic matter" that the CMB tells us about.
Neutrinos, with mass, in fact are dark matter. Hot dark matter, but dark matter none the less. All the phrase "dark matter" means is "matter that's not luminous" - i.e., matter that does not emit photons. Neutrinos never will emit photons.
The statement that I made was exactly to point that out. Dark matter is not a crazy addition to physics, simply because we already have particles which act very much like dark matter needs to.
not blindly accept a theory that has its own problems
What the heck makes you think I'm blindly accepting it? It's simply the best candidate explanation available. If a better one comes along, I'm all ears. But none of the objections are fundamental enough to convince me that it's wrong.
All fundamental theories have problems of some degree. The solution of those problems typically lead to more fundamental physics. There are not enough serious problems with the basic theory of non-baryonic cold dark matter causing the rotation of galaxies and the rotation of galaxies in galactic clusters to believe that this theory isn't correct.
This is how science works. You have data, you come up with a theory to explain the data, you test that theory, and if more data arises that the theory can't explain, you try to modify the theory. You don't discard the theory right away.
which I was already aware of
Then I'm sorry, but I do not believe you understand the implications of the evidence.
Another problem of this theory will to explain dense nutrino flow which was detected for some (far more adjacent) explosions in that Japanese neutrino detector. Other question is what are pulsars and how they form.
Neutrinos are not explained by this theory. This is a pure electromagnetic theory. It can't explain neutrino production at the level that supernovae produce them - fusion produces far too much of its energy in gammas, and far too little in neutrinos. The only reason neutrinos are a significant product of stars is because the stars are optically thick. Production in thin filaments obviously wouldn't be optically thick.
Supernovae release vastly more of their energy in neutrinos, because they produce them via electron capture and beta decay, which allows neutrinos to cool the neutron star. We saw these neutrinos from SN1987A. There's too much to be explained by this theory. By far.
'Dark Matter' is just one example of modern science inventing something, with no basis on observed data, to explain observations that their own theories cannot.
No, it isn't. When dark matter was first proposed, it was laughed at. A bunch of other theories were proposed to try to defeat it. Modified Newtonian gravity, extra dimensions, etc. But dark matter just kept coming back - galaxies rotate wrong, and two galaxies with the same visible mass don't rotate the same. Galaxy clusters don't rotate right - there looks like there's a large clump of matter that isn't luminous that a bunch of galaxies are speeding towards (The Great Attractor).
And then came the CMBR results, that said that there's about 20% of the critical mass in matter in the Universe, and there's nowhere near enough luminous matter to account for that. So now you've got two independent pieces of evidence, completely unrelated to each other, which say "there is matter out there that you can't see". No basis in observed data? Hardly. If anything, there's a plethora of it.
In fact, the entire idea isn't crazy at all - neutrinos, if it wasn't for their low mass, would be a perfect dark matter candidate. In fact, with mass, they could make up the majority of matter in the universe! We know neutrinos exist. We see them all the time in various huge detectors. That's a given. In essence, whatever dark matter is found will act very much like neutrinos - barely interacting, but dominating the universe at large scales.
WHATEVER model that best explains the observed data, is the one to be used for a given event.
No way! Whoever told you that was more than wrong - he was committing a terrible crime by perpetuating the belief that modern science is hodgepodge. General relativity and the Standard Model are currently disjoint theories, yes. They each have domains of validity, and they are each used in their domains of validity. In the regions where they both are valid, they both agree. (Hint: all of classical physics is the region where they both agree).
It is not pick and choose! The regions where GR and the Standard Model disagree are the regions outside of their validity - i.e. where the energy density becomes too high for the assumptions the two are built on to be valid.
If the EUM can better explain current observations
It can't. It doesn't even begin to address neutrino creation. The vast majority of the energy of a supernova is in neutrinos. This is observed data, not theory. Neutrinos are not produced in the processes this site is talking about. It's bunk.
Calling people crackpots, is not a very scientific way to behave.
If you don't respond to your critics, justify your assumptions, or attempt to reconcile your theory to all available data, you're a crackpot: you're not following the scientific method. This guy falls in that category.
Re:Site seems down; here's that article's text
on
Supernova 1987A Decoded
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· Score: 2, Informative
It is indeed true that most of them do emit X-rays
Most of them, in fact, emit X-rays, low energy gamma rays, and probably TeV gamma rays as well. The Crab is so bright in TeV gamma rays that it's the basic unit of flux in that region of the spectrum.
But the bigger "this article is crap" flag that should go off in your head is the question "what about the neutrinos?" Magnetic reconnection can't create neutrinos, and SN1987A had a flux of neutrinos way, way above background, and consistent with the majority of the energy of the collapse going into neutrinos.
The only way you can get that kind of a flux of neutrinos is via the URCA process: p+e->n+v->p+e+vbar+v, which means you're at a ridiculous pressure, and you're creating neutrons.
