Friday, November 7, 2014

Water Boys

Click the arrow to watch. Video source: NASA's Marshall Center YouTube channel.

The International Space Station was envisioned as humanity's permanent microgravity research platform. Materials may behave differently in microgravity than on Earth.

A simple demonstration of that is with water. The above video, posted November 3 on the Marshall Space Center YouTube channel, shows how surface tension becomes a dominant property when gravity is absent.

To quote from Wikipedia:

The cohesive forces among liquid molecules are responsible for the phenomenon of surface tension. In the bulk of the liquid, each molecule is pulled equally in every direction by neighboring liquid molecules, resulting in a net force of zero. The molecules at the surface do not have other molecules on all sides of them and therefore are pulled inwards. This creates some internal pressure and forces liquid surfaces to contract to the minimal area.

Surface tension is responsible for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a spherical shape by the cohesive forces of the surface layer. In the absence of other forces, including gravity, drops of virtually all liquids would be approximately spherical. The spherical shape minimizes the necessary “wall tension” of the surface layer according to Laplace's law.

In the NASA video, U.S. astronauts Steve Swanson and Reid Wiseman are joined by ESA astronaut Alexander Gerst to demonstrate the properties of surface tension — by inserting a GoPro camera into a blob of water.

Boys will be boys.

If you have red-blue 3D stereoscopic glasses, click here to watch the video in 3D.

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