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The Big Bang

  1. May 7, 2012 #1
    I am not sure if this belongs in General Relativity or Quantum Theory or just General -but here goes.

    First , I have to say that I do assume Space-Time to be quantized (since anything else seems too difficult!) and this is my question.

    I have often read that physicists have peered back in time to within a few million(?) light years of the BB and that experiments have been done that recreate conditions within a few milliseconds (?-again) of the Big Bang.

    If , as I hypothesize, space-time is quantized could these milliseconds correspond to an actual finite number of quantized Space-Time events in such a way that , as we approach the Big Bang (in simulation) we would be able to , in theory, knock off these events one by one until we got to ,say, one space-time event that had been the first ST event immediately after (and prior to -if we are talking about a Big Crunch) the Big Bang?

    A separate question I have ,if anyone has patience to explain is ,if gravity is accepted to change the fabric of Space-Time why should it be that the other Forces that act on matter don't ? (I am not sure what all the Forces are but I think some are weak and strong nuclear Forces)
    Excuse my ignorance if that is an obvious question!
     
  2. jcsd
  3. May 7, 2012 #2

    phinds

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    1) Observations of the CMB are 400,000yrs after the singularity, not millions of years
    2) Recreations of early events are now done to, I believe it is, a tiny fraction of a microsecond, not milliseconds.
    3) There is no evidence one way or the other as to the quantization of space-time and this is a topic of considerable interest to scientists.
    4) IF space-time is quantized, the level of quantization will almost certainly (I think it IS certainly) be less than one Plank time / the Plank distance, not WAAAYYYY up into the ranges that we are currently able to measure.
     
    Last edited: May 7, 2012
  4. May 7, 2012 #3
     
    Last edited: May 7, 2012
  5. May 7, 2012 #4
    Can you please elaborate on your question in relation to these epochs for the purpose of clarification?

    Excerpt Synopsis:

    Chronology of the universe

    Planck epoch
    Up to 10–43 seconds after the Big Bang

    Grand unification epoch
    Between 10–43 seconds and 10–36 seconds after the Big Bang[3]

    Electroweak epoch
    Between 10–36 seconds (or the end of inflation) and 10–12 seconds after the Big Bang[3]

    Inflationary epoch
    Unknown duration, ending 10–32(?) seconds after the Big Bang

    Quark epoch
    Between 10–12 seconds and 10–6 seconds after the Big Bang

    Hadron epoch
    Between 10–6 seconds and 1 second after the Big Bang

    Lepton epoch
    Between 1 second and 10 seconds after the Big Bang

    Photon epoch
    Between 10 seconds and 380,000 years after the Big Bang

    Nucleosynthesis
    Between 3 minutes and 20 minutes after the Big Bang[5]

    Matter domination
    70,000 years after the Big Bang

    Recombination
    377,000 years after the Big Bang

    Dark ages

    Structure formation

    Reionization
    150 million to 1 billion years after the Big Bang
    The first stars and quasars form from gravitational collapse

    http://en.wikipedia.org/wiki/Chronology_of_the_universe
     
  6. May 8, 2012 #5

    Chronos

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    What is unclear is when gravity broke free from the other forces of nature. We have a pretty good idea when the nuclear strong force and electroweak forces emerged, but, no real clue about gravity. This vitally important in constructing a sensible model of the very, very early universe. Assuming inflation is the correct model, it is not unreasonable to suspect gravity did not emerge until after the initial inflationary epoch [around E-35 seconds].
     
    Last edited: May 8, 2012
  7. May 8, 2012 #6
    that is very interesting but I am sorry I couldn't begin to clarify that point as my level of understanding corresponds more to plankton than Planck!

    But I am very grateful for all your tolerant replies.

    By the way , if Space-Time as modelled quantatively as against Classically can be viewed as equivalent by some is this a possible pathway to unify GR and Quantum Mechanics?
    Might this be because the quanta can exist at ever decreasing levels of scale? (Like Russian dolls)
    (again please take into account my "level of knowledge")
     
  8. May 10, 2012 #7
    Well ,conversely, do we know for sure that the other 3 fundamental forces -strong,weak,electromagnetic- do not affect the fabric of Space-Time?

    Maybe the effect is too small to discern?
     
  9. May 10, 2012 #8

    phinds

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    I'd don't know that we DON'T but we certainly don't have any theories or observations, as far as I know, that would suggest that they DO.
     
