omenti

very light narrative structures

I first heard about Norwegian Slow TV a decade after it began.  I watch a half hour of one of the rail trips. It didn't do anything for me.  Other than hearing about other hits like chopping wood and knitting, I almost forgot about it.  Two months into the pandemic I found my watching a semi-live train trip across Norway.  Much of the  scenery was similar to where I grew up and I found myself watching.   It wasn't long until I found myself daydreaming, creating my own narrative to match the flowing images.  Two hour later I stopped a dream-like story in my head.  

 

About four in the morning the next day I was jolted out of bed with an interesting approach to some physics that I had abandoned months before due to lack of process.    Having your mind work on something when you're not working on it is well known.  I suspect the neural connects I had was making in the narrative I was writing in my imagination had a good deal to do with it.   

 

This morning I caught an episode of Invisibilia that dives into the subject.  Recommended if you have an interest in narrative in any form.  Slow TV is an hours or days long TV show without plot, characters, or tension.  How Norwegians responded as a shared experience is the most fascinating part

I've done a bit of work in remote audio ambiances.   A few created serendipity.  Here's an excerpt from an old post on one:

 

5:25 am - excellent!

 

I brush the last of the snow from my coat and switch on the lights before taking my seat.   few minutes of silence and then a door opens and closes reverberating for about three seconds.  The clicking of shoes echoes through Warner Hall as she makes her way to the bench.  A minute of preparation and then the Praeludium in G by Bach fills her space and mine.  I sit back and shut all but the Bach from my mind.

 

She's doing an excellent job until - rats.  Bach derails and I sit up in my chair looking around.  A female shout fills the space reverberating for about three seconds.

 

sh*tttttttttttttttttttttttttttttttttttttttt!

 

She goes back a few bars and dances through the problem smoothly.  Now a piece I don't recognize, but it is still clearly Bach until about 6:55.   Her shoes and coat go on and steps click to the door in the distance.

 

And a little magic as a female voice is softly singing Bach.

 

A door opens and closes.  The reverberation is about three seconds and then silence. Time to switch off the amplifiers and make some hot chocolate before getting to work.

She was an organ student in Oberlin and I was in a special room in New Jersey where we were working on the reconstruction sound fields.  A special seven microphone array had been installed in the hall with a computer handling compression mixing and compression in realtime.  The bitstream made traveled eastward to our room where a reasonably convincing illusion of the hall's sound space was created.  We had created a virtual acoustic reality.

 

brain power

your brain runs a 5k every day

 

let me explain:

On a walk a few days ago I found myself thinking about the power people need to live.  A ballpark figure is about one hundred watts of power or, over the course of a day, 2.4 kilowatt-hrs of energy.   A remarkable feature of people is that our brain requires a good deal of this - something like fifteen to twenty percent.

Thinking about at the energy requirements for a few physical activities it struck me that the amount of energy your brain uses in a day is roughly the same as an average person running a 5k.  

I mentioned this to Charlie who asked  the right question.  What is the difference between concentrated and unconcentrated thought?  Some time ago I came across some work that suggested there's little to no difference - at least within the accuracy of measurement.   I checked with a neurology researcher who was aware of more current work.  Serious amateur chess players playing against a computer program where the program was set to play a bit beyond their level represented hard thought.  The same people not focusing was the baseline.  There was a small difference - hard thinking would require a couple of regular (not peanut) M&Ms over an eight hour period.  Mediation appears to be the same as normal thinking.    

(Note:  energy is power times time.  Power is the rate of energy use.)

 

dancing the parabola

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.

 

the heart of sol, lizards, and the olympics

gee-whiz mini-post

The Sun is usually associated with mind-wobbling huge numbers.  It's 109 times the diameter of the Earth and a third of a million times more massive.  Almost all of the energy from fusion is produced in its core.  A relatively small region that only extends to about a quarter of the Sun's radius.  The average density of the core is about 150 times that of water and it's approximately hot. Hot enough that fusion can proceed.  Six hundred million tonnes of hydrogen are turned into helium every second.  Even as far away as we are, the amount of solar energy striking the Earth is about 10,000 times the world's current energy use.  

Big numbers, but it gets curious when you take a deeper look.

It turns out fusion in the Sun is very slow.  That's not a bad thing as the leisurely pace allows the Sun to last a long time.  Long enough to get intelligent life started.  While 600 million tons of hydrogen a second may sound like a lot, the Sun is mind boggling big.   Trying to recreate the the Sun's fusion in an Earth-bound reactor would be a fool's errand.  The process is so slow you'd never get enough power out to make it practical.  Fusion reactors need much greater temperatures and somewhat different fusion processes to be practical. That turns out to be a non-trivial problem. 