It's just embarassing that people like this get any press.
Re:Site seems down; here's that article's text
on
Supernova 1987A Decoded
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· Score: 4, Informative
The better counterargument to the kookdom is neutrinos.
The vast majority of the energy in supernovae is emitted in neutrinos - upwards of 90%. The neutrinos from SN1987A aren't theoretical - we saw them. They were, in fact, the first extrasolar particles other than photons we've been able to associate with an astrophysical object.
Neutrinos get produced when electrons and protons are forced into neutrons via inverse beta decay, which only happens at ridiculous pressures. They can't be produced by electromagnetic processes - they're weak byproducts only.
There is nothing in that article to explain why the star would produce 10 times more energy in neutrinos than in photons. A magnetic pinch would not produce this much energy in neutrinos. There's simply not enough energy.
I played around with the Google translator for a while. I work in Japan and am half-way fluent. Google couldn't even turn my most basic Japanese emails into comprehensible English. Same is true for the other translation programs I have seen.
You haven't seen the Google translator he's talking about. It isn't public yet, I don't believe.
Well, if you read the site, there's a list of reasons why certain captchas are bad.
For instance:
Too few fonts (or only one font)
Constant rotation (or no rotation)
No deformation
Constant colors
And a list of reasons why certain captchas are good. It's a pretty good summary of the strengths (and weaknesses) of a lot of them.
One thing you may notice is how complicated (and difficult to read as a human!) some of the broken ones are (like linuxfr.org, or vBulletin), and how easy to read (yet hard to defeat!) the ICQ one is.
One easy thing to take away from this page would be: if you have to have one, for crying out loud, use a ton of fonts and a ton of backgrounds.
I don't dispute that. What hasn't been demonstrated experimentally is that the corresponding interactions propagate slower than lightspeed.
I don't get the problem. Are you proposing that a massive particle might travel at the speed of light?
I mean, the creation and decay of a real W/Z boson is a long-distance weak interaction. The fact that they decay at all means they don't travel at the speed of light.
Is your problem basically that a W hasn't been created with enough energy to live long enough to be observed?
While this is definitely true, I don't think that the fact that the weak nuclear force doesn't travel at the speed of light hinges upon this kind of a direct observation.
even with the proposed gravity sensors, you can't actually see the gravity waves, you can just see weights moving.
Gravity waves distort spacetime, which light follows. If you were near to a gravitational wave source, you'd see it. Light would bend like hell through it.
You'd also feel it if it were strong enough, too. Not many people enjoy their bodies being stretched in one direction and compressed in another.
People have attempted to measure it, but the trouble is that there doesn't seem to be agreement on whether those results are correct. Until there is, the question remains open.
The results are correct. The question is how precise the results are. So gravity propagates at approximately the speed of light. The question of how exact that approximation is needs to be measured better. But it's not, say, infinity.
So?
If something can't propagate, why bother talking about the speed at which it propagates? It's like asking whether or not dinosaurs would enjoy baseball.
While that is a plausible hypothesis, it's not a fact until it has actually been determined experimentally.
Uh, it has. The W and Z do have mass. Measured, and all. Really.
Hardly. They're two representations of the same effect - you ever derived the three W boson fields and the B field?
Yah. It's basic Standard Model stuff.
they're from the same fundamental force.
Yes, but when you're far from the electroweak breaking point, it's pointless to consider them the same force. The weak nuclear force operates orders of magnitude slower than the electromagnetic force when you're in normal, non-insane-energy regimes.
It's like saying the electric field is just like the magnetic field. Yes - two representations of the same thing. Sure. You can, in fact, convert the two fields by reference frame changes. But that doesn't change the fact that in electrical engineering, you treat electric and magnetic fields very differently.
More importantly, the statement that I said stands. The electromagnetic force - on its own - always has an infinite range, and so propagates forever. The weak nuclear only has a range where the W and Z are negligibly massive, and so propagates only over those distances.
The electroweak force, however, is only unified at high energies, where the W and Z are negligibly massive. So the electroweak force propagates with the speed of light.
Note the point here: at high energies, you can describe the electromagnetic and weak nuclear with one statement. At low energies, however, you have to describe the behavior of the two separately.
It's just like electromagnetism. Even though you could perfectly well describe all 4 of Maxwell's laws with one equation, it'd be useless to work with at low energies, as it doesn't describe the behavior of the two fields easily. In much the same way, referring to low-energy electromagnetism and weak nuclear as the same force is pointless. Sure, they're the same. But the interaction between the two forces is so suppressed due to the W and Z mass that it's pointless.
Speed and range of the interaction are related. If the force doesn't propagate, then its speed is effectively zero. You can't really talk about the speed of a force if its range is limited. The electromagnetic and gravitational forces are not range limited. They both propagate at the speed of light.
And I said that I was talking about the residual strong interaction (*residual*, not effective). It's still the strong interaction that causes those effects, even if it's diluted down because of the mass of a pion.
