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It's time for the US to use the metric system

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Re: It's time for the US to use the metric system

#61

Post by fluffyllemon »

bhousel wrote: post #23
raverbashing wrote: post #18

Earlier quoted context omitted.

This is similar in Canada Yes, it's difficult to make people think about it. At the same time, sometimes the units "don't matter" (like speed limits, 50 is 50 in the speedometer, just make sure you're not looking at the mph scale) I want to slap somebody when I hear about "pounds" or "feet/sq ft", or even worse, Fahrenheit (since this is a non-linear transform) At least everything in the supermarket is marked per pou…

> Fahrenheit (since this is a non-linear transform) huh?

For a function to be a linear transform it needs two properties[1]:

  1. F(c1 + c2) = F(c1) + F(c2)
  2. F(k*c1) = k*F(c1)
Converting from Celsius->Fahrenheit (or vice versa) is does not have these properties.

  F(c) = 9/5 * c + 32

  F(c1 + c2) = 9/5 * (c1 + c2) + 32
  F(c1) + F(c2) = (9/5 * c1 + 32) + (9/5 * c2 + 32) = 9/5 * (c1 + c2) + 64

  F(k*c1) = 9/5 * (k*c1) + 32
  k*F(c1) = k * (9/5 * c1 + 32) = 9/5 * (k*c1) + k*32
Admittedly, I'm not entirely sure why being a non-linear transform gets the OP so riled up.

[1]http://mathworld.wolfram.com/LinearTransformation.html

Re: It's time for the US to use the metric system

#62

Post by sjwright »

sophacles wrote: post #53

Some thoughts on a conversion that I don't generally see brought up: * From an economic standpoint, the US is a big enough market that it is profitable to make things in weird US units, you have 350M people to sell to, most of whom are pretty well off by world standards. It makes sense to make a line catering to them. If businesses can start making a true or good economic argument it will happen more. * Tooling that…

It's not like America is the only country that will have ever transitioned. Many other countries have gone through all those issues without much complaint. It's not some untested experimental process being advocated.

It's not like the US is going to be using weird-arse inches, furlongs, horses and stones forever.

Re: It's time for the US to use the metric system

#64

Post by cpwright »

trothamel wrote: post #37

The strange thing about articles like this is that they seem to assume that converting between units is something that happens all the time, such that doing so is a huge drain on the economy and engineering time. I don't know if my experience is the common one - but with a few exceptions (inches/feet, oz/pounds) such conversions seem kind of rare. Instead, you pick an appropriately sized unit to begin with, and stick…

Because I don't want to look at 243.82cm on my tape measure, or if I am trying to lay something out to match the 16 in on center studs 40.64 cm, 81.82, 121.92, 162.56, 203.2, and then 243.82 cm.

For new stuff you could probably cheat and just base it on 40cm, which would be fine and perfectly acceptable, but for the old stuff which is still out there over the 8 feet, I'm already off by more than an inch which is enough to not hit the stud. Most framing isn't great, but still the error is additive and fractions are hard enough to work with that I'd want to avoid it.

I think the transition for lots of things really has an additional cost. Is that speed limit sign metric or imperial? Sometimes its obvious, other times not, and there are thousands and thousands of different governments responsible for them.

Re: It's time for the US to use the metric system

#65

Post by IgorPartola »

I challenge you all to make two changes today with regard to this. First, switch your phone to give you the weather in Celsius. It gets super simple fast:

0 and below - Freezing. Wear a warm jacket and closed toe shoes or boots.

1 - 10 - Cold. Wear an overcoat (a light one if you are used to colder weather)

10-15 - Early spring time. Long sleeves are probably in order, maybe even a sweater.

15-20 - Late spring. Wear short sleeves.

20+ - Warm to hot. Wear short sleeves. If it gets to be 24+ shorts are appropriate.

I am deliberately not giving conversions to Fahrenheit here because I think that's how you just go back to using it. Try to internalize the metric system here.

The second challenge is to switch your clocks/watches to the 24 hour mode. Not strictly metric system related, but you will not have to worry about AM vs PM again.

For the advanced users: switch your car to show your speed in km/h instead of m/h.

For the super-advanced users: try to figure out how many liters per 100 km does your car consume :).

Edit: if you cook (and you really should), use a scale set to grams instead of measuring cups for any recipes you are making. Almost all foods list both oz's and grams on them. You will get much more accurate measurements this way and will learn to gauge what 150 grams of cheese looks like, etc.

Re: It's time for the US to use the metric system

#66

Post by hkarthik »

sjwright wrote: post #62
sophacles wrote: post #53

Some thoughts on a conversion that I don't generally see brought up: * From an economic standpoint, the US is a big enough market that it is profitable to make things in weird US units, you have 350M people to sell to, most of whom are pretty well off by world standards. It makes sense to make a line catering to them. If businesses can start making a true or good economic argument it will happen more. * Tooling that…

It's not like America is the only country that will have ever transitioned. Many other countries have gone through all those issues without much complaint. It's not some untested experimental process being advocated. It's not like the US is going to be using weird-arse inches, furlongs, horses and stones forever.

We're by far the largest country (in terms of population) to attempt a conversion. That counts for something.

Re: It's time for the US to use the metric system

#67

Post by icegreentea »

drdeca wrote: post #58
icegreentea wrote: post #28

Earlier quoted context omitted.

There's a constant offset between F and C, so it's not linear in the actual engineering/math (or whatever) sense.

It's not proportional, but the equation for going from one to another is that of a line. I would think this would be called linear, but that mean something more specific?

In engineering, linearity refers to having two properties: a) f(x+y) = f(x) + f(y) where x, y, are two values, and f is a linear transform/function b) af(x) = f(ax) where a is constant In this case, the transform is the conversion between C and F. Since there is +/32 in there depending on direction, neither of these properties hold.

For example, yards to meters is a linear transform. 3 yards converted to meters + 2 yards converted to meters = 5 yards converted to meters. This is not true of temperature. Adding 32F to 32F gives 64F, which is not the same as adding 0C to 0C.

Re: It's time for the US to use the metric system

#68

Post by sophacles »

PythonicAlpha wrote: post #59
sophacles wrote: post #53

Some thoughts on a conversion that I don't generally see brought up: * From an economic standpoint, the US is a big enough market that it is profitable to make things in weird US units, you have 350M people to sell to, most of whom are pretty well off by world standards. It makes sense to make a line catering to them. If businesses can start making a true or good economic argument it will happen more. * Tooling that…

I am not sure, if the paper sizes (A4, ...) are belonging to the metric system ... but of course, here a standardization would be nice. At least software producers seem to know (most of them) now, that there are also other formats as the "standard US formats".

A0 is a square meter, and everything in the A series has an aspect ratio of sqrt(2) and different sizes are achieved by simply folding (or cutting) in half. It's actually pretty neat... check out:

http://en.wikipedia.org/wiki/ISO_216

Re: It's time for the US to use the metric system

#69

Post by ppereira »

drdeca wrote: post #58
icegreentea wrote: post #28

Earlier quoted context omitted.

There's a constant offset between F and C, so it's not linear in the actual engineering/math (or whatever) sense.

It's not proportional, but the equation for going from one to another is that of a line. I would think this would be called linear, but that mean something more specific?

In geometry, this would be an affine transformation.
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