KM vs Miles

[Dogtrousers]

An interesting fact is that the acceleration due to gravity is 9.81 metres/sec/sec and pi squared is 9.87. Coincidence?

Actually not. There was at one time a standard to use the length of a pendulum with a period of 2s. as a reference length. That's independent of the mass of the pendulum and amplitude so a good candidate for standard length, right? Well, actually not, as there's a small error so it's good, but not good enough. The metre as finally chosen was very close to that of a seconds pendulum, but not quite the same. And this is what makes g almost equal to pi squared.

 

[Punkawallah]

Fun fact. The metric meter is almost exactly half of their traditional ‘toise’.
“Oi! Marcel! Wot’s this ‘meter’ thingy?”
“No probs, Giles me old mucker - s’just ‘arf a Toise, innit?”

 

[Aravis]

Cesium

Yuk. But I wholeheartedly agreed with your post otherwise.

 

[Dogtrousers]

Yuk. But I wholeheartedly agreed with your post otherwise.

I'm going to claim it was autocorrect but it may not have been.

 

[Dogtrousers]

Stand by for another interesting fact.

Lets think about gearing. There are gear inches, as used by pipe smoking English gents in plus fours with diamond pattern socks, and there are metres of development as used by Frenchmen smoking untipped Gitanes and sipping red wine.

Here's a fun fact, these two are related by a simple factor of 8.

So a 70" gear has a development of 560cm (or 5.6m)

Isn't that just absolutely amazing?

Unfortunately, it's not quite true, the real answer is 558.6 cm but it's damn close.

This is because the conversion factor from Inches to cm is equal to 8/π (near as dammit - to within 0.25%) and development is π x the wheel diameter.

So what is an inch? An inch is 2.54 cm exactly, by definition. It's how the inch is defined. It has been since July 1st 1959 "International Yard Agreement", which adopted a 1930 recommendation from the British Standards Institute that an inch should be exactly 25.4 mm. No more, no less. By definition. Before that there were several different inches in use.

That's how the two length systems are tied together. That 1 inch = 25.4mm definition is the fundamental basis of the inch. And by sheer coincidence it happens to be roughly equal to 80/π (25.4647...)


https://meterstofeet.com/guides/why...e-1959-international-yard-and-pound-agreement

 

[andrew_s]

Much like the Metric meter being standardised despite the distance between the pole and the equator changing.

When did the size or shape of the earth change?

 

[Electric_Andy]

I always assumed bars was old money and therefore imperial. It's only when I think of pounds per square inch that it naturally sounds like psi is not metric. I've always used psi because it's a bigger number and seems more sensible I.e 32 ish for cars, around 5 for a rugby ball, and 100 ish for skinny bike tires.

 

[Electric_Andy]

I always assumed bars was old money and therefore imperial. It's only when I think of pounds per square inch that it naturally sounds like psi is not metric. I've always used psi because it's a bigger number and seems more sensible I.e 32 ish for cars, around 5 for a rugby ball, and 100 ish for skinny bike tires.

Having looked up conversions, much like inches vs mm, it makes far more sense to go from 30 to 32 psi instead of 2.06 to 2.20 bar