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Ask HN: Teach me something new

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Re: Ask HN: Teach me something new

#311

Post by mirekrusin »

ajb wrote: post #229

In statistics, the mean and median are both averages, but are technically quite different. The mean is the sum of all items divided by the number of them, while the median is the middle item in the sorted list. When they are different, this can have strange effects. For example, when estimating engineering tasks, the mean error is often positive while the median is often negative. This is why your manager believes th…

If the project is planned according to median, you accept up front that there is 50% chance the project will be late.

Re: Ask HN: Teach me something new

#312

Post by acqbu »

"The mutual transformations of matter are not an accidental feature, but the very essence of nature. Without change, there would be no world. Heraclitus seems to acknowledge this in his praise of war and strife:

We must recognize that war is common, strife is justice, and all things happen according to strife and necessity. War is father of all and king of all; and some he manifested as gods, some as men; some he made slaves, some free.

Conflicting powers of opposites, including those of elemental bodies, make possible the world and all its variety; without that conflict we would have only lifeless uniformity."

From: https://plato.stanford.edu/entries/heraclitus

Re: Ask HN: Teach me something new

#313

Post by tiktaktow »

vermarish wrote: post #225

An electric guitarist usually has a pedalboard that they use to make different guitar tones. Let's approach this like an electrical engineer might. Time is a straight arrow: call it t. The guitarist plays, and their guitar pickup records a signal. At any time t, measure the value of this signal's waveform: call it x. That signal can go into a pedal that maps each value to create an output signal. Call it f(x, t). The…

This method of convolution of the sound is nowadays utilised in "profiling" amps like the ones made by Kemper. There are these particular amps, effects, speakers, and/or their specific combos, which are considered sacred/sweet/holy which are highly sought after. But most of them cost a lot. There's also the problem faced by touring bands where they have to lug around huge setups. And then there's the issue of maintenance and repairs. These profiling amps help musicians capture the sound of their favorite setups and replicate it in a compact setup. Hugely popular, if not for the price. There are still purists who swear by the sound of 'analog' setups, but for most of the purposes the sound is identical. Fascinating stuff.

Re: Ask HN: Teach me something new

#315

Post by stavros »

DavidSJ wrote: post #291
schoen wrote: post #132

In the 1800s, scholars who knew a lot of languages (including, often, several modern and ancient European languages, and increasingly also Sanskrit) started to notice some amazing patterns about similarities in words among all of these languages, including languages from very far apart and that had no visible connection at all from the point of view of their present-day speakers. As these patterns were explored, they…

On this general topic, I recently learned that the words undulate and water have the same origin in Proto-Indo-European: wódr̥ (PIE) → udōr (Proto-Italic) → unda (Latin) → undulātus (Late Latin) → undulate (English) wódr̥ (PIE) → watōr (Proto-Germanic) → *watar (Proto-West Germanic) → wæter (Old English) → water (Middle English) → water (English) In fact, I'm now noticing that the t in the Proto-Germanic line corresp…

Interesting about udor, as water in ancient Greek is ύδωρ.

Re: Ask HN: Teach me something new

#316

Post by scrollaway »

Take a few minutes to learn the NATO phonetic alphabet

Alpha, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliet, Kilo, Lima, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-ray, Yankee, Zulu

Gotta spell anything over a voice line? Use it. No more screwing around with "B.. like Bryan, and then U, like .... under". s-c-r-o-l-l-a-w-a-y: sierra charlie romeo oscar lima lima alpha whiskey alpha yankee.

I learned it when I was 14, and I genuinely used this a TON in the decade and half since.

Re: Ask HN: Teach me something new

#317

Post by MaanuAir »

Adrig wrote: post #260

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…

Thanks for this! As a French, I always wondered why this oddity.

That should also be introduced when teachers explain hexadecimal :-)

Re: Ask HN: Teach me something new

#319

Post by someweirdperson »

vermarish wrote: post #225

An electric guitarist usually has a pedalboard that they use to make different guitar tones. Let's approach this like an electrical engineer might. Time is a straight arrow: call it t. The guitarist plays, and their guitar pickup records a signal. At any time t, measure the value of this signal's waveform: call it x. That signal can go into a pedal that maps each value to create an output signal. Call it f(x, t). The…

> The pedal is a time-invariant system when it satisfies f(x, t1) = f(x, t2). In English, a time-invariant pedal does not warble over time. > Reverb, delay, EQ, and wah are all LTI effects.

The math doesn't work, assuming scalar f, x, t1, t2 as implied by their description. For a delay the x passed at t1 has no correlation to what f calculates to. It needs vectors F(X, t) and X I think.

Re: Ask HN: Teach me something new

#320

Post by goodpoint »

callmekatootie wrote: post #72
silisili wrote: post #63

I'm going to go a bit random...get a styptic pencil! Nobody I've met even knows what they are. I came across them years ago in the shaving section, and was blown away by their utility. They are solid pieces of some saltlike material that are super effective at stopping bleeding. We don't even have bandaids in our house anymore, the pencils are way more useful.

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

NEVER share anything that gets into contact with blood, flesh or anything else that is not just skin!

Otherwise you risk spreading virus and bacteria between people - this is hygiene 101.

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