One kilogram weighs about 2.2 pounds. Actually, it weighs a shade over that, closer to 2.205 pounds, and if you want to be really precise, if you want to pin it down with the merciless precision of an Emma Raducanu service return, you could keep throwing in decimal places, could climb up to 2.20462 pounds, 2.20462262 pounds; you could keep going. Compared to the pound, which dates back millennia—at least to the Roman libra (hence lb.)—the kilogram is a relatively recent invention. It was devised in France in 1795, at the dawn of the metric system, when it was defined as the mass of a single liter of water. In 1799, a platinum cylinder weighing exactly one kilogram was fabricated and deposited in the National Archive in Paris, and after ratification by the French Bureau of Weights and Measures, this platinum Kilogramme des Archives became the official kilogram. That is, it wasn’t an approximation or a representation. It was the thing itself. Whatever that cylinder weighed at any moment was, by definition, one kilogram.
It’s a strange thing to imagine a unit of measurement, something that seems inherently abstract and ideal, being embodied like that, existing in concrete form in the physical world. I don’t know; if you’ve followed tennis for the past 15 years or so, during the era of Novak Djokovic, Roger Federer, Rafa Nadal, and Serena Williams, maybe the notion of an abstract ideal taking physical shape will seem less strange to you than it might to other people. Still: With the right key, you could walk into a room and see the kilogram. If you rubbed it, and an atom of the cylinder came away on your hand, you had just changed the fundamental meaning of the unit.
The Kilogramme des Archives remained the official standard for 90 years, until 1889, when it was replaced by a new cylinder, one with iridium added to the platinum, to increase its hardness. The new cylinder was called the International Prototype of the Kilogram. It was about the size of a golf ball. Six sister copies were made, and the original and all six copies were stored—they still are—in an environmentally controlled safe in the lower vault of the International Bureau of Weights and Measures in Paris. Three separate keys, which are controlled by three different people, are needed to open the vault. I’ve always thought this would make for an incredible heist movie. The standard is there, but accessing it? Not so easy.
I started thinking about the history of the kilogram deep in the third set of the men’s U.S. Open final, somewhere around the time Daniil Medvedev, who was leading two sets to none, went up 4-0 over the top-ranked Djokovic. Djokovic, as you might have heard, had already won the Australian Open, the French Open, and Wimbledon this year; he was trying to become the first man since Rod Laver in 1969, and the first player since Steffi Graf in 1988, to complete a calendar Grand Slam. He was also trying to win his 21st major singles title, a total that would have seen him inch ahead of Federer and Nadal, his rivals and fellow all-time greats, who are tied with him atop the all-time majors list at 20.
To say that Djokovic thrives in moments like this one is an understatement. Against the Russian world no. 2, though, he looked totally flat. Medvedev is a gangly scarecrow of a player whose height (he’s 6-foot-6) doesn’t prepare you for his slippery mobility. For most players Medvedev’s size, “variety” means corking a 127 mph serve instead of a 136 mph one, but Medvedev has a way of sailing across the court with an implausible, elongated grace, somewhat reminiscent of the way Peter Crouch used to play soccer. His body whirligigs from the baseline to the net, quirking into shapes like the ones hovering over the head of a clubbed cartoon character, and the ball comes zinging back at a tidy and often imaginative angle. He has a thundering flyswatter of a backhand and a dry on-court demeanor: He stays loose and reacts to points as if he’d been handed a cheap glass of wine and asked whether he liked it. “Not bad,” he seems to say, or “Meh! A little syrupy.” He’s not exactly new to the tour, having previously reached major finals in 2019 (at the U.S. Open) and 2021 (at the Australian). But the dominance of the Big Three has been such that 25 doesn’t seem as old as it used to. Medvedev, like several other players in the so-called next generation of men’s stars, seems like a bit of a kid, despite being an age when past generations of male players had come fully into their primes.
