from Radiolab on the history American Football (fans may want to listen)
excerpted from the show:
JAD: Which gets us to that game. November 23rd, 1907, Carlisle plays the University of Chicago. Last game of the season. We're in Chicago. And the Chicago team is arguably the best in the nation.
ROBERT: The best. I don't think it's even arguable.
JAD: Well, Carlisle's good at this point, though.
ROBERT: Yeah. But Chicago's like Stagg Field, whoa!
JAD: And there are 27,000 people in the stands.
SALLY JENKINS: Well, what happened was the Chicago players had decided to try to defeat Carlisle's innovative forward passing by just knocking the crap out of their receivers every time they came off the line of scrimmage.
JAD: And so Carlisle's greatest receiver, Albert Exendine, our guy, had been stymied the entire game, because the minute the ball was snapped the Chicago players would ...
SALLY JENKINS: Hit him and try to throw him down or knock him out of bounds. So Pop Warner said to Exendine, here's what we're gonna do. Next time they hit you out of bounds, sneak around the bench and get back on the field.
JAD: By some accounts, this was Exendine's idea. But whoever thought of it, on the next play Albert Exendine as expected ends up out of bounds, but he keeps running.
SALLY JENKINS: He runs around the back of the bench.
JAD: Runs around the spectators, maybe around the band.
SALLY JENKINS: And comes back on the field.
JAD: Right at that moment ...
SALLY JENKINS: Hauser, the quarterback of Carlisle ...
JAD: Lets loose a vicious spiral.
JAD: Can I have you read something?
SALLY JENKINS: Sure.
JAD: Hold on.
JAD: This is Sally's description of that moment from her book The Real All Americans.
SALLY JENKINS: For a moment, it was a frozen scene in a staged drama. The ball hung in the air, a tantalizing possibility. Could Exendine reach it? Would he catch it or drop it? Defenders wheeled and stared down field. Spectators watching from the stands found that the breath had died in their collective throats. The spiraling ball seemed to defy physics. What made it stay up? When would it come down? In that long moment, 27,000 spectators mashed together on benches and crammed on platforms may have felt their loyalty to the home team evaporate in the grip of a powerful new emotion. They may have noticed something they never had before: that a ball traveling through space traces a profoundly elegant path. They may have realized something else. That it was beautiful. The ball struck its human target. Exendine caught the pass all alone and trotted over the Chicago goal line. The stadium exploded in sound and motion. It was the game breaker. The rest was just anti-climax. The final score was 18 to 4 for Carlisle. But the very next year, the Ivy League passes a rule that you can't leave the field and then come back on to it.
JAD: Oh, that's where that rule came from.
SALLY JENKINS: Yes. That's where that rule comes from.
JAD: And I've got to say that that description of the ball in the air is -- is timeless, in a way.
ROBERT: Beautiful.
JAD: That's exactly why football is still beautiful at times.
SALLY JENKINS: That's -- that's when -- Carlisle in 1907 is when American football becomes the sport that you watch today.
The parabolic path of a ball in flight. For many there's something profound and even beautiful about the path. Physics dictates it. Throw something in the presence of gravity and you get a parabolic trajectory. Well - almost parabolic. Air resistance slows the projectile and change the path anywhere from a little to a lot and some things crafty humans have done can further deviate the path - and sometimes the perception of the path - making sport and art even more interesting. It's something to watch for as the Olympics unfolds.
Jumping is a parabolic motion. A person launches themselves into the air and their center of mass traces out a parabolic path. It happens in the long jump, high jump, pole vault, dance, basketball, volleyball and much more. Athletes often change their shape and orientation around their center of mass to achieve a goal. A high jumper folds their body around a bar even though their center of gravity passes beneath (the Fosbury Flop). A ballet dancer appears to hang in the air when executing a grand jeté while their center of mass traces a parabola. The same illusion of hang time appears in basketball and volleyball. And gymnasts are masters of dancing their bodies around the parabolas they've created fractions of a second earlier.
Dimples on a golf ball minimize drag and have a large impact on range. Spin on a golf ball creates a force known as the Magnus effect that changes the ball's path a bit. Backspin, for example, creates lift. This effect has an impact on most other sport balls giving the athlete some control on the deviation from an expected parabolic path. In sports like soccer, table tennis and volleyball the effect is pronounced.
Some balls pass through interesting speed ranges where the drag on a ball can change dramatically on different parts of the ball adding a bit of chaos to the parabola. The screwball is a good example. These unpredictable paths are often difficult to master, but have become weaponized in a few other sports than baseball.
I've written about most of these effects in more detail, but it's fun to watch for these deviations from the expected parabolic trajectories. I started with American football and should mention the spiral.
