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welcome!!

i will be sharing cool things i learn here! 🔥🔥

sometimes i want to share cool small facts and other things i learn, but i don't want to make constant feeds about every small thing. that's what this is for!
subscribe to the forum thread if you're interested in the highlights of what i've learned today :)

most of the things i share will be nerdy and related to STEM (science, technology, engineering, math), because i absolutely love STEM (TIL nerd edition real 😂). but there might be some other topics scattered throughout as well!

you're free to post here about facts and experiences relating to what i learned or posting your own cool 'today you learned!' :)

i will do my best to share what i learned and try to explain it according to my own understanding :)
i may be wrong sometimes! double check my info before sharing around if you're interested!

let's now roll into... the first fact!

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today i learned about half even rounding!

normally, when one is rounding numbers, they round digits 1-4 down to 0 and 6-9 up to 10. but what about 5?
in half even rounding, 5 is always rounded to the nearest even number (of the digit before it)!

for example:
- 3.5 would be rounded to 4, since 4 is the nearest even number.

- 4.5 would be rounded to 4 as well :)

this half even rounding is useful to average out rounding with the digit 5.
this is important because rounding half up (5 rounds to 10) or half down (5 goes to 0) constantly will get you a slightly inaccurate number over time! the idea is that with half even rounding, by probability, it should round up 50% of the time and round down 50% of the time. a comment under this answer explains it well!

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a few days ago i learned calculators can have floating point inaccuracy!

computers (including calculators) are run on binary language. this is a language with only 0s and 1s. because of this limitation, some decimals are impossible to represent accurately. if a decimal is too small or complex, a calculator may not be able to compute it correctly and must round it.

in my calculator, inputting 0.99999999999 and pressing the '=' button outputs 1. can you believe it?

my calculator says that 0.99999999999 = 1 !!

i learned this from this wonderful youtube video! more cool calculator errors featured in the video if you're interested!

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yesterday, i learned to use the greeting "good morning" when it's not morning!

before, i only knew the greeting was used during the morning time. but i remember my mother telling me before that the term can be loosely used to mark the start of something, notably a shift on a job. for example, night shift people may use "good morning" as a greeting— even when it's clearly not morning—to wish a good start of the shift.

yesterday, a public transit bus driver was greeting everyone entering with "good morning." due to my knowledge of what i learned beforehand (learned from me being totally thrown off from a previous bus driver saying the same outside of morning hours), i managed to naturally say "good morning" in return :) maybe that driver just started their shift today !!
i feel like this is one of those things people don't teach you, but that is just picked up or something. like one of those social cues that are just known or whatever that makes little sense to those unaware of it.

tdlr, i used "good morning" outside of the morning time !!

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a few days ago, i learned the science behind why ice is less dense than water!

afaik, all liquids freeze into more dense solids, except water turning into ice! ice is less dense than water and ice floats on water. for many years, i did not know why this was. but now, i learned that it's because of the molecular shape of water (chemistry) and kinetic plus thermal energy (physics)!

in a basic short summary, the H2O molecules in water are close together and can easily flow past each other. but when it freezes (loses thermal energy/heat), the molecules slow down in a particular way that forms hexagon shapes, which make the molecules further from each other! less molecules in one spot means less dense. therefore, ice is less dense than water because there is more space between the H20 particles in ice.

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today i learned about geographic north vs magnetic north!

geographic north, also called true north, is the north end of the axis upon which earth spins.

on the other hand, magnetic north is where a compass needle points—the north pole! earth is an imperfect magnet; north is not perfect north and south is not perfect south. and since earth is complicated with its rotations and stuff that happens at its core, the magnetic north is not fixed and can move around!
(fun fact: the north pole is actually the south end of earth's magnet! north is attracted to south, and your north compass needle points toward the north pole, the south end of the magnet!)

therefore, geographic north is not the same as magnetic north. geographic north is north on earth, and magnetic north is dictated by fancy processes in earth's core that ends up different from geographic north.

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today i learned why eating sugar causes tooth decay!

chemistry time! teeth are compased of some chemical compound called hydroxyapatite, containing calcium and hydroxide (a base).
eating sugar produces lactic acid (an acid).

in short, these two compounds, hydroxyapatite and lactic acid, react with each other to displace calcium out of teeth!

extension! since this compound teeth are made of is slightly basic, eating acidic foods will also cause a neutralization reaction (funky combination when acid and base mix!) and remove calcium from teeth.

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today i learned why certain cheeses emit oil in room when it heats up!

this wondering came from me eating cheddar cheese as a snack. when it was still cold, fresh out the fridge, it was more solid and non-oily. but after i leave it out a little bit, it becomes more bendy and more oily.

in cold, solid cheese, the fat is a solid! but when it warms up, the fat melts into a liquid!
that liquid fat means the cheese is held together weaker; the cheese becomes more bendable!
the liquid fat also ends up on the surface of the cheese, so it's the oil!

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