Gravity:general question.

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Snoopd0ug, Feb 18, 2011.

  1. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    http://en.wikipedia.org/wiki/State_of_matter

    Four is "one of the lies to children" as Stewart and Cohen like to say.
     
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  3. AlexG Like nailing Jello to a tree Valued Senior Member

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    Introduction to the Effective Field Theory Description of Gravity

    Did you read the paper Vern? Because I did, and there is no discussion of photons producing mass. None at all.

    In fact, the ONLY mention of photons in the paper occurs in this line on page 22

    Perhaps you could point out where you see what isn't there?

    Otherwise, I call bullshit.
     
    Last edited: Feb 26, 2011
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  5. KilljoyKlown Whatever Valued Senior Member

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    Maybe they should say only 4 primary states of ordinary matter. But I like your explanation and that was a very informative link, thank you.
     
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  7. prometheus viva voce! Registered Senior Member

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    Your choice of font... :bugeye:

    Photons don't have a mass. Experiments cannot show the mass of the photon is exactly zero because that's the nature of experimental physics, but the conservative upper bound on the mass of the photon is 7 × 10^-17 eV. For comparison the mass of the electron is 510 MeV, or 22 orders of magnitude greater than the highest possible photon mass by experiment.

    Experimentalists will never say the photon is massless, and your link to John Baez page on the subject doesn't suggest the photon has a small mass either.

    General relativity showed that for something to interact with gravity it doesn't need to have a mass, but it does need to have an energy. Remember that in relativity mass is a form of energy, so the most fundamental concept is energy and it's not to big a leap to go from there to "gravity interacts with energy."

    Photons have no mass but they do have an energy given by E = p.
     
  8. prometheus viva voce! Registered Senior Member

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    Force=Mass x Acceleration
     
  9. Vern Registered Senior Member

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    Call it what ever you want. Did you miss the posts that show that photons do gravitate? What are you trying to do?

    Do you still insist that photons do not? What about lensing? What about all the other physics that don't work if photons do not gravitate?

    This from physicsforums.com is the moderator explaining that GR demands it.
     
    Last edited: Feb 26, 2011
  10. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    Aaargh! Kill me now!
    I read as far as "force=Ma..." in NMSquirrel's reply and assumed he'd written "acceleration" (because I knew what I meant when I wrote F=MA).

    And I'm sure Squirrel will say it was just a "brain fart" (i.e. wrong word used rather than a misunderstanding on his part of what the "A" stands for).
     
  11. KilljoyKlown Whatever Valued Senior Member

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    I only use comic sans MS because I find it more readable (easier on the eyes) than most other fonts. However, I don't really have a problem not using it.

    What you said about photons makes a great deal of sense, and I do like that what I believed most of my life to still be true. Can you explain why so many scientists got side tracked on believing photons have mass? Surely they should know the same information on experiments that you do?

    Also, your comments about mass, energy and gravity clarified my thinking on that subject and was very much appreciated.
     
  12. NMSquirrel OCD ADHD THC IMO UR12 Valued Senior Member

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    ok..thats how the A got in there..
    dyw actually i couldn't figure what A stood for so i guessed velocity cause it made sense to me..
     
  13. tashja Registered Senior Member

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    Maybe you are referring to the 'relativistic mass' of a photon. Which used to confuse people into thinking that light had some 'rest mass,' but was in fact the total energy content of a photon. I've read that photons have E=mc^2=0 Joules of rest energy, but I'm not sure how zero 'rest energy' and 'total energy,' which I think is equal to 1, are defined.

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  14. AlexG Like nailing Jello to a tree Valued Senior Member

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    I asked you to source your claim. You linked to a paper which has nothing to do with your claim. You then link to a forum post, as though that were a source. You also said, look in any physics book. You seem unable to provide a source for your statements. BTW, I don't consider your Photonic Theory of Everything web site as a source, although you are skilled at drawing colored pictures.

    You seem to think that if photons are effected by gravity, they must themselves gravitate. Why?

    Actually, never mind. Arguing with a crank is usless, aside from the amusement it provides.
     
  15. NMSquirrel OCD ADHD THC IMO UR12 Valued Senior Member

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    um..
    1, arguing with a crank is useless ONLY if you are looking to change his mind,
    what about all those listening in who have the same questions but do not want to go public with their opinions.

    2, never underestimate the value of a good laugh..
     
  16. KilljoyKlown Whatever Valued Senior Member

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    You may be correct, but if anybody else has a comment about that, I would like to hear it.
     
  17. Vern Registered Senior Member

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    Exactly!
     
  18. Saquist Banned Banned

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    More than likely we're dealing with the acceleration of space time (according to the principle of equivalence.)

    Literally speaking, the closer an object gets to a comparatively larger mass, space/time slows down in it's vicinity. That's what the facts show us. The difference in speeds looks like attraction but it's not, it's velocity Because gravity behaves in a field (not like a electromagnetic form but field as an area of influence) the trajectory of the object changes because the change in field isn't instant or uniform therefore the acceleration on object is on a gradient.

    You bring up an interesting question.