You're absolutely correct that on short scales, the weak nuclear and strong nuclear propagate basically at the speed of light, because at short scales, the virtual W/Z are far off mass shell, and might as well be massless.
The strong interaction does not propagate at the speed of light. Its coupling constant increases with decreasing momentum. Its strength increases with increasing distance. This means that after a short distance, you've got way too much potential energy for a gluon to be the channel particle. Instead, you form pion pairs, and pions mediate the interaction. This is what happens in a nucleus - it's called the residual strong interaction.
Since pions are massive, the residual strong interaction (which is what most people think of, and indeed, what was originally considered, the "strong nuclear force" - the force that binds nuclei together. The force that gluons mediate binds quarks together.) also does not propagate.
As for "speed of light" or not, that's pointless. The strong and weak nuclear force don't propagate, so saying what speed they propagate at is a little pointless. You can't set up "weak nuclear waves".
No, it's not. It's just that after a certain distance (less than a fermi) the interaction becomes strong enough that pions are created. So after a certain distance, pions mediate the interaction. Pions are massive, so you get the same problem as the weak-nuclear - this is often referred to as the residual strong nuclear force.
Also, lose bonus points for not complaining about description of electromagnetism and weak force as separate fundamental forces
They are separate fundamental forces. It only makes sense to combine them at high enough energies where the W's mass can be neglected. Past that point, they're unified. But if you're talking about "propagation" over distances anywhere near meaningful (even, say, oh, the size of an atom) you're far, far below the electroweak scale.
Gravity propagates at the speed of light - we think. It's kinda been measured. The question's meaningful because gravity waves will propagate at the speed of gravity, just like electromagnetic waves travel at the speed of light.
Gluons do not have mass. But the strong nuclear force has an opposite distance dependence as the others - it gets stronger as you get farther away. So after a short distance (say, 1 fm), the potential energy becomes enough that pions are formed, and so at distances greater than that, it's mediated by pions, which do have mass.
For forces mediated by massive particles, they don't propagate much at all - basically, they don't propagate more than the distance equivalent to the mass of the massive particle. So the weak doesn't propagate more than the size of a baryon (much less, actually) and the strong doesn't propagate more than the size of a nucleus.
That has only been demonstrated for electromagnetism; for the other forces, it's a hypothesis.
Nah. For gravity, it's (kindof) been measured. It looks like it's the speed of light. Kinda. There are a couple caveats there. But it (kinda) was measured.
For strong and weak nuclear, they don't propagate at all (much more than a femtometer). The weak nuclear force is mediated by a massive boson, anyway, so it won't propagate at the speed of light at all.
All 4 basic forces: electromagnatism, gravity, strong nuclear, and weak nuclear (not Nukular; bite me, George) forces propogate at the speed of light in their reference frame
Electromagnetic and gravity (most likely) propagate at the speed of light, because their carrier particles (photons and gravitons respectively) are massless.
By "propogation speed" you really mean "what's the mass of the channel particle when you've got a really low-momentum transfer (far distance)"? For electromagnetic and gravity, the channel particle is on-mass shell, and is massless, so the connection between the two points is lightlike.
The strong nuclear force, however, gets stronger at large distances. So the carrier particles (gluons) move farther and farther off mass-shell: so the strong nuclear force does not propagate at the speed of light over distances much more than the size of a proton! Even over the size of the nucleus, the mediating particles are virtual pions (the residual strong interaction), which do have mass.
The weak nuclear force is mediated completely by the W, which is massive. It will not propagate at the speed of light over distances where the W's mass is significant.
It's better to think, in colloquial terms, as the interactions having a range, not a speed. Electromagnetic and gravity both have an infinite range. The strong and weak nuclear both have a range about the size of a proton.
This is an important distinction - you can communicate with both the electromagnetic force and gravity, but not with the strong or weak nuclear force. Thus, speaking about "speeds" for them is quite wrong.
Do you think Google is focusing on indexing dictionary lists? Or that Yahoo are ignoring them in particular?
Well, the latter would be an intelligent thing for a search engine to do in returning results, but Yahoo could also feasibly have a crawler which doesn't bother indexing dictionary lists - i.e. once you get to some ridiculous number of independent words in the page, you toss it. It'd be a nice antispam tool, actually.
Or it could focus on HTML pages rather than text files, as most of the dictionary lists seem to be text files.
Maybe it's not valid to generalize from dictionary list sites to all sites, but I don't think it's clearly invalid either.
It isn't clearly invalid. If you remove the dictionary-list results, you still get the same answer. That doesn't mean the original conclusion wasn't wrong, though - just that by luck, they heavily oversampled a subset that was a representative sample of the whole.
Interestingly, when Yahoo returns the estimated number of searches (on non-dictionary-list searches) it returns about 2X as many results as Google. But when you go through them, it's only about a third. So not only does Yahoo actually have about half the indexed pages of Google, but they lie to you and say they've got about twice - on each result.
