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Ask HN: Teach me something new

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581–590 of 782 posts

Re: Ask HN: Teach me something new

#581

At any moment there is atleast one pair of diametrically opposite points on Earth's surface which have same atmospheric temprature and pressure. And that's because Maths. It's quite fascinating to me

(pretty sure that's related to 'can't comb a hairy ball flat', so assuming a topologically spherical earth)

and any four-legged table that wobbles can be rotated to a position so as not to wobble (assuming the floor has no cliffs or other topological oddities in its unevenness)

Re: Ask HN: Teach me something new

#582

Earlier quoted context omitted.

Interesting. I always learned mean/median/mode were different things. The mean is the average, the median is the middle value, and the mode is the largest value. I wasn’t aware of this issue with conflating mean/median. That being said, I remember learning that and always wondering why I needed to know what “mode” was haha

The mode is the most common value, if it exists.

Whelp that shows you how much I remember from middle school

Re: Ask HN: Teach me something new

#583

By far the most important martial arts skill is the ability to function effectively after receiving a powerful blow to the face, solar plexus, etc. The only way to develop this skill is by practicing it; very few people do, for obvious reasons. If your martial arts training does not include this, it may have many benefits, but is severely lacking as training for actual fighting.

I guess the two questions that come to mind after I read this are 1. How can I OW objectively OW tell oww the difference ow where being seriously jarred (ow) ends and being significantly injured begins? 2. As a person ages, is it possible to train in this way without ending up seriously banged up with long-term ramifications? Or is this more of a "don't use a skateboard" type of thing with no leeway?

1. Practice getting hit. (Preferably with a partner who has enough knowledge and skill to avoid injuring you.)

2. You can practice at low risk of being seriously injured. Again, you need a partner who is sufficiently knowledgeable and skilled to help you without hurting you.

Grappling arts that emphasize groundfighting give you more practical experience of fighting usefully with lower risk of injury. Because you more often start out on the ground, you're much less likely to be injured in a fall. Because you strike less, you're less likely to injure yourself either by striking something or by being struck.

If you want to get past the non-useful reactions to being struck, though, then you probably also want to do some striking artor sport with contact--boxing, kickboxing, muay thai, et. al. Just be sure to use safety equipment and work with someone who has both skill and empathy.

Re: Ask HN: Teach me something new

#584
post #442
post #38

The Boltzmann brain hypothesis suggests that it would be more likely for a single brain to spontaneously and briefly form in a void (complete with a memory of having existed in our universe) rather than for the universe to come about in the manner cosmologists think it actually did. In this physics thought experiment, a Boltzmann brain is a fully formed brain, complete with memories of a full human life in our univer…

Well then it’s equally likely that badgers the size of Earth could be forming from time to time, and since they’re the size of earth they would decay much more slowly than our puny local badgers… so shouldn’t we see the occasional Earth-sized badger through the Hubble? Or how about the much lower odds needed for a copy of Shakespeare’s plays translated to Klingon inscribed on a giant sheet of titanium to appear spont…

What Hubble? If you're a Boltzmann brain, the Hubble is just an idea you have in your temporary brain, before it pops like a soap bubble.

Re: Ask HN: Teach me something new

#585

The saying "blood is thicker than water" is from the Bible. The full quote is "the blood of the covenant is thicker than the water of the womb," which means the opposite of how "blood is thicker than water" is used.

Any idea where in the Bible it says that? I spent a couple minutes searching and found many sites saying the same thing you did, but nobody cited which verse. I searched a dozen or so translations of the bible and did not find it, either. Which makes me wonder even more, as there were just as many sites saying it originated in 12th century writings.

I could have sworn I read this in one of the gospels, but going back it appears you're right and this is not found in the old or new testament. I must have read this somewhere and taken it for granted. I apologize for not doing my research!

Re: Ask HN: Teach me something new

#586

Earlier quoted context omitted.

I guess the two questions that come to mind after I read this are 1. How can I OW objectively OW tell oww the difference ow where being seriously jarred (ow) ends and being significantly injured begins? 2. As a person ages, is it possible to train in this way without ending up seriously banged up with long-term ramifications? Or is this more of a "don't use a skateboard" type of thing with no leeway?

1. Practice getting hit. (Preferably with a partner who has enough knowledge and skill to avoid injuring you.) 2. You can practice at low risk of being seriously injured. Again, you need a partner who is sufficiently knowledgeable and skilled to help you without hurting you. Grappling arts that emphasize groundfighting give you more practical experience of fighting usefully with lower risk of injury. Because you more…

All good points.

Re: Ask HN: Teach me something new

#587

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…

wow you had described so well. Curious, what is the book? wondering if that is the confounding variable

Re: Ask HN: Teach me something new

#588

ok I'll have a go ! Here is my favorite mental-model for problem solving (and my favorite analogy) So I have this problem: I love eating scramble eggs, I hate cleaning up the pan and have been trying over the years many different techniques to make sure the egg's doesn't stick to the pan. (No I don't want teflon thanks). So I tried different oils, temperatures and techniques, all with the goal of getting those delici…

I had a girlfriend in Amsterdam who taught me to make scrambled eggs in a double boiler. This keeps the eggs at the temperature of boiling water. The result is so much better (light and fluffy) that you will never use your skillet again. I have heard that there are special large double boilers that are used to prepare scrambled eggs for restaurants, but I have never seen one.

.

Re: Ask HN: Teach me something new

#589

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.

This is not medical advice, but... Cyanoacrylate (also known as "Super glue"). I've been using it to cover some small clean cuts. I think today there's even variants approved for such use.

> I think today there's even variants approved for such use.

Yeah, look up ‘Vetbond’ and ‘Dermabond’. They are not strictly superglue, but longer chain cyanoacrylates, which confer them some properties such as higher flexibility and bacterial growth inhibition.

Re: Ask HN: Teach me something new

#590
post #440
post #107

White dwarfs and neutron stars are both "stellar corpses", the remnant of stars. White dwarfs roughly cram the Sun's mass into an Earth-sized sphere, neutron stars cram that amount of mass into a sphere of about 10km diameter. Oh, and neutron stars have mountains: height differences on their crust of a few centimeters or less. Scaling that height difference takes more energy than scaling Mount Everest. Gravity is wei…

Robert L Forward wrote a fascinating novel about life on a neutron star: https://en.wikipedia.org/wiki/Dragon's_Egg

It's one of my favorite books.

Another great Forward read is Rocheworld.

Forward was a physicist, and created settings that only a physicist would be likely to think of.

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