St. Patrick's Day Lesson

I love this holiday. Many people use this day as a reason to drink, and so do I. In fact, I took the day off for an entire day of drinking with good friends - one of my favorite things in the world to do. But while I do love drinking a good pint (or more) of the Johnny Jump-up, I am not a believer of blind drinking. One must never stop learning new things, and I took this opportunity to learn a little bit more about my favorite beer, Guinness.

One of my favorite things about Guinness is watching the famous cascade of bubbles. It is wonderful to behold, and mesmerizing every time I drink it; I can't stop looking! But what causes it? On the surface, it doesn't make sense why the bubbles fall down. They are, after all, less dense than the actual beer itself, otherwise the famous 'Bishop's collar' would be at the bottom of the glass (ha! Bishop and bottom in the same, non-ironic sentence!). This seemingly glaring violation of physics is actually easily explained.

In the interior of the pint glass, bubbles are, in fact, rising to the top, creating that delicious, delicious head. But, since those bubbles take up space, small as they are, they push other bubbles out of the way. The bubbles right up against the glass have nowhere to go (poor them).

Pint glasses, like most other smooth objects, are actually really rough when looked at with a scanning electron microscope. That roughness creates drag. When the poor little bubbles run up against this rough glass, the bubbles have nowhere to go but down, carried along with the falling nectar. So the falling bubbles are only the ones on touching the glass; all others are rising up to create the head. But don't take my word for it, read for yourself!

Now enjoy St. Patrick's Day with some good friends, music, and of course a properly poured Guinness!