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

About the Big Banger

  1. May 31, 2013 #1
    A number of years before the Internet was born,
    I read an article in which the author claimed that,
    at the site where the Big Bang happened,
    a "naked singularity" should exist.

    Like the Big Bang itself, which brought the Observed
    Physical Universe into existence, a naked singularity
    should also be able to violate the Energy Conservation
    Law, and continuously spew stuff.

    The implication is that the Big Bang might still
    be happening! It's just happening farther away than
    we can see. Let me see if I can explain my understanding
    of the situation (should there happen to be something "to" it).

    Cosmologists describe the expanding Universe in terms of
    a balloon, something we all are familiar with. But their
    simplification of the situation is "off" a Dimension. After all,
    any small portion of the surface of a balloon resembles a
    mostly-flat 2-Dimensional area, and our Universe is obviously
    3-Dimensonal, at least.

    Mathematicians know that the circle (a 2-D thing) and the
    sphere (3-D) have a 4-Dimensional equivalent, which they
    call a "hypersphere". Any portion of the surface of a
    hypersphere is a 3-Dimensional volume, equivalent to what
    I described above about a portion of the surface of an
    ordinary sphere.

    As we stand on the surface of the basically spherical Earth,
    we see that there is a limit to our ability to view its surface,
    known as "the horizon". Similarly, the Observable Universe
    has a kind of "horizon", too, usually known as the "red shift
    limit". It is not impossible that our entire 3-D Observable
    Universe is just a tiny portion of the overall surface of a huge
    huge 4-D hypersphere.

    I'm aware that cosmologists have been looking for evidence
    that Space has some "curvature", which would be strong
    evidence in favor of a hyperspherical Universe, and that so
    far, Space appears to be entirely "flat". Well, we know how
    long it took humanity to find evidence that the surface of
    the quite-larger-than-us Planet Earth was curved instead
    of flat. The verdict is still "out", awaiting more evidence.

    Imagine we could teleport instantly from the Earth to a distant
    place, say 13 billion light-years away. We could look back
    toward the Earth and see our Milky Way Galaxy to be very
    strongly red-shifted, and possibly spewing a powerful jet
    from its nucleus, like a quasar (because we would be seeing
    it as it existed 13 billion years ago).

    But suppose we turned around and looked farther away in
    the direction we had just teleported? What would we see?
    Even more galaxies, occupying an additional segment of the
    surface of that huge huge 4-D hypersphere? To be determined!

    Anyway, I've gotten distracted from the Big Banger.
    It's location, whether still spewing or not, would obviously be
    at the center of that 4-D hypersphere, and we have no way
    of "looking" in that direction! Stuck in the 3-D surface we are,
    unable to access the Dimension of "hypervolume".

    However, just like we imagine Planet Earth to consist of various
    layers, like "crust", "mantle", and "outer core", we can imagine
    that 4-D hypersphere to be layered, too, like an onion. Each
    layer could be a vast 3-D volume, such that any small portion of
    it could be equivalent to our Observable Universe. We might not
    actually be occupying the outermost layer!

    Now the reason for writing this message is actually to ask a
    Question. I just had to present the background information
    before I could ask it.

    So, IF the Big Banger is still Banging away, it logically follows that
    the overall mass of that 4-D hypersphere has been growing for
    a long long time. Might it eventually become massive enough
    to stop the accelerating expansion of the Observable Universe,
    and eventually lead to a Big Crunch???


    Thanks in advance!
     
  2. jcsd
  3. May 31, 2013 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    The author was talking a load of rubbish - there is no site where the big bang happened: the big bang happened everywhere all at once.

    Which would call for speculation .. which is against the rules of the forum.

    What you are talking about sounds a bit like a steady-state Universe except with fast matter creation.
    However, most of the description is too confused to work out.
     
  4. May 31, 2013 #3
    It does sound like Hoyle"s steady state model where he tried to explain expansion through matter creation. However I can't be positive with whats provided either.
     
  5. May 31, 2013 #4
    Part of what he was saying sounded more like Chaotic Inflation Theory, which is in some ways similar to Hoyle's Steady State Model. I can see how someone could view Inflation as 'Big Banger still banging away.' I can also see how some could call it speculation and then I wonder how we could discuss any theory no matter how many scientist think it does the best, but not complete, explanation. Sometimes it is hard to present facts without wanting to give conclusions. If you cling too tightly to only one theory or even to one understanding of a theory you become as the three blind men describing an elephant by what they feel. I will go drink my hemlock now, and I owe Asclepius a rooster.
     
    Last edited: May 31, 2013
  6. May 31, 2013 #5

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    @Ogr8bearded1:
    That is an understandable position and I remember arguing something similar when I first showed up.
    However, this is a forum with rules ... at first it seems quite restrictive: as you point out, how can we discuss anything? However - there are other forums with different rules, people are free to visit those forums and discuss whatever "what if"'s they like.

    A quick look at the rules tells us the reasonable limits to the kinds of discussions that are desired here.

