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Mass or matter occupy space ?

  1. Mar 11, 2013 #1
    Hello all .
    I have a little problem hope you will solution it .

    Suppose there is a box that inside it is vacuum and Suppose box is massless .
    Consider we import one million photons in the box
    Now box has mass equal to m=E/c^2 and E is total energy of photons .
    In this case , inside box should not occupy space because photons do not occupy space .
    I know this example is not very good for particles but much same .

    So i think just matter can occupy space because it has many properties and one of them is mass . right or wrong ?

  2. jcsd
  3. Mar 11, 2013 #2
    Matter is ill defined. Mass is well defined. If you want to think about things scientifically, I would forget the word "matter". Its not going to help.

    Mass is that which has the unit of kilogram, or equivalent. Fundamental particles are considered to be point particles. That means they occupy no volume.

    Volume is not a property of fundamental particles. You only get a volume when you have many particles together and can roughly enclose an area with them. Or you might be able to get a volume out of one particle by considering the average space it resides in. This can get complex...
  4. Mar 11, 2013 #3
    Closer to the truth, its even better to think of matter as nothing substantial, unsolid, it is merely energy manifesting itself in a certain state.
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