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Universe from nothing, again...

  1. May 13, 2015 #1
    Dear PF Forum,
    Sorry to ask this question again after so many threads here and in google that explain nothing!
    And many controversies, too.

    1. Does the universe really comes from nothing? Yes or No?


    2. if "YES" then...
    What is this? This is 100% not 0%. Is this free lunch?

    Other question, while I was still reading.
    That CERN article, as many you already know, is about 1 second (more likely less) after big bang.
    1 in a billion!. So..., 999,999,999 other particles * 2 for anti matter * c2 are roaming around the universe as energy, is that right?
    3. Where are the energy?
    Does it present as 2.7K warming the universe?
    Or 2.7K comes ONLY from sum(volume of each star * each temperature)/volume of the universe?
    Or 2.7K come from the energy from 999,999,999 particles and stars?
    But intergalactic space has 1 million K temperature??
    Hardly 2.7K?

    Thanks for any answer.
    Last edited: May 13, 2015
  2. jcsd
  3. May 13, 2015 #2


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    Philosophy, or at least not decidable with current observations and theories.

    The universe evolved significantly since that time, but if you count the number of photons in the cosmic microwave background (which was emitted much later), you will still get a number larger than the number of other particles in the universe.
    The amount of light from stars is very small compared to that, unless you happen to live very close to one (as we do).
  4. May 13, 2015 #3
    Thanks mfb for your answer, again. I remember you replied to my question, "Universe Frame of reference" such a good explanation.
    Perhaps I should calculate 700 000 km3 (sun radius) * 4/3 * π * 6000K * number of stars / universe volume before I ask.
    Those number,
    Sun radius: perhaps not the medium radius of all stars in the universe
    6000K: perhaps offs by some considerable degree, as I only take sun temperature as an example.


  5. May 13, 2015 #4


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    Just one comment regarding your point 3 : 2.7K is the temperarure of the CMB, which is completely distinct from the radiation emitted by stars (much hotter and very far from equilibrium with the CMB yet, thankfully for us). Also I am not sure about the "warming" part since that CMB radiation is cooling down gradually since its emission.
    The high temperarure in outer space is also (obviously ! )not in equilibrium with the CMB, but as I understand it, it represents the temperature of a very dilute gas and doesn't contribute much to the total energy density.
  6. May 13, 2015 #5


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    Yes and no. The other particles annihilated with one another, mostly becoming electromagnetic radiation. Essentially, when the temperature got low enough, the particles would annihilate faster than they were produced. This caused the energy of the annihilating particles to be dumped into other relativistic fields, which in turn caused the temperature to stabilize for a time before it started dropping again once all of the matter/anti-matter pairs had annihilated.

    Redshifted away, mostly. The expansion of the universe causes radiation to lose energy over time.

    If you have a box that is expanding with the universe, and that box is filled with radiation of a certain temperature, and that box expands by a factor of two, then each photon in the box has its wavelength doubled, which cuts the energy in the box in half and the temperature to also drop in half.

    But if you have the same box with normal matter in it, the energy of the normal matter stays constant over time.

    So while we started with normal matter only being that one part in a billion of leftover imbalance, the matter has stuck around while the radiation has lost its energy with the expansion.

    Yes. That is the remainder of the redshifted radiation energy.
  7. May 14, 2015 #6
    Dear PF Forum,

    Reading further, I find this.
    1. Is that true? Or it is limited to some region?
    2. Isn't it 2.7K?

    And some links suggest million of Kelvin tempererature. It's a rather overwhelming for me.
    Are they trying to say, that between, let's say, the outer star of Wilky Way to Andromeda (and other intergalactic space), for 2 million ly, in that vastness of space, the temperature is million of Kelvin?

    3. If that's true. Is that condition only applied to intergalactic space? What about interstellar medium, is it that hot? Or interplanetary, say within our solar system. But I 'know' that inside solar system, it can't get that hot, or we wouldn't have comets, or ISS for that matter.
    So, if it's true. What's the difference between intergalactic and interstellar medium?

    Thanks for anyone reading this.

  8. May 14, 2015 #7


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    It is true for many regions.
    Some gas is that cold, dust is at this temperature, but gas can be much hotter.

    Which just means there are few isolated particles flying around at high speed. It's not like you would burn there - the gas is way too thin to have a notable effect on larger objects. Same for the interstellar and interplanetary medium.
  9. May 14, 2015 #8


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    It might help to read up on Reionization, which is the time when the intergalactic medium became hot:
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