Here's something you don't see every day: 2,000 ping pong balls and 30 middle-school teachers floating around in zero gravity.

This weightless snapshot was taken in the skies above Cincinnati/Northern Kentucky International Airport, to capture a moment when teachers were demonstrating Newton's laws of motion for their students. [Photo: 2000 ping pong balls in zero gravity.]

The recent zero gravity jaunt was part the Weightless Flights of Discovery program, an effort to engage middle-school students in science and math. Weightless Flights, in its fifth year, is led by aerospace and defense firm Northrop Grumman.

The teachers and ping pong balls achieved weightlessness aboard a specially modified Boeing 727 operated by the Zero Gravity Corporation. After reaching a cruising altitude of 24,000 feet (7,273 meters), the jet flies in a parabolic motion. It climbs at a 45-degree angle to 34,000 feet (10,303 meters), then levels off, flying in a gentle arc for 20 to 30 seconds.

During this part of the flight, the centrifugal force exerted on the plane and its passengers cancels out the force of gravity, and ping pong balls are free to float. Then the plane dives to the parabola's trough, where it can begin another climb, starting the process over again.

Typical Zero Gravity outings complete 12 to 15 parabolas during a flight, according to the company's website, delivering up to 8 minutes of weightlessness during a 1- or 2-hour flight.

After their Sept. 14 trip, teachers planned to return to their classrooms to discuss their experience ? and Newton's laws ? with their students. The kids may be jealous they didn't get a taste of zero gravity for themselves, but at least they didn't have to help clean up all those ping pong balls.