The International Bureau of Weights and Measures (its initials are BIPM because it is in France, the Bureau International des Poids et Mesures) recently redefined the kilogram. Meera wrote about it late last year in Size (of the Kilogram) Matters. They didn't actually change the kilogram, they switched the official definition from being the mass of a particular block sitting in Paris to a definition in terms of Planck's constant. There are a number of problems with a block of platinum and iridium sitting under a bell jar on the other side of the world, the most obvious of which is how you use that block to do anything since it is far too important to let people touch it. Plus, in a problem familiar to people who work with semiconductor fabrication, you have to deal with particles. In manufacturing, they mess up the lithography and we end up with non-functional chips. In the case of the kilogram, the mass changes slightly.

Prefixes

Well, here's another change that involves the BIPM and semiconductors. There is a recent paper in Measurement (although it is already available, that edition of the journal is dated April 2019). The paper is On the nature of SI prefixes and the requirements for extending the available range. The SI prefixes are things like nano and pico on the small end, and giga and exa at the high end. I don't know how many industries use both the very small measurements, and the very large, but we certainly do, with dimensions in nm, delays in ps, but also data volumes in exabytes (EB) and frequencies in gigahertz (GHz) and up.

You've probably noticed that the SI units, like common usage in English and other languages, go up in units of three zeros. Thousands, millions, billions. You might think this is universal, but at least a couple of billion people will tell you that's not so.  If you learn how to count (beyond the small numbers) in Chinese, you discover they count in units of four zeros. So 10,000 is 1 wan. So you have to remember things like a million is 100 wan. If you need larger numbers, you get to yi (100Ms). When I had a development group in India in the 1990s, I had to discover that Indians count with FIVE zeros, lachs, which are 100,000 of something, usually rupees. But the next unit up, the crore, is just 100 lachs, so 10M. It is surprisingly difficult to think in wan (China) or lachs (India) when you are completely used to numbers being split up into groups of three. I guess Chinese and Indians have that problem the other way around.

Gate oxide thickness is often measured in Ångstrom units (Å), which is 10^-10 meters, and about twice the diameter of a hydrogen atom, or the diameter of a chlorine atom. But that's not an official SI unit (they only have multiples of three). One thing I learned working for Virtutech, where our engineering was in Sweden, was the Å is a character in the Swedish alphabet. It is not an A with an accent on it, like the way the French alphabet consists only of the unaccented characters, and the accents are added later. The alphabet runs from A to Z but then has 3 more characters, Å, Ä, and Ö.

At the other end of the scale, another unofficial unit is the Googol. Apparently the founders of Google named their company after it (because they were dealing with a lot of data), but didn't get the spelling right. A googol is 10¹⁰⁰. The term was invented by the 9-year-old niece of mathematician Edward Casner, who used it in his famous 1940 book Mathematics and the Imagination. Somewhere in one of the boxes in my garage, I have a copy. But to be honest, in the Amazon era, it is probably quicker for me just to pony up $18 and get a new one in a couple of days, rather than searching the garage. Yes, despite the 1940 publication date, the book is still in print almost 80 years later. Even available on Kindle. The book also introduced the name googolplex, which is 10^google, not to be confused with the Googleplex, which is in Mountain View.

The Proposal

Anyway, back to that paper. The author is Richard Brown, who is the chief metrologist for the National Physical Laboratory in Teddington in the UK. That's in the West of London. Trivia fact of the day, nearby Teddington Lock, which is actually a weir that can be bypassed by three locks (for different sized boats) is the tidal limit of the River Thames.

Richard is worried that if we don't come up with new units to extend the scale that we have, then informal words that are starting to come into use will become ingrained. So a proposal has been made to the aforementioned International Bureau of Weights and Measures, BIPM, in Paris. As Emilio Prieto (who works at the Spanish Metrology Center) told Science magazine:

Once people start using the wrong prefix names it is impossible to go back.

Brontobyte and geobyte are apparently already becoming popular.

So what are the newly proposed prefixes that Richard came up with? There are four of them, two big ones and two small ones. They preserve the very valuable ability to abbreviate them with a single letter (like we say GB and nm), which is a challenge. X, W, and V are apparently out, and U is out since we commonly use um (instead of the official µm) for microns. I'm not sure why S is not acceptable, maybe because 1ss looks silly for a tiny unit of time. But carrying on from zetta and yotta (abbreviated as Z and Y) we get to R and Q as the next available letters.

So the current high prefixes are mega, giga, tera, peta, exa, zetta, yotta. The proposal is to use ronna for 10²⁷ and quecca for 10³⁰. 

The current low prefixes are micro, nano, pico, femto, atto, zepto, yocto. The proposal is to use ronto for 10^-27 and quecto for 10^-30 (with r and q as their abbreviation).

If the proposal is accepted, the new units would (probably) be introduced in 2022. The previous big and small prefixes were added almost 30 years ago in 1991.

After that, there is only one available letter pair left and that is B/b. So, in the future, if a new prefix gets added, that would be the way to bet.

The names to get used to again:

• ronna and quecca for really big numbers (next after yotta)
• ronto and quecto for really small numbers (next after yocto)

XKCD

There's an XKCD for everything, but not yet for these new prefixes. But there is one for the redefinition of the kilogram.

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