Hohmann transfers are not always the minimum orbit energy orbit.
Hohmann transfers are never the minimum energy orbital transfer. IPS (interplanetary superhighway) orbits are lower energy for all cases, although they take much longer. (To be fair, IPS orbits are new - 1997-ish - and before that, Hohmann transfers were the minimum energy orbital transfer). IPS orbits are so low energy that it basically takes the same delta-V to get almost anywhere in the solar system - the delta-V to get to a Lagrange point.
For manned missions, however, you don't really care about lowest-energy, because orbits are always tradeoffs between transit time and energy, and manned missions want the shortest transit time feasible.
What if the searches that showed Yahoo to search more pages (assuming for the moment that this is in fact the case) were those that blew the 1000 hit limit?
Unless the extra pages that Yahoo has all contain similar text, this is unlikely. Otherwise, you can always find word combinations which will be below the 1000 hit limit which will return pages in Yahoo's extra corpus.
Randomly going through words is a good way to do this, except for the bias produced by word list pages. There are a few ways to fix this bias - only use results which return more than 100 hits, which is probably safe, but kills your statistics (10,000 searches down to 300) - or rerun, taking the results which gave you more than 1000 results and add a third word from the results which gave you more than 1000 results, and you'll probably get a high-statistics set of data with less than 1000 results that doesn't include many dictionary lists.
Can we conclude that when you pick two English words that when entered into both Google and Yahoo, both return less than 1000 results
Two random words.
The study essentially is showing that there are more dictionary lists in Google than there are in Yahoo. The vast majority of the included searches return few (~10 ish) results, and they're extremely similar results each time. So that result gets magnified a ton.
Now, the interesting thing is that if you look at results which return between 100 and 1000 results (i.e. not dictionary list results) you get a similar conclusion (but with much, much lower statistics! ~300 vs 10,000). Which in some way, makes sense - there's nothing special about the sample of dictionary list sites, and so if there are more of them on Google, there's likely to be more of the normal sites, too. But the original study can't really even make the claim that it's making.
Correction to myself: the total responses to their list was ~150,000 to ~10,000 searches for Yahoo, and ~400,000 for Google. So the average is 15 results for Yahoo and 40 for Google. Given that most "dictionary list" results were between 10 and 40, that should pretty much tell you that their entire result is just a massively multiplied reflection of those searches.
As an interesting aside, though: if you dig through their log, you can see several interesting things. If you look at only results which return between 100 and 1000 results, you get things like "battening liberate", which returned 186 for Google, and 97 for Yahoo. Those aren't dictionary list results - the interesting thing is that in almost all of those results, you see an extremely similar pattern.
"battening liberate": Ratio of Google/Yahoo for this query:
Duplicates Omitted Estimate: 0.522305
Duplicates Omitted Total: 1.917526
Duplicates Included Estimate: 0.533962
Duplicates Included Total: 2.350427
"convexity hac" Ratio of Google/Yahoo for this query:
Duplicates Omitted Estimate: 0.573593
Duplicates Omitted Total: 3.340000
Duplicates Included Estimate: 0.583700
Duplicates Included Total: 2.490566
"meekness goatee" Ratio of Google/Yahoo for this query:
Duplicates Omitted Estimate: 0.607053
Duplicates Omitted Total: 2.207692
Duplicates Included Estimate: 0.604010
Duplicates Included Total: 2.745562
So Yahoo claims it has 2X as much as Google, but actually only returns about 30-50%.
Interestingly, these mimic the "dictionary list" results, which is curious. So their conclusions seem right, but their methodology seems very wrong.
Or it could mean that Google has more Ispell lists in its index.
Which appears to be the case.
A search for "inabilities hydrocephalic" returns almost all dictionary lists in Google, except 2. There's only 2 results in Yahoo, one of which is a dictionary list (or equivalent).
But the official results for this? 16 for Google, 2 for Yahoo.
The reason this is a problem is because almost every search returns the same dictionary lists, so it amounts to double (or probably around 5000-fold) weighting of those sites in the results.
Without excluding results that are just dictionary lists (which is quite hard from a simple analysis like this) you heftily bias your results to mimic the "Number of Google dictionary list sites/Number of Yahoo dictionary list sites" ratio.
They probably should've only included sites that returned between 100 and 1000 results, but I'd bet that would take a ton more time, as it looks like almost all of the results they used were the "10-50" result range.
Slashdot Mirror
The cooling of a neutron star via neutrinos occurs via the Urca process named because the process removes heat as effectively as the Urca casino removes money.
The Urca process is p+e->n+v->p+e+v+vbar.
The neutrinos are from both electron capture and neutron decay.
fanciful magical dark matter
That's right. Fanciful, crazy dark matter.
I mean, c'mon! It's ludicrous! Particles that have mass, barely interact with anything, and don't emit photons. What a stupid idea!
