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  1. Standard member sonhouse
    Fast and Curious
    23 Nov '17 10:25
    https://phys.org/news/2017-11-earth-high-energy-neutrinos-tracks.html

    It has been found these highest energy neutrinos DON"T pass through the Earth like a knife through butter but in fact don't make it all the way through at all.

    My question is this: is there a way to understand or visualize somehow the difference between high and low energy neutrinos?

    Like it is of course very well known EM radiation is easy to understand in terms of energy, higher energy basically just means smaller wavelengths.

    What is an analogy for Neutrinos?
  2. Standard member mchill
    Green Lantern
    23 Nov '17 12:07
    Originally posted by @sonhouse
    https://phys.org/news/2017-11-earth-high-energy-neutrinos-tracks.html

    It has been found these highest energy neutrinos DON"T pass through the Earth like a knife through butter but in fact don't make it all the way through at all.

    My question is this: is there a way to understand or visualize somehow the difference between high and low energy neutrin ...[text shortened]... , higher energy basically just means smaller wavelengths.

    What is an analogy for Neutrinos?
    This is a bit out of my league, but the best I could do in defining the difference between high and low energy neutrinos are in the links below.


    High:
    https://www.nobelprize.org/nobel_prizes/themes/physics/hulth/

    Low:
    http://iopscience.iop.org/article/10.1088/1742-6596/718/2/022012/pdf
  3. Standard member lemon lime
    blah blah blah
    24 Nov '17 04:22
    Originally posted by @mchill
    This is a bit out of my league, but the best I could do in defining the difference between high and low energy neutrinos are in the links below.


    High:
    https://www.nobelprize.org/nobel_prizes/themes/physics/hulth/

    Low:
    http://iopscience.iop.org/article/10.1088/1742-6596/718/2/022012/pdf
    High:
    https://www.nobelprize.org/nobel_prizes/themes/physics/hulth/

    "... a star in the Large Magellanic Cloud exploded as a supernova, which was later named SN1987. The neutrinos from the inner part of the collapse reached the earth after a journey of 170,000 years, a few hours before the arrival of light."


    The neutrinos were travelling faster than light?
  4. 24 Nov '17 07:44
    Originally posted by @lemon-lime
    High:
    https://www.nobelprize.org/nobel_prizes/themes/physics/hulth/

    "... a star in the Large Magellanic Cloud exploded as a supernova, which was later named SN1987. The neutrinos from the inner part of the collapse reached the earth after a journey of 170,000 years, a few hours before the arrival of light."


    The neutrinos were travelling faster than light?
    No, they started earlier.
  5. Standard member sonhouse
    Fast and Curious
    24 Nov '17 17:56
    Originally posted by @lemon-lime
    High:
    https://www.nobelprize.org/nobel_prizes/themes/physics/hulth/

    "... a star in the Large Magellanic Cloud exploded as a supernova, which was later named SN1987. The neutrinos from the inner part of the collapse reached the earth after a journey of 170,000 years, a few hours before the arrival of light."


    The neutrinos were travelling faster than light?
    Neutrinos have a small amount of mass and therefore cannot go even at c but they get close. The large Magellanic cloud is about 160,000 light years away and it is reasonable for the Neutrinos to take 170,000 years to get here. No superscience here, walk away folks.
  6. Standard member DeepThought
    Losing the Thread
    25 Nov '17 06:06
    Originally posted by @sonhouse
    https://phys.org/news/2017-11-earth-high-energy-neutrinos-tracks.html

    It has been found these highest energy neutrinos DON"T pass through the Earth like a knife through butter but in fact don't make it all the way through at all.

    My question is this: is there a way to understand or visualize somehow the difference between high and low energy neutrin ...[text shortened]... , higher energy basically just means smaller wavelengths.

    What is an analogy for Neutrinos?
    Higher energy means means shorter wavelength for neutrinos and for that matter any particle. As a rule scattering cross-section decreases with energy, so one would expect the higher energy neutrinos to interact even less than low energy ones.
  7. Standard member sonhouse
    Fast and Curious
    26 Nov '17 04:53
    Originally posted by @deepthought
    Higher energy means means shorter wavelength for neutrinos and for that matter any particle. As a rule scattering cross-section decreases with energy, so one would expect the higher energy neutrinos to interact even less than low energy ones.
    But the electromagnetic field of photons have two parts, a magnetic part and an electric field part, welded together but still it is easier to understand the wavelength bit that way.

    What is it about neutrino's that would lead to a wavelength? What is 'waving'?
  8. Standard member lemon lime
    blah blah blah
    04 Dec '17 04:06
    Neutrinos have energy and momentum... hence, wavelength.
    λ = h/p
  9. Standard member sonhouse
    Fast and Curious
    04 Dec '17 19:26
    Originally posted by @lemon-lime
    Neutrinos have energy and momentum... hence, wavelength.
    λ = h/p
    But they are not electromagnetic waves. What kind of waves then? Plancks constant divided by momentum. Fine, that tells you the physical picture of the size of the wavelength but what is waving? In and out of existence? What?
  10. Standard member lemon lime
    blah blah blah
    05 Dec '17 04:27 / 4 edits
    Originally posted by @sonhouse
    But they are not electromagnetic waves. What kind of waves then? Plancks constant divided by momentum. Fine, that tells you the physical picture of the size of the wavelength but what is waving? In and out of existence? What?
    After a bit of reading and contemplation (and a headache) I can now confidently say I have no idea what is waving, or why it's waving.
    (it's waving bye bye to the supernova?)