 

The power density (the power per cubic meter inside the core turns out to be astonishingly small - about 275 watts per cubic meter.   That's about the same as a lizard's metabolism!  Being warm blooded and active, ours is higher.  The average metabolic power density of an adult human is about 1400 watts per cubic meter.

 

One of you is competing in Tokyo in about a week.  When Sarah's running around in the sand during a beach volleyball match her metabolic power density is six to eight times greater than average.  Even at the lower figure her power density is thirty times that of the Sun's core!

 

the fundamentals

mini-post

The Standard Model of Physics dates back to the mid 70s and is far and away the most complete and accurate description of three of the four forces of Nature.  Add General Relativity for gravity you have the basis to  answer fundamental questions like what we're made of and the forces. That's the bedrock of physics.    (the Standard Model with General Relativity tacked on is sometimes called Core Theory)  It's something that almost every physicist wants to see fail as there are hints of something deeper.

It's very elegant physics with beautiful mathematics, but good enough non-technical descriptions aren't easy.  Here's the best short discussion I've seen.  

 

I should note that while physics can describe all of these interactions, there's a problem with calculation.  Our mathematical techniques are often too weak so we have to resort to clever and not so clever approximations.  A lot of physics turns out to be applied mathematics.

 

an olympic-scale audio uncanny valley

a pre-Olympic minipost

An hour into the first of last year's AVP beach volleyball tournaments a warning clickthrough page appeared on the event's Amazon Prime Video page. Amazon had been covering the AVP tournaments since 2018, but the pandemic forced a strict spectator-less bubble.  During the previous two years they hadn't spared any expense. Now they had to keep viewers engaged.  Rather than using sampled crowd audio and cutout spectators, they they focused on highlighting the event's audio.  A sports audio specialist was brought in and dozens of microphones were installed on the main court, players chairs, coaches, referees,  along with a number of moving microphones.   The first match immediately was sprinkled with some rather colorful language - enough to trigger Amazon's warning clickthrough.  

 

Watching the matches was something of a revelation. Sounds of the game ranging from sound normally masked by crowd noise to coaches discussing tactics with players during timeouts.  The announcers had been coached to work around the new sound field. By the end of the first tournament the viewer experience was excellent.  Similar things happened in other sports that took the "honest" route. Viewership often increased, while many of the major sports saw drops.  Now NBC and other large networks around the world have to deal with an Olympics with empty stadiums.  How will they react?  A miscalculation could damage viewer engagement.  It's a very interesting social technology experiment.

 

It turns out a lot of work has been done over the past sixty years.  Sports like football (not the American variety), tennis, rowing, past Olympic games, and online games have driven innovation.  Seven years ago 99% Invisible aired a radio documentary produced by Peregrine Andrews on the sound of sports.  It's fascinating and worth the hour.  Listen with stereo headphones or earbuds.  

Roman Mars · 99% Invisible-127- The Sound Of Sports

There's another fascinating question.  How do athletes react to empty stadiums? That experiment has been underway for a year now.  It's not simple.

 

beyond the swimming obstacle course and horse long jumping

A pre-Olympic minipost

 

Early on rope climbing, tug-of-war, and shooting live pigeons were Olympic events.  Over time there's been both churn and growth as audiences have changed and grown.   The International Olympic Committee recognizes a number of sports federations which government Olympic sports, potential Olympic sports and sports that would never be candidates (non-physical sports like chess and bridge and sports like auto racing and aerobatics that motors).   Getting a new sport into the Olympics involves politics and the television target market of the games.   The IOC has been worried about attracting a younger viewership so we have several Winter sports, BMX biking, skate boarding, sport climbing and surfing appear in recent years.  

 

Many of the new events are interesting from an amateur science point of view.  I was going to write about surfing, but there are a couple of key points that are better communicated visually.   This video does an excellent job covering the basics of why it is possible to surf including how you can travel faster than the wave.

 

 

the art of keeping a ball off your sand

A pre-Olympic post

 

Now a bit on one of my favorite sports - beach volleyball.   It's played on a sixteen by eight meter rectangular court on fine grained loosely compacted sand that's at least 40 cm deep.  The net is 2.43 meters high for me and 2.24 meters for women.  From there it's mostly similar to indoor volleyball.  Rather than going into rules it's more interesting to take a look into what's happening. (as with most sports there's much more going on than can be described in a few paragraphs, so just a few points - the videos give a better sense)

 

First a short segment featuring Canadians Sarah Pavan and Melissa Humana-Paredes. 

 

As the blocker, Sarah tends to stay near the net removing attack options from the other side.  Her height and jump gives her a larger set of options for placing the ball close to the net on the other side in very difficult to return locations.  Melissa's job is to cover the rest of the court - not exactly the easy task.  At 1.75m (5'9) Melissa is considered undersized, but makes up for it with amazing athleticism.  In the past decade both positions have become taller.  Five foot eleven female and six foot five male blockers are considered undersized.  Blockers, like basketball players, often have wingspans that are longer than their height.  Defenders are usually smaller as shorter limbs tend to accelerate faster.

