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Comment by Fiveplus | Hacker News Reader

Nice! The author touches on the area properties and here's the most practical life hack derived from the standard I personally use. It uses the relationship between size and mass.

Because A0 is defined as having an area of exactly 1 square meter, the paper density (GSM or grams per square meter) maps directly to the weight of the sheet.

>A0 = 1 meter square.

>Standard office paper = 80 gsm

>Therefore, one sheet of A0 = 80 grams.

>Since A4 is 1/16th of an A0, a single sheet of standard A4 paper weighs 5 grams.

I rarely need to use a scale for postage. If I have a standard envelope (~5g) and 3 sheets of paper (15g), I know I'm at 20g total. It turns physical shipping logistics into simple integer arithmetic. The elegance of the metric system is that it makes the properties of materials discoverable through their definitions.

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The 5 grams per sheet of common printer paper has certainly proven handy once or twice in some of my interactions in the informal economy.

Same for the US 5 cent coin. Defined mass of 5 grams.

Don't tell the current administration that there's something so un-American about the currency: they will insist on fixing it, and probably retire Jefferson as well.

Fun fact: While the US spent more than 3 cents for every penny minted and distributed, it spends about 14 cents for every nickel minted and distributed!

Which is pennies compared to the amount of economic activity that those pennies facilitated.

> activity that those pennies facilitated

Do you mean in the zinc mining and Coinstar? Pennies have been a bizarre ritual for years, wherein the government made zinc worth less than its pre-minted value, distributed them to banks nationwide, banks in turn to stores, stores using them once to give meaningless amounts of money to customers, customers in turn immediately throwing them on the ground or at best eventually dumping them into a coinstar, and coinstar returned those to banks.

Nothing of value was going on there. I'd rather pay any zinc miners and coinstar drivers who have been displaced to play video games all day while still saving all those resources, fuel, and most of all, time.

When they decided to stop minting pennies I think they should have gotten rid of nickels and (I know this will be controversial) quarters as well!

Keep dimes and ramp up production of half dollars. Then we can just drop the second decimal place and standardize pricing everything in 0.1 dollar increments.

The fact that quarters are still somewhat commonly used in machines (vending machines, parking meters, laundry) is probably the biggest practical obstacle.

This may be the most practical go-forward plan. The Euro's .20 coins are also attractive too. But you're correct that quarters, as the smallest common currency that you can plausibly buy something with just a couple of them, are just everywhere, from laundry to car washes, so the pain in retiring them would be widely felt.

What I've learned from the penny retirement is that people are deeply distrustful of simple high school level statistics! Millions of people have angrily seethed that somehow stores are or will be using the penny retirement to rob them, despite knowing that most transactions have an unknowable amount of different items, and sales tax, so attempting to manipulate prices to gain a statistical advantage out of rounding would be incredibly difficult and would yield a pitiful return. Let alone how the cash transaction share is declining every year.

We need to keep the physical dimensions and material properties of the quarter, but why not change the face value? Demote them to 20 cents, or even better, make them 50 cents because the real half dollar coin is obnoxiously huge and impractical.

What of the economic impact of doubling the value of all quarters? Eh, it'll probably be fine. We'll just write it off as an AI datacenter loan somehow

I have long believed that changing coin value upward would be the #1 way to get 100% of citizens on board with currency reform. Or at least buy them from citizens at above face value.

Unfortunately, I think that vending machines specifically would frustrate this scheme though, because you can bet that most operators of them would, rather than reprogramming the machines which would be expensive (especially given how many old machines must be out there without any manufacturer support available), just leave everything the same physically and double all their prices.

I would have gotten rid of nickels and dimes; then everything is priced in 1/4 dollars.

I mean really, everything smaller than a quarter should go.

Erasing small coins will be an interesting race between inflation and electronic payments.

I’m in New Zealand and haven’t had a wallet in a decade, never using cash.

Theoretically one should carry a drivers licence when driving but it’s never come up and I have a photo of it thats worked with police before.

I, for one, look forward to the new 5oz "Donald Trump Freedom Nickel". Probably resulting from a deal he did with the Big Trousers lobby groups to wear out coin pockets faster.

