The April stories at the Flying Circus of Physics web site:

1. Pub trick of the month: A coin lies below an empty glass drinking container. When you pour water into the glass, the coin disappears. How can water hide a coin? And once hidden, how can you make the coin reappear without removing the water from the container? Ah, I bet you can win a few pub wagers on this trick.

2. What physics lies behind the whip move in roller derby? (How can we find physics amid all the head bashing?)

3. If you are lucky, you can see a shock front out on an airplane wing -- a shadowy distortion that shimmies in the air turbulence that oscillates the wing.

4. My old article about shock fronts and other physics amusements to get you through a otherwise tideous airplane journey.

5. Strange to relate, some gun sights that provide illumination in dim conditions owe their light to quark transformations.

Come find these stories (and hundreds others) at www.flyingcircusofphysics.com. Also visit the new Facebook site: google "Facebook flying circus of physics". You don't have to be a member of Facebook to visit. Consider signing up as a fan of the site. I am producing and posting new videos there every month. The first in the series is about the Cheerios effect.

As always, if you have an idea for a story, please leave a message on Facebook, either on the FCP wall or my personal wall.