XKCD: It's more than a comic

Meh, it's a conversion like any other, and most people only do a handful of them. If remembering 12 inches in a foot and 3 feet to a yard is difficult, you may want to consider remedial math. I will grant you that I keep forgetting the value of 5280 feet (or 1760 yards) to a mile, although I know the rough value of 5200 or so feet off of the top of my head.

It still bugs me that they used "ounce" twice, as a measure of volume and of weight. And, of course, the United States and Canada couldn't agree on a standard Gallon.

And who knows how many different miles are there. At least 3 to my knowledge.

But the metric system is not always sugar and candy either. For speed, km/h and m/s are in the same range (1 m/s is 3.6 km/h). While scientists prefer m/s, in transportation km/h is used, sometimes, for example wind speed, both is used, and I have to convert. And I have to say, it's much more pain in the ass than multiplying or dividing with 10.

And how many inches to a mile? How many feet to a mile? What's one unit down from inch - and how many of those are in a mile?

If you always remember one step in the transition at a time, you have to convert, with a different multiplier, every step of the way.

How about this: How many times can an object that's 1 yard, 2 foot, 9 inches fit in a line that's 2.3 miles? If that calculation takes more than about 3 seconds, you system is just plain inferior.

(For us, the conversion is always a matter of moving the comma.)

You're right about that. Anything per second or per hour is always a bit tricky because the units of time are not always 10 times the previous (or a tenth of the next). That problem arises from the fact that we don't have sensible units of time, unfortunately.

Oh, and I forgot to comment on "remedial math" - since it's "mathematics", it's "remedial maths".

edited 19th Apr '18 7:05:49 AM by BestOf

math/maths is the same as color/colour. It's just a dialect thing

x5 Regarding the kilogram, it's still defined by the cylinder in France. It's the only SI unit not based on a natural definition, but they are working on a definition based on the planck constant. Interestingly, the imperial pound is defined in terms of the kilogram too now.

edited 19th Apr '18 7:26:31 AM by frosty

IIRC the metre is no longer based on a natural definition either, because of the theory (1/20000 of a meridian) not holding up to practice (earth isn't perfectly round).

Edit: And in fact, unless I'm mistaken, if the metre were still based on a natural definition, so would the kilogram, since it's the mass of a cubic decimeter of water.

edited 19th Apr '18 7:27:59 AM by Medinoc

It's currently the distance travelled by light in a vacuum in a certain fraction of a second, so still natural.

I really should've said reproducible, since the mass of water changes depending on purity, pressure, etc

edited 19th Apr '18 7:29:06 AM by frosty

And what's the natural definition of that fraction of a second (unless it's a perfectly round number like the aforementioned 20000)?

edited 19th Apr '18 7:31:39 AM by Medinoc

One litre (10cm*10cm*10cm of water (probably at sea level to get the pressure just right, and at something like room temperature in a lab) does, indeed, weigh exactly 1kg.

EDIT: I meant to say that I know math/maths is just a regional thing. I was just being cheeky.

edited 19th Apr '18 7:33:24 AM by BestOf

1/299,792,458th of a second. The second is defined as 9,192,631,770 vibrations of a cesium-133 atom. These admittedly unround numbers were picked so that the official, scientific definition matched up with the previous and common-usage definitions. Of course the original definition will still match up, it's just not precise enough for scientists.

edited 19th Apr '18 7:38:21 AM by frosty

Yeah, those weird definitions are there to make it possible to measure it very precisely. By the way, the kg is 1 l of water at 4 C temperature. This is pretty exact (unlike the one with the circumference of the Earth for the mater), but cannot be measured as precisely as those other ones.

A kg can be defined as Avogadro's number times the mass of a proton (even if it's not the current official definition), but onthologically it's the other way around: Avogadro's number is the result of the measurement of the proton's mass.

You mean a gram, not a kilogram.

