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Physical simetries

  1. Oct 9, 2005 #1
    Can somedody explain me in a relatively plain languaje what are physical simetries
  2. jcsd
  3. Oct 9, 2005 #2
    in what sense please? Here are some simple degrees of rotational and mirror symmetries for solid geometric objects:

    A sphere is symmetrical in all rotations and mirror-images. It looks the same in any aspect.
    A cylinder is symmetrical when rotated about its central axis, and is mirrror-symmetrical when its central axis is flipped 180 degrees.
    A cone is symmetrical when rotated about its central axis, but does not possess mirror symmetry when that axis is flipped 180 degrees - the apex is now on the "wrong" end.

    If you're looking for explanations of symmetries that ought to exist for our Universe to have been able to arise from "nothing", that's a huge project.
    Last edited by a moderator: Oct 9, 2005
  4. Oct 9, 2005 #3
    When I refer to physical simetries I'm talking about all that stuff saying that at some moment in the past (in fact a little fraction of a second after the big explosion) the 4 forces (electromagnetism, the weak and strong and gravity) were the same. The particles involving the forces were the same and the fields too. Sorry if I'm not too rigurous in my exposition but the main problem is that I do not understand it
  5. Oct 9, 2005 #4
    Nobody understands it. That symmetry (believed to exist by BB theorists before one Planck time) represents an unknown singularity. In this cosmology, all symmetries were spontaneously broken in about a billionth of a second.
  6. Oct 9, 2005 #5


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    The answer to include all forces will require an understanding, or reasonable theory of the "Grand Unified Theory" (GUT), but none are workable as of this date last I heard.

    where part states that:
    (My Italics)

    Also see the whole page at: http://en.wikipedia.org/wiki/Grand_unified_theory where it is mentioned several times.
  7. Oct 10, 2005 #6
    thanks, I will take a look at this page and try to understand something
  8. Oct 10, 2005 #7
    But how can a particle turn to another. I can't conceive a Z particle turning into an electron or a photon. they are just not the same and I suposed that they have always benn different
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