From the brains behind brains on, this is the moment of um.

Um, um, um, um, um, um, um, um, moment of um comes to you from APM studios. I'm Mr Prim.

Um.

Hello, pleased to meet you. I'm the owner, proprietor, and founder of Mr. Prim's Prim and Proper Etiquette School.

We specialize in teaching the basics of proper behavior, such as how to properly pass gas in the company of others.

Simply, excuse yourself to an adjoining room, open a window, and point your derrier in the direction of said window.

Hum loudly to distract your guests from any distasteful sounds.

Or how to properly inform your best friend they have a booger in their nose.

I'm so sorry to bother you, sir, but it appears you have a bat in the cave,

also known as a snop monkey or schnaz goblin.

And of course, here at Mr. Prim's Prim and Proper Etiquette School, we instruct all

students in the proper way to stir a cup of tea. Three slow stirs in the clockwise direction,

followed by a single stir in the counterclockwise direction. Do not, I repeat, do not, stir your tea too quickly. It is quite

unseemly and will create what appears to be a tiny tornado in the tea, a wee little whirlpool,

if you will. So improper. Why does it happen? Beckett would like to know too.

When you stir a liquid very quickly in a circle, you can end up getting a tornado type structure forming. My name is J.C. Bird, and I'm an associate professor in mechanical engineering at Boston University.

And my particular area of focus is looking at interfacial fluid dynamics, which is another way of saying drops and bubbles.

By stirring the liquid, you've created a circular flow.

And what happens is that the motion that you have changes the pressure.

If you were to look at a liquid, or fluid in the air, if it's moving faster, the pressure will drop down as opposed to when it slows down.

Similarly, if you have fluid that's accelerating, the pressure will go down as a result, and it's going faster.

So in the case of your spinning tea, you're going to have the velocity closer to the middle of this vortex as being faster than the velocity further away in the center of that vortex. Where the velocity is faster, the pressure is lower.

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