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#11
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Do I understand this correctly?
On Nov 24, 9:25*am, Joe Snodgrass wrote:
Am I correct in my understanding that, although it was discovered in 1998 that the neutrino does indeed have mass, people still don't know what that mass is? *TIA. Yes, and although the way that the mass has shown up relates directly to SRT, I will take the liberty of reviewng it here, where the topic has risen, rather than our sister newsgroup. The flux of neutrinos picked up on earth from the sun iin experiments was much smaller than expected. A curious fact about neutrinos is tghat they come in different flavors, and the experiment was designed to detect only the flavor that was predicted to be emitted by the sun. An even more curous fact is that neutrinos, in principle, can change flavors in time -- referred to as oscillation in flavor, and even at the speed of light, it takes 8 minutes or so for them to travel from sun to earth. So could the missing neutrinos have simply changed flavor in transit? Not if they have no mass, because massless particles travel at c, and at c, clocks freeze, to put it very loosely.. Someone (no doubt a reader can supply the citation) dared to speculate, however that maybe they have a tiny bit of rest mass! The experiment was changed to include detection of the other flavors, and there there they were. So, neutrinos have mass (rest mass). Uncle Ben |
#12
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Do I understand this correctly?
On Nov 24, 9:25*am, Joe Snodgrass wrote:
Am I correct in my understanding that, although it was discovered in 1998 that the neutrino does indeed have mass, people still don't know what that mass is? *TIA. No. |
#13
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Do I understand this correctly?
On Nov 24, 4:25*pm, Joe Snodgrass wrote:
Am I correct in my understanding that, although it was discovered in 1998 that the neutrino does indeed have mass, people still don't know what that mass is? *TIA. -------------------- mass is as Newton defined it!! no other pompous definition does it better 2 not only the neutrino mas mass the photon as well ie not relativistic mass but just mass the only ordinary mass!! ATB Y.Porat ---------------------- |
#14
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Do I understand this correctly?
On Nov 25, 11:42*am, "Y.Porat" wrote:
On Nov 24, 4:25*pm, Joe Snodgrass wrote: Am I correct in my understanding that, although it was discovered in 1998 that the neutrino does indeed have mass, people still don't know what that mass is? *TIA. -------------------- mass is as Newton defined it!! no other pompous definition does it better 2 not only the neutrino mas mass the photon as well ie not relativistic mass but just mass the only *ordinary *mass!! ATB Y.Porat ---------------------- xxein: When you can measure an effect you can describe it as a mass- momentun. Is it or not? |
#15
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Do I understand this correctly?
On Nov 25, 10:42*am, "Y.Porat" wrote:
On Nov 24, 4:25*pm, Joe Snodgrass wrote: Am I correct in my understanding that, although it was discovered in 1998 that the neutrino does indeed have mass, people still don't know what that mass is? *TIA. -------------------- mass is as Newton defined it!! Nope. Not any more. No amount of wishing will make it so. no other pompous definition does it better 2 not only the neutrino mas mass the photon as well ie not relativistic mass but just mass the only *ordinary *mass!! ATB Y.Porat ---------------------- |
#16
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Paul Draper, what is mass, fundamentally?
"PD" wrote:
"hanson" wrote: snip. Paul "PD" snip "hanson" wrote: PD, kindly clarify, delineate, describe, IOW, do teach, IYOW, what mass is, fundamentally, so that neutrino oscillations can be explained without you resorting to abstract terms, such as "flavor" like you did below. TIA, hanson snip Pau wrote: OK. Mass has had its meaning refined, especially over the last 100 years or so. What it means now is the frame-independent quantity of a physical system (where a physical system is a collection of physical things, possibly interacting with each other) that can be calculated from measured energy and measured momentum: (mass) = sqrt ((Sum (energies))^2 - (Sum (momentum))^2). The fact that it is invariant regardless of inertial reference frame is what makes it interesting. For a closed physical system -- one where no net interaction crosses the boundary -- the fact that the mass is also conserved is also what makes it interesting. This conservation means that it will have the same value in a closed system, no matter what happens INSIDE the system. Conserved quantities always point to some fundamental law of symmetry in nature. There is the tendency to ask, "But what IS it, other than a quantity?" This is a misplaced question, because some quantities are interesting in their own right in physics, because they exhibit frame-independence and conservation. They don't have to have another "explanation" other than these circumstances. What we also know is that mass is not what we once thought it was, though it is close. For example, we once thought mass was a measure of "the amount of stuff". This rule doesn't work, though, because mass isn't additive -- you can't get the mass of a system by adding the masses of the parts of the system. We once thought that mass was a measure of the *inertia* of an object, where that is the ratio of the force applied to the acceleration observed. That rule doesn't work either though, because there is a velocity-dependent factor missing in that relationship (which just happened to be close to 1 for most of the everyday examples we looked at). Since these previous qualitative descriptions have fallen short, we now just talk about it as a quantity with the observed frame-independence and conservation behaviors -- which is about the same as what we do with a number of other properties like electric charge. hanson wrote: THANK YOU, Paul. Let me fine-comb thru it for a while & then tell you how it came across to me and what I perceived you have meant to tell me, from my pov. I appreciated it, Paul. I'll be back. hanson Paul wrote: snip |
#17
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Paul Draper, what is mass, fundamentally?