 

Some women can serve the ball around 90 km/h (about 55 mph)  and men are about twenty percent faster.  The fastest serves deliver about 8,000 watts of power in the women's game and over eleven in the men's.   Putting things in perspective eight kilowatts is about eleven horsepower and a good reason for serious weight training.  Or consider that an electric cooking element on a range is about 1,800 watts.   But thanks to the fluid dynamics of the ball in flight and a need to test the other team the highest speeds aren't used all of the time.

 

Calculating the power of a jump is difficult - particularly in the sand - but the most athletic women probably generate an average power of 2,000 to 2,500 watts in their greatest efforts.   This is only for a few tenths of a second, but for reference Usain Bolt averaged about 2,600 watts for nearly a second at the beginning of his record race.  (These power levels are unsustainable - if you could average 500 watts for thirty minutes you could probably win the Tour de France.)  Near the net a player sometimes adjusts their center of gravity in a jump giving them hang times similar to that of a ballet dancer performing a grand jeté.  It's part of extending the window of being where you need to be and deception. 

 

You've probably noticed putting spin on a ball can add curve to its path.  It's called the Magnus effect and the size and low weight of the volleyball gives a more pronounced effect than most of the other sports (table tennis is the exception). Topspin is most commonly used and will drop the ball short of the expected flightpath - sometimes up to a meter with a lot of spin at an optimal speed.   And like baseball there's a narrow airspeed window with little or no spin on the ball where knuckleballs can occur.¹  The airspeed window for beach volleyball  is usually somewhere around 50 km/h  - a speed that is much more common in the women's game.   Like baseball it's difficult to master, but properly done the ball can unpredictably deviate from its normal path by as much as a ball  diameter by the time it makes it to the other side of the net making reception more difficult.

Sand wind sun and heat. 

The elements are part of the game.  Try running around in the sand,  particularly deep sand, changing directions and jumping.  Walking in the sand takes  at least one point six times as much energy as a solid surface. Running and jumping can take more - up to three times as much.  Agility is difficult without a lot of practice.  On the other hand diving into the sand is much safer than diving onto a harder surface.

 

Since the ball has only weighs about five eights as much as a soccer ball (football for most of the word), wind is an issue.   Players watch flags around the court to gauge the wind and will  drop sand to gauge it closer to the court. Windspeed and direction lead to "good" and "bad" sides of the court.  To even things out players switch sides at regular intervals.  As with other outdoor games heat, humidity, sunlight and shadows are issues. Moderate rain won't stop a game, but nearby lighting or heavy gusts associated with a storm will.

 

Games like baseball, volleyball, cricket and tennis share a feature based in our neurology.  Court size and ball speed are such that the fastest points average about four tenths of a second. Recognizing what's going on and reacting chews up a good deal of that time so players need to react without thinking.²   In beach volleyball deception is a common weapon.   Melissa "reads" the dynamic posture of her opponent and might notice a shift of weight to one leg.   She might change her own movement to make the other player think their intended move is correct.   Then, at the last moment, she'll make a small change and put the ball slightly out of reach on the other side of her opponent causing them to lose balance and miss the ball.   

 

You'll notice  most points see the receiving side touch the ball three times.  It can be done one or two, but usually the ball is carefully set and the two touches before the final touch allow time to read the other side and more accurately place the ball.  The best sets have incredible precision - usually within a few centimeters of where they need to be when the team is playing well.  

 

Sarah will tell you what separates the elite game is the mental component dealing with short term tactics and longer term strategies.  Communication between players and being able to "read" what the other side is doing - properly used it's probably the most powerful weapon they have.  Sarah and Melissa read simultaneously and have a sense of what the other sees.  They can communicate very rich contextual information to each other verbally and non-verbally. Each has to have a lot of trust in the ability and judgement of their teammate. Long term teams where each player knows each other physically, mentally and emotionally - who have the right "chemistry" in several dimensions - tend to dominate.

 

Here's another look at some long rallies where each team is reading well and reacting

 

 

__________

¹ There's a critical speed for a ball traveling through a fluid like the air at the boundary between turbulent and laminar flow.  Turbulent flow dominates at higher speeds, laminar at lower speeds.  Part of a spinning ball at this critical speed will be faster than the other so the drag on that part of the ball will be lower.   A zero spin an instability in airflow wanders oscillates around the edge of the ball somewhat unpredictably giving the swerving path of a knuckleball. 

² This is a very rich area in neurology.   Physical Intelligence by Scott Grafton is a great non-technical introduction to the neurology of movement.