 Huh. So, just now I learned that you can convert miles to kilometers with the Fibonacci sequence? A mile is 1.609 kilometers. The Golden Ratio, the ratio between Fibonacci numbers as they get large, is 1.618. So, within about 1%. And large doesn't need to be that large, it's actually pretty accurate from about 8 onwards. 1 1 2 3 5 8 13 21 34 55 89 etc etc 5 miles is 8 km. etc etc. Kinda neat IMO. 65 comments
 @macbraughton @mhoye wow! Now instead of getting annoyed when people use the wrong units I'll be happy at the opportunity to use my newfound conversion skills š   @mhoye That is interesting. I find the 5<->8 conversion to be enough to work out useful conversions in my head. It works very well for all the speed limit conversions.  @LovesTha @mhoye 5<->8 also provides the same-ish error term. In English, it helps that kilometers get measured in multiples of 8 for some unknowable reason. (Oh! You could do both, average them, and come out basically dead on! Just need to remember enough Fibonacci numbers to cover the face of a circular slide rule firstā¦) @cpontvieux @LovesTha @mhoye @xek Kmph, while not official/scientific notation (as in notation encouraged by the SI) is apparently a widely used abbreviation. For example, see the link below. It's potentially interesting (context dependent) to make people aware of SI conventions. Possibly not so useful to scold people on social media for employing widely used everyday alternatives in an "everyday" context? https://www.oxfordlearnersdictionaries.com/definition/english/kph @level98 @cpontvieux @mhoye @xek kph would irk me, thousands of what per hour? As does KMPH, case does matter. (using a capital K at the start of a sentence is an awkward argument about which norm is more important) @LovesTha @cpontvieux @mhoye @xek "k" for "kilo" as in "thousands" is lower-case. The "official" notation, as mentioned by Cyrille, is: km/h or km hā»Ā¹ If you (or anyone passing) happens to be interested / are not already aware... the organisation who determines such "official" things is the BIPM. A description/documentation of the SI system of units (overseen by the BIPM) can be found on their website. km/h is not an SI unit... just "accepted" for use with the SI. @LovesTha @cpontvieux @mhoye @xek Pascals is Pa, but that;s close enough for comic effect! š "Kelvin Mega" could be a death metal band?  @mhoye @LovesTha In some American-authored stuff, maybe some UK works as well, places wind up being 40 or 16 or (my favorite) "about 24" kilometers away surprisingly often. It amuses me to no end. What human would say "about 24" km instead of "about 25 km away? (Aside from Babylonians and other base-60 cultures.)  @LovesTha @mhoye the hex based conversion covers what I needā¦ 30 mph is about 0x30 km. The other direction is not as trivial but gives a good approximation if you can recall all seven bit numbers in both bases ā 64 km āisā 0x40, so 60ish kms are 40 miles. It gets funky with things like 55 miles as 55 m is not 85 km but 5 needs to be converted separatelyā¦  @screw_dog This is 39, not 40 miles. And since this isn't actually conversion but rough estimation giving lower-than-the-actual-value in km. Removing one full mile adds even more to the errorā¦ Maybe, people from the US should just stop using the Moronic System of Units ( = Imperial) and use the International System of Units instead. @mhoye 8/5 is way more practically useful imo b/c of base 10. for Fibonacci you either need to have a boatload of numbers memorized (to divide by the appropriate power of 10) or only be talking about very specific comparisons.  @michaelchirico @mhoye  @mhoye Huh, thatās not by design, right? As in, when deciding upon metric will work, they didnāt start with imperial and say, letās apply the golden ratio- and Smythe up the back didnāt recall the third and fourth digit correctly. Or did they? Because otherwise itās a bit too neat, maths-wise  @mhoye When I first moved from a miles nation to a kilometre nation I did "divide by five and multiply by three". After a few months I realised there was no point and just mentally switched to kilometres. I lived with a languages student who'd spent a year in France. She said that after a while she stopped having to translate into English; her thought processes had adapted to her environment. @mhoye @xi_timpin I can believe it too. The human brain adapts well to changing environments. @mhoye Nifty. As they're pretty close to 0.6/1.6, I just add a half and a tenth to go km -> mi, and add that to the original value to go the other way mi -> km. Some prefer to divide by 5 then multiply by 3 (same 0.6 ratio) but I find 2 simple additions to be easier (for my brain).  @0xThylacine Yep, my way exactly. And for some reason when we talked about miles at school, the number 1.609344 got burned into my head. Though I can't seem to remember the value for nautical miles... ~1.8... from the top of my head. You're supposed to fit a whole number of nautical miles into a section of a great circle, measured in degrees and seconds. @hlangeveld And this has to be on the equator if were talking about driving from longitude to longitude. And then a nm is a minute on the circle. 1.8 seems right, had to look the 1.852 up as well. Bonus for me: It seems I finally got the latitude/longitude thing right. ("all longitudes are equally long" helps me out) ;-) @hlangeveld @jesterchen I wrote this yesterday and deleted it coz I felt I've hijacked the OP. But for completeness... Equator to pole is very close to 10,000km (it was defined as that but an error crept in). Similarly, a nautical mile is one minute of (latitudinal?) arc, so 90 degrees x 60 mins = 5,400 nm. Again errors occurred. So km -> nm is roughly 0.55 (11/20ths), so the reverse is approximately 20/11 (~1.818...), which is close to (2-0.2) for easy calcs. @mhoye there was a glorious time when the GBP/USD exchange rate was about 1.618 too, and you could do this with UK/US currency conversions. @mhoye also 1/1.6 = 0.6 (again from the golden ratio), so 1.6 and 0.6 are the multiples you need for conversion. @mhoye But the conversion gets less accurate (closer to 1.618) as they larger. @mhoye One of today's lucky ten thousand! š I learned this running cross country in high school, because at least at that time and place, HS men's courses were 3 kilometers or 5 miles, and HS women's courses were 2 kilometers or 3 miles, which was still sufficiently close to notice the start of that series. š  I don't think I understand that math. 5^5 is definitely not ~8. Oh, e raised to, I see. So, while that's interesting I don't think I would be able to casually raise e to the power of anything but zero off the top of my head, and that's where the argument sort of falls over. @mhoye Are you saying that if everyone on earth only used km the world would lose some of its beauty? @mhoye And if you write your numbers in a Fibonacci base, converting between them simply becomes a shift (left for miles -> km, right for hm -> miles). You can sort-of cheat and use binary numbers, as long as you never have two consecutive "1" (they'd add up and carry to the left), but doing addition that way is actually shockingly complicated.  @mhoye @timixretroplays I just divide by ten and double four times I a row. The other way round is easy too.  @owen @mhoye It depends on how you define "useful", but since the ratio between consecutive Fibonacci numbers gets closer to 1.618... as you go higher, it's always going to be within 1% once you go beyond 5mi (8km). So I'd say it stops being useful once you no longer have a use for numbers that large š  @mhoye @mattgrayyes trick (for me at least) is remembering which way they go @mhoye It would be even neater if the US just adapted to m/km when it comes to distance/length and speed. That would be the neatest.  @stadsplanering @mhoye "just" @mhoye Love thisā¦. Iāve always just multiplied KM by 6 and stuck a decimal in. 7(km) x 6 = 4.2 miles. Close enough. :-)    |
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