Friday, January 16, 2009
The Pitch Drop Experiment
Not exactly faster than speeding bullet or more powerful than a speeding locomotive, nonetheless the ability of gravity to induce creep flow in extremely high viscosity materials is relentless. Ignoring this can lead to peril, such as when the ceiling collapsed in Boston a few years back. It can also lead to extremely long duration experiments such as the pitch drop experiment. While the experiment and the imponderablely slow motion (barely) captures the imagination in the ways that astronomical distances and geological time does, the links within the site lead to many further discussions on attempts at quantification of the experiment - no small task. Seasonal/monthly/daily temperature changes all impact the viscosity, as does the more recent addition of air conditioning to the building.
No mention of oxidation of the pitch. And since the stem is not of constant diameter, there is an element of extension in the flow field that is not captured. And given that l/d for the stem is less than 20, you can even argue that the flow field is not fully developed, thus invalidating the use of Poiseuille's law. But they have won an Ig Nobel prize, so I'm quite green with envy.