Yes, neutrinos are not the dark matter that they're suggesting. But it's not like they're suggesting a ludicrous kind of matter the likes of which we've never seen. Pauli's proposal of the neutrino is in fact almost a direct analog of dark matter: proposing a new particle to explain the failure of classical physics in a regime where it should be accurate.
Sounds like you've made up your mind there.
Because that's what the evidence indicates. The CMBR evidence strongly hints that it's non-baryonic dark matter. The only non-luminous non-baryonic particles that we know about are neutrinos. Plus neutrinos, with mass, will make up a large portion of the "non-baryonic matter" that the CMB tells us about.
Neutrinos, with mass, in fact are dark matter. Hot dark matter, but dark matter none the less. All the phrase "dark matter" means is "matter that's not luminous" - i.e., matter that does not emit photons. Neutrinos never will emit photons.
The statement that I made was exactly to point that out. Dark matter is not a crazy addition to physics, simply because we already have particles which act very much like dark matter needs to.
not blindly accept a theory that has its own problems
What the heck makes you think I'm blindly accepting it? It's simply the best candidate explanation available. If a better one comes along, I'm all ears. But none of the objections are fundamental enough to convince me that it's wrong.
All fundamental theories have problems of some degree. The solution of those problems typically lead to more fundamental physics. There are not enough serious problems with the basic theory of non-baryonic cold dark matter causing the rotation of galaxies and the rotation of galaxies in galactic clusters to believe that this theory isn't correct.
This is how science works. You have data, you come up with a theory to explain the data, you test that theory, and if more data arises that the theory can't explain, you try to modify the theory. You don't discard the theory right away.
which I was already aware of
Then I'm sorry, but I do not believe you understand the implications of the evidence.
Another problem of this theory will to explain dense nutrino flow which was detected for some (far more adjacent) explosions in that Japanese neutrino detector. Other question is what are pulsars and how they form.
Neutrinos are not explained by this theory. This is a pure electromagnetic theory. It can't explain neutrino production at the level that supernovae produce them - fusion produces far too much of its energy in gammas, and far too little in neutrinos. The only reason neutrinos are a significant product of stars is because the stars are optically thick. Production in thin filaments obviously wouldn't be optically thick.
Supernovae release vastly more of their energy in neutrinos, because they produce them via electron capture and beta decay, which allows neutrinos to cool the neutron star. We saw these neutrinos from SN1987A. There's too much to be explained by this theory. By far.
'Dark Matter' is just one example of modern science inventing something, with no basis on observed data, to explain observations that their own theories cannot.
No, it isn't. When dark matter was first proposed, it was laughed at. A bunch of other theories were proposed to try to defeat it. Modified Newtonian gravity, extra dimensions, etc. But dark matter just kept coming back - galaxies rotate wrong, and two galaxies with the same visible mass don't rotate the same. Galaxy clusters don't rotate right - there looks like there's a large clump of matter that isn't luminous that a bunch of galaxies are speeding towards (The Great Attractor).
And then came the CMBR results, that said that there's about 20% of the critical mass in matter in the Universe, and there's nowhere near enough luminous matter to account for that. So now you've got two independent pieces of evidence, completely unrelated to each other, which say "there is matter out there that you can't see". No basis in observed data? Hardly. If anything, there's a plethora of it.
In fact, the entire idea isn't crazy at all - neutrinos, if it wasn't for their low mass, would be a perfect dark matter candidate. In fact, with mass, they could make up the majority of matter in the universe! We know neutrinos exist. We see them all the time in various huge detectors. That's a given. In essence, whatever dark matter is found will act very much like neutrinos - barely interacting, but dominating the universe at large scales.
WHATEVER model that best explains the observed data, is the one to be used for a given event.
No way! Whoever told you that was more than wrong - he was committing a terrible crime by perpetuating the belief that modern science is hodgepodge. General relativity and the Standard Model are currently disjoint theories, yes. They each have domains of validity, and they are each used in their domains of validity. In the regions where they both are valid, they both agree. (Hint: all of classical physics is the region where they both agree).
It is not pick and choose! The regions where GR and the Standard Model disagree are the regions outside of their validity - i.e. where the energy density becomes too high for the assumptions the two are built on to be valid.
If the EUM can better explain current observations
It can't. It doesn't even begin to address neutrino creation. The vast majority of the energy of a supernova is in neutrinos. This is observed data, not theory. Neutrinos are not produced in the processes this site is talking about. It's bunk.
Calling people crackpots, is not a very scientific way to behave.
If you don't respond to your critics, justify your assumptions, or attempt to reconcile your theory to all available data, you're a crackpot: you're not following the scientific method. This guy falls in that category.
It is indeed true that most of them do emit X-rays
Most of them, in fact, emit X-rays, low energy gamma rays, and probably TeV gamma rays as well. The Crab is so bright in TeV gamma rays that it's the basic unit of flux in that region of the spectrum.
