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Comment by mechanical_fish | Hacker News Reader

I'm not sure I understand what you're trying to say. As a US-trained scientist, I never used anything but the metric system except when standing inside a machine shop.

Scientists are among the US citizens most likely to relate to the metric system. Although I have to confess that my personal temperature meter is still calibrated in degrees Fahrenheit. ("Uh, it's 25 degrees in Rome today. Is that really hot? I can't remember.") For some reason temperature is my brain's last holdout: I'm pretty well used to meters and liters and even kilos. Perhaps that's because a liter is like a quart, a meter is like a yard (and a kilometer is close to a half mile) and a kilo is about two pounds, but Fahrenheit is completely nuts because there's an offset as well as a ratio in the conversion.

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I googled without luck, but I remember reading a study awhile ago that demonstrated that Imperial is easier for a human to estimate. Of the the experiments was asking for people familiar in each to guess the length of some objects. The people who gave an answer in feet and inches were more accurate than people using centimeters.

They postulated that it was because the values in the Imperial system "evolved", and are they way they are because of their convenience for measuring objects in a human scale. Eg, when eyeballing something hand-sized, its easier to pick out a few inches than it is dozens of centimeters.

I'll post a link to that article if I can find it.

Imperial units also tend towards being more division oriented, for instance a foot divides cleanly into halves, thirds or quarters.

A gallon divides into 4 quarts which divide into two pints, which divide into two cups.

That same series would be (starting from 4 liters), 4l, 1l, 0.5l, 125 ml, 62.5 ml.

In your volume example, imperial units only divide cleanly for certain factors (e.g. 2 in your example), from certain starting points (e.g. two pints) and within certain ranges (keep dividing a cup by 2 and it stops dividing cleanly).

Yep. But it stops at ... one ounce. So a gallon can be divided cleanly by two seven times. It's naturally no coincidence that a gallon is 2^7 ounces. :-)

I'm in favor of the US switching to metric (I'm American, but have lived in Europe for the last 7 years), but just trying to give some context on what I believe are some of the niceties of the Imperial system.

A "cup" is a much easier notion to get your head around than "about 50-70 ml".

A "cup" is a much easier notion to get your head around than "about 50-70 ml".

This opinion can only come from exposure. Whenever I see "one cup" in a recipe I'm 100% baffled. A big cup? A tea cup? One of those larger coffee mugs? Trying to judge what is actually meant here can leads to volumes differing about two to three times in scale.

Give me centiliters, desiliters and liters any day.

I still have no idea what a cup is. And 50-70 ml seems way too little to make sense, so I will just assume you pulled those numbers out of thin air.

1 cup = ~250 mL = ~1/4 Liter = 237 mL

Fortunately, all ingredients in a recipe are usually given in 'cups'. If you use the same cup for all ingredients, the proportions of the ingredients stay the same, which is the most important part of a recipe.

It does not matter if you use a big cup, a tea cup or a coffee mug. The meal will still taste good, as the proportions are kept.

While for a 'metrical' recipe you need something that can measure weight and volume, for a 'cup' recipe you just need a cup, no matter what kind of cup.

I realize this is totally derailing the original topic, but I'd just thought I'd correct one incorrect assumption you've made:

Fortunately, all ingredients in a recipe are usually given in 'cups'.

Not even remotely true. Especially with "cups" of water and "tablespoons" of chilli the results can be rather interesting ;)

Fast ballpark conversion that's easy to do in your head that works for most outdoor temperatures -- F -> C: subtract 30, divide by 2

Oh, that's really useful. I had my own mental approximation, but it was much mushier than this, and this is pretty darn accurate.

Much easier than multiplying by 5/9ths. Or 9/5ths. Whatver.

Seems like imperial is used http://edition.cnn.com/TECH/space/9909/30/mars.metric.02/

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