h a l f b a k e r yNot so much a thought experiment as a single neuron misfire.
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I want to have thin cord that, while appearing outwardly
to be normal string, has a core made of heavy wire. This
wire is heavy enough that, after tying the string onto a
helium balloon, the string can be cut to the exact length
for it to exactly counterbalance the balloon's lift. Thus,
the
entire setup is neutrally buoyant, floating in space
without
rising or sinking.
Why? Well, this way, as I prance around town carrying
my
helium balloon, I can grip the string somewhat towards
the
middle of its length. Thus, I'm carrying the weight of the
string's bottom half, and the balloon floats upwards
without being encumbered by the string's full mass.
However, if I let go of the string, the balloon won't float
upwards as it would normally be expected to; it'll just
float
in place with the string hanging under it. To anyone
else,
it'll seem like the balloon is held down by magic. To me,
it's just a neat trick.
Anti-Gravity Boulder
http://amasci.com/amateur/gravrok.html
[Wrongfellow, May 20 2011]
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Annotation:
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You'd have to carry a pair of wire cutters, and, as
helium leaked out of the balloon, be continually
trimming bits of wire of the end. Oh, and if you let
go of the balloon, a slight breeze might blow it out
of reach. But a lovely concept.
[+] |
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(+) In a restraurant I once worked in we would tie match packs to the string and remove matches, adding back part matches, until they were neutrally bouyant.
Customers seemed to like batting them around the place. |
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<in high squeaky voice> I like helium. Bun [+] |
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I used to ballast balloons and let them float around in the house. Fish shapes were lovely. |
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Ballasting to a hover only works well with full Mylar balloons, in my experience, and only indoors. Latex balloons and half-empty Mylar change volume and do not hover. Tight Mylar balloons are really resting on thermal-density gradients, which usually only happen inside. |
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Cute idea, but reality says [ ]. |
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If the string were weighted with a material which degrades over time at a suitable rate, boyancy could be maintained. |
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Perhaps a series of very small versions of the (little paper bundles of crystals which explode when thrown at the ground - what the hell were they called?). When the srting drags on the ground, a little at a time is blown away. |
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// what the hell were they called // |
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The string could be dipped in a liquid which slowly evaporates; but matching the diffusion rate (which is dependent on environmental factors) would be extremely difficult. |
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You can get a balloon to hover by tying it to a long piece of string, long enough that it pulls the balloon downwards, and then letting it float with some of the string on the floor. |
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It's self-correcting - if the balloon moves too far upwards, more of the string is lifted off the floor, and pulls the balloon back down; if it moves too far down, more string rests on the floor, and the weight is taken off the balloon. |
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I've done that with a hydrogen-filled balloon. Tie a long strip of paper to the balloon so it drags on the ground. Light the paper. As it burns, weight is lost, and the whole thing rises, ending in a mid-air explosion. |
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Again with the hydrogen... |
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That is a great link, Wrongfellow. I really want to
make one of those now! |
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And yes, as many of you have pointed out, helium
does escape from balloons - but that's the advantage
of this idea. When the balloon starts to fall, all you
have to do is trim the wire a bit. |
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