Ask HN: Teach me something new • Hacker News Board

Re: Ask HN: Teach me something new

#251

Post by I_complete_me » Sat, Apr 30, 2022, 8:42 AM UTC

nstart wrote: post #239

aspaviento wrote: post #209

Harmonicas are amazing instruments. At first people assume them to be like toys (you can buy really cheap ones everywhere) and initially the concept seems really easy: 10 holes, drawing air produces some notes and blowing air produces other notes. But the more you get into it, the more amazing it gets. Soon you discover that you can bend notes by positioning your tongue in a specific way and your repertoire increases…

Fabulous addition. For anyone looking to see what a master harmonica player looks like, highly recommend looking up blues traveller / John Popper. In particular, there’s a live performance of no woman no cry that has John Popper alongside Ziggy Marley. Mind blowing. Watch it. You won’t regret it. https://youtu.be/9zk0HFG5mDw

Yep. And I'd add La Cavatina[1] among others. [1] https://www.youtube.com/watch?v=Io0Ta9LzASs

Re: Ask HN: Teach me something new

#252

Post by sph » Sat, Apr 30, 2022, 8:43 AM UTC

hiisukun wrote: post #123

In a lot of terminals, Alt+. (or Option+. on Mac) will paste in the last argument of the previous command. $ mkdir hi $ cd You can hit . several times to cycle through earlier final args.

Holy shit, I have gone 35 years without ever learning this fact.

Re: Ask HN: Teach me something new

#253

Post by tetris11 » Sat, Apr 30, 2022, 8:44 AM UTC

mhh__ wrote: post #167

stevenhuang wrote: post #58

The study of unidentified aerial phenomena (UFOs) and the acknowledgement of the extraterrestrial hypothesis (or extra dimensional) will become mainstream. https://www.gillibrand.senate.gov/news/press/release/gillibr... Soft disclosure has happened already via the USS Nimitz encounter. If UAPs are true, then the floodgates are open and will lead to a forced re-evaluation of other high strangeness phenomena (telepathy…

The SR-71 was designed in the 1950s, unless progress has stalled I don't see why these reports aren't just DARPA playing with their new toys. And besides, the floodgates will not open, that isn't how the scientific method works. If the little green men arrive, the evidence we have showing everything is mumbo jumbo doesn't cease to exist.

Funding stalled too, cheaper to just use satellites. At the same time I want to hear what happened to Ning Li's antigravity research.

https://en.m.wikipedia.org/wiki/Ning_Li_(physicist)

Re: Ask HN: Teach me something new

#254

Post by elric » Sat, Apr 30, 2022, 8:45 AM UTC

mikelevins wrote: post #28

I've described this on HN before; forgive me if you've already seen it. I have chronic migraine. It sounds worse than it is; I rarely suffer attacks anymore, and when I do, they're usually mostly harmless, as in the case I'll describe below. Contrary to popular belief, migraine is not a headache. It's something a little more like an epileptic seizure. Intense headaches are one common symptom, but there are a lot of o…

Generally speaking, scintillating scotomas don't fill the entire field of vision. They can do, and when they're caused by migraine auras they tend to grow and then shrink again within a 20-60 minute window. I can certainly read when I'm experiencing one. I can continue to work if I really want to, but I find that having a coffee and taking a break is much more comfortable.

Migraine auras suck, but are pretty fascinating. Depending on which part of the brain they affect, different symptoms can manifest. Visual auras à la scintillating scotoma are probably the most common, but slurred speech can happen as well, or reduced sensation in half the body, probably other things as well ..

Re: Ask HN: Teach me something new

#255

Post by Engineering-MD » Sat, Apr 30, 2022, 8:45 AM UTC

silisili wrote: post #75

callmekatootie wrote: post #72

Earlier quoted context omitted.

Can the same pencil be used on more than one person? Or does that lead to infections?

I'm not an expert, but my family shares. They are best when wet a bit, so typically we douse the cut or wound with peroxide, then apply. That said, they are cheap enough for everyone to have their own if that's a concern for you.

No need for peroxide, just slightly salty water is better unless visibly contaminated. By using peroxide, scars are often worse, which is thought to be due to killing cells which contribute to wound healing. Furthermore, peroxide doesn’t significantly help prevent infections.

Re: Ask HN: Teach me something new

#256

Post by sph » Sat, Apr 30, 2022, 8:45 AM UTC

leephillips wrote: post #99

Most rape victims in the United States are men: https://www.hrw.org/reports/2001/prison/report.html Caution: that’s hard, explicit, distressing reading.

I assume it applies uniquely to the United States, given the high percentage of incarcerated people?

Re: Ask HN: Teach me something new

#257

Post by elric » Sat, Apr 30, 2022, 8:46 AM UTC

ToJans wrote: post #110

I watched a piano/music teaching video from the 60s yesterday that made it all "click" [1] Most modern music chords patterns are easy to find out on piano. Start on any of the white keys, and play 7 white keys left to right. That is called a mode: a series of notes separated by certain intervals to compose a song. Different modes have different vibes. Atmosphere of the song ( sad or happy) is directly correlated by h…

> correlated by how "willing" the notes are to resolve to the mode root (the first key of 7 you hit).

I've heard this explanation many times before, and I still don't understand how notes can be "willing" to do anything, or how a note can "resolve" to the root. Can someone ELI5?

Re: Ask HN: Teach me something new

#258

Post by tromp » Sat, Apr 30, 2022, 8:47 AM UTC

The number of legal chess positions has now been estimated with 2 digits of accuracy as ~ 4.8 x 10^44: https://github.com/tromp/ChessPositionRanking For the game of Go, we know all 171 digits of the number: https://tromp.github.io/go/legal.htm

Re: Ask HN: Teach me something new

#259

Post by tetris11 » Sat, Apr 30, 2022, 8:47 AM UTC

Jtsummers wrote: post #13

darrelld wrote: post #10

In your terminal Ctrl+a will return you to the start of whatever line you have typed, and ctrl+e will return you to the end.

This is if you have emacs-based keybindings (which is the default). M-f/M-b (Meta, often the alt key or option key) will move forward/backward a full word. C-f/C-b moves forward/backward a character. C-w kills the previous word (if you're in the middle of a word it leaves everything from the cursor to the end intact). C-r will search backward in your history allowing you to type partial matches (like, "I know I compi…

Aren't all terminal bindings emacs-based, since they inherit from libreadline?

Re: Ask HN: Teach me something new

#260

Post by Adrig » Sat, Apr 30, 2022, 8:47 AM UTC

You probably heard about the quirks in the French numerical system. For example, 99 is translated "quatre-vingt-dix-neuf" which is literally "four twenty ten nine".

This is a legacy of the base 20 numerical system used by the Celtics thousands of years ago before the modern Romance language drove it out. The hybridization with our current base 10 system came with the Roman conquest of the Gaul.

Another example of the base 20 in use is the Quinze-Vingts National Ophthalmology Hospital in Paris, where Quinze-Vingts (fifteen twenties) refers to the original capacity of 15*20 = 300 beds available when built in the Middle Ages.