Novice Ponderance....

[dwolsten]

I measure speed in furlongs per fortnight...

[gjbivin]

I measure speed in furlongs per fortnight...

I've always preferred femtoparsecs per microfortnight...

[scorrpio]

In the current metric system weight is measured in Newtons.

Actually, unit of mass is a kilogram. Newton is a unit of force, and is defined as force that, applied to a 1kg object, will give it an acceleration of 1 meter/second squared. Cofusion with mass comes from following: as Earth gravity acceleration is 9.8m/s^2, and force equals mass times acceleration, a 1kg item near Earth is affected by a force of 9.8N. In a physics lab, when wanting to apply downward force to something, they often use weights of 102.04 grams, which impart a downward force of 1N. It is a common mistake to say that these weights 'have a mass of 1 Newton'.

Here's from recent Fine Homebuilding:
Q: In Canada, they've been using the metric system for decades, but carpenters still measure in inches. What gives? Isn't it easier to use decimals than fractions?
A: (partial) Standard answer is that USA uses a vast amount of 4x8 feet sheet goods and dimensional lumber. Canada, being a major exporter of these products, wants its products acceptable for huge US market.
But there's another reason for carpenters to stick with the imperial system, one related to numbers, not materials. The number 10 can be divided evenly by 2 and by 5. But 12 can be divided by 2,3,4 and 6. Makes for a lot less skull sweat.

Now, having grown up in 100% metric Russia, and having worked with wood there, adapting to US system upon coming here at age of 18 took some time. However, I find that these days I don't use metric at all. I find feet and inches a reat deal more convenient when I lay out my project designs. I used to have a couple tapes and rules marked in both inches and cm, but have long since stopped using them. I find a machinist rule, graduated in 1/8, 1/16, 1/32 and 1/64, a whole lot more handy.
I also find feet and inches to be more 'organic'. A meter is simply 1/10,000,000th of the distance from a pole to the equator, and is not contingent upon any human dimensions.

Think about it:
A comfortable workbench/countertop height for most people: 3 feet. All but rather tall people will find 1 meter high countertops awkward. Comfortable width to reach across, or an opening to fit through: 2 feet. Half a meter would be a bit cramped for most. All but most beefy finger will fit through a 1 inch hole. Optimal ceiling height? 8 feet. Optimal eye level placement? 5 feet. Simple numbers.

Nope, not missing metrics at all here.

[dwolsten]

I also find feet and inches to be more 'organic'. A meter is simply 1/10,000,000th of the distance from a pole to the equator, and is not contingent upon any human dimensions.

Actually, a meter is the length of the path traveled by light in vacuum during a time interval of 1/299,792,458 of a second. It was originally intended to be one ten-millionth of the the distance from the equator to the north pole, but since measurement wasn't that great in the 1700s when the meter was first conceived, it's slightly off. The original definition of the meter, during the 1800s, was a rod of metal kept in Paris, measured at a specific temperature.

The whole reason for the meter was that for a measurement to be universally repeatable, it had to be defined in such a way that anyone with sufficient means could replicate it. Until the SI system came around, there was no standard for the foot or the inch. So how do you know that your ruler is accurate? Well, these days it's simple: you check to make sure that 1 inch on your ruler equals exactly 2.54 centimeters. Inches were defined based on the metric system a long time ago.

Nope, not missing metrics at all here.

That's because you aren't doing any unit conversions. The big strength of the metric system, besides standardized measurements, is that it's easy to convert between units, not only within the same type of measure (length, volume, etc.), but also between different types of measurements (length->volume, acceleration->speed, energy->power, etc.) since higher-order units (L, J, W, N, Pa, etc.), are all defined in terms of lower-order units (m, s, kg, K, cd, A, mol).

Quick, if you build cubic enclosure one meter to a side, how many liters will it hold? 1 m^3 * (100 cm/1 m)^3 * (1 L/1000 cm^3) = 1000 L. The key to this is that 1 cubic centimeter = 1 milliliter.
Ok, how many gallons will a cube, one yard to a side, hold? I have no idea. Is there a simple conversion between gallons and feet or inches? I doubt it, since Google tells me the answer to this problem is 201.974025 US gallons.

In woodworking, this kind of thing really doesn't come up too often. How often do you calculate the volume of your wood projects? How often do you deal with forces or frequencies? Probably never. You deal with length, and that's it; the most difficult conversion you have to deal with is 12 inches in a foot. The only real issue in woodworking that applies to metric vs. SAE is the difficulty in dealing with fractions of an inch. In scientific and engineering fields, there's far more to measurement than things like this, which is why the SI system is predominantly used there.

[scorrpio]

I am afraid you are highly incorrect here.
1. Metre was set to be 1/10,000,000 of pole to equator distance, and that is what it is. The distance was measured to their best ability, and the standard was established. Later, when needing a more precise difinition, scientists expressed *existing standard* in relation to speed of light. They did not 'redefine a previously imprecise unit', or they would probably make it a nice round number like 1/300,000,000th of a second. (And if I recall right, second was fundamentalized by expressing it in terms of half-life period of a certain carbon isotope)

2. The foot and its derivatives (inch and yard) were standardized as early as 12th century, long before metric system came around.

