Not necessarily the part for calculating the day of the week for any arbitrary day centuries ago, that’s just a useless party trick, but for the current year so you don’t need to pull out your phone to check. Knowing that 1/3 (or 1/4 on a leap year), the last day of February, 3/14, 4/4, 5/9, 6/6, 7/11, 8/8, 9/5, 10/10, 11/7, and 12/12 are all the same day of the week, that this year they’re all Tuesdays, and next year they’re all Thursdays, is mostly easy to remember and very frequently useful.
I always just used the knuckle trick for counting. The ones that have 31 days are at the top of the knuckle and the 30 (or 28/9) day months are in between the knuckles.
A completely random ordering of a deck of cards. You can have a deck pre-stacked in this order, learn some false shuffles, have someone pick a card and place it back anywhere they want without marking its location in any way, and when you inspect the deck you know exactly what their card is. And they’ll never guess that the way you did it was memorizing the order of every card in the deck.
I’m sure there are a lot more advanced ways to take advantage of this, just a handy ability to have in your back pocket (literally).
If you’re going to memorise a deck of cards, you’re better off learning something like the Mnemonica Stack as you can use it as the basis for a whole load of card tricks.
“I solemnly swear that I am up to no good.” vs. “053250411391271”
But to be fair, I never end up with nice sentences. It’s more like “Thank you, rainbow. Clock firework” and I imagine myself thanking a rainbow and telling it to “clock firework”, whatever that means…
As to how long, I think it could’ve been a couple of months doing a dozen or so conversions. In total it’s a very small investment of time, assuming you space it out and don’t cram. It really helps to use the Wikipedia mnemonics (like how 4 is kinda like a mirrored R).
We wish they were that cool, the inventors of the modern mile were more concerned about land measurements. A square mile is 640 acres. Which neatly can be cut into quarters 3 times. 160, 40, 10.
I think the way to formally prove this is to find the difference between the Fibonacci approximation and the usual conversion, and then to find whether that series is convergent or not. Someone who has taken the appropriate pre-calculus or calculus course could actually carry it out :P
However, I got curious about graphing it for distances “small enough” like from Earth to the sun (150 million km). Turns out, there’s always an error, but the error doesn’t seem to be growing. In other words, except for the first few terms, the Fibonacci approximation works!
This graph grabs each “Fibonacci mile” and converts it to kilometers either with the usual conversion or the Fibonacci-approximation conversion. I also plotted a straight line to see if the points deviated.
The ratio of consecutive terms of the Fibonacci sequence is approximately the golden ratio phi = ~1.618. This approximation gets more accurate as the sequence advances. One mile is ~1.609km. So technically for large enough numbers of miles, you will be off by about half a percent.
I have this thing about astronomy. Kind of a perspective thing of our place in the cosmos. I try to remember all the distances of planets from the sun and distances of moons from their planets. Also the diameters of solar objects. There’s other factoids I try to remember about neighboring solar systems and galactic bodies. For example I remember the black hole at the center our galaxy is called Sagitarius A and its mass is 4M suns. The black hole at the center Andromeda our closest major galaxy at 2.5M light years is 25M suns. The black hole at the center M87, the closest active galaxy at 50M light years is 4B suns. I didn’t look that stuff up so tell me if I didn’t get it right.
Learn some alphabets of foreign languages. Russian is fun because some of the characters looks like English letters but have completely different sounds. Korean is also cool because it looks crazy complex but it’s actually extremely simple.
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