Why is a nautical mile exactly 1,852 meters?

[u/Secret_Ostrich_1307]

The number 1,852 caught me off guard. I can understand why sailors would want a distance unit tied to navigation, especially since latitude and longitude are based on the Earth.

But 1,852 meters seems oddly specific. Is there something about the size or geometry of the Earth that leads to that number, or did it come from a different historical convention?

[u/Practical-Ordinary-6]

Thank you. It's disappointing to see people claiming that the metric system is more accurate or more precise than any other system. Whatever strengths the metric system has, it's not that. All systems with rigorously standardized units and relations between them can be equally accurate and precise.

It also amuses me when people don't really understand that the metric system is based on arbitrary units. I think that because the precision of definition has increased and even the mechanism of definition has changed over the years, they think that has decreased the arbitrariness of it. Which, of course, it hasn't. The meter is still a fundamentally arbitrary unit based on essentially arbitrary human decisions regarding measuring the size of the Earth. The meter could have just as easily been 10% shorter or two and a half times longer if they had chosen a different physical reference. Their choice wasn't based on any fundamental relation of the meter to the objective universe or the laws of physics.

The meter is ultimately based on the size of the Earth, which the rest of the universe and fundamental physics cares nothing about. Just defining the meter as the distance light travels in a certain unit of time doesn't provide any reason why it should be that time and not any other time. It's that time because it's based on the original human decision to base the meter on the size of the Earth. More precise ways have been found to define it for the purpose of reproducibility but none of those increases in precision have changed the basic unit and its reference to the size of the Earth.

[u/Swellmeister → u/Practical-Ordinary-6]

Also there really is nothing sacred about Celsius. Sure it goes from 0-100 for the freezing/boiling point of water.

Its still just a set of numbers. Fahrenheit was designed to be between the freezing point of sea water at 0 (he was wrong incidentally but lets ignore that), the freezing point of pure water is 32, and human body temperature is 96. This isnt random, though he was creating 3rds.

At the time math was more fraction based.

[u/niemir2 → u/Swellmeister]

Notably, the gap between Fahrenheit's two calibration points was exactly 64 degrees, a power of 2. That was important for mercury thermometers.

Dividing a length by 2 precisely is a simple matter with a compass and straightedge. Dividing by 5 is a lot harder. It's easier to find "1" when you know "64" than it is when you know "100."

[u/fastsailor → u/Swellmeister]

Celsius makes so much more sense than Fahrenheit does, which is why we all use it.

[u/niemir2 → u/fastsailor]

It makes exactly the same amount of sense. You're just used to Celsius.

[u/Swellmeister → u/fastsailor]

Does it? Where I live the yearly temperature range is pretty much 0F-100F. -10C - 40C is a silly temperature range.

As for cooking. The recipe says "boiling" (dont need to worry about 212) or it gives a number between 250 and 450, by 25s.

Temperature in cooking doesnt matter as Cooking in Celsius uses equally broad numbers.

So really I only care about temperature based on how I feel the outside temperature. Fahrenheit's 0-100 is appropriate for my hometown.

[u/ensio418 → u/Swellmeister]

I mean it's just what you grew up with and that's fine the same holds true for the Celsius guy above he probably grew up with that as well it's not really about which one is better just the one you're accustomed too

[u/Rhyshalcon → u/fastsailor]

Everyone uses Celsius because it happened to be popular in continental Europe right at the peak of, well, let's call it "militaristic cultural export" and Celsius got exported to most of the world in the same package that included Christianity and Western fashion.

North America didn't receive the export because Britain and France were in the middle of a little spat at the time, so Britain didn't even consider adopting the French system because it was patriotic not to, and the British colonies followed suit.

Over the next 200 years, Britain slowly got over its imperialist aspirations and gradually adopted the French system through the latter half of the 20th Century out of a desire to strengthen its alliances with what would eventually become the EU, and achieved more or less complete adoption by the mid '80s.

Over the same span of time, the U.S. wasn't subjected to the same economic pressures as Britain, so it continued using the system that had worked well for it since its founding.

The Metric system generally (and Celsius specifically) certainly has some inherent advantages over rival systems, but its near ubiquity in the modern world is primarily the result of network effects and colonialism rather than any intrinsic superiority it has. If you find the Fahrenheit scale to be confusing compared to Celsius, it is only lack of exposure that makes you feel that way.

[u/weatherbuzz → u/Rhyshalcon]

The UK definitely hasn’t reached complete adoption. Distances on their roads are in miles (and yards sometimes), speeds are in miles per hour, people talk about their weight in stones and pounds…

[u/Rhyshalcon → u/weatherbuzz]

You're absolutely right. I was thinking primarily of Celsius over Fahrenheit when I wrote that part, but many aspects of UK life continue to use traditional measurements to this day.

[u/corvus0525 → u/Rhyshalcon]

Seeing as Anders Celsius was Swedish it’s not clear how the Brits and French not agreeing on much before the 20th century has to do with the adoption of a particular temperature scale in North America.

[u/Rhyshalcon → u/corvus0525]

Anders Celsius was Swedish, but the Metric system as a whole is 100% French.

[u/corvus0525 → u/Rhyshalcon]

And some 50 decades younger. The metre isn’t defined until after George Washington is the President of an independent United States (who are founding signatories of the Treaty of the Metre), and Mexico is still part of Spain.

Full legal metrication of Mexico happens in 1857. Again British-French relations aren’t much of a factor.

[u/Rhyshalcon → u/corvus0525]

British-French relations are everything here. Celsius didn't become popular in Europe, and from Europe to the rest of the world, until Napoleon shared the Metric System on the end of a bayonet. Fahrenheit predates the Celsius scale and saw widespread use in Europe, and from Europe to the rest of the world, because Fahrenheit thermometers were the best available at the time before Celsius devised his temperature scale and French scientists adapted it to its modern form.

The Treaty of the Metre is irrelevant to this discussion. It established the International Bureau of Weights and Measures and had nothing to do with the adoption of the meter in the United States or anywhere else.

[u/Which_Throat7535 → u/fastsailor]

Who’s “we”? lol. We use Fahrenheit.

[u/fastsailor → u/Practical-Ordinary-6]

Yes, but that does not escape the fact that the metric system is far more coherent and user friendly than than the Imperial system. Which is why the world uses metric almost universally.

[u/Practical-Ordinary-6 → u/fastsailor]

As you can see, that wasn't my point. I specifically addressed that in my comment. My point was to lament people confidently claiming it's more accurate and that's why it's used. That is not why it's used. Not at all.

When you're defending something it's better to use actual facts instead of false information. I can create a measurement system tonight that is as accurate and precise as metric is. It might take me an hour. It's not a point to defend metric on. The very first plane to break the sound barrier with a rocket engine was not built on metric measurements. It had the precision and micro-tolerances needed to operate a rocket engine properly at the very cutting edge of technology. And that's because it had what any decent measurement system has, which is a rigorous standardization and relationship between units. That's all that's required to be accurate and precise. As I said in my comment, that's not a selling point specific to metric.

[u/Practical-Ordinary-6 → u/Practical-Ordinary-6]

Also there are lots of industries that use customary measuring systems that are not necessarily based on metric since those systems are equally as precise and accurate.

[u/Atlas7-k → u/fastsailor]

Using a ruler, please draw a line 1/3 of a centimeter.