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If the universe is expanding

  1. Nov 15, 2009 #1
    What is it expanding into?
  2. jcsd
  3. Nov 15, 2009 #2
    "The universe is not expanding into anything, almost by definition; there is simply more space at later times than at earlier times. It may be that the size of the universe is infinite, which is easy to conceptualize.

    But even if the universe is finite, it is possible to make more space without having any "outside" space. A common analogy is to consider that it is possible to increase the surface area of a balloon by inflating it, without needing any additional balloons to facilitate the expansion. However, a balloon is a two-dimensional surface expanding into a three-dimensional space. There is not theorized to be a higher-dimensional space which three-dimensional space is expanding into; more of it simply appears as if by stretching.[7]

    This finite universe theory supposes that the universe has no "edge", but wraps around on itself. If it were possible to travel the entire length of the universe without going faster than light, one would simply end up back in the same place, not unlike going all the way around the surface of the balloon (or a planet like the Earth).

    The notion of "more space" is local, not global; we do not know how much space there is in total. The embedding diagram has been arbitrarily cut off a few billion years past the Earth and the quasar, but it could be extended indefinitely, even infinitely, provided we imagine it as curling into a "spiral of constant radius" rather than a circle. Even if the overall spatial extent is infinite we still say that space is expanding, because locally the characteristic distance between objects is increasing."

    This is a quote from wikipedia.

  4. Nov 16, 2009 #3
    Yeah, but what does the balloon stretch into?
  5. Nov 16, 2009 #4
    http://en.wikipedia.org/wiki/Null_(computer_programming [Broken])
    Last edited by a moderator: May 4, 2017
  6. Nov 16, 2009 #5
    Take any N dimensional space (line, for example, is 1 dimensional)
    Multiply all positions (and distances) by 10.
    This is expansion.
    Where did the line expanded into?
  7. Nov 16, 2009 #6
    The balloon is a two-dimensional analogy of how space can increase between dots on the balloon’s surface
  8. Nov 16, 2009 #7
    Well no a line is actually 2 dimensional, just like a square is 3 dimensional otherwise it would be invisible.
  9. Nov 16, 2009 #8
    No, line is 1D
    Square is 2D
    Space is 3D (do you visit iMax or something?)
  10. Nov 16, 2009 #9
    No dimensions is nothing, the first dimension is a point, information is the real 2nd dimension.
  11. Nov 16, 2009 #10
    I would like for you to post to any paper that states the second dimension is only information.

    Well a 0 dimension space usually means a single point. Imagine a point on an infinitely thin thread.
    1 dimension has forward and backward motion/measurements. So using the above analogy it would be the entire infinitely thin thread.
    2 dimensions includes sideways movement/measurements as well as forward and backwards
    3 dimensions includes up and down. Which is what we live observing.
    Regardless of if a line drawn onto a paper has 3 dimensions once you zoom in enough it is just a representation of the 1st dimension.

    The first 3 are spatial dimensions most people include time which is a temporal dimension. Some theories require many more dimensions than what we can't perceive. String theory for instance has about 10-11 dimensions. These are all spatial dimensions (I'm not sure if this is correct).

    So the post by dmitry is correct. The definition of dimensions vary slighty between mathematics and physics but I'm sure for the purposes of this thread those differences are not required to be talked about.

    EDIT: Had to change 'can perceive' to 'can't perceive' made a typo while trying to get this all typed out quick lol.
    Last edited: Nov 16, 2009
  12. Nov 16, 2009 #11
    The 3rd dimension has 3 dimensions true.

    But you wouldn’t be able to see a square if it was infinitely thin.

    A square is 3 dimensional.
  13. Nov 16, 2009 #12
    Drawings of these shapes are ABSTRACT REPRESENTATIONS.

    Just as a drawing of a sqaure is an ABSTRACT REPRESENTATION.

    A 3 Dimensional square is known as a cube or rectangular prism. So therefore if you don't think that squares are 2 dimensional then you don't think they exist at all (on their own).

    Just learn to accept that you will not always be correct about everything you try to argue about. Instead of continuing to try and spread misinformation just give up learn and move on.

    Unless of course you have one of those papers which describes these dimensions that you speak of. In which case you should just post a link because I'm certainly interested.
    Last edited: Nov 16, 2009
  14. Nov 16, 2009 #13
    Any representation would be a fallacy.

    I’m not denying the 3rd dimension has 3 dimensions.
  15. Nov 16, 2009 #14
    Abstract line is 1D
    Line is a mathematical concept, not a physical one.
    It does not need to have any thickness to be 'visible'
  16. Nov 16, 2009 #15

    Vanadium 50

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    Superheavy, virtually everything you have posted is incorrect.

    Please desist in posting misinformation. If you don't understand something, it's better to ask questions than make pronouncements.
  17. Nov 16, 2009 #16
    Do you understand what the term fallacy indicates? There is nothing wrong with using visual representations to depict 2D or 1D objects.

    The fallacy here is that you don't accept them as representations instead you seem to be stuck on the mindset that they are being passed of depicting exactly 2 dimensions or 1 dimension. Which isn't true. This is known as the Straw man fallacy and is quite common.
  18. Nov 16, 2009 #17
    How exactly is a line 2 dimensional when it can be completely parametrised by a number in real^1? This is nonsense!
  19. Nov 16, 2009 #18
    “Straw Man Fallacy” - Isn’t that what you’re doing? Except in a massive group?
  20. Nov 16, 2009 #19
    No, because I'm the one defending the original position. You're the one that has taken that original position twisted it to something that you CALL the original position and you're arguing that it is wrong.

    No this does not make the original position wrong, yes you should take a few math courses above grade 10 highschool and no IDC what the rest of the group states I'm just stating facts.

    EDIT: As well it would be quite nice for me to point out that even in THIS post you are commiting the straw man fallacy. Hahahaha life goes on.
  21. Nov 16, 2009 #20
    A line is really a square if you think about it; a true line is the beginning and end of a point.

    Does this really not make sense?
  22. Nov 16, 2009 #21
    One dimension - one number to describe coordinate - x
    Two dimensions - two numbers - x,y
    Three dimensions - three numbers - x,y,z

    How many numbers do you need to specify any arbitary position on a line?
  23. Nov 16, 2009 #22
    A 3D graph right? It’s all a fallacy.
  24. Nov 16, 2009 #23
    No. I think your point of view is more based on incorrect semantics than some fundamental misunderstanding of dimensions though. Just shift your dimensions one upwards and you're fine.
  25. Nov 16, 2009 #24
    No, a line is parametrised by one number. The fact that an object of n dimensions can exist in m dimensional space, for n<m, does not mean the n-dimensional object is somehow therefore m dimensions.

    So a line is n=1, and in 3D space, m=3. So lines can exist in 3D space. But that doesn't make them 3D. You can have lines on a plane (2D space), or in any higher dimensional space. I could specify the equation for a line in 50-dimensional space, that doesn't make the line 50-dimensional, just that I need ... let me think.... 99 numbers to specify the orientation of the line (a 50-vector to the nearest point to origin, and a 49-vector specifying the direction along the line, which is 1 less dimension because it's normalised, and therefore lies on the S^(n-1) unit sphere.
  26. Nov 16, 2009 #25
    Superheavy, you are certainly worthy of your nick.
    What is the width of the line that connects, say, center of Earth with center of Moon?
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