On a clear day in 1991 off the coast of California, I landed with my crew in our Navy H-3 Sea King helicopter aboard the aircraft carrier USS Nimitz after flying on plane guard.

On plane guard you fly in perpetual orbits on the starboard side of the carrier, waiting patiently to rescue survivors of aircraft mishaps or those unfortunate flight deck crew members blown overboard. After we landed, I hopped out the helicopter’s cargo door onto the Nimitz’s flight deck. I signaled the enlisted aircraft signalman standing in front of the helicopter for permission to walk under the spinning rotors.

As I walked under the rotor arc, the signalman started to point to the sky. It was a hand signal that I had never seen before and I had no idea what he was attempting to communicate. A moment later, I was knocked to the deck by an intense pressure wave. After seeing stars, I looked up and saw two F-14 Tomcat fighter jets in full afterburner, racing straight up into the sky at unfathomable speeds.

When an object moves faster than the speed of sound, it produces a shock wave that forms a cone of pressurized air that moves across the Earth's surface. The sharp release of pressure is heard as the sonic boom.

The speed of sound in air at sea level is about 761 mph, depending on air density. Generally, the higher your altitude, the less dense the air will become and the slower the speed of sound. For example, the speed of sound is about 100-mph slower at 50,000 feet.

In 1947 Chuck Yeager became the first person to fly faster than the speed of sound in the X-1 rocket-powered aircraft. He had the courage to break through the "wall" of intense pressure that builds up in front of the aircraft before achieving supersonic speeds.

I had the honor to meet Chuck Yeager while standing next to our helicopter while he toured the USS Carl Vinson. I will never forget how his face lit up when he saw the helicopter’s rescue hoists.

John Lindsey is Pacific Gas and Electric Co.’s Diablo Canyon Power Plant marine meteorologist and a media relations representative.

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