Metric only tape measures

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The ability to make the measurement in 1790 was somewhat questionable
Yes, but that wasn't (and never has been ever) the point.
That's why you've had centuries of metrology since; you could improve the measurement.
It's why the meter since has been redefined to be the distance light travels in a set unit of time.
Specifically, the idea is that your system of measurements is based on a physical characteristic of the universe that isn't likely to change, as opposed to (say, for example) the size of Agrippa's foot (to steer clear of the imperial system for the sake of political correctness :) ). So this year we can measure the meter to within a set error level, next year a better measurement can be made and so goes progress for the human race :)

Meanwhile, measurements based on a specific artifact (like Agrippa's foot or the standard kilogram mass) can't ever really be improved on so you're stuck at a set level of accuracy, which affects your ability to do manufacturing, science, engineering, and generally push up the quality of the beer you drink on a friday evening. Said alcoholism being why the metric system has been trying to get a better unit of mass for a few hundred years.

Not that it matters if you do woodworking the right way, without all these machines and just cut pieces to fit :p :D

legs it
 
MarkDennehy":31126dhc said:
The ability to make the measurement in 1790 was somewhat questionable
Yes, but that wasn't (and never has been ever) the point.
That's why you've had centuries of metrology since; you could improve the measurement.
It's why the meter since has been redefined to be the distance light travels in a set unit of time.
Specifically, the idea is that your system of measurements is based on a physical characteristic of the universe that isn't likely to change, as opposed to (say, for example) the size of Agrippa's foot (to steer clear of the imperial system for the sake of political correctness :) ). So this year we can measure the meter to within a set error level, next year a better measurement can be made and so goes progress for the human race :)

Meanwhile, measurements based on a specific artifact (like Agrippa's foot or the standard kilogram mass) can't ever really be improved on so you're stuck at a set level of accuracy, which affects your ability to do manufacturing, science, engineering, and generally push up the quality of the beer you drink on a friday evening. Said alcoholism being why the metric system has been trying to get a better unit of mass for a few hundred years.

Not that it matters if you do woodworking the right way, without all these machines and just cut pieces to fit :p :D

legs it

This year is actually a big year for the kilogram and for the fundamental units. There is a conference later in the year at which it will be redefined away from the lump of platinum in Paris. It's the last of the fundamental SI units to be defined by an arbitrary artefact. There are two competing methods, the watt-balance and the X-ray interferometer for measuring the size of silicon atoms and thereby counting atoms in a certain volume. Only one of them will be selected (likely the watt balance) but the unit cannot be redefined until there are two methods that have similar precision and accuracy, as a crosscheck.

I'm sure you all wanted to know that.

Keith
 
MusicMan":1ifqqwi8 said:
This year is actually a big year for the kilogram and for the fundamental units. ... Only one of them will be selected (likely the watt balance) but the unit cannot be redefined until there are two methods that have similar precision and accuracy, as a crosscheck.

If it means my bandsaw gets lighter, I'm all for it.
 
NickN":3foyh1kl said:
MusicMan":3foyh1kl said:
This year is actually a big year for the kilogram and for the fundamental units. ... Only one of them will be selected (likely the watt balance) but the unit cannot be redefined until there are two methods that have similar precision and accuracy, as a crosscheck.

If it means my bandsaw gets lighter, I'm all for it.

Mass, not weight :p
 
MarkDennehy":2yz66vmm said:
NickN":2yz66vmm said:
MusicMan":2yz66vmm said:
This year is actually a big year for the kilogram and for the fundamental units. ... Only one of them will be selected (likely the watt balance) but the unit cannot be redefined until there are two methods that have similar precision and accuracy, as a crosscheck.

If it means my bandsaw gets lighter, I'm all for it.

Mass, not weight :p

There's no meaningful difference on earth.
 
Just wanted to make a couple of pedantic points (this being the internet and all):

1) “meter” is what you measure things with, “metre” is what you measure things in

2) the speed of light is not constant, the reference is the speed of light in a vacuum.

:)
 
Oh does that mean we can join the Europeans and call the distance travelled a "Kilo Metre" instead of the British equivalent "Kilometre" that then begs the question do I have a "Speedo Meter" or a Speedometer?

Mike
 
Brandlin":37finxr7 said:
MikeG.":37finxr7 said:
MarkDennehy":37finxr7 said:
Mass, not weight :p
There's no meaningful difference on earth.
There's a significant measurable difference on earth, depending on your altitude and latitude.
You don't even need to worry about altitude or latitude. Just put whatever the thing is on a good set of wheels and try to push it (or stop it when it's moving)...
 
Talking as a rope access worker, I'd reckon you'd be surprised at just how meaningful the difference is between mass and weight especially when taking altitude into account.
I used to clean the pyramid roof of One Canada Square (Canary Wharf). At 770 feet or 235 metres up when you're hanging off a 10mm rope I'd suggest you'd be well aware of the difference too.
Funny how perspective changes things. Especially when the particular perspective includes tiny ant size people and tiny ant size buses when you look down.
Formulaic equations aside, in those situations weight and mass are really quite different.
When you're a weight you're generally fine. It's the moment you become a mass that you need to worry about.
Generally, if you do become a mass you won't be worrying for long though. Which is nice of course. Very presently you'll just become a mess which is another thing entirely.

Like I say. Perspective.
:D
Regards
Chris
 
MikeJhn":2s2qumfn said:
Oh does that mean we can join the Europeans and call the distance travelled a "Kilo Metre" instead of the British equivalent "Kilometre" that then begs the question do I have a "Speedo Meter" or a Speedometer?
Nope, it's kilometre and speedometer in the official international spelling already.
 

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