Comment by jasode
8 years ago
>Do you remember the insights that were crucial in learning to ride a bike or drive?
The author mentioned bicycles and inadvertently missed an opportunity to show another "unknown reality" that beautifully illustrates his point.
Consider typical adults (not physicists) with 20+ years of bicycle riding. If you ask them, "how does a bicycle turn?", they'd respond that "you just lean into the direction of the turn and it turns."
But that's not the complete picture of what actually happens.[1] If you were to capture the bicyclists with a high-speed camera, you'd notice that there's always a micro movement of countersteering to make the bike momentarily lose its balance and "fall into" the turn. Then there's an immediate correction of the steering to match the turn. This all happens in the span of milliseconds.
Even though the human body "discovered" the countersteering by way of kinesthetic feedback, the bicyclists' brains don't explicitly communicate this intermediate step to others. (Tacit knowledge.[2])
It's not always the case that we "simplify" reality for innocent purposes of pedagogy. (E.g. we tell "lies" to children about "numbers", "functions", etc and as they get older, we successively remove the layers of lies as they get into high school and college math.) Instead, we often don't even know the reality (e.g. bicycle countersteering) to consciously omit it.
That extra reality may not even be important. If one human is teaching another human, you can leave the "countersteering" detail out and it won't matter. The 200 years of people learning how to ride bicycles is evidence of that. However, if you're a robotics scientist and want to build a self-driven motorcycle, the reality of countersteering becomes a crucial detail.
For guitar nerds, there's a whole online business by a guy named Troy Grady about fast picking techniques (he has a ton of extremely polished videos on YouTube - start with whatever "Cracking the Code" videos are up). He decoded the seemingly-magical techniques that allow players like Yngwie Malmsteen and Eric Johnson to play at what feel like impossible speeds, and illustrates them. (tl;dr the core trick is "pick slanting", striking the strings at an angle so the pick goes in and out of the plane of strings, rather than across it, and then switching strings only when the pick is "out". That, and "chunking", breaking into units of fixed length on a single string and using the fixed length to do a clock reset on the beats).
For a guitarist, it's almost impossible to explain the myriad tiny details that go into something as seemingly simple as picking a note. Troy's analysis of instructional videos by great players, where they obviously don't understand what they're doing, is kind of amazing. And a real eye-opener, for those of us who have played a long time.
See also: https://www.youtube.com/watch?v=MFzDaBzBlL0 YouTube channel Smarter Every Day tries to ride a bike that has been hacked to reverse which way the wheel goes when the handlebars are turned, which also reveals how much bike riding skill is implicit.
(I also experience the "clicking" he refers to around 6:10 when I switch between QWERTY and Dvorak layouts. It takes about 15-30 seconds to switch, even after all the years I've been doing this, and I can "feel" it slide into place. This despite the fact that I use Swype (or whatever it is spelled as) on my phone all the time, which means I stay very familiar with the QWERTY layout every day... but somehow that qualifies as a different "thing", because I always get that instantly.)
I had this the first time I rode a motorcycle. The first day, everything was really jerky and uncoordinated because I had to do everything consciously. Woke up the next morning and my brain had remapped clutch from left foot to left hand, throttle/brake from right foot to right hand, gears from left hand to left foot, and the bike "just worked" the way I expect cars to.
About your keyboard, my experience after having used both a (Canadian multilingual) QWERTY MacBook and other computers with regular AZERTY keyboards for years, is that everytime I use some keyboard that vaguely feels Apple-y (with flat keys, white or grey) I somehow try to use it as a QWERTY. Then after a few seconds of mistyping things, I can eventually use it correctly, but it really seems like it's the look of the keyboard that makes me choose which layout I use.
It's probably different for everyone, in my case my brain has found the look of the keyboard to be the best predictor, for others it could be something else. But it's really interesting, sometimes it takes me a while before I notice that, indeed, this keyboard looks a bit like a Mac keyboard.
A long part of my scientific career has been unpacking simple statements about things like bike riding, and finding the underlying process is subtle, and reveals many interesting things.
When I was a kid, I had a teacher who said that cutting paper wasn't a chemical change- no bonds were broken. That seemed odd to me, but after I had a PhD, I understood a few things better. That when you cut paper, mostly hydrogen bonds- bonds, but a particularly weak form of bonds- are broken, but threre is enough kinetic energy to break some covalent bonds too. This turns out to have huge implications (besides the fact that the teacher was wrong).