On Fri, 26 Nov 2010 10:53:41 -0800, hanson wrote:
"PD" wrote: "hanson" wrote: snip. Paul "PD" snip "hanson" wrote: PD, kindly clarify, delineate, describe, IOW, do teach, IYOW, what mass is, fundamentally, so that neutrino oscillations can be explained without you resorting to abstract terms, such as "flavor" like you did below. TIA, hanson snip Pau wrote: OK. Mass has had its meaning refined, especially over the last 100 years or so. What it means now is the frame-independent quantity of a physical system (where a physical system is a collection of physical things, possibly interacting with each other) that can be calculated from measured energy and measured momentum: (mass) = sqrt ((Sum (energies))^2 - (Sum (momentum))^2). The fact that it is invariant regardless of inertial reference frame is what makes it interesting. For a closed physical system -- one where no net interaction crosses the boundary -- the fact that the mass is also conserved is also what makes it interesting. This conservation means that it will have the same value in a closed system, no matter what happens INSIDE the system. Conserved quantities always point to some fundamental law of symmetry in nature. There is the tendency to ask, "But what IS it, other than a quantity?" This is a misplaced question, because some quantities are interesting in their own right in physics, because they exhibit frame-independence and conservation. They don't have to have another "explanation" other than these circumstances. What we also know is that mass is not what we once thought it was, though it is close. For example, we once thought mass was a measure of "the amount of stuff". This rule doesn't work, though, because mass isn't additive -- you can't get the mass of a system by adding the masses of the parts of the system. We once thought that mass was a measure of the *inertia* of an object, where that is the ratio of the force applied to the acceleration observed. That rule doesn't work either though, because there is a velocity-dependent factor missing in that relationship (which just happened to be close to 1 for most of the everyday examples we looked at). Since these previous qualitative descriptions have fallen short, we now just talk about it as a quantity with the observed frame-independence and conservation behaviors -- which is about the same as what we do with a number of other properties like electric charge. hanson wrote: THANK YOU, Paul. Let me fine-comb thru it for a while & then tell you how it came across to me and what I perceived you have meant to tell me, from my pov. I appreciated it, Paul. I'll be back. hanson Paul wrote: snip I think this will be helpful for me in understanding concept, but I stumbled over this: (mass) = sqrt ((Sum (energies))^2 - (Sum (momentum))^2). It seems to need factors of 'c' for consistency in conventional units: (mass) = sqrt ((Sum (energies))^2 - (Sum (momentum * c))^2) / c. |
#18
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Do I understand this correctly?
On Nov 24, 4:25 pm, Joe Snodgrass wrote:
Am I correct in my understanding that, although it was discovered in 1998 that the neutrino does indeed have mass, people still don't know what that mass is? TIA. Yes, that is correct. There are both lower and upper experimental bounds on delta(m^2), the difference in the masses-squared of the different neutrino mass eigenstates, but these are dependent on the values of the various mixing angles, some of which are highly uncertain. From tritium decay an upper bound of a few eV/c^2 on nu_e_bar has been known for a long time. The neutrino oscillation experiments put limits on delta(m^2) in the range of a few eV^2/c^4 for some pairs, and ~1,000 times smaller for others. These limits are very much smaller than the mass of the lowest-mass particle for which the mass is known, the electron at 510,999 eV/c^2. Look up "neutrino oscillations" for more information. Tom Roberts |
#19
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Do I understand this correctly?