It was Djokovic who beat Medvedev in that Australian Open final, played not even eight months ago. Actually, he didn’t just beat him, he crushed him, winning in straight sets and losing only four games combined over the last two. The International Bureau of Weights and Measures has not defined an official standard for an ass-kicking, but 7-5, 6-2, 6-2 is pretty close. On Sunday, though, in Flushing Meadows, it was the Serbian player who had no answer for his opponent. From the start of the match, he looked tired and cowed, which are usually the last two things he looks. A player of legendary physical fitness, he moved with a startling heaviness, slapping his legs between points as if to wake them up. A player whose killer instinct and refusal to succumb are, to me, almost unfathomable, he dumped sure-thing shots into the net, failed to exploit the poor passing shots or get to the gettable drop shots Medvedev repeatedly sent his way. He smashed his racket; it didn’t help. Not even the support of his sometime nemesis, the crowd, which came ready to will him to make history, seemed capable of firing him up. He wound up losing 6-4, 6-4, 6-4.
Locked away in its controlled Parisian vault, the platinum-iridium International Prototype of the Kilogram remained the official standard for the unit for more than a century. In the late 1980s, it was discovered that the weight of Prototype was about 50 micrograms lighter than expected. After a lot of deliberation, a new standard was ratified in 2019, and what supplanted the Prototype was something both less concrete and less prone to fluctuation: an abstract formula based on universal constants.
This new definition allows for an inalterable and theoretically eternal unit of mass, but it’s close to within a whisper to both the platinum cylinders and the original 1795 construct: It’s within 30 parts per million of the mass of a liter of water. Unlike the mass of water, though, it doesn’t depend on Earth’s gravity or anything else to remain constant; as long as the fundamental laws of the universe hold, the kilogram can be reconstructed anywhere in space or time.
Novak Djokovic has a winning record against both Federer (27-23) and Nadal (30-28). He’s won the career Grand Slam twice, something neither of them has managed (Federer has won only one French Open, Nadal only one Australian). He’s spent more weeks ranked at no. 1 than either of his rivals (337 vs. 310 for Federer and 209 for Nadal). He’s dominated a decade of tennis in which the field included two players who, in his absence, would have been regarded as the runaway best of all time. Djokovic has done plenty of things I don’t like—bailiff, please bring forward Exhibit A, labeled “Pandemic Dossier”—but doing things I like isn’t a necessary condition of being great at tennis. I think Djokovic is better at tennis than anyone else who’s ever lived, and the idea that he might lose this match seemed so far-fetched to me—even when he was way behind during the third set, even though he’d lost his bid to win the Golden Slam at the Olympics—that with Medvedev leading 6-4, 6-4, 4-0, I texted a friend that I figured the odds were about 50-50 that he’d win.
But watching him struggle, I thought: So often in sports I expect greatness to behave like an inhuman standard. It is represented by, I don’t know, Pete Sampras (the tennis equivalent of one liter of water if I ever saw one), and then a slightly more perfect version is devised, and then another, each one becoming a little more refined, a little more durable. Federer sits secure in a vault in Paris (and in fairness, I assume he does spend a lot of his time this way) until Djokovic masters the sport to an even more perfect degree and the standard passes officially to him. What is a kilogram? Consult the universal constants. What is tennis greatness? Consult the man with the thin face and the return of serve that makes you sort of gargle and slide off the sofa onto the floor.
It’s the mistake we make, thinking any of this is really predictable. The greatest tennis player of all time is not a math formula. He is a person whose apparent conquest of human weakness disguises the fact that human weakness is essentially unconquerable. Perfection is a major you will always eventually lose, for precisely the same reason that you can’t beat the ocean in a sword fight. Djokovic is the best tennis player of all time, and sometimes even his legs get tired. He’s the best tennis player of all time, but sometimes the ball looks smaller and faster than others; sometimes his head feels a little off; sometimes the irreducible complexity of variables in the moment filters through his brain in a way that leads to a flubbed backhand.