But the bigger "this article is crap" flag that should go off in your head is the question "what about the neutrinos?" Magnetic reconnection can't create neutrinos, and SN1987A had a flux of neutrinos way, way above background, and consistent with the majority of the energy of the collapse going into neutrinos.
The only way you can get that kind of a flux of neutrinos is via the URCA process: p+e->n+v->p+e+vbar+v, which means you're at a ridiculous pressure, and you're creating neutrons.
It's just embarassing that people like this get any press.
The better counterargument to the kookdom is neutrinos.
The vast majority of the energy in supernovae is emitted in neutrinos - upwards of 90%. The neutrinos from SN1987A aren't theoretical - we saw them. They were, in fact, the first extrasolar particles other than photons we've been able to associate with an astrophysical object.
Neutrinos get produced when electrons and protons are forced into neutrons via inverse beta decay, which only happens at ridiculous pressures. They can't be produced by electromagnetic processes - they're weak byproducts only.
There is nothing in that article to explain why the star would produce 10 times more energy in neutrinos than in photons. A magnetic pinch would not produce this much energy in neutrinos. There's simply not enough energy.
I played around with the Google translator for a while. I work in Japan and am half-way fluent. Google couldn't even turn my most basic Japanese emails into comprehensible English. Same is true for the other translation programs I have seen.
You haven't seen the Google translator he's talking about. It isn't public yet, I don't believe.
Here was the original article on it.
Old: "Alpine white new presence tape registered for coffee confirms Laden"
New: "The White House Confirmed the Existence of a new Bin Laden tape"
Well, if you read the site, there's a list of reasons why certain captchas are bad.
For instance:
And a list of reasons why certain captchas are good. It's a pretty good summary of the strengths (and weaknesses) of a lot of them.
One thing you may notice is how complicated (and difficult to read as a human!) some of the broken ones are (like linuxfr.org, or vBulletin), and how easy to read (yet hard to defeat!) the ICQ one is.
One easy thing to take away from this page would be: if you have to have one, for crying out loud, use a ton of fonts and a ton of backgrounds.
I don't dispute that. What hasn't been demonstrated experimentally is that the corresponding interactions propagate slower than lightspeed.
I don't get the problem. Are you proposing that a massive particle might travel at the speed of light?
I mean, the creation and decay of a real W/Z boson is a long-distance weak interaction. The fact that they decay at all means they don't travel at the speed of light.
Is your problem basically that a W hasn't been created with enough energy to live long enough to be observed?
While this is definitely true, I don't think that the fact that the weak nuclear force doesn't travel at the speed of light hinges upon this kind of a direct observation.
even with the proposed gravity sensors, you can't actually see the gravity waves, you can just see weights moving.
Gravity waves distort spacetime, which light follows. If you were near to a gravitational wave source, you'd see it. Light would bend like hell through it.
You'd also feel it if it were strong enough, too. Not many people enjoy their bodies being stretched in one direction and compressed in another.
People have attempted to measure it, but the trouble is that there doesn't seem to be agreement on whether those results are correct. Until there is, the question remains open.
The results are correct. The question is how precise the results are. So gravity propagates at approximately the speed of light. The question of how exact that approximation is needs to be measured better. But it's not, say, infinity.
So?
If something can't propagate, why bother talking about the speed at which it propagates? It's like asking whether or not dinosaurs would enjoy baseball.
While that is a plausible hypothesis, it's not a fact until it has actually been determined experimentally.
Uh, it has. The W and Z do have mass. Measured, and all. Really.
Hardly. They're two representations of the same effect - you ever derived the three W boson fields and the B field?
Yah. It's basic Standard Model stuff.
they're from the same fundamental force.
Yes, but when you're far from the electroweak breaking point, it's pointless to consider them the same force. The weak nuclear force operates orders of magnitude slower than the electromagnetic force when you're in normal, non-insane-energy regimes.
It's like saying the electric field is just like the magnetic field. Yes - two representations of the same thing. Sure. You can, in fact, convert the two fields by reference frame changes. But that doesn't change the fact that in electrical engineering, you treat electric and magnetic fields very differently.
More importantly, the statement that I said stands. The electromagnetic force - on its own - always has an infinite range, and so propagates forever. The weak nuclear only has a range where the W and Z are negligibly massive, and so propagates only over those distances.
The electroweak force, however, is only unified at high energies, where the W and Z are negligibly massive. So the electroweak force propagates with the speed of light.
Note the point here: at high energies, you can describe the electromagnetic and weak nuclear with one statement. At low energies, however, you have to describe the behavior of the two separately.
It's just like electromagnetism. Even though you could perfectly well describe all 4 of Maxwell's laws with one equation, it'd be useless to work with at low energies, as it doesn't describe the behavior of the two fields easily. In much the same way, referring to low-energy electromagnetism and weak nuclear as the same force is pointless. Sure, they're the same. But the interaction between the two forces is so suppressed due to the W and Z mass that it's pointless.
