John Gay, USA, US Navy
F/A-18 "Hornet" Passes Through Water Vapor Cloud at Speed of Sound
1st prize (of 42,000 entries) Science and Technology World Press Photo Contest 2000

Here is the story behind it:

Through the viewfinder of his camera, Ensign John Gay could see the fighter plane drop from the sky heading toward the port side of the aircraft carrier Constellation.  At 1,000 feet, the pilot drops the F/A-18C Hornet to increase his speed to 750 mph, vapor flickering off the curved surface of the plane. In the precise moment a cloud in the shape of a farm-fresh egg forms around the Hornet 200 yards from the carrier, its engines rippling the Pacific Ocean just 75 feet below, Gay hears an explosion and snaps his camera shutter once.

"I clicked the same time I heard the boom, and I knew I had it," Gay said.  What he had was a technically meticulous depiction of the sound burrier being broken July 7, 1999, somewhere on the Pacific between Hawaii and Japan.

"At sea level a plane must exceed 741 mph to break the sound barrier, or the speed at which sound travels. The change in pressure as the plane outruns all the pressure and sound waves in front of it is heard on the ground as an explosion or sonic boom. The pressure change condenses the water in the air as the jet passes these waves. Altitude, wind speed, humidity, the shape and trajectory of the plane - all of these affect the breaking of this barrier. The slightest drag or atmospheric pull on the plane shatters the vapor oval like fireworks as the plane passes through," he said. "You see this vapor flicker around the plane that gets bigger and bigger. You get this loud boom, and it's instantaneous. The vapor cloud is there, and then it's not there. It's the coolest thing you have ever seen."