(And actually it's 1/12th of the mass of a carbon-12 atom, but that's not much of a difference.)

edited 19th Apr '18 1:36:10 PM by Aetol

AFAIK, Avogadro's number is the number of atoms of Carbon-12 in 12 grams of the stuff.

Eh, I measure distance by how long it takes to get there, and for building things, I just mark distances off on a conveniet piece of paper. We coukd be using cubits for all I care.

Well, since atoms always have exactly the same mass, it makes sense to express weight in terms of a number of atoms.

i measure distances in units of my pets

"eh, it's about 30000 Nemos away, i'd say"

"Just go about 1000 Baileys north, take a left and head about 2500 Lattes that way"

"Oh that? It's roughly 20300 Patróns south from walmart"

As always, it depends on the precision you need. If your concern for distance is how long it'll take you to drive to work, and your concern for weight is how much you need to put in a recipe, then approximations are perfectly adequate. If you're trying to build a laser interferometer gravitational-wave observatory, you need a tad more accuracy.

FYI, the ground-based LIGO is merely a toy compared to what we're doing next. We're going to launch a laser observatory soon that will arrange itself along Earth's orbital trajectory to give us a several million kilometer baseline for interferometry: it'll be the largest man-made telescope ever. And if that weren't enough, we are developing a form of telescope called a pulsar timing array to measure supermassive black hole mergers and the fluctuations caused by primordial black holes in the cosmic microwave background with a baseline of millions of light years. So yeah, precision helps.

edited 19th Apr '18 2:09:22 PM by Fighteer

Even in a scientific context, its usually more important to estimate accurately, than to be precise to an nth degree. In scientific notation, for example, the exponent of 10 is usually more important than the actual number. You might see something like 2.14x10 (4th) vs 9.84 x 10 (2nd). The first number is very roughly 100 times larger than the second. You can usually ignore the rest of it (unless, as Fighteer points out, you're the one building it).

I encourage everyone to pick up a book on math hacks. It makes life so much easier.

I’ve never had to convert yards to miles, I’ve done inches to feet, feet to meters and occasional meters to yards.

But I live in the UK, we actully use both metric and imperial. For me the unit under an inch is a centermeter.

Intra-system conversions of length pretty much stick to feet/inches, feet/yards, and feet/miles. Maybe a little bit of inches/yards, because 36 inches to a yard is easy enough to remember.

In the long run, the US will eventually come around. As the global economy becomes ever more interconnected, and cultural exchange becomes more rapid and widespead, we'll have to standardise about many things, including units of measure. Fortunately, only a few countries on the planet still use the imperial system, and since it has no merits over the metric system (despite its apparent hegemony from the nation with the largest population of the native speakers of the current global lingua franca), the metric system will win out.

Meanwhile, the rest of us just have to get used to America's quirks if we're interacting with them enough for it to matter (usually it can just be safely ignored). I know my only interactions with the imperial system come in pop culture and literature, where I hope my guesstimate is usually good enough that I don't have to convert the measurements cited.

The more troubling international inconsistency is whether a billion is a thousand million or a million million.

Even when that happens, the disguised imperial isn't going away. Schools re-introduced the imperial system so that students would understand it when they got jobs, especially in construction. If you try to use metric in a Canadian construction company, you get some weird looks and a lot of trouble getting supplies. My driver's license gave my height in feet until about 3 years ago. Pop cans are 355 or 591 ml (12 or 20 oz), canned foods are 398 ml (14 oz), shots are 42 ml (1 oz), spirits are 375 ml (13 oz), 750 (26 oz), or 1140 (40 oz). In all fairness, they are labelled as metric first.

It's even in soccer. That wall in front of direct free kicks is 9.15 metres away. 10 points if you can guess how many yards that is.

It's 10 yards

edited 20th Apr '18 5:39:06 AM by frosty

Roughly about 30 yards.

Isn't metric the official system in the US, despite most people still using imperial?

I don’t understand why the temperature of 1 litre of Water makes a difference when defining a gram if it’s a unit of mass?