It was 15 years ago last Sunday that New York City experienced an event so horrific it realized the impossible — it stopped time in the city that never sleeps. When two commercial airplanes, hijacked by terrorists, were deliberately crashed into the World Trade Center’s iconic towers, New York City, as we know it, vanished.

A city notorious for high-speed living, hustle and bustle and a seemingly endless supply of human energy became eerily quiet in the days following Sept. 11. Wall Street’s opening bell didn’t toll. Subways didn’t run. Streets normally crowded by millions occupied by the push and shove of daily urban life became unrecognizably empty. And over ten long and painful days, no professional sports were played in New York. How ironic, then, to recall that something as simple as a baseball game finally marked New York’s return to normalcy, reasserting the city’s storied resilience.

On Sept. 21, 2001, ten days after the attacks, New York’s beacon of hope came in the form of a dramatic home run. That night, the New York Mets matched up against the Atlanta Braves in the city’s first major sporting event since the attacks.

With the Mets down 2–1 in the bottom of the eighth, Mike Piazza — a star catcher and the undeniable soul of a gritty team — stepped up to the plate. There was one runner on base. Braves pitcher Steve Karsay, a native New Yorker himself, was on the mound. His catcher, Javy Lopez, called for a delivery away, but Karsay missed and the ball came across the center of the plate, belt high, a tantalizing opportunity for any hitter and one that Piazza instinctively seized. He sent the pitch soaring high into the New York night. With one swing of the bat, Piazza gave the Mets the lead, and the crowd the cathartic release that they so desperately craved. Buoyed by the strength of 41,235 fans, the Mets went on to win the game 3–2.

At the time, I was five years old and unable to comprehend the significance of such a moment. But as I grew older, Piazza’s home run became the way I remembered 9/11 and New York’s resilience — albeit with the help of my dad.

In the years following, replays of Piazza’s home run frequently aired on TV around the anniversary of 9/11. Each time it was replayed, it became a way my dad and I would talk about 9/11 and, eventually, how I came to view such a complex event. Emotional but serious, clearly still moved by the drama himself, my dad described how important Piazza’s home run was to repairing New York’s psyche, to bringing back the New York we knew and loved.

“It was as if, during that moment, with that one swing of the bat, everything was okay,” he said. “It was the message that, ‘yes, we will get through this, we will rise again,’ and that was the glimmer of optimism so many New Yorkers at that moment needed.”

As the memories of 9/11 begin to fade, supplanted in the mind by new atrocities, it is professional sports that have continued to remind us of its singular importance. More than any other institutions, professional sports have continued to honor the victims of 9/11 and, in so doing, remind us of what was lost that day.

Last Sunday, New York Yankees manager Joe Girardi and Yankee relief pitcher Dellin Betances placed a wreath next to the 9/11 Memorial in Monument Park. In a ceremony before the Yankees’ game that day, the mournful sound of bagpipes, so reminiscent of the funerals that followed the attack, rippled through the air. Fire Department of New York veteran Frank Pizzaro was honored, and a massive American flag was unfolded covering the outfield.

At AT&T Stadium in Arlington, TX, the Dallas Cowboys and the New York Giants prepared to battle on the opening day for the 2016 professional football season, but before they began, all listened to former president George W. Bush deliver a message of remembrance and encouragement.

And last Sunday, the New York Mets played the same team they had played on that fateful day back in 2001, the Atlanta Braves. Things were different, of course. Mike Piazza long ago retired and this summer he was inducted into the baseball Hall of Fame. The Mets are battling for a playoff spot and the Braves, no longer a contender, are looking to finish out a miserable season. Still, before the game, both teams warmed up in FDNY and New York Police Department hats. And after the end of the game, both teams came together to shake hands, just as they had during the game following 9/11.

Fifteen years may have passed, but baseball remembers.