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Houston, station on two.

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I'm Don Pettit.

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I'm on the International Space Station,

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and I'm going to show you some interesting
observations about water sheets.

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Here in a weightless environment
on the International Space Station,

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you can make films of pure water.

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It's like trying to draw, stick a loop, in
a bottle of water and pulling out a film.

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You just can't do that on Earth.

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You have to have soap.

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And I'm going to use a number of different
geometries, a number of different kinds

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of loops, and a number of different
experiments with these water films.

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So you can look for example at
diffusion in water, say a food coloring

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or any other substance you want in water.

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You can look at the diffusion
in a two dimensional sheet.

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Because these water sheets are
so thin, convection perpendicular

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to the sheet will not be a factor,
and you can just look at fluid motion

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within the plane of the water sheet.

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So here I put a drop of blue food
coloring, a drop of red food coloring,

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and a drop of green food coloring, and
then you give it a little puff of air.

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And the viscous forces in these thin sheets
are small compared to the fluid motion,

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so they will continue to spin
like this for five or ten minutes

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until the viscous forces will
eventually have them slow down.

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And the food coloring will get
stretched out and leave streak lines.

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And if you do too much convection in here
then you end up with just this black sheet.

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Here's another water sheet
example, and this one is thin.

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This one is about 200 microns thick.

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And again I'm putting red food coloring on.

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And when you put a drop of red food
coloring on, notice those little vortices,

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those little swirls that kind
of look like mushroom caps.

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Really what you're seeing is a
cross section through a vortex ring.

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And here I'm going to put a little puff of air.

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I'm going to generate another
two-dimensional equivalent of a vortex ring.

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And again it looks more like a mushroom cap,
but this is what a vortex ring would look

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like if you were able to
take a slice through it.

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And now I've got a sheet that's about ...

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actually it's a little thinner than
the wire now that's suspending it.

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You can see if these things are slightly
convex that means they're thicker in the middle

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than at the edges, it makes a convex
lens and it's a positive lens.

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If they're slightly concave, then, which means
it's thinner in the middle than at the edges,

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it makes a negative lens,
so things look smaller.

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And this one is actually pretty much parallel.

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It doesn't seem to make my face there...

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Actually, I think it makes me look better!