Tempest in a Teacup

What’s that you say? You want ANOTHER post on the physical properties of hot, caffeinated liquids? Well, you’re in luck!

I know I’m sitting on the edge of my seat…

In this month’s issue of Physics Today (sorry, articles are by subscription only), there is a little story on how your morning cup of coffee relates to celestial dynamics and our planet’s weather patterns.

When cold milk is added to hot tea, it drops straight to the bottom, but billows to the surface due to evaporative cooling and convection in the cup. As the surface of the tea cools and sinks, it displaces the underlying milk layer. The initial movement is actually a mathematical analog of the surface of the sun!

What’s more, if you rotate the cup (as I do with the help of Supertramp), rotational and convection forces interact to create vortices between the cold and hot fluids. Despite the admittedly low quality of the video, take a look at the lighter spots of the tea spinning around the cup, these spots are helping physicists model hurricanes, ocean currents, and even Jupiter’s unsettled atmosphere.

As the tea attempts to achieve uniform rotational motion of every molecule, it is hindered by the up-and-down motion created by convection. These very same properties and effects, accompanied by others such as the moon’s gravity, are those that cause the Coriolis Effect and Earth’s weather patterns.

The vortices in this cup of tea model the behaviour of hurricanes.

Tomorrow morning as you mix your wake-up cup, try to resist stirring for a moment and watch a tiny example of the forces that shape our universe.

This entry was posted in Experiments, Explanations and tagged , , , . Bookmark the permalink.

One Response to Tempest in a Teacup

  1. pawsitivelife says:

    Im still confused…if only I had an advanced science degree…Biology, what is it good for?


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