How can you make water invisible? The magicians silk-gloved hands dance through the air, delicately pulling back a sheet to reveal the prop for his next trick: a glass fish tank. It appears empty, and yet the illusionist insists that the aquarium contains a most remarkable substance: invisible water. To demonstrate, he places a tinfoil boat inside the tank, and it merrily bobs up and down, as if afloat on some unseen surface. Next, the magician produces a plastic cup and begins bailing out the tank. It appears as if hes doing little more than miming, and yet the unseen water level seems to lower with each cupful. The little boat even bobs more and more, as if each dip of the magicians hand disturbs the surface more. Perhaps youve seen this feat performed on a talk show or in Internet videos such as this one. Hows it done? The practitioner isnt using sleight of hand, wires or digital special effects to float the tiny boat. The magic at work is none other than an invisible gas called sulfur hexafluoride (SF6). This curious vapor behaves like phantom water because its heavier and denser than air. When poured into a fish tank, it sinks to the bottom and can support the weight of very light objects floating on its surface. Sulfur hexafluoride is completely nontoxic and nonflammable, making it ideal for various scientific uses. Medical professionals use it as a test gas when studying the respiratory system, and the electric power industry widely uses it as insulation.
Posted on: Sat, 29 Nov 2014 11:21:06 +0000
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