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Offline neilep

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New Topic -Neutrinos !
« on: 04/09/2007 17:47:03 »
Pauls question about walking through walls got me thinking about Neutrinos !

Neutrinos are like.....well weird bit's of small stuff !

They travel all over the place really fast and have no issues passing through stuff  !!...which is nice !!

So....what is a Neutrino ?....what's the history of neutrino joy ?

Does gravity have an effect on Neutrinos ?

Can they be destroyed ?



 

Offline DoctorBeaver

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« Reply #1 on: 04/09/2007 18:23:30 »
 

Offline syhprum

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« Reply #2 on: 04/09/2007 18:34:18 »
There is so much authoritative information already published on Neutrinos that I hesitate to say my little bit.
I wonder if we can view the Neutrino as an electron stripped of its charge and hence the greatest proportion of its mass.
 

Offline neilep

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New Topic -Neutrinos !
« Reply #3 on: 04/09/2007 18:56:20 »
Whilst I realise there is plenty of information out there ....(thanks for the excellent link Eth)..personal insights are always welcome !
 

Offline DoctorBeaver

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« Reply #4 on: 04/09/2007 19:00:45 »
The neutrino is still largely a mystery. We know certain things about it, but not much.
 

Offline Negin -(Universe)

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« Reply #5 on: 04/09/2007 21:14:56 »
i'll write what little knowledge I have of neutinos from my physics A-level:
neutrinos are fundemental particles, and so cannot be subdivided to anything else. they are part of the lepton group which also contains electrons, muon and tau. neutrinos are massless and neutral. they're not affected by gravity since they have no mass, neither are the affected by magnetic field since they have no charge! having said this it has been suggested that they might be the constituents of dark matter and the result of dark energy(research is being carried out).
 

Offline Negin -(Universe)

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« Reply #6 on: 04/09/2007 21:15:43 »
by the way good to be back on the forum after exams and results!
 

Offline Negin -(Universe)

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« Reply #7 on: 04/09/2007 21:19:03 »
just to add the three types of neutrinos: electron neutrino, muon neutrino and tau neutrino. overall there are 6 leptons and each have an antiparticle with the same mass and a different charge. I'm sure all of this is mentioned in the website DoctorBeaver has mentioned
 

another_someone

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« Reply #8 on: 04/09/2007 22:10:24 »
Don't know that we can ever say that any particle cannot be subdivided - we used to say that about hadrons, but now we decide that hadrons should be considered to be composed of sub-particles called quarks.

The problem with neutrinos is that since the don't have charge, and have zero or almost zero mass (there seems to still be some debate about this), and really don't interact with anything very much (hence why they can pass through the Earth with very little probability of their being stopped), so it is very difficult to study their direct effects on anything, but merely assume their existence from their indirect effects upon things.
 

Offline Negin -(Universe)

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« Reply #9 on: 04/09/2007 22:16:27 »
yep I totally agree with you, we cant really say anything directly related to them. it is just because of the symmetry in the existance of particles that scientists say they exist and of course their effect on other matter and antimatter inthe universe
 

Offline DoctorBeaver

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New Topic -Neutrinos !
« Reply #10 on: 04/09/2007 22:38:03 »
yep I totally agree with you, we cant really say anything directly related to them. it is just because of the symmetry in the existance of particles that scientists say they exist and of course their effect on other matter and antimatter inthe universe

That's not strictly accurate. Neutrinos were first detected in 1953 (I remember that as I was born that year. NB. I don't recall the actual event, obviously! I just remember reading that it was in that year.). Some were also detected by a Japanese team when that supernova went bang a few years ago. They didn't find many, though (I seem to recall it was 9 or 10 they detected).

There have been other detections (i.e. IMB) so these particles are certainly more than merely summised by symmetry.

P.S. Having read your reply again I assume your statement about their effect on other matter refers to their actual detection. My apologies if that is the case.
« Last Edit: 04/09/2007 22:40:12 by DoctorBeaver »
 

another_someone

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« Reply #11 on: 04/09/2007 23:54:17 »
That's not strictly accurate. Neutrinos were first detected in 1953 (I remember that as I was born that year. NB. I don't recall the actual event, obviously! I just remember reading that it was in that year.).

I agree that you cannot remember the year (or was it the year of your birth you cannot remember) :D

http://en.wikipedia.org/wiki/Neutrino_experiment
Quote
The neutrino experiment, also called the Cowan and Reines neutrino experiment, was performed by Clyde L. Cowan and Frederick Reines in 1956. This experiment confirmed the existence of the antineutrino—a very small and neutrally charged subatomic particle.
1956 is the year of my birth :P

The point is that although one can design experiments that one can detect the effects of a neutrino (e.g. the conversion of proton to a neutron and a positron), you cannot track the path of a neutrino, or in any way actually detect anything about the actual physical neutrino except that you have a particle reaction that requires a source of energy from somewhere (or its converse reaction that has an energy deficit that must be explained).

