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Do I understand this correctly?



 
 
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  #11  
Old November 24th 10, 10:39 PM posted to sci.physics,sci.astro
Uncle Ben
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Posts: 46
Default 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  
Old November 25th 10, 04:20 AM posted to sci.physics,sci.astro
Darwin123
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Posts: 247
Default 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  
Old November 25th 10, 05:42 PM posted to sci.physics,sci.astro,sci.physics.relativity,sci.physics.particle
Y.Porat[_2_]
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Posts: 180
Default 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  
Old November 26th 10, 04:45 AM posted to sci.physics,sci.astro,sci.physics.relativity,sci.physics.particle
xxein[_4_]
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Posts: 23
Default 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  
Old November 26th 10, 06:08 PM posted to sci.physics,sci.astro,sci.physics.relativity,sci.physics.particle
PD
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Posts: 1,572
Default 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  
Old November 26th 10, 07:53 PM posted to sci.physics,sci.astro
hanson
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Posts: 2,934
Default 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  
Old November 26th 10, 08:55 PM posted to sci.physics,sci.astro
Matt
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Posts: 44
Default 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  
Old November 26th 10, 09:48 PM posted to sci.physics,sci.astro,sci.physics.relativity,sci.physics.particle
Tom Roberts
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Posts: 344
Default 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  
Old November 26th 10, 11:27 PM posted to sci.physics,sci.astro,sci.physics.relativity,sci.physics.particle
mpc755
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Posts: 818
Default 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  
Old November 28th 10, 05:35 PM posted to sci.physics,sci.astro,sci.physics.relativity,sci.physics.particle
Tom Roberts
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Posts: 344
Default 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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