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4th dimension space

  1. May 31, 2012 #1
    Not sure if its the right place to post but still:-

    I am confused over 4th dimension space( not time ). Does 4th dimension space really exist?
    If it exists why we cannot see or visualise the 4th dimension?
  2. jcsd
  3. May 31, 2012 #2
    Higher dimensions are important for data sets that take multiple values. For instance wing length, height, weight, roundness, et cetera are multidimensional data sets that a aerospace engineer might consider.
  4. May 31, 2012 #3
    According to relativity, in order to define an event anywhere, we require 4 parameters x,y,z and t
    these represent the 4 dimensions. 3 dimensions of space and 1 dimension of time makes 4 dimensions of 'spacetime'. This spacetime can get curved i.e both space and time can curve in the presence of matter. This is called spacetime curvature. We can very well experience the 4th dimension i.e time. Time can get 'slowed down' near a massive object. The amount of curvature due to matter can be calculated mathematically. Consider time as a river and spacetime as the riverbed(i.e surface on which the stream flows). The speed of the river slows down at deep areas of the riverbed.These areas correspond to curved spacetime. You may now visualise the slowing of time due to the curved geometry of a 4 dimensional spacetime.
  5. May 31, 2012 #4
    in mathematics, a hypercube is a 4 dimensional computer generated figure. It is built on a 3D wireframe.Mathematically, n-dimensions are possible. To create a n-dimensional figure, you need a (n-1) dimensional wireframe.
    Unfortunately, geometric figures with more than 4 dimensions is hard to visualise using human brain. Humans cant percieve higher dimensional objects,but computers can.
  6. May 31, 2012 #5
    Just for knowledge :
    a space with more than 3 dimensions is called 'hyperspace'-a term used frequently in science fiction
  7. May 31, 2012 #6
    I think this is misleading and partially untrue. You can't accurately portray an nth dimensional object in any dimension<n. You can sketch a cube on paper, but you need to know what a cube looks like to interpret what you've drawn.

    Likewise 3D wireframes of tesseracts are based off that idea. They are a distortion of the tesseract that is the result of compressing it into 3 dimensions. A fourth dimensional creature would see the 3D wireframe and be able to extrapolate what it is representing accurately, but we cannot.

    The n-1 dimensional thing isn't correct because I can doodle a picture of a tesseract on paper. Now this is a compression of a compression, and when I imagine it I am only infact constructing a compression of the original, but still a 4th dimensional creature could visualize the tesseract from my paper sketch.

    To clarify, those wireframes you see of tesseracts are not what tesseracts look like. You can think of them as what the shadow of a tesseract would look like in 4-space, but I don't think this is a really useful view.
  8. May 31, 2012 #7
    First, I would not take the number of dimensions all that seriously. All it really means is that our theories are easier to calculate when such a number of dimensions ischosen. Different theories have different numbers of dimensions. For example, I can think of the Universe as a vibration and use the Fourier transform, which gives us an infinite number of dimensions. I think that something like the Universe cannot be pinned down to a specific number of dimensions.

    As far as 4D space-time goes, start with what Albert E. has to say. He wrote that time is what a clock measures and space is what a ruler measures. Already we are anthrocentric. He then showed that these two measurements depended on one another, contrary to what almost everyone thought. Time depends on space and vice versa.

    But no, time is not at all like space. We perceive it quite differently, and treat it differently mathematically.
  9. May 31, 2012 #8
    I would disagree, the universe can be pinned down. We know there are only three 'large' spatial dimension and one time dimension. Absolutely no less than that.

    There are theories that suggest more than that, but these are testable theories (or at least will be when matured) that can be substantiated or forgotten about.
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