    Generally, discussion topics should be traceable to standard textbooks or to peer-reviewed scientific literature.

    The statement "what if the big banger were still banging" fits neatly into "Personal theories or speculations that go beyond or counter to generally-accepted science" ... but if we squint a bit it is possible to see some aspects of post #1 which may be made to fit into: "Challenges to mainstream theories (relativity, the Big Bang, etc.) that do not go too far beyond current professional discussion" (see the rules under "discussion guidelines").

    Therefore - we need clarification from OP to figure it out.
    No need for hemlock ;)
     
  7. May 31, 2013 #6

    Fredrik

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    As Simon Bridge said, there's no such site.

    This violates the forum rules against speculation.

    A naked singularity that spews forth matter is something very different from the big bang.

    A circle is a 1-D thing, and a sphere is a 2-D thing. (What's inside the sphere is called a "ball". The "sphere" is just the surface). The spheres that represent space at different times in some solutions of Einstein's equation are however 3-dimensional, and can therefore be called 3-spheres.

    This is false. If it had a location at all, it would be on the 3-sphere. That's what it means to have a location.

    It would also follow that space isn't a 3-sphere. The solutions that describe space at different times as 3-spheres with different radii, are found when we assume that space is homogeneous and isotropic. A naked singularity that spews forth matter would certainly violate that assumption, and probably general relativity too.

    This is the sort of speculation we don't do at Physics Forums.
     
    Last edited: May 31, 2013
  8. May 31, 2013 #7

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    There once was a Big Bopper, there is now a Big Dipper, but I don't know nothin about a Big Banger.
     
  9. May 31, 2013 #8

    phinds

    User Avatar
    Gold Member
    2016 Award

    Gee, I thought "Big Banger" was one of the more coherent parts of the OP's post :smile:
     
    Last edited: May 31, 2013
  10. May 31, 2013 #9
    lol that was the one term i sort of liked, rolled off the tongue
     
  11. May 31, 2013 #10

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    @VernonNemitz: any of this any use?

    OP has been active since this thread was started...
    I was wondering if a big banger could be a kind of sausage... hmmm... sausage...
     
  12. May 31, 2013 #11

    phinds

    User Avatar
    Gold Member
    2016 Award

    I think you mean he has NOT been active since ...
     
  13. May 31, 2013 #12

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    I may have misunderstood or misread:
    OP's profile says last activity was 6am-ish today (my time?), it's 1pm-ish now, and post#1 was "19 hours ago" which would be late yesterday evening... sooo... OP's been here since making the post?
     
  14. May 31, 2013 #13

    phinds

    User Avatar
    Gold Member
    2016 Award

    Well, we don't seem to be reading the same info. According to what I see he made a post 2 weeks ago and nothing else since starting this thread which on my browser shows as 1:38am today.

    EDIT: ok, doing time conversion we are seeing the same thing, you just misinterpreted it.
     
  15. Jun 1, 2013 #14
    What I explained about a hypersphere was my personal understanding of
    what I've read about the expansion of the universe. That is, if a 3D balloon
    expands, its surface stretches; if a 4D hypersphere expands, its surface
    stretches. And since the surface of a hypersphere really is a volume of "curved
    space", just like the surface of a sphere is a curved 2D area, then for an expanding
    hypersphere, its curved-space surface expands in all of the regular 3 Dimensions.
    Uniformly!

    That's because multidimensional geometry is very consistent about certain things.
    I will therefore disagree strongly with Fredrik. A circle is a 2D thing, period.
    You can call it a "curved line", but while the line is a 1D thing, you cannot
    curve it without invoking the 2nd Dimension
    . Likewise, a sphere is a 3D thing.
    Its surface is a curved area (and normally an area is a 2D thing), but you cannot
    get that curvature into that area without invoking the 3rd Dimension. And so,
    if the Space of the Universe is curved, however slightly, it will most logically
    involve the 4th geometric Dimension. Very simple!

    Here is how those shapes are related. Start with a straight line segment (1D), and
    select its center point. Rotate the line around the point to generate a 2D circle
    (not just the edge, but the area as well). With the original line bisecting that circle,
    we can now imagine rotating the circle around the line to generate a 3D sphere.
    The next stage is perfectly logical, but mind-bendingly difficult to imagine: With
    the circle bisecting the sphere, imagine rotating the sphere "around" that circle to
    generate a 4D hypersphere.... Despite the difficulty of imagining that, it remains
    very true that multidimensional geometry is extremely consistent about certain
    things!

    Anyway, if a hypersphere is large enough, it could quite logically be difficult
    to detect the curvature of its surface. I did note in the original post that
    so far we haven't been able to detect any large-scale curvature, in the Observable
    Universe.

    It is therefore quite possible that my understanding of the situation has been
    faulty for a long time. I am fully aware that the phrase "curved space",
    especially when talking about gravitational fields, might be nothing more than
    an analogy, while the real-thing-going-on is something else altogether.
    And the expansion of the Universe doesn't have to be associated with a
    hypersphere.