On Nov 26, 3:48*pm, Tom Roberts wrote:
On Nov 24, 4:25 pm, Joe Snodgrass wrote: Am I correct in my understanding that, although it was discovered in 1998 that the neutrino does indeed have mass, people still don't know what that mass is? *TIA. Yes, that is correct. There are both lower and upper experimental bounds on delta(m^2), the difference in the masses-squared of the different neutrino mass eigenstates, but these are dependent on the values of the various mixing angles, some of which are highly uncertain. *From tritium decay an upper bound of a few eV/c^2 on nu_e_bar has been known for a long time. The neutrino oscillation experiments put limits on delta(m^2) in the range of a few eV^2/c^4 for some pairs, and ~1,000 times smaller for others. These limits are very much smaller than the mass of the lowest-mass particle for which the mass is known, the electron at 510,999 eV/c^2. Look up "neutrino oscillations" for more information. Tom Roberts http://www.ps.uci.edu/~superk/nuosc.html "Neutrino Oscillations and Neutrino Mass In five distinct measurements, Super-Kamiokande finds neutrinos apparently "disappearing". Since it is unlikely that momentum and energy are actually vanishing from the universe, a more plausible explanation is that the types of neutrinos we can detect are changing into types we cannot detect. This phenomenon is known as neutrino oscillation. Neutrino oscillation is not black magic - there are very specific predictions for the behavior of our data if neutrinos oscillate, and we have uniformly found the data in good agreement with these predictions. Unfortunately, a non-mathematical explanation of why neutrino oscillation and neutrino mass are inseparable is difficult." A non-mathematical explanation is not difficult at all. Albert Michelson figured it out over 100 years ago. http://home.netcom.com/~sbyers11/ Quote from Albert A Michelson's lecture circa 1899. "Suppose that an aether strain corresponds to an electric charge, an aether displacement to the electric current, aether vortices to the atoms; if we continue these suppositions, we arrive at what may be one of the grandest generalizations of modern science, namely that all the phenomena of the physical universe are only different manifestations of the various modes of motion of one all-pervading (substance), the aether. The day seems not to distant when the converging lines from many apparently remote regions of thought will meet on some common ground. Then the nature of the atom and the forces called into play in their chemical union, the interactions between these atoms and the non- differentiated aether as manifested in the phenomena of light and electricity , the structure of the molecule, the explanation of cohesion, elasticity and gravitation, all of these will be marshaled into a single compact and consistent body of scientific knowledge." Ether and the Theory of Relativity by Albert Einstein' http://www-groups.dcs.st-and.ac.uk/~...ein_ether.html "Since according to our present conceptions the elementary particles of matter are also, in their essence, nothing else than condensations of the electromagnetic field" The electromagnetic field is a state of aether. Matter is the condensation of aether. When a neutrino 'disappears' it has simply 'evaporated' into aether. |
#20
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Do I understand this correctly?
mpc755 wrote:
When a neutrino 'disappears' it has simply 'evaporated' into aether. How about the ones that appear? At a rate consistent with the disappearance measured in other detectors, with momenta pointing back to the source, and with timing consistent with that of the source. Remember that the different neutrino detectors are sensitive to different types (flavors) of neutrinos, and the different sources generate different types of neutrinos. For instance, the LSND source cannot generate tau neutrinos, but the MINOS source can and does. The MINOS detector cannot cleanly distinguish electron from tau neutrinos but can determine the sign of muons (i.e. nu_mu vs anti-nu_mu in quasi-elastic scattering). Other detectors have difficulty identifying muon neutrino events. Early radiochemical detectors were sensitive only anti-nu_e. Etc. The whole collection of experiments is MUCH better modeled as oscillations among neutrino flavors than as "evaporating into aether". Indeed, if "evaporating into aether" was common, then given that NOBODY has ever observed aether, then 4-momentum conservation would NOT be experimentally observed (because the energy and momentum carried by the aether is unobservable). Instead, 4-momentum conservation is solidly established in elementary particle interactions. Historically, of course, neutrinos were postulated in order to preserve energy-momentum conservation in certain decays, and they were triumphantly observed with the appropriate properties. Contrast that with your GUESSES about aether.... Tom Roberts |
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