(I would have made a gag about a 7g replacement nickel, but you people have already used up the team "quarter" for different denomination. Although the idea of a new 40 cent coin called an "eight ball" amuses me...)

And $20 in dimes or quarters is 1 lb. US silver coins are 0.2268 grams per cent.

Paper's uniform mass per area makes it useful calibrating very tiny scales. 1mm² of 80 gsm paper will weigh about 80 micrograms.

"Measure the mass of an eyelash with a DIY microbalance" by Applied Science https://youtu.be/ta7nlkI5K5g

TIL GSM is just g/sq m. Like duh, feel so stupid xD

It's not you who should feel stupid.

The person deciding to use nonstandard "GSM" as a unit instead of the proper "g/m²" needs to feel stupid...

I'm not sure I agree. "GSM" is three syllables, versus four for "grammes per square metre". You can write it correctly using only characters everyone knows how to type quickly on their keyboard, versus either finding a way to get that superscript ² or else typing something like g/m^2 which is uglier and longer. And you can use it comfortably even if you are a complete mathematical ignoramus (you just need to know things like "larger numbers mean heavier paper" and "cheap printer paper is about 80gsm" and so forth) without the risk of turning g/m² into the nonsensical g/m2 or something.

(But arguably what whoever decided on "gsm" should have done was to just use "g", with the "per square metre" left implicit.)

I beg to differ. You can totally get away with g/m2 which is not hard to type and crucially has a / to hint you what it could be about

"gsm", or even more so "GSM", belongs to the reign of abbrevations and put my brain on the wrong track

Roughly no one already says GSM. When talking about paper you'll hear people say things like "That's a sheet of 120 gram"

GSM basically only ever appears in print. If someone DOES ask "what does 120 gram mean here?" the clarification is going to be "Oh that's grams per square meter" and not "Oh that's gee es em"

I should mention GSM is also probably an americanism. I'm in the EU and out of the five packs of different kinds of art paper four are labeled in g/m2, and one has no labeled weight at all. None of them are marked in GSM as that abbreviation only works in english, while g/m2 works in all languages.

In the UK, "gee es em" was the usual term I heard at the local paper merchants when I was a regular customer in the late 90s - early 2000s.

Of the four reams of paper/card I have at home, two are labelled in "gsm", one is "g.m⁻²", and one uses both "g/m²" and "gsm" in different places. Weirdly, it seems that the specialist stuff is more likely to use "gsm" than the everyday 80 g/m² A4.

I guess the fact that over here GSM was also the term for a mobile phone for the longest time has affected things some.

> The person deciding to use nonstandard "GSM" as a unit instead of the proper "g/m²" needs to feel stupid...

mph, kph, cps, etc

Yeah, the people insisting on writing those are on the wrong.

Agreed but we do have to interact with them. I once tried to sell a car with 140 Mm and got nowhere. I then changed the add to 140_000 km and got a lot more interest.

My interdental brushes claim that the wire is 0.8 megamolar wide, which is not a normal measure of width.

I wonder if the international society of dentists keeps a standard molar in a safe somewhere

> My interdental brushes claim that the wire is 0.8 megamolar wide, which is not a normal measure of width.

0.8 megamolar = 800,000 teeth? That, uh, seems pretty wide for an interdental brush.

0.8 Mmol?

0.8 MM

The symbol for molar is just the "M". "mol" denotes the Avogadro constant.

That would be 4.82x10²⁹ somethings wide.

It is probably an indication that they should fix their caps lock keys, however. Like the guys who sells bottles with volumes in ML.

I most definitely grew up with km/h, not kph. "k" is not an acceptable way to abbreviate kilometer in a world where kilograms are used.

Curious what you're doing that "kilograms per hour" might get used by normal people in everyday conversation. Fast food restaurant or a weight loss clinic?

The whole point of SI units is to not live in a world of uncertainty, ad hoc terminology, and name collisions.

"The person deciding to use nonstandard "GSM" as a unit instead of the proper "g/m²" needs to feel stupid..." ---> This is the sort of HN comment that I can't figure out if it's serious or a joke. I can read it in different voices and come to opposite conclusions haha

While we're at it, mph and the abomination that is "kph" (= km/h) even more so need to die in a fire.