    NOTE:
    Wiki
    Anomalies and discrepancies


    Extra fast stars: Stars in galaxies follow a distribution of velocities where stars on the outskirts are moving faster than they should according to the observed distributions of normal matter. Galaxies within galaxy clusters show a similar pattern. Dark matter, which would interact gravitationally but not electromagnetically, would account for the discrepancy. Various modifications to Newtonian dynamics have also been proposed.

    Pioneer anomaly: The two Pioneer spacecraft seem to be slowing down in a way which has yet to be explained.

    Flyby anomaly:
    Various spacecraft have experienced greater accelerations during slingshot maneuvers than expected.

    Accelerating expansion:
    The metric expansion of space seems to be speeding up. Dark energy has been proposed to explain this. A recent alternative explanation is that the geometry of space is not homogeneous (due to clusters of galaxies) and that when the data are reinterpreted to take this into account, the expansion is not speeding up after all,[21] however this conclusion is disputed.[22]

    Anomalous increase of the astronomical unit: Recent measurements indicate that planetary orbits are widening faster than if this was solely through the sun losing mass by radiating energy.

    Extra energetic photons: Photons travelling through galaxy clusters should gain energy and then lose it again on the way out. The accelerating expansion of the universe should stop the photons returning all the energy, but even taking this into account photons from the cosmic microwave background radiation gain twice as much energy as expected. This may indicate that gravity falls off faster than inverse-squared at certain distance scales

    Dark flow: Surveys of galaxy motions have detected a mystery dark flow towards an unseen mass. Such a large mass is too large to have accumulated since the Big Bang using current models and may indicate that gravity falls off slower than inverse-squared at certain distance scales.[ I believe this is refered to as THE GREAT ATTRACTOR]

    Extra massive hydrogen clouds: The spectral lines of the Lyman-alpha forest suggest that hydrogen clouds are more clumped together at certain scales than expected and, like dark flow, may indicate that gravity falls off slower than inverse-squared at certain distance scales.[23]


    ------------
    So in reference to your inquiry on Spin:
    If acceleration and decleration is an equalization principle to gravity, in other words increasing speed, Then are all these anomalies a factor of rotational motion that we yet don't understand?
     
  19. NMSquirrel OCD ADHD THC IMO UR12 Valued Senior Member

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    its been shown that gravity has an effect on time..

    not sure if i understand all that,

    if you make any money from it, i want some..

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    isn't there data that would say something?

    um..consider;the only actual science i have done on this subject was to go to the library and compile a list of gravity and spin rates for our solar system,then sat down for an hour studying it and realized i do not know the math for it..and gave up..
     
  20. KilljoyKlown Whatever Valued Senior Member

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    I'm interested in this particular observation. I'd like to know what others think about it, and sense no one can really know for sure what might be causing it, I'd like to get your best speculation.

    Let's review what's known:

    1. Many thousands of galaxies moving in a direction not consistent with the expansion of the visible Universe.
    2. Whatever the gravity source is, it's not visible, but it must be very large to cause the movement of so many galaxies.
    3. If enough mass to cause that kind of influence can't be detected it must be beyond the limits of our instrumentation.

    I know many scientists are flat out unwilling to speculate and some of those that do refuse to believe in the possibility of a Behemoth massive black hole. I define behemoth massive black hole as one that has billions of super massive black holes or galaxies in orbit around it. I think all those galaxies in the dark flow are actually now in the orbit of a behemoth which itself is outside our visible Universe. If anybody has a better explanation I really want to hear about it.
     
  21. prometheus viva voce! Registered Senior Member

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    umm... as far as I'm aware, scientists in general believe photons are massless. In fact, I don't think I've ever met anyone in the physics community that thinks the photon is anything other than massless.

    The masslessness of the photon is a pretty robust result - from experiments we know that electric charge is conserved. One can show that for every conserved quantity (like charge) there is a corresponding symmetry of the theory, which in the case of electric charge is called gauge invariance (I can explain what that is if you really want). The fact that electromagnetism conserves charge means that any theory you write for electromagnetism must be gauge invariant, and it's impossible to have a mass for the photon without breaking gauge invariance. This means the mass of the photon must be zero.

    It could also be that you're thinking of electroweak theory. It's possible to show that at some very high energy the electromagnetic force and the weak nuclear force become the same single force. The gauge boson (read: force carrying particle) for EM is the photon (massless), while for the weak force there are 3 gauge bosons (the W+, W- and the Z) which all have some non zero mass. Physically that means EM can act over long ranges but the weak force can only act over small distances (much smaller than the size of a proton for example). At high energies the masses of these weak gauge bosons is reduced and eventually vanishes, meaning we have a single force with only massless gauge bosons.

    No problem.

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  22. D H Some other guy Valued Senior Member

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    Conservation of momentum.

    Vern is right in this case. See http://authors.library.caltech.edu/1544/1/TOLpr31a.pdf.
     
  23. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    I am not disputing the fact that photons "make gravity" but am somewhat troubled by the fact that both my eyes see the same star field.

    If photons have travel to my eyes from very far away and arrive at the same time, why has not their mutual gravitational attraction during their long and essentially parallel journey not made them into discrete (in space) streams? One of which might fall into my right eye, but there not be any “light stream” from that star falling into my left eye as millions photons have coalesced during the long journey into discrete "light lines."
     

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