How come people say 5,000 km and not 5 Mm?
why not just say millions of meters or Mega meters?
Familiarity I guess. Mega isn’t really a widely used prefix outside of computers. We even say tons instead of megagrams.
But only in regards of nuclear bombs. Maybe it’s because of the scientific origins of these fields. Probably the same reasons why Americans measure firearm munition in mm.
Firearm’s ammunition is a mixed bag because many military sizes are standardized with the rest of NATO. 5.56, 7.62, and 9 mm sure; but then you get a bunch measured in caliber .308, .45, .50.
To be fair, mass is weird because the base unit is kg (yes, the name includes a prefactor). I have no idea how they managed to fuck it up that badly.
Yes, I think it’s a question of use. I can’t think of many examples where you would quickly need to know the measurement to the nearest Mm. Maybe if for some reason you deal with a lot of lunar orbits? Diameters of exoplanets?
Any earth distances we need to know with greater precision, and any stellar distances are probably better measured in light years, etc.
megaton, megawatt, megapascal, megacandela (for military flares), megahertz, megajoule, megaohm, megabequerel
Main reason is nearly no one needs to measure things in megameters. Megameters would be a unit to measure the diameter of planets in, maybe the orbital altitudes of some moons. Our moon for example is ~384Mm away. Distances between planets, distances between stars, and distance between galaxies are many, many orders of magnitude farther than that.
As most of us rarely travel more than 1,000 kilometers very often, it’s the biggest unit most people are familiar with on an intuitive level.
I’m still convinced people don’t actually use the metric system’s power of ten design. Like no one uses centigrams or kiloliters either. They’ve picked out units that are pretty close to the ones in the Imperial/Customary system, kilograms are used instead of pounds, grams are used instead of ounces, kilometers are used instead of miles, meters are used instead of yards, centimeters are used instead of inches, millimeters are used instead of sixteenths of an inch and so on. Want to confuse a European? Draw up some blueprints in hectometers.
When measuring lengths and time, metric units are super useful. Micrometers, Millimeters, Centimeters, Meters and Kilometres are easily and often converted in a lot of technical jobs.
Same with nanoseconds, milliseconds and seconds when dealing with time in simulations or other computer programs (e.g. game development).
Milliliters, Centiliters and Liters are commonly used in cooking.
What’s wrong with hectometers? I don’t know how often they’re used but dealing with a factor of 10 or 100 to the next “regular” unit (meters or kilometers) is no big deal.
Your assumption that an imperial system is some kind of default tells us more about your limited worldview than about measurement units.
Yeah, the everyday usage is limited to, well, everyday sizes.
As you pointed out there is no difference in everyday usage. But for anything outside of the most trivial of comparisons, the imperial system breaks down hard.
The advantage of the metric system is the possibility to scale both bigger and smaller when you need it, and always does so with a consistent factor. Sure, not needed when you want to know how many 8 cm strips are needed to cover 50cm. But for 1m? With inches and yards you already have to handle two conversation factors. How many sixteenth of an inch do you need to cover a foot? 192. Possible to calculate, but not nice and you’ll approximate with 200 if you need to do some calculations in your head. How many feet are in a mile? 5280. And yards? 1760. Do you really know these conversation factors? Do you want to calculate "there’s a street light every 30 yards, the street is 2 miles long, that’s xx streetlights? Or “there’s a street light every 30 meters, the street is 3.2km long, that’s 3200/30 = 107 streetlights”?
Oh, and the weird units do actually get used when it is a convenient size.
Cooking uses lots of in-between units for example. Centiliters (cl) are common in cocktail recipes or for shots, in some cookbooks you will find dekagrams, etc.
Hectare is commonly used to give area measurements (it’s origin is hekto-are, and “are” in turn is hekto-square meters, though “are” is not commonly used.). Want to convert hectare to square kilometers? Simply divide the number by 100! 3000hectare of forest burned down? That’s 30km^2, so 5kmx6km. Easy to visualize.
The US customary system makes such conversations really really really hard. How many square feet, yards or miles are in an acre? I just looked at the Wikipedia page and there is no way anyone will be able to convert an area given in acre into “well, it’s approximately x by z miles”. Or “my house have xx square foot of living space, so that’s yy acres”.
Btw, no one uses kiloliters, because that’s equivalent to cubic meters. Easy conversions!
Megamind?!
In our primary schools, we learn our children mili, deci, centi, deca, hecto and kilo, and how to calculate between them.
Beyond that or below that is used either in science classes or specific usecases and not known by the whole population at large.
Since people use what they know, they’d never use mega as a common way of measuring. We mostly use km for distance, and only in specific cases we might use, say, hectometers or decameters.
5 megameter is not wrong, but I don’t call 34 cm 3,4 decimeters either(unless decimeters make sense of course :p)
It is 2.445 kilomiles from Los Angeles to New York.