Speed and range of the interaction are related. If the force doesn't propagate, then its speed is effectively zero. You can't really talk about the speed of a force if its range is limited. The electromagnetic and gravitational forces are not range limited. They both propagate at the speed of light.
And I said that I was talking about the residual strong interaction (*residual*, not effective). It's still the strong interaction that causes those effects, even if it's diluted down because of the mass of a pion.
You're absolutely correct that on short scales, the weak nuclear and strong nuclear propagate basically at the speed of light, because at short scales, the virtual W/Z are far off mass shell, and might as well be massless.
The strong interaction does not propagate at the speed of light. Its coupling constant increases with decreasing momentum. Its strength increases with increasing distance. This means that after a short distance, you've got way too much potential energy for a gluon to be the channel particle. Instead, you form pion pairs, and pions mediate the interaction. This is what happens in a nucleus - it's called the residual strong interaction.
Since pions are massive, the residual strong interaction (which is what most people think of, and indeed, what was originally considered, the "strong nuclear force" - the force that binds nuclei together. The force that gluons mediate binds quarks together.) also does not propagate.
As for "speed of light" or not, that's pointless. The strong and weak nuclear force don't propagate, so saying what speed they propagate at is a little pointless. You can't set up "weak nuclear waves".
The strong force is indeed confined.
No, it's not. It's just that after a certain distance (less than a fermi) the interaction becomes strong enough that pions are created. So after a certain distance, pions mediate the interaction. Pions are massive, so you get the same problem as the weak-nuclear - this is often referred to as the residual strong nuclear force.
Also, lose bonus points for not complaining about description of electromagnetism and weak force as separate fundamental forces
They are separate fundamental forces. It only makes sense to combine them at high enough energies where the W's mass can be neglected. Past that point, they're unified. But if you're talking about "propagation" over distances anywhere near meaningful (even, say, oh, the size of an atom) you're far, far below the electroweak scale.
Gravity propagates at the speed of light - we think. It's kinda been measured. The question's meaningful because gravity waves will propagate at the speed of gravity, just like electromagnetic waves travel at the speed of light.
Gluons do not have mass. But the strong nuclear force has an opposite distance dependence as the others - it gets stronger as you get farther away. So after a short distance (say, 1 fm), the potential energy becomes enough that pions are formed, and so at distances greater than that, it's mediated by pions, which do have mass.
For forces mediated by massive particles, they don't propagate much at all - basically, they don't propagate more than the distance equivalent to the mass of the massive particle. So the weak doesn't propagate more than the size of a baryon (much less, actually) and the strong doesn't propagate more than the size of a nucleus.
That has only been demonstrated for electromagnetism; for the other forces, it's a hypothesis.
Nah. For gravity, it's (kindof) been measured. It looks like it's the speed of light. Kinda. There are a couple caveats there. But it (kinda) was measured.
For strong and weak nuclear, they don't propagate at all (much more than a femtometer). The weak nuclear force is mediated by a massive boson, anyway, so it won't propagate at the speed of light at all.
All 4 basic forces: electromagnatism, gravity, strong nuclear, and weak nuclear (not Nukular; bite me, George) forces propogate at the speed of light in their reference frame
Electromagnetic and gravity (most likely) propagate at the speed of light, because their carrier particles (photons and gravitons respectively) are massless.
By "propogation speed" you really mean "what's the mass of the channel particle when you've got a really low-momentum transfer (far distance)"? For electromagnetic and gravity, the channel particle is on-mass shell, and is massless, so the connection between the two points is lightlike.
The strong nuclear force, however, gets stronger at large distances. So the carrier particles (gluons) move farther and farther off mass-shell: so the strong nuclear force does not propagate at the speed of light over distances much more than the size of a proton! Even over the size of the nucleus, the mediating particles are virtual pions (the residual strong interaction), which do have mass.
The weak nuclear force is mediated completely by the W, which is massive. It will not propagate at the speed of light over distances where the W's mass is significant.
It's better to think, in colloquial terms, as the interactions having a range , not a speed. Electromagnetic and gravity both have an infinite range. The strong and weak nuclear both have a range about the size of a proton.
This is an important distinction - you can communicate with both the electromagnetic force and gravity, but not with the strong or weak nuclear force. Thus, speaking about "speeds" for them is quite wrong.
Do you think Google is focusing on indexing dictionary lists? Or that Yahoo are ignoring them in particular?
Well, the latter would be an intelligent thing for a search engine to do in returning results, but Yahoo could also feasibly have a crawler which doesn't bother indexing dictionary lists - i.e. once you get to some ridiculous number of independent words in the page, you toss it. It'd be a nice antispam tool, actually.
Or it could focus on HTML pages rather than text files, as most of the dictionary lists seem to be text files.
Maybe it's not valid to generalize from dictionary list sites to all sites, but I don't think it's clearly invalid either.
