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Shape of universe

  1. Aug 22, 2003 #1
    The universe is infinite in size. All the theories about a warped universe are wrong. From where you are standing, hold a yard stick and pick any direction including up/down and imagine traveling out into the universe along a STRAIGHT line parallel to the yard stick. Lets say (just for fun) that you could travel at the speed of light. You will NEVER / EVER come to the end of the universe because there is no end. And forget about coming back to where you started. I am talking about a straight line PARALLEL to the yard stick at the starting point. Forget about the line eventually bending because again, you are always traveling straight relative to the yardstick.
     
  2. jcsd
  3. Aug 23, 2003 #2

    wolram

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    "space", may be infinite, but our universe is finite, the rest of your statment would be true if GRAVITY did not exist.
    best wishes.
     
  4. Aug 23, 2003 #3
    Would you agree that the empty "space" between galaxies is part of our universe? If you answer is yes, then our universe is infinite because you can't simply draw lines somewhere in space and say "this is where the universe ends, and space begins"
     
  5. Aug 23, 2003 #4
    No. There is another column where I spoke on this.

    Between universes is NOT nothing, and NOT something. It is neither.

    It does not exist. This is a difficult concept for some to swallow. Our universe has it's boundaries by matter and light - it is a closed system.

    Other universes to not connect ours, because the moment they did we would become one universe.

    But the distance one would travel between universes is a distance of not nothing and not something, it's just ______.

    It's not in existance - that is to say that once you are traveling, you being matter, is extending your universe and turning it into something.

    Nothing - Empty space
    Something - filled space
    _____ - a nonexistant coordinate that doesn't exist.
     
  6. Aug 23, 2003 #5
    Please stop parading theory around like it is fact.
     
  7. Aug 23, 2003 #6
    Theory and fact have no necessary boundaries.

    A theory adheres to evidence - and so does a fact. A theory might be a fact, in fact many of them are.

    Our universe has it's boundaries of matter and light. This is as accepted as (if not more than) the opposing claim.

    I would be no more sure of myself if it was fact. And I would not ever present a theory in any manner differently than a fact. Because they have no necessary boundaries.
     
    Last edited by a moderator: Aug 23, 2003
  8. Aug 23, 2003 #7

    jcsd

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    Our universe, from recent WMAP results looks to be infinite, this is a result of it having apparently flat geometry on a global scale.
     
  9. Aug 24, 2003 #8
    There is only one universe. Too often the so-called “thinkers” make it too complicated. Uni means one (single) The theories of parallel universes are wrong. If it were correct, we would have for years been referring to the size and shape of the multiverse. There can be only one Uni-verse. It includes everything that is and everything that is not. Space refers to those places in the universe that are completely void of physical particles. The universe is infinite in size therefore has NO shape. I has also existed for an infinite amount of time ergo it has no age. The only things that can have age (by our calculation)are physical particles, and time, as we know it, can only be measured by observing the travel of the OBSERVABLE particles. There are most likely trillions of particles far beyond anything we have ever observed and they may have existed trillions of times longer than the 15 billion years age of objects that we can currently observe. That’s easy to swallow because those big numbers against infinite time are quite small.
     
  10. Aug 24, 2003 #9
    Don't assume that you know anything beyond observation, zydubion. I have a theory where the universe and time are infinite, but it is just that, a theory. I have visualized a lot of finite universes, occilating universes, and momentary universes. We don't know yet what our universe is. Saying it is one certain way at this time is at best presumptuous.
     
  11. Aug 24, 2003 #10

    Hurkyl

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    Might I suggest, zydubion, that you do some studying on Hyperbolic geometry? And make sure that relative consistency is on your cirriculum... one of the pertenint points is that any mathematical proof that Euclidean geometry is the only geometry works as a proof that Euclidean geometry itself is a logical contradiction.


    There's plenty of evidence that space-time can be described by a non-Euclidean geometry. For example, according to General Relativity, the path that the earth takes around the sun IS a straight line through space-time.

    In general, lines don't have to bend to return to their starting points. A common example (at least it was a couple decades ago) is a video game like Asteroids; when you go off of one edge of the screen you appear on the other side. Believe it or not, but the "universe" in which those video game objects live is a perfectly valid geometry. We see edges since we've embedded the geometry into our 3-dimensional universe in a non-faithful way, but there are no edges to those living in this geometry, and it's everywhere flat to boot... yet you can go in a straight line and end up back where you started.

    (Incidentally, this geometry is called the flat two-dimensional torus)

    Mathematics (and the laws of physics) certainly permit this type of geometry for the universe, and even much stranger ones. Currently we only consider geometries of space that look Euclidean on small scales (actually, geometries of space-time that look Minowski on small scales), but theoretical physical theories consider more exotic things.
     
  12. Aug 24, 2003 #11
    Parallel lines

    In mathematics there are many geometries in which parallel lines converge. In more realistic terms, mass distorts space-time, essentially changes the path that a straight line will travel. As mass distorts space, there are 3 possible geometries for the universe, depending on mass; zero curvature, positive curvature and negative curvature. In a universe with a positive geometry (imagine being confined to the surface of a sphere), two parallel lines will intersect (imagine on a basketball), and also if you set off in one direction you could keep travelling in a line and come back to the same point. One problem when people talk about the geometry of space is when they get confused about 'infinite yet finite' space. However if you are confined to the surface of a sphere, you can keep going to infinity and never reach the 'end', but the sphere has only a finite surface area.

