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Can space itself act as an fuel?

  1. Nov 25, 2015 #1
    Hey guys,

    I've been running this though experiment in my head for a while now and to be honest, I am not that much of a physics guy so I figured I'd ask a few questions to see if what I'm thinking about it even physically possible. (Not that it is even realistic, but hey.. who cares right?)

    From what I understand about the subject, space is expanding, at an accelerating speed. Since space is expanding at all points, the bigger the space, the bigger the expansion. (Note one: Since this force is basically pushing galaxies and stuff, there should be a lot of energy if you gather up a lot of space right?)

    Now let's say that hypothetically you put this huge balloon in space, this should technically blow itself up right? But what if, you have a closed room which won't allow itself to expand, could you redirect the energy of this expansion into an engine and make this turn? (Or would the expansion also take place in say, the atoms between the "space-ship" itself, thus dissolve itself or break?)

    Now I do realize that these kind of ships would be way larger than even the biggest planets in our solar system, but I just started thinking about it when I saw this guy claiming dark energy couldn't be harvested. I mean, it's pushing physical planets away so logically it just doesn't make sense to me that this stuff can't be harvested.


  2. jcsd
  3. Nov 25, 2015 #2


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    There are lots of thought experiments that touch on this area. The Tethered Galaxy is one of the most well-known.
    One reason none of them can be put into practice is that to use this 'energy' you need to connect something on Earth to something millions of light years away by something like a wire. We don't have enough wire, couldn't reel it out and if we did it would break.
    And that's before we even grapple with how we firmly knot the end of a wire around a galaxy.
    A balloon would require even more material, and thereby be even more impractical.
  4. Nov 25, 2015 #3


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    No, even a galaxy size balloon will only 'blow up' a little larger than what it would have done without accelerated expansion and then settle where the "cosmic tidal force" is equal to the "stretch-force" in the material of the balloon (that is unless the material is not strong enough and simply breaks). As for extracting useful energy? Not practical.
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