    There is still a Question, though. Please recall that teleportation thought-
    experiment in the original post. What is the most logical thing that might
    be seen, looking further away from the Milky Way, if one was doing the
    looking after being teleported 13 billion light-years from here? I'm almost
    certain that I've read articles that basically say, "if you keep going in
    that direction (or any other direction) far enough, you will end up back
    at the Milky Way" ---and that, folks, can very accurately be
    called "circumnavigating the surface of a hypersphere!" Which is why
    cosmologists have been looking for some large-scale curvature of Space!
     
  16. Jun 1, 2013 #15

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Fair enough - you realize you are not the first to consider the multidimensional topology of the Universe? So many people have thought about this that a standard language has been developed to help people talk about it.

    You should think of Fredrik's descriptions as providing you with that common language - which will help you communicate your ideas to others. What you have been calling a "sphere" is known to mathematicians and physicists as a "ball".

    http://en.wikipedia.org/wiki/Ball_(mathematics [Broken])

    Hence - the surface of a 3-ball is a sphere.
    Spheres are 2D - viewed from the inside.

    The surface of a 2-ball is a circle - 1D from the inside.

    Since there is no "outside" to the Universe, it is the view from the inside that counts.

    Two straight lines intersecting a third at the same angle will be parallel.
    The curvature of the Universe would be manifest if the two lines would ever intersect each other.
    That sort of thing has other consequences that should be detectable - that's what all the "large scale curvature" is about.

    Per your question - an observer at, say, the limit of the observable Universe from us would see much the same Universe as us. The Universe is very very big and expanding, so it won't be possible to travel far enough to end up approaching your starting place.

    The field that covers what you are talking about is "topology". It's a big topic, see:
    http://scientopia.org/blogs/goodmath/2010/08/19/an-introduction-to-topology/
    http://www-history.mcs.st-andrews.ac.uk/Extras/Kuratowski_Topology.html
    http://en.wikipedia.org/wiki/Spacetime_topology

    Texts on general relativity should give you a crash course.
     
    Last edited by a moderator: May 6, 2017
  17. Jun 1, 2013 #16

    phinds

    User Avatar
    Gold Member
    2016 Award

    I think the way you use the term "inside" throughout your post, regarding various shapes, is unfortunately subject to easy misunderstanding and could generate argument.

    EDIT: for example, if I am "inside" a circle sitting at the center point of the circle, I can't see the points on the circle without looking in 2D directions.

    Wouldn't "on the surface" be a better way of saying what you're saying?
     
    Last edited: Jun 1, 2013
  18. Jun 1, 2013 #17

    phinds

    User Avatar
    Gold Member
    2016 Award

    I'm sure you have read such articles but that being one hypothesis (the "pac man universe") does NOT make it fact. It MAY be a valid hypothesis but stating it as a fact is personal speculation.
     
  19. Jun 1, 2013 #18

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Yeah - it's far from mathematically rigorous and I am hoping the context will carry it forward. If not then I can deal with it when it comes up.

    You can follow what I am trying to do there?
    If you can come up with a better way, do tell.
     
  20. Jun 1, 2013 #19
    That is not correct. There is the concept of intrinsic curvature, which does not require the manifold to be embedded in a higher dimensional space. This is well defined in a mathematically rigorous way.
    So yes, you can indeed "curve" it without invoking a 2nd dimension.
     
  21. Jun 1, 2013 #20

    Fredrik

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The dimension of a manifold is how many real numbers a coordinate system assigns to each point in its domain. For a circle, this is 1. For a sphere, it's 2. This is not an opinion, it's how these things are defined in mathematics. The definitions also ensure that curved manifolds don't have to be subsets of higher-dimensional Euclidean spaces. There are however theorems that say that there's always another manifold, that is a subset of a higher-dimensional Euclidean space, and is still equivalent for all practical purposes to the one we're interested in. But the point is that we don't need a higher-dimensional space to define curvature.

    This part of your understanding is good enough. But 3-spheres (what you call 4-D hyperspheres) is only of three possibilities that's consistent with the assumption that the space is homogeneous and isotropic. It's the "positive curvature" option, but there's also a "flat" option, and a "negative curvature" option.

    If the curvature is positive, then you might be able to travel along the surface of the (expanding or shrinking) 3-sphere until you come back to the same point from the other direction. I don't know if this is possible though. I know that in the simplest solutions (which end with a big crunch), you don't have time to go all the way before the crunch. And I expect that in solutions with accelerating expansion, you won't be able to do it in a finite time.

    The other possibility is that the universe has a non-trivial topology, like e.g. the universe in the classic video game Asteroids. Then you might be able to "come back from the other direction" in a finite time, even space is flat or has negative curvature. That may be what you have read about. (I know that I've seen a sciam article about it). There is however no evidence supporting this idea.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: About the Big Banger
Loading...