Michael Jordan is working out in a gym alone, just shooting around. A door opens on the other side of the building, and in walks none other than Michael Jordan.

Only this is the young-legs MJ, the circa-'87 MJ, complete with a No. 23 Bulls uni, a pair of the old, bold red-and-black Airs on his feet, and hops for days and days and days. The game is on.

Experience versus hunger. Wisdom and guile head-to-head with brilliant abandon. Head-fakes and shoulder leans on the perimeter against head-fakes and acrobatics around the rim. Trash talk in both directions. Playoff intensity and playground swagger in the air.

	That sound you hear is David Stern crying.

It's a David Stern fantasy and a fan's dream. It's the kind of idea Michael probably uses to get his 39-year-old body and mind geared to go each night. It's the new Gatorade commercial, "23 vs. 39."

And when it plays, whether you're seeing it for the first time or the 10th, you stop what you're doing and watch. You watch like you're eating candy, like you can't get enough. And when it's over, when you shake yourself out of the sweet, fantastic stupor of living in a world where Michael takes on Jordan in the ultimate cager match, you have one question: How did they do that?

Glad you asked.

The creative team at Element 79 in Chicago gave birth to the concept last summer, with a Photo-Shopped graphic of the two Jordans face-to-face and the title: "23 vs. 39."

"We wanted it to be a very simple, clean idea," says Dennis Ryan, chief creative officer at Element 79. "We wanted to treat it like a character study. Just Michael vs. Michael."

They sent MJ a rough-cut video trailer of what the spot would be like, because, Ryan says, "with a star as big as Michael, we actually have to court him."

Lucky for them, lucky for us, Michael was into it.

The problem from the get-go, of course, is that you can't double Mr. Jordan for something like this (it's usually been a loser's gambit on the court, too) -- he's too recognizable. Trot out a fake MJ and watch credibility and cool go waltzing out the door.

Rumor has it the Raelian sect was offering a cloning option for a while, but Ryan and company decided to give the make-me-an-MJ (there, you're an MJ) gig to James "King of the World" Cameron's Digital Domain, a crew who'd just come off an impressive, photo-real replication of Vin Diesel in action in "XXX."

Ryan and director Joe Pytka ("Space Jam") scoured the country looking for a kid who could bring the hammer down exactly like the brash, young Jordan did. After exhaustive interviews and tryouts in four major cities, they eventually turned up Kevin Daley, a 6-foot-6, 210-pound slam-alike who'd been playing on the Harlem Globetrotters traveling team. "We found only one guy," Ryan says. "Literally, he was the only one."

What you see in the ad is actual footage of Michael and Daley in a spirited game of one-on-one. The sniping, and most of the moves, are improvised.

Fred Raimondi, Digital Domain's visual effects supervisor, took the footage from that game, and he and his team set about making Daley into what he's (what we've all) always wanted to be: the young MJ.

They first did what's called a cyber scan on Jordan's head and shoulders. "Essentially, you sit in front of a laser beam and it scans your head and makes a 3-D model of it," Raimondi says.

Added to that were thousands of photographs of Michael's head, neck and chest -- close-ups, wide shots and every conceivable angle -- and the result was a very accurate digital sculpture of Michael Jordan in the computer.

A 3-D sculptor then took that model and, working with archived images of the 1987 Jordan for reference, touched it up and re-sculpted it to look like the younger Jordan (and then did it again, to look like the even-younger Tarheel Jordan who calls "next" at the end of the spot).

At the same time, another team worked on a program for "intelligent skin."

"Skin is translucent," Raimondi says. "It absorbs light. Light goes into it one color, bounces around, and comes out a different color."

To account for this, his colleagues analyzed human skin properties and wrote a "shader" program telling the computer how the skin should look at a given angle in a particular light.

A third team was all the while building a digital skeleton and musculature of Jordan's upper-body, based on the original cyber scan.

Why the bony-and-fleshy sub-structure? They didn't want Jordan's digital head to look like a cardboard cut-out riding shot-gun on Daley's body. Raimondi says they were going for skin on CG Michael's face and neck that would "do the things skin actually does when it's stretched over a body."

	"Man, this kid has potential"

Company animators then got the whole ball of wax -- a damn-near living, breathing Michael Jordan head that was a dazzling realization of the old Gatorade idea of being "Like Mike" -- and it was their job to tack it onto Daley's shoulders, and make it move the way MJ would, on every frame of film.

