robryk @robryk@qoto.org

Ah, PSA: if you do actually collide with a bat, check very thoroughly whether (a) you got scratched in any way (b) you got your face in contact with the bat. If either happened, wash the scratch/your face thoroughly and urgently visit a doctor due to the risk of rabies.

I think I nearly collided with a bat today. I was riding a bike along Sihl just north of Sihlcity (the path is between a small forested hill and a river with a highway overpass over it; it's sparsely lit with streetlamps) and saw (~single frame only, because of timing wrt my blinking) a dark concave-sided diamond shape in front of me and felt a gust of wind.

It's not that surprising, given that a bit further north friends of mine would semi-regularly notice bats over the rive (and I did once or twice), but the near collision is surprising given my very predictable motion.

Eh, why does the most recent #Sachgeschichte consequently use value and cost interchangeably~~~

@freemo

Putting "https://mas.to/@TechConnectify/112328384373243115" in qoto's searchbar results in an error toast saying "500". When I look at network requests involved, I see a request to "https://qoto.org/api/v2/search?q=https:%2F%2Fmas.to%2F%40TechConnectify%2F112328384373243115&resolve=true&limit=5" returning an error page with status code 500.

But also, the volume of the sound I was hearing wasn't that high, so either I failed to notice the same effect when I was hearing louder lowish frequency sounds, or this is more pronounced because eyes are "closer" to teeth than ears.

I guess I can bust out my bone conduction speaker that I have somewhere and try using that to have a continuous frequency variability (without messing with play-doh).

Vibrating your head blurs your vision (try taking a metronome or substitute, striking it, and then touching your teeth with the stem while looking at something with a well defined edge or ridge: the picture will become slightly blurry).

I wonder what's the frequency dependence. I have two (nonlocking) forceps that, when measured with my phone's accelerometer, give similar amplitudes of ~50Hz+harmonics and resp. ~60Hz+harmonics. Maybe I'm placeboing myself, but it seems to me that the blur from 50Hz one is significantly larger.

How thick (perpendicularly to the surface) is a stroke of a nonerasable marker? Does it depend on its color? I assume it does depend on the surface -- I would expect it to have no thickness on paper but some thickness on e.g. metal.

Totally random: videos on https://www.youtube.com/@Shaddicus give a perspective on powerplant operations that's otherwise hard to get (for me they explained a few things that I found surprising in simulators).

Disclaimer: quarter-baked

Roughly half of primary school students have some experience with the concept of braids and maybe with the practice of making them. At the same time braids are nice objects to study, because they form a noncommutative group with infinite order elements.

So, would it be possible to pose some interesting-but-approachable problems about braids[1] to primary school kids? Obvious ideas for me are:
- how can we describe a braid?
- do two braid descriptions describe the same braid? what does this even mean? this can naturally introduce a concept of "invariants" (in the sense of a function from a braid representation that is equal for all representations of the same braid) and the concept of transformations of descriptions (and then maybe completeness of that)
- is every braid a commutator of two braids? (sadly this doesn't seem very natural here),
- what generator sets are there? is it sufficient to flip adjacent strands only?

[1] morally similar to "how many isometries does a cube have?"

Silly me, obviously for any larger exponent the thing diverges and for any smaller it converges to constant 0 (at least pointwise). It's sufficient to look at stddev of position at some fixed time.

I'm curious if this is some common writing system that I'm unfamiliar with. Anyone recognizes it? (A person from my city's road construction office signs announcements like this.)

TIL that the sequence of increasingly finegrained random walks that converges to Wiener process has walks that increase their speed as they get finer (speed grows with square root of scale). Post factum it seems kinda obvious: you'd otherwise converge to a constant function. I haven't yet figured out how this changes as one adjusts the exponent.