It's impossible to understand the way NBA offenses and defenses operate without understanding gravity. No, not the force Sir Isaac Newton discovered that keeps you from dunking without a trampoline. We're talking about the basketball version of it, the one that governs where defenders position themselves and helps determine the success and failure of offenses.
Every offensive player has gravity -- but not all players have the same gravity. (More on that in a second.) Beyond them, the ball has gravity, because of the need to pressure the ball-handler and keep him from getting a wide-open shot. And the basket itself has gravity, since the highest-percentage shots tend to be taken from close range.
More than anything else, the primary factor determining a player's gravity is their shooting ability. Defenders can't stray from good shooters like Kyle Korver lest they give up an open shot -- and then get chewed out by their coach. Against weaker shooters, defenders can cheat an extra step toward the ball or the paint, making it easier for them to offer help to teammates.
Crucially, though, gravity is contextual. Shooting ability is most important when players are off the ball. When it's in their hands, the ability to drive and make plays for teammates become paramount factors. Consider the difference in how a player like Tony Parker is defended with and without the ball. And location on the court also matters. A put-back specialist with limited range has almost no gravity when he plays on the perimeter, but high gravity inside the paint because of the threat he poses on the offensive glass.
The best offenses account for all of these factors, and put their players in positions where they have the most gravity. Bad offenses feature low gravity, which means poor spacing and limited driving lanes to the hoop.
The gravity theory is simple enough, and I've been using it to describe offenses for years. Quantifying gravity to understand how it actually plays out on the court is another matter entirely. While it might be teased out of plus-minus data, nothing in the box score reflects a player's gravitational pull.
Over the summer, STATS Inc. introduced a pair of new statistics utilizing SportVU data to measure the gravitational force of players without the ball. The first, named "gravity score," measures how closely the primary defender defends a player off the ball at any given time. The second, "distraction score," quantifies how much attention the primary defender gives the ball-handler.
The graphic below, courtesy of STATS, shows what each of these metrics measures for Los Angeles Clippers forward Matt Barnes. The gravity score is how close his defender (Kevin Durant) is to Barnes, and the distraction score is how close his defender is to the ball-handler (Chris Paul).
Gravity is one of the four fundamental forces in the universe, alongside electromagnetism and the strong and weak nuclear forces. Despite being all-pervasive and important for keeping our feet from flying off the Earth, gravity remains, in large part, a puzzle to scientists.
Where F is the force of gravity, m1 and m2 are the masses of two objects and r is the distance between them. G, the gravitational constant, is a fundamental constant whose value has to be discovered through experiment.
The German-American physicist Albert Einstein brought about the next revolution in our understanding of gravity. His theory of general relativity showed that gravity arises from the curvature of space-time, meaning that even rays of light, which must follow this curvature, are bent by extremely massive objects.
Gravity perplexes scientists in other ways, too. The Standard Model of particle physics, which describes the actions of almost all known particles and forces, leaves out gravity. While light is carried by a particle called a photon, physicists have no idea if there is an equivalent particle for gravity, which would be called a graviton.
But gravity has still been used to uncover monumental findings. In the 1960s and 70s, astronomers Vera Rubin and Kent Ford showed that stars at the edges of galaxies were orbiting faster than should be possible. It was almost as if some unseen mass was tugging on them gravitationally, bringing to light a material that we now call dark matter.
Although our primary motivation is in constructing a consistent theory of gravity and quantum mechanics, the approach considered here has several other consequences. The theory does not require the controversial measurement postulate of traditional quantum theory. Rather, the interaction of the quantum degrees of freedom with classical space-time necessarily causes the quantum systems to localize. The theory also has implications for the black-hole information paradox and has an experimental signature, owing to the inherent stochastic and unpredictable nature of space-time curvature.
The fundamental force of attraction that all objects with mass have for each other. Like the electromagnetic force, gravity has effectively infinite range and obeys the inverse-square law. At the atomic level, where masses are very small, the force of gravity is negligible, but for objects that have very large masses such as planets, stars, and galaxies, gravity is a predominant force, and it plays an important role in theories of the structure of the universe. Gravity is believed to be mediated by the graviton, although the graviton has yet to be isolated by experiment. Gravity is weaker than the strong force, the electromagnetic force, and the weak force. Also called gravitation See more at acceleration relativity.
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