They were able to track the exact location of Daley's head in the original footage, because he wore white-dot markers on his face during the shoot, allowing them to later map his outline in numeric coordinates, and then paste the new-old Jordan head precisely onto them.

Bingo. Out with the taxi-squad Globetrotter, in with the second coming of the second coming.

The rest is details (what am I talking about, it's all details), the kind of delicious little features that make a techie's heart sing. Five guys worked on getting the tongue wag on the dunk right. Others were in charge of the glares, shrugs and laughs. And, of course, there was the talking.

It was all about verisimilitude, baby, and so rather than routinely animating young Jordan's lips, they dotted up the present-day MJ's face with tracking markers (like they had Daley's), put him in front of three cameras, and had him repeat things Daley said as the young Jordan during the game. The animators used the film for reference, and made sure their Jordan, like the real deal, talked just a little bit out of the side of his mouth, and spoke with what Raimondi calls "sticky lips."

"When Michael opens his mouth, his lips kind of stick together a tiny bit as he talks," he says. "So we wrote that into the computer model, too, so it would look authentically Jordan."

Nice, eh? Would you have thought of it? Me neither.

So that's how it works: the emergence of some new technology, what had to be a ridiculously healthy project budget, a bull-dog approach to working every layer of the problem and an artist's feel for nuance, and the next thing you know, you have an ad (about the ages) for the ages.

As for why the ad works? This stuff is subjective, of course, but I'll offer up a short list of why I think it strikes a chord:

1. It's bitchin' -- Camaro bitchin', cherry, sweet, clean, cool and fly. Do people still say "tight"? If they do -- even if they don't -- I'll say it: This ad is tight. You don't analyze this kind of thing too closely, you just know it when you feel it and you're glad of it. It's the kind of thing you know by its symptoms: a slow, sloppy head-wag and chuckle, a little spike in the heart rate, some shallow breathing, an urge to grab somebody and make them watch and wait with you for the next time it comes on -- this kind of thing.

2. The young Jordan, the one who dunked everything he got his hands on, from any spot on the floor, the one who seemed to tear through defenses like the Alien screaming through Ripley's ship, is somebody any of us who've watched the game in the last 15 years still carry around in our heads -- some with delight and some with fear. And either way, there's a wild kind of rush in seeing him again, not in some clip we know from before, but in a new context, against a new foe.

3. No soundtrack, just voices and crashing game sounds -- like that, that's nice.

4. The intricate marriage of technology and biology that went into making the ad are actually almost invisible in the end. The extraordinary technique ends up making things seem ordinary. What I mean is, the impossibility of the scenario gets squeezed out by the believability of the images of MJ-young and MJ-old, staring each other down. And what you have left feels like a familiar, genuine showdown, the kind of thing that could be played out in a gym, in a driveway, on a Nerf hoop in somebody's den, anywhere.

	There's only one person that can wear down MJ.

5. The yesterday-vs.-today fantasy matchup stuff is deep in the vein of the way sports fans think all the time. The elders-teaching-the-youngsters, youngsters-bucking-the-elders thing is even older and deeper than that.

6. There's a bit of farewell in the spot. We know we're seeing something close to the end of the MJ-era now, and by calling up the young man in Chicago, and the very young man in Chapel Hill, it gives us a chance to think of the scope of that era, to appreciate and reminisce.

7. The present-day MJ isn't surprised to see his younger self stroll onto the floor. It's like he's always known he was lurking, like he's been thinking about him, playing against him in his mind, using himself to push himself. There's an intriguing little peek inside one of the more guarded personalities of our generation in this, I think.

8. The powder-blue-and-white punch line is just right.

9. Every one of us can imagine (probably has imagined) being where MJ is in this moment. Were we more powerful back then, when our reflexes were quicker, when we could jump and reach a little (maybe a lot) higher than we can now? Or is experience the thing? Can we think our way into and out of possibilities and scrapes now that we would only have stumbled through then? And is that the power?

And the beauty of the ad is that it doesn't resolve the question. Both young and old Michael have their moments. The game is fierce, but it's never decided. "Michael said he couldn't let either his young self or his present-day self win," Ryan told me. "Because that would mean one of him would lose." It's a sweet stroke on MJ's part: We're left to wonder, but also to trust in and appreciate both versions -- young and old -- of him, and maybe even on some level, of ourselves.

10. Um, he's Michael Jordan.

Eric Neel reviews is a regular columnist for Page 2. You can e-mail him at esn@cox.net.