    I have a different question:

    Is the Magellanic cloud 170,000 light years away now, or was it 170,000 light years away at the time of the supernova?

    The reason I ask is because if we witness an event happening 170,000 years ago, and the universe is expanding at an accelerated rate, does this mean light must have traveled more than 170,000 light years before reaching earth?
  11. 05 Dec '17 07:47 / 2 edits
    Originally posted by @sonhouse
    But they are not electromagnetic waves. What kind of waves then? Plancks constant divided by momentum. Fine, that tells you the physical picture of the size of the wavelength but what is waving? In and out of existence? What?
    It is a very long time since I studied quantum physics and my memory of it is a bit rusty but if my memory from my university physics studies a few decades back serves me well enough, according to quantum physics, ALL particles have a 'frequency' or 'vibration' associated with them, including photons, electrons, protons, etc and thus I assume this must surely include neutrinos. I could be wrong but I took that to mean that this 'vibration' generally occurs in space so all particles vibrate in space including neutrinos.
    So, I could be wrong but, a possible answer to your question is; what is 'waving' in this case is the neutrino itself and it is specifically 'waving' in physical 3D space.

    ANYONE;
    Please correct me if I got that wrong.
  12. Standard member sonhouse
    Fast and Curious
    05 Dec '17 12:41
    Originally posted by @humy
    It is a very long time since I studied quantum physics and my memory of it is a bit rusty but if my memory from my university physics studies a few decades back serves me well enough, according to quantum physics, ALL particles have a 'frequency' or 'vibration' associated with them, including photons, electrons, protons, etc and thus I assume this must surely ...[text shortened]... s specifically 'waving' in physical 3D space.

    ANYONE;
    Please correct me if I got that wrong.
    I was trying to picture this 'vibration' and wonder if it is connected to the way Gravitational waves work? A stretching and pulling of spacetime somehow inherent in all particles.
  13. Standard member DeepThought
    Losing the Thread
    12 Dec '17 17:21 / 1 edit
    Originally posted by @sonhouse
    I was trying to picture this 'vibration' and wonder if it is connected to the way Gravitational waves work? A stretching and pulling of spacetime somehow inherent in all particles.
    The major difference between neutrinos, which are basically just uncharged electrons, and photons, or Ws, Zs, gluons and gravitions, is that neutrinos are fermions and so only one can have a given set of quantum numbers, You are happy with the idea of an electromagnetic field waving, so why not an electronic field? Basically the only difference is that the occupation number of field quanta is restricted to zero or one for fermions but can be any integer for bosons. What is waving is the field in each case, it's just that the way that the field behaves makes fermions seem more particle like. Basically the "billiard ball" picture of particles is what is at fault. There is a vector (known as a spinor) associated with spin half particles like electrons and neutrinos that fulfils the same role as the vector potential in electromagnetism and it is that that is doing the waving.
  14. Standard member DeepThought
    Losing the Thread
    12 Dec '17 17:36 / 1 edit
    Originally posted by @lemon-lime
    After a bit of reading and contemplation (and a headache) I can now confidently say I have no idea what is waving, or why it's waving.
    (it's waving bye bye to the supernova?)

    I have a different question:

    Is the Magellanic cloud 170,000 light years away now, or was it 170,000 light years away at the time of the supernova?

    The reason I ask is bec ...[text shortened]... te, does this mean light must have traveled more than 170,000 light years before reaching earth?
    The Large Magellanic Cloud is gravitationally coupled to the Milky Way, so it doesn't recede with the expansion of the universe. Rather in the way a fly on the end of a fishing line doesn't recede from the angler with the flow of a river. We see the supernova where it was when the light was emitted. So the LMC will have moved in its orbit since the supernova happened and we see it where it was and not where it is. So the answer to your question depends on details of the orbit of the LMC that I don't know such as the orbital eccentricity (how far from circular the orbit is).

    This is somewhat complicated in the case of more distant supernovae where the galaxy is very distant (and redshifted) as the space its light moves through has expanded during the motion of the light. I'm not sure about this but I'd guess that the figure quoted in those cases is the apparent distance, loosely speaking the total distance the light "thinks" it has travelled. If you dig around in the relevant Wikipedia pages they probably say somewhere.
  15. Standard member sonhouse
    Fast and Curious
    12 Dec '17 17:56
    Originally posted by @deepthought
    The Large Magellanic Cloud is gravitationally coupled to the Milky Way, so it doesn't recede with the expansion of the universe. Rather in the way a fly on the end of a fishing line doesn't recede from the angler with the flow of a river. We see the supernova where it was when the light was emitted. So the LMC will have moved in its orbit since the s ...[text shortened]... t has travelled. If you dig around in the relevant Wikipedia pages they probably say somewhere.
    One thing I wonder about: So the universe as a whole is expanding and that makes light change wavelengths too If I am correct, and the wavelength gets longer. So the energy of that photon, say, is now lower, then how do you reconcile the reduced energy available with the idea of conservation of energy, somehow, I thought the energy content of the universe as a whole was somehow stable, with X amount of actual matter of whatever variety, and the energy in the various fields, EM, gravitational radiation, whatever, all that should add up to about the same value now as it was 10 billion years ago when the uinverse was quite a bit smaller and therefore pound for pound, more energy back then in total than the much larger universe of today. What happens to conservation of energy then?