In many sports spin is used to make a ball's path less predictable while in American football it's used to make the path more predictable and easier to catch. The difference is the odd shape of the ball. Drag from air resistance depends on the football's orientation. This is fine when the ball is kicked. The fact it's tumbling makes the path a bit more unpredictable to the opposing team.
A spiral pass is a different matter. Here the quarterback puts spin on the ball as it's thrown. The higher the spin, the more stable the football. This turns the ball into a gyroscope of sorts. If the ball is thrown pointed slightly up, for example, it will retain that orientation throughout its flight. The coefficient of drag remains constant and deviation from the expected parabola will be constant. That and the ball won't be tumbling when the receiver catches it.
There is a tradeoff. A quarterback has a finite amount of energy that can be transferred to the ball. Putting spin on the ball reduces how fast the ball can be thrown. Six hundred revolutions per minute is something of a minimal sweet spot. The ball is stable at that spin rate and it doesn't reduce range as much as a faster spin would. There's also another constant force from the direction of spin that makes the ball curve a bit to the right or left depending on the handedness of the quarterback, but that's another discussion and something quarterbacks compensate for.
manpo-kei, gold plated teaspoons and home runs
A friend had been struggling to find regular physical activity for a few years. She complained enough about a lack of motivation that her brother gave her a low-end Fitbit for Christmas. Somehow the pedometer function clicked for her. Being able to see the numbers of steps was as motivating for her as filling in circles on an Apple Watch is for other people. On top of this she'd heard about the magic 10,000 step number. Initially the goal was beyond her, but she was motivated and within a couple of weeks she was there. She's kept it up and regularly does 15,000 a day along with increasing her speed. Her blood pressure is down from last year's number and she feels healthier.
The NY Times recently ran an article on some inaccuracies in smart watches. It doesn't surprise me. I've been around Olympic programs and athletes for a few years and know some horror stories about the over-reliance of data when you don't know it's accuracy or the context of the measurement or its use. Like anything else with data, you need to know why, what and how you're measuring, manipulating, and finally interpreting and using the information. In sport that turns out to be difficult. There are a number of interesting approaches to deal with the issues, but that's another post.
The NY Times piece and elite training experience suggest broad trends over time are much more important than local accuracy and precision If you're trying to improve your fitness level or play amateur level sports, the motivation from a smartwatch can make a big difference. If you're an elite athlete there are many other things to consider and it's likely you're taking advantage of them.
The notion of broad trend over local accuracy has utility in many areas. One that frustrates me is building carbon dioxide removal technology. It's something of a delaying tactic being cheerleaded by the petrochemical and coal industries. In reality it's extremely expensive, requires a large amount of energy and diverts funding from much more effective technologies and behaviors. Currently four 1 million ton class plants are on the drawing board. With luck each could remove a million tons of carbon from the atmosphere by 2030 or so with a projected cost of about a billion dollars each. So how much of an impact is that?
A million tons of carbon dioxide is about 1/40,000 of current yearly emissions. That's roughly the same ratio as a teaspoon to a bathtub full of water. Imagine running the tub and in the time it takes to fill it, you can remove a teaspoon of water. The bathtub keeps running.. in the time another tub of water comes out of the spigot, you can remove a second teaspoon. And then a third, forth and so on.
We currently have many deployable technologies and behaviors that will turn the tap down much more than a teaspoon worth for far less money. When we're finally down to the point where we're only putting a gallon or so of water into the tub each year, then it might make sense to deploy a number of teaspoons to make a difference for where it's difficult to turn the tap (aviation and shipping for example)
Spend some money and talent learning how to improve the process, but don't count on it in the near term as it isn't, and will never be, a silver bullet. Nothing it. all we can hope for is silver buckshot and using as much as we can possibly afford. It makes sense to use the buckshot with the greatest cost/benefit ratio - things like wind, solar, better power grids, efficient transportation (full sized EVs don't count!), and any number of energy thrifty behaviors.
And finally home runs and climate change. Recently a paper made the major news outlets with projections that climate change will have an impact on Major League Baseball home runs: "Several hundred additional home runs per season are projected due to future warming." The paper is poorly done .. basically a sensitivity analysis based on a single variable. I won't give it the credibility of a link. Something that doesn't work in the real world with something as complex as baseball. I have a some expertise in the fluid dynamics of balls flying through the air and would argue the effect is small. In fact they note the same thing, but word the conclusion to make it appear there is an effect and climate change impacts everything. This is pure clickbait for news organizations and probably has the impact of diverting attention from much more serious issues associated with global warming. It's trivial to see the home run impact is insignificant, but a poorly done analysis can lead to fuzzy thinking and even harm.
Posted at 07:50 AM in building insight, critical thinking, general comments, society and technology, sports | Permalink | Comments (0)
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