sequential,

countries and facts about countries!

Ultraviolet,

The Doomsday rule.

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.

feral_hedgehog,
@feral_hedgehog@pawb.social avatar

Powers of two, squares and cubes up to 20 and the NATO phonetic alphabet.

torknorggren,

Baseball-reference.com

hsl,
@hsl@wayfarershaven.eu avatar

Thirty days has September, April, June, and November.

frogfruit,

My school taught it as “30 days hath September, April, June, and November. All the rest have 31, except the second month alone.”

Notyou,

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.

Deelala0516,

This is definitely the way.

penguin_in_suit,

With 28 there is only one All the other are thirty one

My mom taught me this limerick when I was little.

teawrecks,

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).

TheHalc,

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.

snek_boi,

If you drive, the 3-4-8 second tailgating rule

RomanRoy,
@RomanRoy@lemmy.world avatar

Subnets

mosiacmango,

/24 and /32 are like 90% of the battle. 256 hosts and 1 host solves most issues.

snek_boi,

The mneumonic major system. Once I learned it by heart, it helped me memorize all kinds of numbers: cards, IDs, passwords, addresses…

Anticorp,

That sounds a lot more complicated than just memorizing the number itself. How long did it take before you felt comfortable with this?

snek_boi,

To give an extreme example:

“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).

Anticorp,

Thank you. I’ll give it a shot, since the example you gave is awesome.

arthur,

Do you remember the Fibonacci sequence? You can use it to convert miles to kilometers .

2 mi ~= 3km

5mi ~= 8km

8mi ~= 13km

13mi ~= 21km

And so on.

soggywhale,

That’s awesome thanks !

DoctorWhookah,

Wait, is this true until its not or is it true forever as you go higher in the sequence?

masochismworld,

Conversion factor of miles to kilometers is about 1.609 and golden ratio is about 1.618, it will be pretty accurate for quite a while…

liam_galt,
@liam_galt@lemmy.blahaj.zone avatar

It’s true forever. The Fibonacci sequence used in this way converges on the golden ratio, which is close to the conversion of km and mi.

Anticorp,

So are you telling me that the inventors of the mile were using the golden ratio?

Maya,

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.

arthur,

Just a neat coincidence

kakes,

Someone already replied with a graph, but I also got curious and checked for some higher numbers. Sure enough, it held up.

For example:
832,040mi => 1,346,269km (actual: 1,339,039km)

snek_boi, (edited )

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.

https://lemmy.ml/pictrs/image/528b1166-8b5d-481d-a7bc-180947c29520.png

Edit: Here’s another graph

https://lemmy.ml/pictrs/image/003c6f1a-5555-45d3-a4d6-e4b5ddae71ec.png

So it turns out:

  • Fibonacci-approximated kilometers are always higher than the usual-conversion kilometers
  • At most, the difference between both is 25%. That happens early on in the terms.
  • After that, the percentage difference oscillates around a value and comes closer to it.
  • When talking about more than 100 miles, the percentage change approximates 0.54.

TL;DR:

  • Yes, the Fibonacci trick is true forever as you go higher in the sequence if you’re willing to accept a 0.54% error.
Akasazh,
@Akasazh@feddit.nl avatar

You just did the math!

snek_boi, (edited )

If someone wants to play around with the code, here it is.

Note that you need RStudio and the Tidyverse package.

klemptor,

Mmm dat ggplot2 but ggthemr::ggthemr(“flat”) is where it’s at.

snek_boi,

Checked it out and love that package! Thanks for the recommendation :)

kogasa,
@kogasa@programming.dev avatar

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.

abejfehr,

It’s always true because the ratio of miles to km is really close to the golden ratio.

If you do it for a zillion miles you’ll be off by a lot of km, but proportionally the same amount as for 1 mile

newpuritan,
@newpuritan@lemmy.ml avatar

That’s brilliant.

ohlaph,

Harlow is in the fireplace, Adobo is in the window, and Sesqua is on the couch.

For some reason, I used the memory palace to remember that several years ago when I first heard about it and I still remember it.

abbadon420,

What does it mean?

ohlaph,

Pure randomness. Just wanted to try and memorize random things to see if it works.

rm_dash_r_star,
@rm_dash_r_star@lemm.ee avatar

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.

Chrobin,

Correction: It’s Sagittarius A*

Kittiesmom13,

Just for fun -

Once a molicepan met a bittle lum Sitting on the sturbcone eating gubber rum Mmmm said the molicepan, simme gum Not on a sam dight said the bittle lum

Growing up in the 1930s, mom said the was the girls favorite pastime - swapping letters of different phrases.

I know you were looking for more serious things, but this was fun for me to memorize years ago and try to put into play with other phrases.

giddy,
@giddy@aussie.zone avatar

Have you heard the tragedy of Darth Plagueis the Wise?

fedev,

I heard there was something unnatural about him.

Zarxrax,

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.

MammyWhammy,

I don’t know any Korean, but the Korean alphabet is by far the best writing system I’ve seen.

The characters make the shape your mouth makes while annunciating that letter. It’s ingenious.

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