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Before the BB

  1. Jun 1, 2012 #1
    This is from Michio Kaku's book Beyond Einstein

    It seems to me that some physicists believe that the universe started 13.75 billion years ago but the time between 10^-43 seconds and 10^-36 seconds was not the Big Bang. They associate inflation, 10^-36 through 10^-34 as the real Big Bang and the time between 10^-43 seconds and 10^-36 seconds as some sort of obscure unknown period.

    I can't tell if Kaku here is talking about some state that existed before the beginning of time or if he is talking about the period between 10^-43 seconds and 10^-36 seconds
     
  2. jcsd
  3. Jun 1, 2012 #2
    Yup.

    You can define things in other terms, but I much prefer "defining" what happens after 10^-36 as the big bang. Personally I define the "big bang" as events between inflation and the emission of the CMB which happened at t=200,000 years.

    The reason that I prefer this definition is that can observe what happened between inflation and the CMB emission, so obviously the "big bang" happened because we see it. What happened before 10^-36 is totally guesswork, and it might not have even been a "bang."

    The idea with superstrings is that when you have a 4-dimensional piece "peel off" that "starts time." Before that happens, there is no such thing as before.
     
  4. Jun 1, 2012 #3
    First off Im sorry to say Kaku seems to have fallen off the rails in the last few years and I would not reccomend him as a reliable source of information.
    I think its important to seperate superstrings makes x prediction and people have used strings to build models of pre bgi bang universe. There are different ideas coming out of string theory re early universe/pre big bang cosmology.
    See :
    http://wwwphy.princeton.edu/~steinh/npr/
    or here:
    http://www.cyberastronomo.org/LinkClick.aspx?fileticket=dvNBo3WeWIM=&tabid=78&mid=432
    So I dont think there is a consensus amongst those working in string theory on the nature of the pre big bang universe.
    As to non string comsologists i would say there is a consesnsus the universe evolved from a hot dense state 13.7 bio year ago. But whether this was really the beginning or not is still an open question and is unlikely to be resolved until we verify a quantum theory of gravity which is someway off yet. There are other aproaches , google "loop quanutm comsology" or "CCC "for examples.
    Inflation I would say has passed all tests to date but there will probably still be doubters until we can detect a primordial grvaitational wave spectrum, read here:
    http://www.nature.com/news/2009/090415/full/458820a.html
    As I understand it some theorists say that what we think of as the big bang is just the end of inflation but again thats justone of many ideas.
    Bottom line : after the inflationary period there is broad agreement,
    inflation itself is mostly agreed upon but theres still room to doubt and certainly there are alternatives.
    Before the inflationary epoch is more specualtive still and there is a very clear absence of a consensus.
     
  5. Jun 1, 2012 #4
    There is a strong consensus among every astrophysicist that isn't a crackpot that the universe evolved from a hot dense state 13.7 billion years ago. You can see the "bang" and it was "big."

    That's why I prefer to reserve the term "big bang" for the thing that we agree that happened rather than what happened before that, in which everyone is just guessing.

    The further you go back in time, the more guess work there is. For inflation, it's a convenient explanation that solves a lot of problems. But it's really vague and murky.

    There's a reason for that. As the universe cools it becomes harder to make up stuff. If I have something at 10^18 kelvin, all sorts of weird stuff could happen. If I have something at 3000 K, it becomes harder to "make up excuses."

    After 1 second, it becomes hard to make up new physics since the temperatures and conditions are those that we can simulate on earth.

    And it's vague and hand-wavy. A lot of problems go away if you make the universe expand really fast. Now as for what could have made the universe expand quickly, people haven't quite figured that out. One thing that's clear is that the general mechanism works well, but the original idea for what caused the inflation (i.e. symmetry breaking due to grand unified theories) won't.

    There are also some severe problems with most string theory scenarios. The big one is that you calculate what a universe that "peels off" would like like, and you find that the basic constants (i.e. fine structure constant, speed of light, dimensionality) are random, and the odds are overwhelming that you'll end up with a universe that won't support life.
     
  6. Jun 1, 2012 #5
    I was wondering if you could elaborate on that.
     
  7. Jun 1, 2012 #6

    phinds

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    Kaku was an excellent and innovative physicist in his day but today he is a popularizer of the worst sort. Do a forum search. There are several threads here where he is slammed for his presenting REALLY far out ideas as though they were mainstream.
     
  8. Jun 1, 2012 #7
  9. Jun 1, 2012 #8

    phinds

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  10. Jun 1, 2012 #9

    Chronos

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    Inflation is an effective theory that lacks any real theoretical basis. It fits observational data well and resolves some important issues - like the flatness problem - which makes it popular with cosmologists. As already noted, we do not have a working theory, or even a good guess, of what happened until after inflation. Dr. Kaku's stringy idea would be disputed in a court of law for assuming facts not in evidence. The popularization thing is fine, but, he could do a better job clarifying what is consensus vs speculation.
     
  11. Jun 1, 2012 #10

    phinds

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    Have you ever LISTENED to him? He doesn't do a poor job of separating consensus from speculation ... quite the contrary, he doesn't do it AT ALL --- he overtly promotes speculative ideas as though they were mainstream consensus.
     
  12. Jun 1, 2012 #11
    Krauss is doing the same thing, and I've seen the same thing with Stephen Hawking.

    I wonder what this happens.

    One guess is that a lot of being a good scientist is to say "I don't know" and there may be social pressures for a popularizer to say "I don't know."
     
  13. Jun 1, 2012 #12
    do you mean for a popularizer not to say "I don't know
     
  14. Jun 2, 2012 #13
    Too bad Kaku has become so full of "kaka".
    His book "Hyperspace - Into the 10th Dimension" is the one book that has had the greatest impact on me as a layman interested in cosmology.
     
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