Did a search for ping pong balls, optical trapping, optical tweezers, etc., and figured this oldie but goodie thread would be the best place to post this.
This is an old experiment that is eye-safe and shows the same principles of a laminar flow imparting force on a spherical "particle."
Take a hair dryer, set to cool, and point it straight up.
Now, place a ping pong ball in the airflow, about an inch up, at the point where the air flow and gravity "balance out"
You now have a hairdryerly trapped particle! Note that you can even rotate the hair dryer and still keep the ball in place in the airstream!
This is kinda sorta like optical trapping, except there is a bit more help from a principle discovered by some bloke named Bernoulli. Same thing that keeps airplanes in the air. The parallels with optical trapping show up when you think about the forces that hold the ball in place, and not so much when you think about how the forces come about.
Anyways, figured this would be a good place to put this random, much safer, demonstration.
