Friday, 10 June 2011

Surface tension of Superfluids

When scientists looked into the stars specific stars called pulsars they found something very very interesting on the surface.  They found superfluids that on the surface of the star behaved very very funny that when rotating at the correct speed they create a vortex which is recently being studied by a supercomputers at the University of Washington. 

These superfluids can be observed on earth by supercooling helium.  Liquid helium-4 itself becomes a superfluid when cooled to within a few degrees of on the Kelvin scale (minus 273 Celsius or minus 460 Fahrenheit), and the resulting lack of allows it to seem to defy , flowing up and over the sides of a container.  It has no viscoscity but does have a surface tension so this weird combination will cause a superfluid when placed in a glass to roll up the side of the glass and go down the other side.

The surface tension of super cooled liquid helium has been calculated to be 0.3 dyne/cm and by levitating it magnetically and studying its vibrational modes the surface tension could be determined to be 0.375±0.004dyne/cm between supercooled helium at the hydrogen interface. (no wonder when stirred it loses its fluid properties-see article above)

Why are superfluids studied?  Who cares.  It probably gets the guys studying them to get some girls back to the lab.  Do you want to see my supercritical fluid? you want to see my errr...  Anyways there must be some point even if laymen do not really understand it.  Besides being really cool (and the girls).  Because of the strange properties particularly the refractive index of the superfluid it can be used for spectroscopy experiments in particular Superfluid Helium Droplet Spectroscopy (SHeDS).  It has also found super precise things like gyroscopes when needing to understand gravity (think about that next time you are in a plane).  Possibly some more studies will help get more appreciation of superfluids so they can really become...super!