When the Fort Wadsworth cannon sounds on Nov. 4, propelling more than 47,000 marathon runners across the Verrazano-Narrows Bridge for the New York City Marathon, Jack Hirschowitz’s first strides will be charged by the steady pulse of three white spheres, looping like electrons orbiting around an invisible core.

“It’s mayhem at the start,” said Hirschowitz, a psychiatrist. “Everyone is excited. People are taking pictures. Elbows are jostling.”

So it’s no one’s fault, he explained, if his flying beanbags are bumped or even dropped.

“I carry two extra in my fanny pack just in case,” he said, adding that other runners need not worry. “They flatten if they get stepped on.”

Strangers may call him a showoff, but if he completes his fifth New York City Marathon, Hirschowitz, 67, will be the oldest person to joggle a marathon.