  10. May 10, 2012 #9
    any reason to suppose they might?(or that it would be important if they did?)
     
  11. May 10, 2012 #10

    phinds

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    Well it would be important if they DID since that would be another clue as to how the universe works, but if there WERE any evidence or reason to suppose they might, I'm sure all kinds of theories would already have been proposed for why/how.
     
  12. May 12, 2012 #11
    To your second question, I believe the most commonly accepted theory is that gravity is caused by massive objects warping spacetime, so it is the massive objects that distort spacetime, not gravity. So if you put a heavy ball on some stretched out fabric, it makes an indention. Anything close to that indention will be drawn towards it. This is kind of paradoxical, because in a real situation that we could use as an analogy, the reason things near the indention will be drawn in is because gravity exists, but this is just a 3D picture to help understand a 4D phenomenon, and will thus have its limits.
     
  13. May 12, 2012 #12
    Thanks- that was a misapprehension on my part.

    So at a subatomic level the nuclear forces play the same role as gravity does in the larger than atomic realms and the reactions that are mediated by these forces have also to be calculated having regard to the local distortions in Space-Time?
     
  14. May 13, 2012 #13
    definitely not..for example, positive charges attract and repel each other..gravity attracts.,,,
    also the strong,weak, and electromagnetic force characteristics differ among each other and also differ from gravity. For example, the weak force governs radioactive decay. Gravity has virtually nothing to do with radioactive decay.


    no. gravitational effects are virtually insignificant with regard to nuclear forces. But if you get into neutron stars and black holes, then gravitational effects become dominant and can overpower nuclear forces with sufficient mass density..
     
  15. May 13, 2012 #14
    I appreciate your patience with my posts.

    I didn't mean (though I may have mistakenly implied) that the non-gravity forces acted like gravity but that in their own little domain and level of Space-Time
    (where they become the dominant force) they move objects with mass along lines of curvature in Space-Time in just the same way that Gravity does when it is the dominant force.

    Also to your reply to the second part of my last post I understood (from Gibby_Canes's post) that it is mass and not Gravity that causes distortions in the fabric of Space-Time.So if the fabric of Space-Time is distorted within the atomic nucleus wouldn't the 3 (non-Gravitational) forces that dominate there also be subject to the local distortions of Space-Time,say between the proton and the neutron or between the electron and the neutron?

    Maybe my point was so obvious that it seemed like I must have been trying to say something else.
     
  16. May 13, 2012 #15
    this seems like a contradictory statement. I don't know what you mean. The electromagnetic force, for example, does not move things according to gravitational spacetime curvature. For example, the electromagnetic force is billions of time stronger than gravity. The energy of an electromagnetic force does have some ancillary gravitational effects but in most particle physics it is so small it is ignored.


    Gravity IS spacetime curvature....Einstein says they are the same thing....and the best textbooks and experts still agree.

    mass is just one thing that causes gravity...thats all Newton included. The source of gravity is the Einstein 'stress energy momentum tensor'...which reflects the effects of mass, energy, pressure, etc....

    not really, The non gravitational forces are not affected...they continue to work the same way, but distortions in space time does cause the particles to behave differently...due to gravitational effects....for example, in a neutron star, gravity forces electrons into the nucleus where protons and electrons become neutrons [hence the name 'neutron star']. But if the gravity were to disappear, the non gravitational forces would again resume their normal interactions.
     
  17. May 13, 2012 #16
    Ok now I am getting further out of my depth but hopefully can summon up an intelligible question.
    When the 3 non-gravitational forces cause interreactions between particles do these particles need to have mass?
    Is that a case by case scenario?
    In cases where the particles do have mass (and are affected by one of those non-gravitational forces) does the mass affect the strength of the attraction or repulsion?
     
  18. May 13, 2012 #17
    In some cases, yes. I don't know if massless particles can interact weakly, but I do know that they can interact strongly (in the case of Gluons.) I'm pretty sure that due to the nature of the Electromagnetic force, massless particles can't interact electromagnetically(?)
     
  19. May 13, 2012 #18

    Drakkith

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    I don't believe they NEED to have mass, but it is a fact that they all DO have mass. (Other than the photon) The amount of mass each particle has does not change the strength of the interactions. For example, a Proton and an Electron both feel the same amount of force from the Electromagnetic force, yet the Proton is thousands of times more massive than the electron. This results in an electron being MUCH easier to accelerate than the proton.
     
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