If you smash a salt crystal with a hammer, all the resulting pieces end up with equal charges of anions and cations, so were any ionic bonds really broken?
That covalent bonds are broken seems obvious if you ditch the paper and cut through a sheet of long-chain polyethylene. The scissors don't just stop if they're about to break a polymer chain.
I think even the salt crystal will have some ionic bonds broken- smashing it with a hammer should generate a bunch of kinetic energy which converts to heat, some of the heat will exceed the ionic bond strength, and break bonds.... right?
How tiny of a charge is so small as to be unnoticable?
Certainly, if an object millimeters across has a charge of 1 electron that isn't noticeable.
I'll bite.. what are the huge implications?
Could striking a match be viewed as cutting paper?
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> If one human is teaching another human, you can leave the "countersteering" detail out and it won't matter. The 200 years of people learning how to ride bicycles is evidence of that.
This is actually a well-known fact about motorcycle, and it's taught in driving schools. It's just that their is no bicycle driving school and people just figure it by themselves. I'm pretty sure it takes more time though.
I don't think regular driving schools teach you to countersteer when you turn.
Perhaps they mean riding schools as any MSF endorsed riders course will teach you to counter-steer to initiate a turn [0] at higher speeds. It is especially important on a motorcycle due to the forces/speeds involved.
[0]http://www.msf-usa.org/downloads/BRCHandbook.pdf (sec.4, pg.8)
My dad owns a motorcycle training school and teaches this.
The motorcycle class I took in the US did in fact teach this.
Oh interesting, in what country do you live ?
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Have you actually tried turning a bicycle without countersteering? I have, the last time the topic was discussed on HN. I found I was able to turn without any perceptible countersteer. It's technically possible that I do have to countersteer for a small number of miliseconds over a small number of milimeters, but my experience leads me to doubt it.
Bikes have "rake"[1]- the tilt in the axis of steering. In a bike with 90 degree rake you would always need to countersteer.
When the wheel is forward of the axis of steering, you don't need to countersteer for small turns. When you turn the bars, the contact point on the wheel moves forward and to the side, dropping the front of the bike down and tilting it into the direction of the turn for you. That mimics the effect of countersteer. It's also one of the factors that makes some bikes, like mopeds, easier or harder to control.
During harder turns, the amount of lean created by the rake angle is less than required and you do need to countersteer. It's very hard to notice even when you're actively looking for it though.
[1]: https://ep1.pinkbike.org/p4pb9516905/p4pb9516905.jpg
If you have a normal bicycle without modifying the steering column then you were using countersteer whether you realized it or not. Even if you weren't toughing the handlebars, the lean initiates a countersteer. And you need countersteer again in the opposite direction to re-center yourself. If there's video or experimental setup info I'd like to see it.
Based on live TV illustrations I've seen, using paint on a wheel, the counter steer can amount to as little as 1cm. I'm not sure if that is perceptible without the paint trick.
A moped (and I assume a motorcycle) is a lot harder to turn without countersteering. I’m not sure if that’s because it’s more massive or what.
Anyway, learning to ride a moped was when I first consciously discovered countersteering. It made things a lot easier after that point.
It could be based on speed rather than mass. Above 5-10 mph or so, you turn a motorcycle with pretty much total countersteering, forcefully pushing forward on the inside hand grip to get the motorcycle to lean over. The faster you're going, the further you need to lean the motorcycle.
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The geometry is set up to be stable at a higher speed. Even then some sports bikes require a steering dampener to prevent "speed wobbles" (which, yes, are an actual thing and are much worse at 260kph than at 30kph on your BMX when you're a kid.)
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There's another neat example of this: asking someone with years of car-driving experience to hold their hands out as if gripping a steering wheel and mime the motions necessary to change lanes. [1] The steps are:
1. Turn the steering wheel towards the lane you wish to enter,
2. Re-center the steering wheel,
3. Counter-steer the same amount as in step 1.
Step 3 is what people tend to forget about.
[1] https://99percentinvisible.org/episode/episode-37-the-steeri...
You skipped the turn signal, which seems accurate to most of the drivers I see on the road.
For step 3, I almost always loosen my grip on the wheel and let it mostly straighten myself. So miming wouldn't include nearly as much counter-steering, even if I did remember to mime the whole process.
If anyone ever refuses to believe this, have them steer using just their palms. Especially, try to turn left or right using just one palm.