I have no idea what cost him the match today. The pressure? Sheer weariness (he played a five-set match against Alexander Zverev on Friday night, and has played several long matches in this tournament, having lost the first set in what feels like 400 matches in a row)? A combination? He wept after the match, and told reporters later that the end of his Grand Slam chase was a “relief.” It’s possibly a measure of the level at which he’s operated for the past several years that it felt like a revelation to me to remember that he’s not an ideal benchmark but a fallible human being.
But then, this U.S. Open was one of the most purely enjoyable tennis tournaments in recent memory, and one of the reasons it was so much fun was that it all seemed to take place in a world of messy, imperfect, optimistic human feeling. Over the past few years, the dominance of older players has meant that tennis has become captive to a kind of static reverence for its past. Even when it’s been exciting and dramatic, it’s often felt solemn; we have been thinking for a long time about pantheons and legacies and high purposes and global icons. This tournament, though? It felt young. Pick your moment—I’ll take Medvedev falling to the ground in a funny sideways slump after his win, then explaining to the crowd afterward that he was doing “L2 plus left,” which is the controller command for the dead-fish goal celebration in the soccer video game FIFA. A sport that often seems to revolve around Rolex ads, Mercedes ads, and Panama hats was suddenly full of surprise. The future, denied access to the grounds by a zealous usher for so long, was suddenly in the stadium.
And yes, I know: Naomi Osaka was and is the future. Iga Swiatek is 20, a major winner, and in the WTA top 10; Dominic Thiem, who won the U.S. Open on the men’s side last year, is … OK, well, he’s 28, but by modern tennis standards that’s adolescent. Youth hasn’t been completely absent from the game. All I can tell you is that the sport hasn’t felt this fresh for a long time. The astonishing, unbelievable run to the women’s title by Emma Raducanu—the first qualifier ever to reach a major final, let alone win one—was like a gust of air blowing away cobwebs. The equally astonishing run by her opponent in the final, Leylah Fernandez, was too.
Raducanu, who’s British, is 18; Fernandez, who’s Canadian, turned 19 during the tournament. Neither was a year old when Federer won his first major. Every match they played seemed to unlock, for the first time, some new dimension of their games. “I’ve started sliding, which I didn’t know I could do until now,” Raducanu said a few days ago. She always wanted to try it, so she figured it out, halfway through winning her first major. (Even there, human unpredictability reared its head: She had to be treated for a scraped knee after a rough slide in the final.) Raducanu had never played a tour-level match before this summer. Read that sentence again, and then read this one: She didn’t drop a set on the way to the title. She’s a major champion who’s never played a tour-level three-set match.
Raducanu, at 18, hits some of the sharpest and smartest service returns you will ever see. I would say they’re Djokovic-like—deep and toward the middle of the court—except at the moment, they’re more reliable. Fernandez has a brilliantly original game, all confounding angles hit from a step or two farther forward than you’d expect. She took out Osaka (third seed, multiple major winner), Angelique Kerber (16th seed, multiple major winner), Elina Svitolina (fifth seed), and Aryna Sabalenka (second seed) on her way to the final. When she was asked at what point she thought she could actually beat Osaka, she said, “From a very young age, I knew I was able to beat anyone.”
Women’s tennis has been so volatile at the top, and the pressures facing young players who break through can be so punishing, that it’s hard to predict the future, though it’s a happy thought to imagine these two playing each other for the next 10 years and more. Right now, they can beat anyone. On match point, at 6-4, 5-3 in the second set, Raducanu hit an ace, after which she put her hands to her face and walked to the net, laughing in something that was not quite disbelief. The weight of the world is said to be about 5.972 × 10^24 kilograms. Djokovic would go on to feel every one of them on Sunday, but at that moment, for Raducanu and everyone watching her, the world seemed to weigh absolutely nothing at all.