There are still more questions than answers regarding neutrinos.

http://en.wikipedia.org/wiki/Sterile_neutrino
Quote
A sterile neutrino is a hypothetical neutrino that does not interact via any of the fundamental interactions of the Standard Model. It is a right-handed neutrino or a left-handed anti-neutrino.

So try and create an experiment to find a particle that reacts to only one of the major forces - names gravity (indeed - one might speculate that it would have the attributes of dark matter).

Then there is the question of where are the right handed neutrinos, or left handed anti-neutrinos?
« Last Edit: 05/09/2007 00:01:44 by another_someone »
 

Offline DoctorBeaver

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New Topic -Neutrinos !
« Reply #12 on: 05/09/2007 00:20:18 »
It's getting late & I've been on the lagers so I'll think about your reply tomorrow  :D
 

Offline Soul Surfer

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New Topic -Neutrinos !
« Reply #13 on: 05/09/2007 08:39:10 »
The point is that neutrinos have no charge and very little if any mass but they do have spin that is just about their only property.  They carry spin and by doing this they enable the conversions that they do.
 

Offline DoctorBeaver

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« Reply #14 on: 05/09/2007 08:46:37 »

So try and create an experiment to find a particle that reacts to only one of the major forces - names gravity (indeed - one might speculate that it would have the attributes of dark matter).

I thought they were affected by the weak force  ???
 

another_someone

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« Reply #15 on: 05/09/2007 11:41:20 »

So try and create an experiment to find a particle that reacts to only one of the major forces - names gravity (indeed - one might speculate that it would have the attributes of dark matter).

I thought they were affected by the weak force  ???

Those that we presently have measured do react to the weak force - the problem is the notion that there might be neutrinos that do not even react to the weak force.
 

Offline neilep

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New Topic -Neutrinos !
« Reply #16 on: 05/09/2007 14:39:44 »
THANK YOU Negin -(Universe), IAN, GEORGE, ETH, SYHPRUM,

I just luff reading your confabulations....

Sometimes (in my opinion) one gets a better picture just by reading the 'to's and fro's' of some peeps dialogues than referring to official texts......that can come later...so THANK YOU ALL.
 

Offline thebrain13

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New Topic -Neutrinos !
« Reply #17 on: 05/09/2007 22:03:05 »
how is it possible that neutrinos are not affected by gravity? doesnt that disprove general relativity?
 

another_someone

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« Reply #18 on: 05/09/2007 23:29:29 »
how is it possible that neutrinos are not affected by gravity? doesnt that disprove general relativity?

As far as we are aware, neutrinos do respond to gravity, but gravity is too weak a force to easily show its effects on a particle with zero, or near zero, mass within a laboratory environment.  Even with light, it is only really practical to see the effects of gravity upon light near stellar sized objects, and since we do not have the capability to detect the direction from which a neutrino has arrived to our experiment, it is thus extremely difficult to prove the path it took, and thus to demonstrate whether it has been bent by a gravitational field.
 

Offline DoctorBeaver

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« Reply #19 on: 06/09/2007 06:02:45 »
I've only ever read that all 3 flavours of neutrinos are massless & respond only to the weak force.

I appreciate that being massless (or, rather, having zero rest mass) does not preclude them being affected by gravity; but if they had any kind of mass, wouldn't that have become evident via the muon & tau neutrinos as they would be correspondingly heavier &, hence, their mass would be more readily detectable? (Unless, of course, they are so massive that colliders haven't yet reached sufficient energy levels.)

I'm quite happy for them to be massless, though. As there are trillions of them zapping through me every second, if they had mass they might tickle! (Wouldn't that be fun - people walking around giggling all the time because of being tickled by neutrinos!  :D )
« Last Edit: 06/09/2007 06:05:50 by DoctorBeaver »
 

Offline syhprum

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« Reply #20 on: 06/09/2007 07:44:29 »
It is well established that Neutrinos oscillate between the three different varieties as they travel, they could not do that if they were massless although the mass of the Electron Neutrino is very small and difficult to measure
 

Offline lightarrow

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« Reply #21 on: 06/09/2007 15:35:31 »
Since a neutrino has spin = magnetic moment, it can interact electromagnetically, that is, with photons; however such interactions hasn't been observed yet.
 

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« Reply #21 on: 06/09/2007 15:35:31 »

 

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