It isn't clearly invalid. If you remove the dictionary-list results, you still get the same answer. That doesn't mean the original conclusion wasn't wrong, though - just that by luck, they heavily oversampled a subset that was a representative sample of the whole.
Interestingly, when Yahoo returns the estimated number of searches (on non-dictionary-list searches) it returns about 2X as many results as Google. But when you go through them, it's only about a third. So not only does Yahoo actually have about half the indexed pages of Google, but they lie to you and say they've got about twice - on each result.
Hohmann transfers are not always the minimum orbit energy orbit.
Hohmann transfers are never the minimum energy orbital transfer. IPS (interplanetary superhighway) orbits are lower energy for all cases, although they take much longer. (To be fair, IPS orbits are new - 1997-ish - and before that, Hohmann transfers were the minimum energy orbital transfer). IPS orbits are so low energy that it basically takes the same delta-V to get almost anywhere in the solar system - the delta-V to get to a Lagrange point.
For manned missions, however, you don't really care about lowest-energy, because orbits are always tradeoffs between transit time and energy, and manned missions want the shortest transit time feasible.
What if the searches that showed Yahoo to search more pages (assuming for the moment that this is in fact the case) were those that blew the 1000 hit limit?
Unless the extra pages that Yahoo has all contain similar text, this is unlikely. Otherwise, you can always find word combinations which will be below the 1000 hit limit which will return pages in Yahoo's extra corpus.
Randomly going through words is a good way to do this, except for the bias produced by word list pages. There are a few ways to fix this bias - only use results which return more than 100 hits, which is probably safe, but kills your statistics (10,000 searches down to 300) - or rerun, taking the results which gave you more than 1000 results and add a third word from the results which gave you more than 1000 results, and you'll probably get a high-statistics set of data with less than 1000 results that doesn't include many dictionary lists.
Can we conclude that when you pick two English words that when entered into both Google and Yahoo, both return less than 1000 results
Two random words.
The study essentially is showing that there are more dictionary lists in Google than there are in Yahoo. The vast majority of the included searches return few (~10 ish) results, and they're extremely similar results each time. So that result gets magnified a ton.
Now, the interesting thing is that if you look at results which return between 100 and 1000 results (i.e. not dictionary list results) you get a similar conclusion (but with much, much lower statistics! ~300 vs 10,000). Which in some way, makes sense - there's nothing special about the sample of dictionary list sites, and so if there are more of them on Google, there's likely to be more of the normal sites, too. But the original study can't really even make the claim that it's making.
Correction to myself: the total responses to their list was ~150,000 to ~10,000 searches for Yahoo, and ~400,000 for Google. So the average is 15 results for Yahoo and 40 for Google. Given that most "dictionary list" results were between 10 and 40, that should pretty much tell you that their entire result is just a massively multiplied reflection of those searches.
As an interesting aside, though: if you dig through their log, you can see several interesting things. If you look at only results which return between 100 and 1000 results, you get things like "battening liberate", which returned 186 for Google, and 97 for Yahoo. Those aren't dictionary list results - the interesting thing is that in almost all of those results, you see an extremely similar pattern.
"battening liberate":
Ratio of Google/Yahoo for this query:
Duplicates Omitted Estimate: 0.522305
Duplicates Omitted Total: 1.917526
Duplicates Included Estimate: 0.533962
Duplicates Included Total: 2.350427
"convexity hac"
Ratio of Google/Yahoo for this query:
Duplicates Omitted Estimate: 0.573593
Duplicates Omitted Total: 3.340000
Duplicates Included Estimate: 0.583700
Duplicates Included Total: 2.490566
"meekness goatee"
Ratio of Google/Yahoo for this query:
Duplicates Omitted Estimate: 0.607053
Duplicates Omitted Total: 2.207692
Duplicates Included Estimate: 0.604010
Duplicates Included Total: 2.745562
So Yahoo claims it has 2X as much as Google, but actually only returns about 30-50%.
Interestingly, these mimic the "dictionary list" results, which is curious. So their conclusions seem right, but their methodology seems very wrong.
Or it could mean that Google has more Ispell lists in its index.
Which appears to be the case.
A search for "inabilities hydrocephalic" returns almost all dictionary lists in Google, except 2. There's only 2 results in Yahoo, one of which is a dictionary list (or equivalent).
But the official results for this? 16 for Google, 2 for Yahoo.
The reason this is a problem is because almost every search returns the same dictionary lists, so it amounts to double (or probably around 5000-fold) weighting of those sites in the results.
Without excluding results that are just dictionary lists (which is quite hard from a simple analysis like this) you heftily bias your results to mimic the "Number of Google dictionary list sites/Number of Yahoo dictionary list sites" ratio.
They probably should've only included sites that returned between 100 and 1000 results, but I'd bet that would take a ton more time, as it looks like almost all of the results they used were the "10-50" result range.