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B What caused the uneven distribution of mass/energy?

  1. Jul 23, 2016 #1
    it's stated that general theory of relativity describes gravity a consequence of the curvature of spacetime caused by the uneven distribution of mass/energy...what caused the uneven distribution of mass/energy?

    And if the universe is said to be expanding what is the universe expanding to, and how does the space that allows the expansion of the universe look like, is this space infinit or does it have a size? im quite confused with many things such as the expansion of the universe...amongst other things. If the universe is expanding shouldn't it collide against something? it's like inflating a baloon in open space verses inflating it in a box eventually it runs out of space...so shouldn't there be some kind of space out there in order for a thing to expand?
     
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  3. Jul 23, 2016 #2

    mfb

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    Initually: quantum fluctuations. Afterwards: gravity enhanced them.

    It is not expanding into anything, there is no "outside". You can find many good explanations via the search function, it is a very common misconception.

    It is unknown if the universe is finite or not.
     
  4. Jul 23, 2016 #3

    Fervent Freyja

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    These videos address your questions:

     
  5. Jul 23, 2016 #4
    i see but why are there teachers and videos that say that the universe is expanding? why is there so much contradiction and differing information about the state of the univer?
     
  6. Jul 23, 2016 #5
    The universe is expanding, that is not in question.
    However there are many unknowns, for instance in regard to what if anything existed prior to the big bang, why is there matter but not in any significant amount of anti matter, is it finite or infinite, what explains dark matter and dark energy? ...
    There are theories about these kind of things, but expansion is not theoretical, that is something which is measurable
     
  7. Jul 23, 2016 #6
    WELL HOW LONG HAS THE UNIVERSE BEEN EXPANDING AND WHY IS EARTH STILL IN THE SAME LOCATION AND NOT FURTHER FROM THE SUN IF EXPANSION ACTUALLY TEARS THINGS APART?
     
  8. Jul 23, 2016 #7

    mfb

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    It is expanding. The information is consistent, it just can look counterintuitive because our intuition is built on things on Earth here.

    The universe has been expanding since it started more than 13 billion years ago, but gravitationally bound systems like the solar system or our galaxy do not expand.

    Please do not write in ALL CAPS, this is rude and also against the forum rules.
     
  9. Jul 23, 2016 #8
    Gravitationaly bound systems such as the solar system are not expanding, galaxies are not expanding, gravity keeps them together.
    It is the (almost) completely empty space between the systems which is expanding.
     
  10. Jul 23, 2016 #9

    phinds

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    I got as far in the second one as the pop-science false statement that the universe started out as a single point of infinite density and decided that's not a good reference. Who knows what else he gets wrong.
     
  11. Jul 23, 2016 #10
    Ok i got it...has it been measured how much empty space there is? or is the answer the same it's infinite? and why is there empty space? was the universe empty space before and how can emptyness create something?
     
  12. Jul 23, 2016 #11
    Though empty space in the universe is expanding it remains matter that is expanding....Wouldn't there be a need to measure if there is space outside empty space in order for it to have room to expand? Have scientists been able to find out what is beyond the observable universe and how big empty space is?
     
  13. Jul 23, 2016 #12

    mfb

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    The universe is not completely empty anywhere. The total volume of the observable universe (=the region where we can receive radiation from) is finite and well-known.
    Note: this is space in our universe. Again: There is no such thing as "outside".
    We don't know if "before the big bang" makes sense at all. If there was nothing before, there is also no physics that could be violated by a big bang.
     
  14. Jul 23, 2016 #13

    ChrisVer

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    the universe is not a balloon as the xyz axis is not a box
     
  15. Jul 26, 2016 #14

    rede96

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    Strictly speaking we don't know there is no such thing as "outside", as we don't know if the universe is finite or infinite.

    It doesn't, well at least not in the sense of creating the universe. So something must have been there in the first place.

    But if you meant where did matter come from, there is something called inflation theory. In very simple terms, it states there was an initial energy field that expanded very quickly at an exponential rate, and that field decayed into particles of matter. This was the beginning of the universe as we know it according to the theory and is what a lot of people refer to as the 'big' bang'.

    We know the universe is 13.8 billion years old, or the light we see has been travelling for 13.8 billions years or less. This is the observable universe. But the size of the observable universe is around 46 billion light years, due to expansion. Of course as we can't see anything past the observable universe, then there is no way for anyone to know anything beyond that.
     
  16. Jul 26, 2016 #15

    Bandersnatch

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    Since you're using GR to describe the universe (and in particular to get those number you cited later on), you should stick to what GR says about it, i.e., that there is no outside or an edge, and that finiteness does not imply an outside but a closed geometry.

    The way to know something beyond that is the same as the way to know there's more Earth beyond the horizon without ever going there - by relying on established physical theories and measuring curvature.
     
  17. Jul 26, 2016 #16

    rede96

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    I'm certainly not arguing against any of the predictions of GR, I'm simply saying, in the context of the OP's question, there is no way of knowing if there is something that exists beyond our universe.

    Sure, no issue there. But what do the physical theories predict about the size and shape of the universe beyond that horizon? The don't tell us a definitive size to universe which is what the OP was asking.
     
  18. Jul 26, 2016 #17

    mfb

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    Be careful with the difference between "our universe" (of unknown size, could be infinite), "observable universe" (=we can receive light from it) and "particle horizon" (=the concept of an observable universe extrapolated back to the big bang, a bit larger than the observable universe). We know the universe is very uniform up to the particle horizon, and this uniformity also suggests that the universe doesn't start looking completely different a bit further away. If you are at sea and you can see a flat featureless surface of water within 5 km around you, you don't expect the world to end after 5.1 km.

    All that has nothing to do with the initial "outside" discussion because it is all inside the universe.
     
  19. Jul 27, 2016 #18

    ChrisVer

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    That is called inflation theory, and if you wanted to be strict it's not verified [at least not like Big Bang is, which actually "starts" a little after inflation]...
     
  20. Jul 28, 2016 #19

    Drakkith

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    To clarify ChrisVer's post, the predictions of the standard Big Bang Theory start after inflation. The "big bang itself", if you're referring to some kind of cosmological creation event, obviously occurs before inflation.
     
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