Conversions might be easier with metric, but in my experience, when dealing with real-life application, conversions are either not that important, or are simply inaccurate, and various constants with a lot of decimals need to be applied in order for the system to work.

Science: you need a container that'll hold 1 litre. You make something which dimensions(in cm) product is 1000.
Real life: you likely will want this container to hold this litre without spilling, account for thermal expansion, etc etc. You have to consider its construction particulars. What if container needs to be round? Quick, how thick would you have to make a 10cm tall cylinder container in order to hold 1 litre? Quick, how thick does a 100x30 cm white oak shelf has to be in order not to sag under 20kg of weight applied in the center? Quick, what I.D. a 4 metre long pipe must have to allow at least 20 litres per minute flow of No2 heating oil with 1 metre of head over operating temperature range between 0 and 30 degrees Celsius? Does using metric units really make any difference in ease of these calculations? If your flow calculations are in gallons per minute over feet of pipe rather than litres per minute over metres of pipe, the only thing different is the constant being used - and in both cases, it will be some ugly number with a lot of decimals.

[MikeCrosa]

Or 2.54cm or .254 meters.

[LCHIEN]

I am afraid you are highly incorrect here.
1. Metre was set to be 1/10,000,000 of pole to equator distance, and that is what it is. The distance was measured to their best ability, and the standard was established. Later, when needing a more precise difinition, scientists expressed *existing standard* in relation to speed of light. They did not 'redefine a previously imprecise unit', or they would probably make it a nice round number like 1/300,000,000th of a second. (And if I recall right, second was fundamentalized by expressing it in terms of half-life period of a certain carbon isotope)

2. The foot and its derivatives (inch and yard) were standardized as early as 12th century, long before metric system came around.

Conversions might be easier with metric, but in my experience, when dealing with real-life application, conversions are either not that important, or are simply inaccurate, and various constants with a lot of decimals need to be applied in order for the system to work.

Science: you need a container that'll hold 1 litre. You make something which dimensions(in cm) product is 1000.
Real life: you likely will want this container to hold this litre without spilling, account for thermal expansion, etc etc. You have to consider its construction particulars. What if container needs to be round? Quick, how thick would you have to make a 10cm tall cylinder container in order to hold 1 litre? Quick, how thick does a 100x30 cm white oak shelf has to be in order not to sag under 20kg of weight applied in the center? Quick, what I.D. a 4 metre long pipe must have to allow at least 20 litres per minute flow of No2 heating oil with 1 metre of head over operating temperature range between 0 and 30 degrees Celsius? Does using metric units really make any difference in ease of these calculations? If your flow calculations are in gallons per minute over feet of pipe rather than litres per minute over metres of pipe, the only thing different is the constant being used - and in both cases, it will be some ugly number with a lot of decimals.

Actually Dwolstein is Highly correct.

The meter was originally defined as a fraction of the earth's circumference but for about 30 years now has been defined as wavelengths of an excited substance.

And although for many years the foot was defined by a physical ruler kept in a vault somewhere, it has been redefined in terms of the meter described above.

The modern standards reduce reliance on a single fixed object with restricted availability and allow those with the resources to reproduce the standard at another location using available standard materials to do so.

[vaking]

Loring,
One more fact to add:
Frequency (and time respectively) are the things that people are able to measure the best today. There are many quarz clocks and frequency generators that are guaranteed to be precise with the relative accuracy of 10 to negative 10 power. Most precise are claiming negative 15 power accuracy. For comparison, if I could measure length of something to negative 10 power I would have been measuring 1 mile with precision of 1/5 of a millimeter, that is 1/100 of an inch. The most accurate tools in my workshop today are micrometer and dial indicator - they measure 1/1000" on a scale of 1", that is 10 to negative 3 relative accuracy. It is logical that people are trying to redefine everything attaching it to frequency. The definition that a meter is X number of wavelengths of a light of specified frequency is much more precise than a fraction of Earth's diameter. This is the driving force for new definitions. Practically any watch you buy today will be accurate to one second in a day - that is more accurate than any woodworking or even machinists tools.

[scorrpio]

*Redefining* something is a completely different thing from *reestablishing* or *standardizing*. Metre might have been redefined in terms of a more constant measurement, but its actual length remains the same: 1/10000000th of the pole-equator distance as measured back in 18th century. You can define it in terms of any object of constant length.

Redefining imperial units in terms of metric ones also did not change them. Rules, measuring tapes, and other instruments graduated in inches did not become any less precise. Foot remains as it was standardized back in 12th century.

So how do you know that your ruler is accurate? Well, these days it's simple: you check to make sure that 1 inch on your ruler equals exactly 2.54 centimeters.

Nope. You look up the manufacturer's credentials. A ruler is not more accurate because it's metric. It is more accurate because it is made to higher standards. How do I know that $0.50 metric plastic ruler is accurate? Simple. I see that its 254mm mark aligns with 10" on my Starrett machinist ruler.