At the Rolling Stones concert, there’s something poetic about the heat index hitting 92 at dusk. But if you don’t believe in weather-as-divine-metaphor, just know that the 21st century was well underway at Maryland’s FedEx Field on Wednesday night, and this band sounded alive. Not “still alive” — a phrase that can feel patronizing and rah-rah — but totally alive, completely present, sweating out songs in real time, elegantly pushing rude noises into an unknowable future.

This wasn’t a band of survivors reenacting their once-greatness. This was the greatness.

What was happening up there? The Stones haven’t sounded this sharp, this tight, this spirited or this centered in more than a decade — and Mick Jagger having a piece of his heart surgically replaced just a few months ago probably has everything to do with it. Suddenly, a band that had spent the past 40 years refusing to die was reminded that its principals most certainly will. For the rest of us, the group’s invincibility myth seems to have finally collapsed under a more universal truth: The only reason life has meaning is because it ends.

Before all that, it had been wild watching our heroes grow old in their immortality. If 1989 marks the year that people officially began wondering whether their favorite rock group should have an expiration date, that means today’s Rolling Stones — Jagger, 75, Keith Richards, 75, Charlie Watts, 78, Ronnie Wood, 72 — have been “old” for longer than they were “young.”

And while it’s been fun listening to fearless old men play the music of fearless young men, we’re past that now. To hear the Rolling Stones perform in 2019 is to hear a gang of sages share a profound knowledge of their own bodies, as well as a consummate awareness of one another’s. As musicians, they’re communicating on the highest frequencies. Instead of mental telepathy, it’s physical telepathy.

Just look at Jagger cut across that stage, strutting and smooth, like a rooster imitating a shark. On Wednesday night, he appeared ready to prance off into the void, but his feet were always tethered to whatever Watts was up to on the snare.

And every time Jagger sang, it was as if he were trying to push the entire world out of his mouth. There was no skimping, no corner-cutting — from the hungry shouts of “Jumpin’ Jack Flash” and “Satisfaction” to the ghostly falsettos of “Miss You” and “Gimme Shelter.”

As for the rest of his body, it performed so much more than sexy air traffic control. He was leading by example in a nonverbal, nonstop way. Look, Jagger said with his swirling hips and punching fists, this is what music can do to you.

Watts acted as the band’s center of gravity, pushing and pulling on space-time in a way that gave the music its nastiness and its dignity. During “Midnight Rambler,” the rest of his body seemed to freeze whenever his left hand slapped down on the snare — as if this gesture needed the entirety of his attention, as if time itself might break apart were he to become a little too careless about it.

And that gave Richards tacit permission to be as careless as the moment demanded. As a guitarist, he’s unmatched when it comes to making something terribly wrong sound exactly right, and he did so many crude things to those delicate guitar strings, making his riffs sound like horn sections and crashing jets.

He and co-guitarist Wood spent the night practicing a style that Richards calls “weaving,” but during “Rocks Off” and “Sympathy for the Devil,” Wood was weaving with silk while Richards was using rebar.

The only reason the tapestry held together was because everyone was locked in with Watts. In Richards’s 2010 memoir, “Life,” he traces all of his band’s deepest magic back to the human body, describing the genius of Watts as “something to do with the way Charlie’s limbs are constructed.”

So physical telepathy then. The drummer’s arms were speaking to the frontman’s feet and the guitarists’ fingertips, and it all sounded hyper-attentive, and ultra-vivid, and as real as real life. Maybe that was the message. Listening is living — and tonight, that’s what we were all here to do. Jagger didn’t mention his surgery. Nobody mentioned the fact that it was the 50th anniversary of the drowning of the band’s founding guitarist, Brian Jones. Death felt very far away.

At least until Richards elbowed his way into “Start Me Up,” a tune in which Jagger’s promise to “never stop” means something new each time he sings it. It used to be a song about living forever. Now it’s a song about living like you deserve to.