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What do we call the dimension measured with time?

  1. Jan 18, 2005 #1
    I am told time is a dimension, indeed the 4th dimension

    but then I am also told time is effected by other things such as gravity

    These two seem to be at odds with each other.

    the three classical dimensions are length breadth and width. yet no one I know of argues that gravity or any other force can effect them. they are indeed simply a means of measuring a physical property.

    If the physical property of an item changes say the force of gravity causes a box to compress in the height dimension. its height is said to have changed. not the dimension we call height.

    if the ruler is effected by gravity such that both the ruler and the box are compressed. no-one argues that the dimension of height has been warped.

    So given the above it tells me that a dimension is unchangeable, it is a concept and has no physical attributes that can be effected.
    The common belief today is that gravity effects time in such a way as the strength of the field is relative to the 'speed of time'.

    This to me says that 'time' is a measuring tool, a ruler. and as a tool it is effected by normal physical means.

    So if time is the tool we use to measure a 'dimension' what do we call that dimension?
  2. jcsd
  3. Jan 18, 2005 #2
    You're mistaken. The fourth dimension accounts for space and time. The three physical dimensions, can be warped under great gravitational and acceleration scenarios. Take a black hole for example. That can warp space, and time.

    However, to account to the last part of what you said... Time is a hard thing to explain. What is the past, future, present, and why things in the past can be "erased", and even if the "past" existed, are all things that take quite a bit of explaining and trying to understand. Braine Green does quite an adequete job explaining the whole situation, if you wish to take a look at The Fabric of the Cosmos.
  4. Jan 18, 2005 #3
    So in a black hole a 1 metre tall box crushed to 1 millimetre in height is still a 1 metre tall box?
  5. Jan 18, 2005 #4


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    In special relativity, both space and time dimensions can change, depending upon who's looking. If a spaceship flies past you at high speed, you'll not only see the spaceship as if it were squashed (change in spatial dimension), shortened in the direction of motion, you'll also see the people inside it moving slowly (change in the temporal dimension).

    - Warren
  6. Jan 18, 2005 #5
    No. General Relativity shows that gravity is a warp in spacetime. It also shows that there is less difference than we usually think between the three dimensions of space and the dimension of time: this is clear from the Lorentz transform. Take a look on Wikipedia. You will find that the Galilean transform (which you are used to thinking in terms of because of your life experience) changes space, but not time; however, the Lorentz transform (which we know to be more correct because of the failure of the Michelson-Morley experiment) changes both space and time, and in fact changes them into one another. Look at the equations and you will see what I mean. The interpretation of this is that spacetime is all one thing. So it is by no means surprising that if gravity warps space as GRT claims, then it warps time as well.
  7. Jan 18, 2005 #6
    Ok I have to ask this question then, Sorry if it seems inane

    If I was to fly into a black hole. as I descended into the black hole would I be crushed or would it appear to the outside observer that I am crushed, but to me I would not notice the change at all?
  8. Jan 18, 2005 #7


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    You would be torn apart by tidal forces but it would appear to a distant observer that it took an infinitely long time to do so.
  9. Jan 19, 2005 #8


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    That would be "duration".
  10. Jan 20, 2005 #9
    Chroot had the answer space (3 dimensions) is relative. I have to stop thinking in layman ways.

    time *and* SPACE does distort, not just time.
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