By George Hart for the Museum of Mathematics






See all of George Hart’s Math Monday columns

Gareth Branwyn

Gareth Branwyn


  • Anonymous

    Ok, here’s an idea I’ve been bouncing around: Vacuum-filled balloons.There’s no way they can be anything but lighter than air. You just need a vessel that can withstand atmospheric pressure, which is what? 15 psi? Make some kind of lightweight carbon/kevlar chamber about the size of a weather balloon and instead of filling it up with something, you suck all the air out. It has to float like a helium balloon.

    Maybe you can’t achieve perfect vacuum, but 75% would be fine. Heck, 50% would probably still float. I’m thinking there’s got to be a way to get that done.

    • Tommy Phillips

      This stirred up an old memory, so I did a quick search of the Usenet archives.  I found this thread from 1997:

      The idea comes up once in a while, but as this thread mentions, the density of hydrogen or helium is so low that you don’t gain much from enclosing a vacuum, but any rigid structure is likely to be much heavier than an equivalent elastic structure.

      If it wasn’t NaNoWriMo, and if I wasn’t 8000 words behind, it would be fun to work out the theoretical limits …

      • Anonymous

        Well I’m not one to be so easily dissuaded. We’ve come a long way since 1997. There’s materials that are incredibly strong and lightweight like aerogels. Maybe a large sponge of such a material wrapped in an airtight coating could achieve the effect.

        There’s no reason it has to be a single, huge vessel. Maybe by nesting vessels containing successively smaller pressure, you could achieve a combined strength and buoyancy. Maybe you could create a foam of bubbles containing vacuum. Maybe complete neutral buoyancy is the wrong goal. Maybe there is an advantage in simply being lighter.

        Instead of putting so much effort into proving why it won’t work, why not put some thought into thinking of a way it could work? When people present ideas, you could use it as a source of ideation for yourself instead of an ego-gratifying endzone dance where you’ve done nothing but shut down a conversation that might have gone somewhere fascinating?

  • TotalMonkey

    As long as the container(uncontainer?) is lighter than an equal volume of air, it sounds possible.

  • TotalMonkey

    Great idea!