Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The big bang ?

  1. Jan 30, 2006 #1
    according to the BB theory, in the first millionth of a second the universe expanded at a rate many times greater than the speed of light, apparently it was able to do this because of the lack of phsical laws, if this is true how do we know that a millionth of a second was in fact a millionth of a second?
  2. jcsd
  3. Jan 30, 2006 #2
    The absence of physical laws before the Big Bang is a philisophical issue, and I have doubts on whether it can be addressed scientifically.

    How do I know that 2 seconds is 2 seconds? They're equivalent by definition. However, according to Relativity, time is not invariable (neither is the "second"). So the "second" depends on which "clock" we are measuring. To agree on time, we must define what the standard clock will be.
  4. Jan 31, 2006 #3
    i think what alkammy is trying to say is how do we know that it was a millionth of a second? it could be more...right?
  5. Jan 31, 2006 #4
    Oh great just the topic I wanted to start :). What my question was (it is closely related to this) is this - How do we explain the laws of the universe. What I mean is, if the universe first started with the big bang ... were all the laws of the universe already made in the big bang or were they developing at the same time as the universe was expanding? For example how hydrogen condensed into helium. Was that physical law already in place or did it become a law while the actual event took place. If so when did they stop to come into being? And so for the present: Is there a finite predetermined number of physical laws in the universe already and we just didn't discover them all yet or is the universe still changing and new laws come into being? Any theories on this?
  6. Jan 31, 2006 #5
    Can you supply a link on this?
  7. Jan 31, 2006 #6


    User Avatar
    Gold Member

    There are no laws governing how fast space itself can expand. It is not limited by relativity. The only thing relativity limits is how fast things can move through space. There could be parts of our universe today expanding faster than c. (Of course, they are forever cut off from us becasue the light from them will never reach us).
  8. Jan 31, 2006 #7


    User Avatar
    Gold Member

    In the first fractions of seconds, there were fields (such as the Higgs field) that were fluctuating wildly (think of it as Heisenberg Uncertainly - writ large). Once the universe had expanded past a certain point, the field "froze" at a specific level. It could have frozen at any level. The thing is, it did not freeze at zero, as it would have if the expansion had been slower.

    Once this value was fixed, it determined how all or most of the properties of universe would manifest later on.

    For example, if the value had frozen at any other level, matter might have no mass (it is speculated that the very property of mass itself is merely "drag" through this Higgs field), protons might not get glued to neutrons, electrons might not orbit nuclei, gravity might not work.

    This why one of the arguments of the Anthropic Principle (I don't remember if it's the 'weak' one or the 'strong' one): our universe is exquisitely tuned. Any other values for some of the fundamental constants and our universe wouldn't even have atoms - let alone life.
  9. Jan 31, 2006 #8
    Hmm interesting. Thanks Dave :)
  10. Jan 31, 2006 #9
    Do we have a measure for the initial outward force of the blast? Is it the Hubble rate?

    Basically, when space itself was expanding outward after the Big Bang, at what rate was it going?

    Is that rate changing as a result of gravity?
  11. Jan 31, 2006 #10
    planck time ATB

    in the 10E-35 seconds ATB , the strong, the weak and the electromagnetic forces were all one big united force so, that confirm that the physics laws were different.

    anyway if we see this definition of time :

    The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.

    we must tought about having a "real time clock" on our speed of light traveling.:surprised
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook