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

Creation of space what exactly does this mean

  1. Oct 31, 2011 #1
    "creation of space" what exactly does this mean

    dear all,

    I must admit, the wording "space is created" sounds to me rather unscientific (forgive me for being provocative). I know that, in general relativity, there are (more or less arbitrary) reference frames and distances within these reference frames. In terms of reference frames, distances and geometry: what does "creation of space" mean? Does it mean that a new reference frame is created? That wouldn't make much sense to me. Is it a synonym for "expansion", i.e. the fact that distances between stationary observes increase? In that case, I don't understand why people say that during the big bang, space was created alongside matter. This would imply that space was created only in the very beginning, while expansion still takes place...

    can you help me?

    -matthias
     
  2. jcsd
  3. Oct 31, 2011 #2

    marcus

    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Re: "creation of space" what exactly does this mean

    Here is one way to think:
    there is no substance called "space"
    instead there are distances that comprise geometry.
    these distances increase according to a certain pattern
    so there is no substance being created

    nothing moves
    geometry simply evolves according to a law discovered in 1915 called the GR field equation.
     
    Last edited: Oct 31, 2011
  4. Oct 31, 2011 #3
    Re: "creation of space" what exactly does this mean

    thanks marcus, I am ready to agree with you. But what exactly do you think of the wording "creation of space". Does it do justice to what you just wrote?
     
  5. Oct 31, 2011 #4

    marcus

    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Re: "creation of space" what exactly does this mean

    I think it is a not so good translation into English from the math model.

    The truth is in the math model. Any translation of anything in another language is just an approximation. Some translations are closer than others.

    Since you ask, I think "creating space" is a not so good translation of the pattern of increasing distances.

    It is not a stuff that anyone makes, so the words have a slightly misleading connotation and give a slightly wrong idea to the reader.
     
    Last edited: Oct 31, 2011
  6. Nov 1, 2011 #5
    Re: "creation of space" what exactly does this mean

    As this boffin understands it, it's not like the expanding distance between, say, two billiard balls. That's the way the average person seems to understand it. But there's a little more to it with "expansion".

    If you put your two billiard balls a light year apart, then it would take a year for light to travel between the two (simplistically). But then you find out that those two billiard balls are separating at faster than light speed because space itself is expanding. Confusing huh? Had me going for a while there too.

    But space (out there in the u) isn't just space. Dark matter and dark energy are hiding out in that void, driving this "expansion". Through some cosmic math that I don't quite follow, the "space" between stars is having extra space added, over and above any actual movement of the stars. It's like the billiard balls are separating under their own movement (at slower than light speed), but the billiard table itself is growing bigger, causing them to separate faster than they are under their own steam. Somehow we still get light from them because of our position as observer, which I haven't quite understood.

    If I had my druthers, I would have become a mathematician when I was younger.
     
  7. Nov 1, 2011 #6

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    Re: "creation of space" what exactly does this mean

    'Space' has no objective existence in science as we know it, it is merely the emptiness between particles in a FLRW universe.
     
  8. Nov 1, 2011 #7

    phinds

    User Avatar
    Gold Member
    2016 Award

    Re: "creation of space" what exactly does this mean

    If I understand it correctly, dark matter has no relevance at all in the expansion. The expansion is attributed entirely to (1) a small amount of non-accelerating distance change that is left over from the earliest days of the universe and (2) a large and accelerating distance change due to whatever it is that we call dark energy.

    Before dark energy was discovered, the belief was that the distance change due to (1) would decrease and eventually reverse due to gravity. In fact, as I recall the belief was that the reversal had already started. When it was found that the situation was quite different, with distance changes accelerating, this was attributed to "dark matter" which is a technical term meaning "hey, we have NO idea what's going on but we've got to call it something".
     
  9. Nov 1, 2011 #8
    Re: "creation of space" what exactly does this mean

    Well, not exactly. If you like to express it that way, then the large portion of recession velocity is what is left over from earliest days. Also, the belief was that universe is deaccelerating, and that deacceleration parameter (q) is positive. Now we know that it is negative. Nobody ever thought that reversal has already started. If you are interested in this stuff, and apparently you are, take a look at this graph: http://en.wikipedia.org/wiki/File:Friedmann_universes.svg" [Broken]. That is the single most important curve in cosmology. Pay attention to the curves with ΩM only. Those describe expansion with only various matter density, but without dark energy.
    Also you can play with on line cosmic calculators. They can be very helpful. My favorite is here:http://www.uni.edu/morgans/ajjar/Cosmology/cosmos.html" [Broken]
     
    Last edited by a moderator: May 5, 2017
  10. Nov 1, 2011 #9

    phinds

    User Avatar
    Gold Member
    2016 Award

    Re: "creation of space" what exactly does this mean

    DOH ! Actually, I DID know that, but misspoke.

    Thanks for the corrections and the links (I'll check out those links for sure)
     
  11. Nov 3, 2011 #10
    Re: "creation of space" what exactly does this mean

    thanks to all. Let me please get back to my original question about space. The question wasn't so much about expansion, rather about what the metaphor "space is being created" may reasonably denote.

    Of course, chalnot's word (there is no objective space in science) is true, but the metaphor is still there and I want to get as much from it as possible.

    I am particularly asking for the difference between two versions of this metaphor:

    1) One is that during the big bang, space (and time and matter...) was created. E.g. German Wikipedia says "Der Urknall bezeichnet ... die gemeinsame Entstehung von Materie, Raum und Zeit aus einer ursprünglichen Singularität." ("Big Bang" denotes the joint formation of matter, space and time out of singularity).

    2) The other is that space is created during expansion. A notion I am beginning to like.

    While I intuitively dislike the former variant, the latter seems instructive to me. What about you (forum members, professionals, beginners...)? how do you like these metaphors? Do you feel that both variants denote the same thing?
     
  12. Nov 3, 2011 #11

    marcus

    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Re: "creation of space" what exactly does this mean


    I think the metaphor "creation" in English is bad in both cases and causes many people trouble. Primarily because of the Religious Myth association.

    http://en.wiktionary.org/wiki/entstehen

    In German the root meaning of Entstehung comes from the verb "to arise" entstehen. This can be natural, something can arise by itself.

    If there is a craftsman or builder, one is more apt to say to make "schöpfen". So Haydn's music about the Creation Myth is called Die Schöpfung. The sense is The Making (by a Creator) and not something naturally arising or coming (by itself) into existence.

    The Wiki dictionary says the translation of entstehen is
    1) to come into existence
    2) to arise

    I said what I think about the expansion of distances around the beginning of the thread, that it is a dynamic change in geometry. Space is not a substance.
    One should simply accept that distances can change, without anything being "created".

    But if one feels compelled to talk about the becoming of "more space" then it would be better to use the metaphor of ARISING of space, rather than CREATION of space.
    ==============================

    Now I have a question for you. The Potsdam branch of the Max Planck Institute has the special name of "Albert Einstein Institute". The AEI is the branch of MPI having to do with gravitation, general rel., fundamental theory etc.
    They have a public outreach website called "Einstein Online". Here is an essay about the Urknall (and some confusions the public has about it.)

    http://www.einstein-online.info/spotlights/big_bangs

    I would like to ask you to have a look at this one-page essay and comment. Notice that they suggest that 'singularity' is not necessarily something that happens in nature. It can simply be a symptom that something is bad in the theory that suffers the singularity. A sign that one needs to fix or replace the theory.

    The AEI website does not, I think, encourage you to believe that the "big bang" was the coming into existence of space, time, and matter. There is no scientific reason to believe that. Some models go back before. There may have been space time matter before the start of expansion. Just something different happening, not experiencing expansion. Please read the essay and see what you think. Maybe you won't like it! I am interested to know either way.
     
    Last edited by a moderator: Apr 26, 2017
  13. Nov 3, 2011 #12
    Re: "creation of space" what exactly does this mean


    Chronos I believe I was told by someone here (maybe Marcus I am not sure) around 6 months ago that top Physicists were holding conferences to try to determine whether this statement is correct. I myself have gone full circle about this question after reading up about older Physics. I had a thread about it:

    https://www.physicsforums.com/showthread.php?t=487911&highlight=properties+of+space


    Marcus thanks for the Einstein online link
     
    Last edited: Nov 3, 2011
  14. Nov 3, 2011 #13

    marcus

    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Re: "creation of space" what exactly does this mean

    *'Space' has no objective existence in science as we know it, it is merely the emptiness between particles in a FLRW universe.*
    I think Chronos is right from a GR perspective. The catch is we don't know for sure that GR is a correct picture of Nature in every regard. But in many contexts we tend to assume it is.
    In the world as described by GR, points in space have no physical existence, but geometry does. GR is about the evolution of geometry as it interacts with matter.

    Geometry does not require a material space substance----it can simply be about the geometric relations among events, about the geometric measurements we make (area, angle, volume etc.) involving actual material, about the other fields that live in a given geometry. It means something operational and definite without being a substance.

    I think that is the GR view of it. Someone may want to correct me on this---what I said may be wrong or incomplete.

    The catch is we aren't sure if GR is the whole story and if it is going to be replaced what the main features of the replacement are.

    As I see it, standard matter physics MIGHT fit nicely into GR. It is about matter fields. Why couldn't the matter fields live happily in GR geometry? It hasn't been like that. Quantum field theory is usually done in a fixed geometry, not a dynamically changing expanding contracting etc geometry. But maybe the theorists can work that out. Or they can first quantize the GR geometry and then get matter fields to live in it.

    Or both have to change----both matter physics and geometry physics have to change a little in order to be compatible.

    You could say that is what some of the conferences have been about. I could have been talking about the June 2011 one in Zurich called "Quantum theory and gravitation." It brought together people from quite a number of research lines all having to do, one way or another, with this problem.
     
  15. Nov 3, 2011 #14
    Re: "creation of space" what exactly does this mean

    thanks Marcus, yes I think that was the conference now I recall.
     
  16. Nov 3, 2011 #15
    Re: "creation of space" what exactly does this mean

    Creation of space, a'la expansion, as I understand it, if you take away the religious connotations (please), seems fine with me. Without the energy or whatever is doing it, objects would be moving apart in regular fashion (if such a thing could even happen, given current understanding). So in a sense, DM or DE (whichever is doing it) is "creating" more space than would be there without it.

    But in the sense that there is nothing in space to expand, then the true sense has to be that DM or DE is putting greater distance between objects than their relative movement can account for, given the limits of c. And my understanding is that the mechanism that does this must somehow be impacting on the forth dimension - time.

    Perhaps it's an exercise in semantics, but if we understand what we really mean, then we can get past that.
     
  17. Nov 3, 2011 #16

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    Re: "creation of space" what exactly does this mean

    DM is what allows for structure formation in the universe, it does not contribute to expansion. Without DM, there is simply not enough mass in the universe to allow the mass density necessary for stars, galaxies, etc., to form after the big bang.
     
  18. Nov 4, 2011 #17
    Re: "creation of space" what exactly does this mean

    Narrator, I think the point that is being made is that space has no objective existance whatsoever, it is just a measurement of distance between two points which is not constant with time due to the complexities of spacetime and also dark energy expansion. Space time is therefore not like ponderable matter, it doesnt need to be created.
     
  19. Nov 5, 2011 #18
    Re: "creation of space" what exactly does this mean

    Barring the semantics, I think that's pretty much what I said.

    But as for the semantics, when your wife asks you to move some of the boxes aside in the closet to make room for her shoes, she might use the words, "to create some space for my shoes darling."
     
  20. Nov 5, 2011 #19
    Re: "creation of space" what exactly does this mean

    Creation of distance means that there is more distance between galaxies. In a very rough way, if at t1 the distance is S at t2 the distance is 2·S for instance.

    Did you never hear of the balloon analogy?
     
    Last edited: Nov 5, 2011
  21. Nov 5, 2011 #20

    phinds

    User Avatar
    Gold Member
    2016 Award

    Re: "creation of space" what exactly does this mean

    I think your point would be better made if you replaced the bolded space with "distance", since that's what's actually the case. "Space" is not a helpful word in this regard.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Creation of space what exactly does this mean
Loading...