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What is Space, Is it Transparent, Does it Weight Anything?

  1. Aug 2, 2013 #1

    I am in high school and would like to understand space.

    a.) What is space? Is it physical? Is it transparent in nature basically?
    b.) Does space weight anything?
    c.) What is outside of space? Anything at all?

    Thank you very much.
  2. jcsd
  3. Aug 2, 2013 #2
    What do you mean by 'what is space'. What is an electron, an electron is something that has the properties of an electron. To know what an electron is you need to know what its properties are. Same with space. Space is nothing more than it's properties. So you need to know what it's properties are.

    When you say, 'is it physical'. What do you mean by that? This is not a trivial question. The more you think about what you mean by is it physical the deeper you go...

    Does it weigh anything? To answer that you first need to know what it is. You also need to know that the current thinking is that there is no such thing as 'space' rather there is something called 'spacetime'.

    Probably the best description of the fundamental property of space is the meaning of the sanskrit word for space which is 'that which accommodates. By that definition when you ask is there anything outside of space you are asking 'what accommodates space'. Which starts to get a bit metaphysical and not really within the scope of a science forum.
  4. Aug 2, 2013 #3


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    I'm going to quote wiki on this one:

    Space is the boundless three-dimensional extent in which objects and events have relative position and direction.[1] Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum known as spacetime. In mathematics, "spaces" are examined with different numbers of dimensions and with different underlying structures. The concept of space is considered to be of fundamental importance to an understanding of the physical universe. However, disagreement continues between philosophers over whether it is itself an entity, a relationship between entities, or part of a conceptual framework.

    To answer some of your questions:

    A. Space is not physical. Physical refers to objects within space. The property of transparency is not one that can be applied to space because it is not an object. (In my opinion at least. You could just consider it to be 100% transparent)
    B. Unknown.
    C. This is similar to asking what is outside our universe. Well, our universe is defined, in many cases, as everything that exists. So it is not possible even in principle for something to be outside of the universe, nor outside of space. *Note that I do not wish to invoke an argument on what a universe is, I'm merely using it as an example.
  5. Aug 3, 2013 #4


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    Another post by xmenfan in which he is concerned with whether or not a given word refers to a material object. Perhaps a good Physics class would help!
  6. Aug 3, 2013 #5
    That kind of sums things up.

    Science mostly explains how things behave as we observe. So you can ask "What is space?" or What is time? or an electron or.....on and on and science has no real good answers.

    I would say space IS physical....[but as noted that depends on just what one means] or has physical effects else, why does a distant 'house' look small and a nearby house look 'big'. We can only stuff so many cans in a box, so many atoms in a material, and so forth. So it seems space does have physical effects and as explained by the theory of special relativity, intertwines with time in such a way that as relative speed changes, so does space and time. Space and time are not unchanging and fixed as they appear in everyday slow speed life.

    There is not even firm agreement among scientists whether space is continuous,meaning smooth even at the tiniest scales, or discrete, meaning whether it comes in tiny lengths. Relativity is a theory of continuous and quantum theory, discrete. Both work well, but not at the tiniest length scales, called Planck length.

    A pair of explanations I find insightful:

    Time is what keeps everything from happening at once.
    Space is what keeps everything from happening to me.
  7. Aug 3, 2013 #6
  8. Aug 4, 2013 #7


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    The word "space" has multiple meanings. It's not 100% clear which one you mean.

    If you mean the "stuff" spacecraft travel through to get to other planets then..

    a.) What is space? Is it physical? Is it transparent in nature basically?


    b.) Does space weight anything?

    No. However quantum theory suggests that a vacuum is full of virtual particles, mostly photons.


    c.) What is outside of space? Anything at all?

    Cannot be answered. There is a limit to how far we can see. Seeing requires light and the light has a finite speed. So by looking into space we are also looking back in time. We can see objects so far away that the light must have left there soon after the universe was formed. We can only ever see back as far as the beginning of the universe. Asking what is beyond space amounts to asking what was there before the universe began.
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