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Comment by Causality1 | Hacker News Reader

I've always been mildly irritated that the name of the SI mass base unit has a prefix. Second, liter, meter, Newton, kilogram. Were I emperor of the world I would slide the name scale up so the mass equal to 2.205lbs was called a gram.

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If you were emperor of the world, I would implore you to finance a multibillion dollar project to measure the gravitational constant to higher percision so that we could move to units that actually make sense.

https://en.wikipedia.org/wiki/Planck_units

Shpx, gung'f n shpxvat terng vqrn.

I have been exposed.

V fcrag na rzoneenffvatyl ybat gvzr penpxvat guvf pbqr...

Came here to mention the Planck units, aka God's units :)

Sadly they are a little outside of the human realm of experience, both in their single units (waaay to small usually) and in the units that the list contains (speed, electrical charge, etc; where we like "introductory" units such as length, time, weight)

With the exception of the Planck mass, which ends up being about that of a gnat.

The units aren't "waaay too small", it's the humans that are big.

Realistically, we might also have shorthands for a convenient order of magnitude for each of the units

http://www.ihst.ru/personal/tomilin/papers/tomil.pdf

but these types of decisions should probably be left for whenever people can economically measure the constants with enough precision to be serious about switching.

How about we keep the current name and use it as a basis for prefixing?

    gram       -> millikilogram
    milligram  -> microkilogram
    metric ton -> kilokilogram

...never mind.

It's almost a crime that a metric ton isn't called a "megagram".

Aside, are the mega and giga prefixes ever used for anything except bits and bytes?

(Edit: OK, OK. I forgot about megaohms, megahertz, megawatts. Also megapixels and Megadeth.)

Megatons of TNT equivalent for big bombs.

Are those metric tons or imperial tons? If metric, why aren't they gigakilograms (teragrams?) of TNT?

Answering my own question, "megatons of TNT" does refer to metric tons.

Here in the Netherlands GJ (gigajoule) is used for buildings that use blockheating.

It always feels a little grating when I hear someone say some number of "thousand kilometers".

Yes, describing my old car's odometer as "250 megameters" is oddly satisfying to let roll of the tongue.

I prefer to mix my references between metric & imperial: 1.55 deca-miles

Mega-, giga- and terawatts are well used and relatively common. More specialised but still common enough are megaohms and mega/giga/terahertz.

> Aside, are the mega and giga prefixes ever used for anything except bits and bytes?

Sure, few examples of the top of my head:

- Megatons, as in yield of nuclear weapons. Which is a bit odd unit, should be in J, goddammit!

- Similarly, energy consumption/production. Commonly used units MWh, GWh, TWh. Again, the proper unit would be J, not Wh. Or Mtoe, for Million tons of oil equivalent.

> Megatons, as in yield of nuclear weapons. Which is a bit odd unit, should be in J, goddammit!

That’s what is odd about it? It should be teragrams.

It's a measure of energy, hence the unit should be J (with some appropriate prefix).

Peta- would be the appropriate prefix. 4.184 PJ is 1 megaton.

Actually, it should be grams. 51.3162(...) grams, to be somewhat precise.

Yield of explosives is generally measured in kilograms of TNT, that's why.

Whoosh.

Megahertz, Megawatt, Megapixel?

Yes! Aside from the extremely common megahertz and gigahertz, commonly used units are megajoules, gigajoules, megawatts, gigawatts, terawatts, petajoules (when countries are negotiating about energy security), exajoules (when people measure world energy consumption), megohms, gigohms, megalitres (for the capacity of a dam, though teraliters would have been more appropriate), megapascals (of some kind of tensile strength typically), gigapascals (of Young's modulus typically), megaergs (back when people still used ergs), and so on.

Um yes, for ..., like EVERYTHING?

How much money do we have left in the budget -> Several k€.

Astronomical distances in kilo, mega and giga parsecs / light years.

Forces (e.g engine thrust) Kilo and Meganewtons.

output of powerplants are usually in the Megawatt to Gigawatt.

Frequencys of radio waves are Megahertz to Terahertz.

Energy of cosmic Ray's goes all the way up to zetta electronvolts.

I could name more

> and Megadeth.)

Laughed at that one.

Megadeth is named after the term “megadeath”, a unit in Cold War calculations of possible nuclear attacks to designate a million deaths. The 80’s were a grim time. (You can actually see in the film Dr. Strangelove a scene where George C. Scott’s character leans over a binder labeled “World Targets in Megadeaths”.)

An engineering mechanics textbook that I used had megagram as a unit.

Gigawatts were popularized in a certain movie :)

Physicists studying the sun and effect on its surface use megameter as a length scale quite a bit.

Such a choice might get you removed as emperor of the world -- the number related of engineering, scientific, and medical errors might be high. Generations of scientists would remember such an emperor, but not in a positive light.

I share your consternation with the kilogram's name, but it is almost as fundamental to our units as Franklin's implicit, and perhaps unfortunate, choice to call the charge of the electron negative.

Furthermore, the pound is a unit of force. One can find locations (poles and equator) on Earth's surface where the measured weights of an object can differ by at least 0.5% [1], making any definition of mass based upon weight troublesome.

[1] https://en.wikipedia.org/wiki/Gravity_of_Earth#Latitude

I'm aware of that, but had I given the value in another mass unit like AMU my meaning would have been less apparent.

The gram was the original base unit in the French revolutionary metric system. It was defined as the weight of 1 cm^3 of water at the temperature of melting ice. The definition was too imprecise and the kilogram turned out to be more practical, but renaming the unit would have been too much trouble I guess.

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