The definition we should have used (and almost did) was that the meter was the length of a pendulum with 1 second swing (in other words, a pendulum with a 2 second period). https://maa.org/sites/default/files/images/upload_library/22...
If we had done that, the gravitational constant of Earth would be exactly pi^2 m/s^2: Neat, right? https://godplaysdice.blogspot.com/2007/09/why-g-2.html
P.S. Not really necessary but in writing this comment, I read these documents, each of which taught me something new:
https://interestingengineering.com/science/a-brief-history-o... https://spie.org/publications/tt82_25_speed_of_light https://en.wikipedia.org/wiki/Luminiferous_aether
Wish what had been defined? the second?
I would assume they meant meter since they wrote that.
> The meter (m) is defined by taking the fixed numerical value of the speed of light in vacuum c to be 299,792,458 when expressed in the unit m s−1, where the second is defined in terms of ∆νCs.[0]
Your proposed change is keeping this the exact same but changing 299,792,458 to 300,000,000?
You said: “I wish it had been defined in relation to the speed of light in a vacuum.”
I believe it is already, as written above.
0: https://www.nist.gov/pml/owm/si-units-length#:~:text=The%20m....
I don't thik foot is particularly useful in day to day life - it's awkward to measure walking distance with that, and for measuring smaller objects it's awkwardly placed, an arm length unit might be more useful for measuring smallish objects.
For example, "10 feet 8 and a half inches" not "10.7 feet" (yes I know the rounding is slightly different). For a smaller distance you might say "three sixteenths of an inch" (since thats what the imperial side of a tape measure is typically divided into) though there are some exceptions eg "0.1 inch spacing".
Pints and fl oz the same (you see this quite often in recipes for example) - "1 pint 3 fl oz" or even "23 fl oz" not "1.15 pints". For gallons I think most Brits would likely use a whole number of pints rather than subdividing (ie "21 pints" not "2 gallons, 5 pints").
But I'll give you that we don't really use furlongs outside of horse racing :)
Lets say a pendulum can swing for about 2 minutes. You just take a 2 minute hourglass, make a bunch of pendulums of different lengths, and assign someone to count the number of swings between the moment you turn the hourglass and the moment the sand has passed trough. The one closest to 120 is the correct length.
Now this solution is mathematically elegant but comes with a lot of problems. First you must rely on a less-than-perfect time measurement device which may suffer from day to day variations due to temperature.
On the contrary, to calculate the distance from the poles to the equator, all you need is a good angle measurement device, from which you can triangulate a distance.
Can you expand on how this can be done please?
Particularly the bit where you measure the semi-major axis and semi-minor axis of the Earth's ellipsoid and how you settle on a particular ellipsoid out of the many that predate WGS84.
https://en.wikipedia.org/wiki/Earth_ellipsoid#Historical_Ear...
"All you need" appears to bury a lot of detail in some hand waving.
It's unclear to me whether you intend to measure a distance along the Geoid (gravitational equipotential surface), along the Ellipsoid (the rotated ellipse of best fit), or the actual suurface (the path that would be walked, floated, traversed from equator to pole).
A complication with the Geoid path family and surface path family, of course, is that these vary by what line of longitude you might follow.
Sorry, couldn't help myself, unlike yourself.
Just recall we're in a thread about precise definitions of reference units, the title posed refers to tens of trillions of oscillations as the definition of a second.
When the kilometer was first coarsely defined by an Earth arc it was already a thousand+ years post shadow of a stick guy.
Once that kind of definition gets refined further the "arc of the earth" approach hits all of the hurdles I outlined .. for the benefit of the person I replied to who somehow believed it was a simple straightforward task to make it "better".
Hand waving a reference is all very well ... until you hit cases that require actual precision finer than the error bars on the hand wavy seat of the pants cowboy antics.
That bar was crossed some decades past.