Neutrino Dilemma: How Physicists Established Existence

[Lakshmi N]

Even though the neutrinos are massless and undetectable,how did the physicists established the existence of such particle?

 

[Gestahl]

Clyde Cowan, Frederick Reines, F. B. Harrison, H. W. Kruse, and A. D. McGuire published confirmation in a 1956 issue of Science that they had detected the neutrino, in which they were awarded the Nobel Prize in 1995.

You can read about the experiment here:
http://en.wikipedia.org/wiki/Cowan–Reines_neutrino_experiment

Or if you have a Science subscription you can find the publication here:
http://www.sciencemag.org/content/124/3212/103

 

[cjl]

Neutrinos are neither massless nor are they undetectable. They are extremely low mass and very difficult to detect. This is a key difference, since if they were undetectable, then we could not have detected them (by definition).

 

[Lakshmi N]

Thank you friends

 

[simpatico]

You can find detailed info at wikipedia: neutrino

But they change often opinion .The current evaluation is from 0.04 to 2 eV.That is 1 millionth of the mass of an electron.

I had the same dilemma myself.
Probably NOBODY knows the answer, probably in this Forum are specialists but they seldom anwer these questions.
After long research I came to the conclusion that actually neutrino IS Undetectable
they consider detection Indirect detection.: From something that happens (production of a neutron + gamma ray)
they deduce that they caught a neutrino. There are many dark points.

I'll expand if you are interested

 

[ZapperZ]

After long research I came to the conclusion that actually neutrino IS Undetectable
they consider detection Indirect detection.: From something that happens (production of a neutron + gamma ray)
they deduce that they caught a neutrino.

Give an example of something that you consider to be a DIRECT detection, and I'll show you that it is an indirect detection!

Zz.

 

[simpatico]

Give an example of something that you consider to be a DIRECT detection, and I'll show you that it is an indirect detection!

Zz.

Hi zz, nice to hear from you.
Welcome!
REJOICE LAKSHMI, you caught an expert who is not on vacation
l
Now,zz,
when I catch a ray of light in my eye!

 

[ZapperZ]

Hi zz, nice to hear from you.
Welcome!
REJOICE LAKSHMI, you caught an expert who is not on vacation
l
Now,zz,
when I catch a ray of light in my eye!

Oh good!

How do you think you detected that "ray of light in your eye"?

Do you realize that the photons hit the light cones at the back of your eyes, and then send out electrical impulses (i.e. motion of current) through your nervous system that then triggers the appropriate grey matter cells in your brain? Then, based on what evolution has given us in being able to understand such signals, you then say "Aha! I detected the light!"

So this is what you consider to be "direct"? Why is this different than neutrino detection?

Zz.

 

[Kiril]

"So this is what you consider to be "direct"? Why is this different than neutrino detection?"

If you'll permit me to answer: The concept of validity does not apply to sense perception, as it does with any man made apparatus of detection(and interpretations from same). This is because the evidence of the senses(not inference from it, eg. bent stick) are the basis for any concept/conclusion which one uses to question their validity.

The Logical Positivsts and Descartes would have us believe otherwise, however they offer nothing but rationalization.

 

[ZapperZ]

If you'll permit me to answer: The concept of validity does not apply to sense perception, as it does with any man made apparatus of detection(and interpretations from same). This is because the evidence of the senses(not inference from it, eg. bent stick) are the basis for any concept/conclusion which one uses to question their validity.

The Logical Positivsts and Descartes would have us believe otherwise, however they offer nothing but rationalization.

I'm not sure how what you wrote here answered my question. Are you saying that his example is the same, or not, with a neutrino detection, or any other detection (such as detecting current in a circuit) for that matter? A simple "yes" or "no", with the corresponding explanation that follows would suffice.

Zz.

 

[Drakkith]

If you'll permit me to answer: The concept of validity does not apply to sense perception, as it does with any man made apparatus of detection(and interpretations from same). This is because the evidence of the senses(not inference from it, eg. bent stick) are the basis for any concept/conclusion which one uses to question their validity.

The Logical Positivsts and Descartes would have us believe otherwise, however they offer nothing but rationalization.

The issue is not HOW the effect is eventually interpreted, it is WHAT is happening at each step in the long chain of events. When a photon is absorbed by your eye, that single event is exactly the same as that photon being absorbed on a CCD or other detector. The physics don't somehow change just because it is now my eye instead of a detector.

