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Are all Atoms the same size?

  1. Sep 30, 2007 #1
    Is there any evidence or even a theory that all Atoms are the same size?

    I was wondering what affect if the Big Bang or Bangs theory is correct, what difference if any would be found in the first atoms and the last atoms ever made?

    Was it a production line of atoms and would that mould not change over time?

    Could there be bigger Atoms at the furthest edges of what we can see and smaller ones as the universal centre?
  2. jcsd
  3. Sep 30, 2007 #2


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    What do you mean "same size" ?

    We cant even talk about size due to the probabilistic nature of the electrons in the atom.

    The "radius" of an atom is usally defined as the mean value of the radial wave fucntion for the higest electron orbital.

    And the theory for this is at very basic non relativistic quantum mechanics, you solve the Shrödinger equation for a spherical coloumb potential.

    The Universe dont have a center...

    What sources have you considered regaring the first 300 000 years of Universe?

    The first atoms where formed when universe was cold enough so that recombination of electrons and nucleis could occur (i.e. the opposite of ionization) in a pace that made the population of atoms grow of course... Just apply Saha's equation =P
  4. Sep 30, 2007 #3


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    See this : https://www.physicsforums.com/showthread.php?t=185953

    PS : If you are unaware that different atoms have different sizes, you need to learn much, much more physics before you can meaningfully speculate about things like cosmogenesis. Be prepared to take a lot of time doing this.
    Last edited: Sep 30, 2007
  5. Oct 1, 2007 #4
    Did you, maybe, intend to ask if an hydrogen atom's size, for example, has always been the same during universe's expansion?
  6. Oct 1, 2007 #5


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    At the age of the universe when atoms where formed, many things are known. We know extremly much about how the elements where formed in nucleogenesis to astonishing accuracy. The atoms where formed long time after the nucleis, and we know much more about atom - forming scince it is much simpler.

    But atoms dont survive long, they get caught inside gas clouds and eventually are beeing processed in stars, so atoms are very fragile. Only very small part has/could have been survivning, without any star processing.

    And by asking if the size of an hydrogen atom was different when atoms was forming, it is the same thing as ask if the electromagnetic force was weaker then. By the time atoms where formed; elektro-weak separation was made 100 000 years before. So the answer should be no, they were not different size.

    And I repet again, Universe has no center or edge.
  7. Oct 1, 2007 #6
    Why?-Is it because the Universe is always expanding?
  8. Oct 1, 2007 #7


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    Big bang what not an explosion in space and time..
    Ask that question in the subforum of Astrophysics. They can give you a structured answer, and there are probably old threads there you can read. I have much home work now :)
  9. Oct 7, 2007 #8
    This isnt really true. I know what your trying to say, but the way you say it is misleading. Any model of the universe has a center and an edge. Its just that in all of the ones possible due to experiments the center is unreachable, and we are always on the edge.
  10. Oct 7, 2007 #9


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    Or vice versa; the obeserver is always in the center.

    Another model is that the space of the universe is like the surface of a sphere that is growing. But the Universe is 3D, and the model show how it would look like if space was 2D, we need a 4D sphere to show how it would look like in reality. In this model, there is no preferred center, and if you started travel in one direction, eventually you would get to the point where you started from.
  11. Oct 8, 2007 #10
    that was actually the main model I was referring to. There are a few models that involve us expanding in the 4th or 5th dimension tho. They all share the fact that anyone in the universe thinks theyre in the center. However the true center lies at t=0 which is unreachable.
  12. Oct 8, 2007 #11
    Is it possible that space would fold in on itself and so not have a centre but something close to the edge but the person in that space would not be able to tell where he or she would be so there is no centre or the universe has a hole in it?

    I'm thinking about the way a doughnut is shaped, like fermat's last theorem and Wiles' proof, what I'm I saying, lol
  13. Oct 8, 2007 #12


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    This thread is going in all directions. It is not even anything resembling a "quantum physics" question. Please ask a specific question in the appropriate forum.

    As a reminder, in case you haven't read it yet, please pay attention to our policy on speculative posts as described in the PF Guidelines.

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