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B Expansion or repulsion

  1. Apr 29, 2016 #1
    I was playing around in the kitchen today. You know how when you drop some pepper in a calm glass of water the flakes instantly seem to repulse from each other and expand over the entire surface? I believe this is due to surface tension in the skin of the water.

    Could expansion be possibly caused by some unknown tension in the space/time that causes everything to repulse from each other in an effort to equalize that tension?

  2. jcsd
  3. Apr 30, 2016 #2


    Staff: Mentor

    First of all, tension in a medium is not the same thing as surface tension--the latter, as its name implies, only happens at a surface, i.e., at the boundary between one medium (in this case, the water) and another (in this case, the air). Spacetime doesn't have a boundary with anything else.

    The concept of a cosmological constant, which is one possible explanation for the accelerating expansion of the universe (it's one possible kind of dark energy, which is the general term for whatever it is that is making the expansion accelerate) can sort of be thought of as something like empty space having a tension. But, as just noted, this only accounts for the acceleration of the expansion; it doesn't account for the expansion itself.

    Anyway, the behavior of objects in our expanding universe isn't the same as the behavior the flakes on the surface of the water. The flakes move apart until tension is equalized, then stop. Objects in our expanding universe continue to move apart.
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