The detection of a photon by your eye in the process that eventually leads to perception and understanding or whatever, is just as indirect or direct as the detection of a neutrino in a detector.

 

[TrickyDicky]

Oh good!

How do you think you detected that "ray of light in your eye"?

Do you realize that the photons hit the light cones at the back of your eyes, and then send out electrical impulses (i.e. motion of current) through your nervous system that then triggers the appropriate grey matter cells in your brain? Then, based on what evolution has given us in being able to understand such signals, you then say "Aha! I detected the light!"

So this is what you consider to be "direct"? Why is this different than neutrino detection?

Zz.

All this indirect chain you describe here is not related to what in physics is considered direct or indirect detection. You described the physiologic path of the signals in an organism.
Actually the distinction direct/indirect detection can get very tricky, and philosophycally could lead very far, so if you want to get philosophical you can argue we can't detect anything at all directly, since we are always separated from the essence of objects thru some medium or machine or whatever. But since we want to stick to physics, what a photodetector does is a direct detection of photons, meaning the signal it gets is attributed to an entity defined as photon (without even entering on how this definition is done). The same can be said for instance in the case of protons, electrons, positrons, muons, etc in a cloud chamber. But this is not the case with neutrinos, their detection is said to be indirect because it involves the detection of something else that thru the current theoretical model leads to the inference that a neutrino was there. So the difference is clear, we detect neutrinos by proxy, meaning we actually detect photons (Cherenkov radiation) or electrons, muons...

 

[simpatico]

If you'll permit me to answer: The concept of validity does not apply to sense perception, as it does with any man made apparatus of detection(and interpretations from same). This is because the evidence of the senses(not inference from it, eg. bent stick) are the basis for any concept/conclusion which one uses to question their validity.

The Logical Positivsts and Descartes would have us believe otherwise, however they offer nothing but rationalization.

congrats kyril,
this is a most elegant way to say
"detection should not be confused with perception,cognition"

 

[Drakkith]

I don't see how that is any different. If i have a CCD camera, how do I know that EVERY detection on it is due to a photon? Could one have been another particle? The only way to tell would be to look at the effects of the detection. How much energy was imparted to the CCD over time, whether any damage was done, ETC. Is that not the same thing in Neutrino detection? They have done everything they can to ensure that no stray particles can get into mess with their detections and can infer from the events of the interaction whether or not it is a neutrino. If you detect an enormous amount of energy imparted to the sensors or whatever all in a very short period of time, it is very unlikely that is a neutrino.

 

[ZapperZ]

congrats kyril,
this is a most elegant way to say
"detection should not be confused with perception,cognition"

But you've eluded to my explanation on why the photon that you observed with your eye is not a "direct" detection. It still needs to be converted to some signal for you to "perceive"! And there are many, many photons that you can't detect. Your eye is a poor detector! Your "perception" is utterly useless in such a case.

I am still waiting for an example of a "direct" detection.

Zz.

 

[Kiril]

I'm not sure how what you wrote here answered my question. Are you saying that his example is the same, or not, with a neutrino detection, or any other detection (such as detecting current in a circuit) for that matter? A simple "yes" or "no", with the corresponding explanation that follows would suffice.

Zz.

No, not similar. Sense perception is different from detection by experimental apparatus, for the reasons I mentioned. It is an epistemological distinction - this means that sense perception involves no inference(deduction or induction) and is therefore axiomatic(direct); indirect detection(including current in a circuit) relies on the reasoning from complex phenomena, based on prior theoretical knowledge - and all the possible errors that implies.

You might say, "yes, but they are both processes" - how did you find this out?

 

[simpatico]

hi folks,
if I read correctly the Guidelines, this thread is risking been hijacked.

Let's not forget we are here only to give dear Lakshmi evidence of existence of neutrinos.
if someone wants highlights on perception, cognition, epistemology, cognitive psychology, better open another thread

 

[ZapperZ]

hi folks,
if I read correctly the Guidelines, this thread is risking been hijacked.

Let's not forget we are here only to give dear Lahshmi evidence of existence of neutrinos.

He someone wants highlights on perception, cognition, epistemology, cognitive psychology, better open another thread

As I recall, you were the one who started to derail this thread when you insisted that it isn't a "direct detection". Now that you can't answer what is not a direct detection, you start to whine about it being derailed.

This thread is closed.

Zz.