    Chris
     
  13. Aug 25, 2003 #12
    Glok, Sorry, I didn’t want to imply that I know anything about the universe beyond observation. That’s why I say preface with “may”. Yes, it’s theory, all of our thinking is theory. We are all humming “What’s it all about, Alfie? We want to know, but all we can do is think. What we are seeking is knowledge of how things really are. That’s where I am, just thinking. And to be very honest, I know very little about even the observable part of the universe. But I do know what a straight line is. So I go right back to my original post. The yardstick is a straight line. And your imagination can travel and take that straight line far beyond the observable. And if certain geometries and mathematics say the line bends somewhere out there within or beyond the observable, I say you need to move it directly back on track RELATIVE to the original 36 inch long straight line.
     
  14. Aug 25, 2003 #13

    Hurkyl

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    You know what a Euclidean straight line is.


    Only in flat geometries (like Euclidean or Minowski) does it make sense to talk about parallel directions at widely seperated points; in general all you can do is say that the line is everywhere straight... geodesics do not bend (relative to space in which they live, anyways), yet they can return to where they started.


    But even flat geometries are capable of permitting straight lines to return to where they started. For instance, take my Asteroids example; that is a flat geometry. If you take your yardstick and point it upwards and draw a vertical line, the line will always be parallel to the yardstick, yet it returns to its starting point.
     
  15. Aug 26, 2003 #14

    You are mistaking unbounded with infinite. If the universe were a two dimensional space curved through a third dimension into a three dimensional shape - say a ball or a torus, then the same argument you use above would be true, yet the area would be finite.

    Take a volleyball. Place an ink pen to the surface. Draw a line, without removing the pen's point from the surface as far as you want to, you will never reach the "end or beginning of the ball".
     
    Last edited: Aug 26, 2003
  16. Aug 26, 2003 #15

    Integral

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    \

    Something is serious wrong with this argument, I just did this experiment. Even leveled the yard stick. Set out walking, swimming, more walking and more swimming, more walking, always following the direction pointed by the leveled yardstick, By golly, I just got home again, there is the other end of the yardstick! But you told me it couldn't happen!

    Your argument falls apart simply by looking at a globe. Toroidal geometries are not necessary, just the simple shpere we live on will do the job.

    EDIT: If simple observation cannot reveal the fact that the earth is not a plane, how can you draw any conclusions about the universe by this argument?
     
    Last edited: Aug 26, 2003
  17. Aug 26, 2003 #16
    Thanks to all for the interesting posts.
     
    Last edited by a moderator: Aug 26, 2003
  18. Aug 26, 2003 #17
    Integral..If you had followed instructions, you would not have wasted so much time on that long hike. I said a STRAIGHT LINE OUT INTO THE UNIVERSE, not a curved line around the globe. Next time you will need some wings after a mile or so. Pleasant trip!
     
  19. Aug 26, 2003 #18

    Integral

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    I did follow a straigt line, I always checked the level of my stick. Like I said you cannot prove anything about the surface of the earth with your argument let alone the universe.

    In other words, with observations from your postition, prove to me that the earth is anything but flat.
     
    Last edited: Aug 26, 2003
  20. Aug 26, 2003 #19

    Hurkyl

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    I went with the toroidal geometry because it's one of the few geometries where the phrase "go parallel to the yardstick" still has meaning once you take a step away from the yardstick.


    Zydubion: Integral was trying to make an analogy to demonstrate to you, without having to try and explain differential geometry, how it is geometrically permissible to for one to travel in a perfectly straight line and return to your starting point.

    Between Integral and myself, we have shown you the two-dimensional analogues of two of the simplest closed three-dimensional geometies, the hypersphere S3 and the hypertorus S1xS1xS1.


    Since you don't accept this, I see only two options at this point: we explain differential geometry to you so we can demonstrate how the universe can have a shape that permits straight lines to return where they started, or you can prove to us that straight lines cannot return where they started. Which do you want to do?
     
  21. Aug 26, 2003 #20
    Ok you guys, I know you are much smarter than I am, but let me take just one more shot at this. The level will always say "level" because the bubble is directed by gravity. So instead of walking, lets shoot a bullet out into space. We all know that gravity will affect it, but lets just pretend it doesn't so I can again ask for a straight line in another way. The bullet travels in a straight line (never looses speed) and if one could look back through the path of travel, one could always confirm the straight line because you could always see back into the barrel of the rifle. I would lay odds and pull the trigger myself and wait for the bullet because it will NOT hit me in the back of my head. If you still say "zydubion, you're gonna die" then I give up on this one, and I think I will just stick with the geometry that I now understand. Thanks again. By the way these different geometries you mention, is this all factual/proven or is this theory? Has anyone ever looked out into space with a good telescope and were surprised when they zoomed in on their bald spot?
     
    Last edited by a moderator: Aug 26, 2003
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