You mean gm⁻² ?

Well, yes. I was just too lazy to find the superscript minus ;)

Some cursory search suggests "gsm" for grammature is confined to the US, everyone else uses g/m² or just g.

It's gsm in the UK too

Ummm, not really, No.

The shorthand "gsm" is a completely standard alternative in some industries.

I work in advanced composites. Different weights and weaves of technical fabrics such as carbon fiber, kevlar, fiberglass, etc. are always specified in "gsm". For example, some common fabrics would be a "Carbon Fiber 3K 200gsm Twill" or a "High Modulus 12K 380gsm Carbon Fiber Plain Weave". (the "3K" and "12K" refer to the number of carbon fiber strands in each yarn in the weave, and the "Twill" and "Plain Weave" refer to the pattern in which the yarns are woven into a fabric.)

I'm sure "gsm" came to be commonly used instead of the more scientific "g/m²" or "g/m^2" because no one is doing that kind of math about the materials, and it is a lot easier to type "gsm" vs either of the other two which require at least a Shift for the caret or getting out the superscript font attribute.

Interestingly, sail cloth (for sail boat sails) is measured in ounces per square yard, and is just referred to by the weight with the square yard assumed - like "8oz Nylon mainsail" or "4oz ripstop spinnaker". (Or at least it used to be, my expertise here is more than 30 years out of date now.)

Oh nice, that is a neat trick! One small nitpick (that makes no difference): The side lengths of the ISO Ax formats are rounded to the next mm, so actually the A0-format has an area of 0.999949m^2

Not to the next, to the nearest, otherwise it would have to be slightly larger than 1m^2.

that reminds me of an old joke: how doe the postal services make their profit? I don't get it. - Ah, that's easy. How much wieght may letters have? - 20g - And how much weight do the average letters have? - About 6g. - See? That's their profit

I really don't get it.

It's technically a 300% margin because they are charging you for 20g but only shipping 6g.

> I rarely need to use a scale for postage. If I have a standard envelope (~5g) and 3 sheets of paper (15g), I know I'm at 20g total. It turns physical shipping logistics into simple integer arithmetic.

...was using a scale for postage a concern? If you're shipping things on the order of three sheets of paper, you're way below any conceivable threshold. USPS charges a flat rate on letters under 370 grams!

If you're sending 1,700 pieces of looseleaf paper in a box... just weigh the box.

French "La Poste" sets the first threashold at 20 g.

You will be using Aerograms soon.

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

On a related subject I just discovered that sending a letter in Denmark now costs a minimum of $4.50.

Given that we are talking about A4 papers and grams, I'd bet this wasn't in the US.

In Europe, the typical flat rate is up to 100g for standard letters. And that's 20 sheets, which is not a particularly unusual letter to send.

But 20 sheets do not fit in a regular DL or C5 envelope so you already have an hint that you may check the limits, you usually send them in a reinforced C4 enveloppe.

>USPS charges a flat rate on letters under 370 grams!

In the UK the limit for a letter is 100 grams:

https://www.royalmail.com/sending/uk/1st-class

And as that link eventually shows there are limits on the dimensions as well. I sometimes think a simple table might be better than these interactive pages, but I suppose it has to work on a phone.

24 by 16.5 by 0.5 cm for the standard 1st class letter. So you could send an A5 booklet made of less than 20 sheets of A4 (80 g/m^2) paper as a standard letter.

If the postage is short, our lovely privatised Post Office holds the letter and makes the recipient pay the excess.

Back on thread: Repeatedly fold an A0 sheet of paper in half. How many folds can you do? A ream (500 sheets) of 80 g/m^2 paper is about 2.5cm thick. (good when teaching geometric progressions).

German postage for letters is under 20g, under 50g and under 500g so I had this issue a few times so far when sending a few letters a day over a few weeks. You can see it here for international letters for example: https://www.deutschepost.de/en/b/briefe-ins-ausland.html

Thankfully I just had a scale, but I can see this being helpful when you don't.

In Sweden, the lowest postage (one stamp, 22 SEK or around $2) is for max 50 grams.

A first class forever stamp only covers 1oz (28g).

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