this post was submitted on 15 Nov 2024
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[Thread] Mental Math (mander.xyz)
submitted 1 month ago by [email protected] to c/[email protected]
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[–] [email protected] 49 points 1 month ago* (last edited 1 month ago) (3 children)

Throwing and catching always amaze me. And it's not something that everyone is always great at, for sure, but anyone can try to toss a wad of paper into the waste basket. Whether or not you make it, the calculations under the hood, happening so quickly, always astound me to think about.

[–] [email protected] 25 points 1 month ago (2 children)

What's amazing is our ability to calculate the path of something in the air.

There's a test they did with Cristiano Ronaldo where someone kicked a ball to him so he could head it. They shut off the lights before the ball was in the air and somehow from the body shape of the person kicking it, he was able to know how to make contact with it without being able to see it.

https://youtu.be/0k2ey_okQ4E?t=1255

[–] [email protected] 4 points 1 month ago* (last edited 1 month ago) (1 children)

Pretty impressive. I think they're underestimating/ignoring the input from hearing, especially with the second one where he probably (subconsciously, of course) heard the ball bounce near his foot. Plus the subtle changes in air pressure around his legs to tell where the ball is, etc.

Cool video, thanks.

Edit: Still watching as they're analyzing his free kick. Cool shit. The human body is wild.

One thing I don't really see people talk about is how Ronaldo (and other soccer/football players) use their opposing leg to kind of hop up and dissipate any energy that they didn't transfer into the ball. Fucking cool. You don't even realize it's happening.

I haven't seen any videos on it, but I remember doing kinematics problems in school involving baseball pitchers and how they throw, and it is actually insane. Each joint and section of the pitcher's arm is like perfectly timed to provide the most velocity to the projectile. So you add up the momentum from the swinging shoulder to the momentum from the elbow to the momentum from the wrist, to the momentum and spin from the fingertips. Baseball is boring as shit, but the physics behind pitching is cool af.

[–] [email protected] 2 points 1 month ago

Hearing is definitely part of it, but I imagine it's only hearing the sound of the ball being kicked. After that it's going to be far too quiet to hear until it gets close, and he's obviously reacting long before that. Maybe hearing helps him adjust in the last tenth of a second, but he's not hearing the ball's entire flight.

As for the body mechanics of a pitch or a kick, it is amazing. Like, a proper powerful punch involves leg muscles, hip muscles, waist muscles, chest muscles, and only then do you start to get to the arms. For most of us, the best way to realize how coordinated everything has to be is to try to do something with your wrong arm/leg. Everything that flows naturally on your strong side is just completely wrong on your weak side.

[–] [email protected] 4 points 1 month ago (1 children)

I'm not a fan of Ronaldo but that was very cool to watch, thanks for sharing!

[–] [email protected] 2 points 1 month ago

Ronaldo's ego is incredible, and he's almost always looking out for himself in everything he does. But, you can't deny that he's one of the best ever players. And his charisma means he's a great choice for something like this where he has to perform and interact with all the "scientists". Someone like Messi could do the same kinds of moves, but he wouldn't be able to chat with the presenters and "scientists" between events in a natural way. (P.S. I love that they got someone named Ronald to be the ordinary guy who couldn't do anything useful, that was just funny.)

I also think Ronaldo genuinely cares about all the biomechanics and all that, as long as it's something that applies to him, and that he could use to make himself better. A lot of other players just play on instinct and don't want to have to think about it.

[–] Valmond 19 points 1 month ago (1 children)

Read somewhere that catching is actually dead simple, just "move towards the image of the incoming target" (I'm not talking about the arm kinematics).

There were a robot paper bin that zoomed under stuff you threw up in the air using no complicated algorithms for example.

Funnily many algos are calked on physical and chemical effects in the real workld, like splines for example were made with a thin metal bar and lead weight bending it to get the lines used in boat hull construction.

[–] [email protected] 2 points 1 month ago* (last edited 1 month ago) (1 children)

Read somewhere that catching is actually dead simple, just “move towards the image of the incoming target”

I mean... there is nothing simple about the calculations involved in something like that lol. That's like countless differential equations per second.

[–] Valmond 1 points 1 month ago (1 children)

No, IIRC it was just : film the ball and repetedly do: "is the ball to the left, go left. Is it a little to the left, go little to the left" etc.

Like a PID but with only the P part. I don't know if it makes any sense :-)

[–] Eranziel 2 points 1 month ago* (last edited 1 month ago) (1 children)

I mean, that's easy enough if you're trying to catch the ball with your face. Usually that's not the goal, so you’ll be standing slightly to the side or the object is moving toward your stomach. ;)

Even then, that's discounting the whole image analysis part of the equation, which your brain does dozens of times per second with incredible accuracy. Your waste bin example would have had to do enough to differentiate the ball from the background, and that definitely qualifies as a complex algorithm.

ETA: also, closing your hand at the right time does require your brain to know how close the object is, not just that you've positioned yourself in its path.

[–] Valmond 1 points 1 month ago

IIRC the imaging was just a black & white camera with the ball being black.

Detecting what is a ball is of course a whole other game, that I think was not the question. But if was then yes, that is more complicated.

[–] [email protected] 16 points 1 month ago

I remember when I was younger and would lay on my back throwing a baseball up in the air and catching it, that I could watch it go up and not follow it with my eyes as it goes down and still have my hand in the right spot to catch it