Welcome to ronnagrams and quettameters! The General Conference on Weights and Measures (CGPM) adopted this Friday new prefixes to express orders of magnitude, tiny or immense, which have become increasingly common in modern science.
This is the first time in more than three decades that the International System (SI), established in 1960 and more commonly known as the metric system, has adopted new prefixes.
The last addition dates back to 1991
If everyone knows the kilo, which expresses, for example, a number of meters or grams in a thousand, with three zeros behind the unit, only scientists use the zetta or yotta, which express a quantity with respectively 21 and 24 zeros behind it.
They were introduced in 1991, when the chemical community needed to express quantities of molecules of this order of magnitude.
Prefixes that are no longer sufficient
But even Yotta can’t meet the need for ever-increasing orders of magnitude due to the explosion of digital technologies, says Richard Brown, head of metrology, the science of measurement, at Britain’s National Physical Laboratory.
“We are very close to the limit for expressing data in yottabytes, which is the highest available prefix,” this scientist, who is the initiative for this change, tells AFP.
This shift isn’t just about the infinitely large: it’s also true about the infinitely small, when we study “quantum science, particle physics, where we measure very, very small things,” adds Richard Brown.
27 and 30 zeros
The new prefixes ronna (R) and quetta (Q) express quantities with 27 and 30 zeros behind the unit, respectively. Symmetrically, the ronto (r) and the quecto (q) express quantities whose unit is respectively the 27th and the 30th behind the decimal point.
With these prefixes, “the Earth weighs about six ronnagrams,” which is a six followed by 27 zeros, observes Richard Brown.
Conversely, something weighing six rontograms would equal a decimal number with the six positioned 27 to the right of the decimal point.
Imaginative denominations had appeared
These changes were adopted this Friday at the Château de Versailles by scientists meeting at the CGPM, which is held every four years.
The British scientist wanted to create new prefixes noting the appearance of extravagant denominations used for data storage, such as “brontobytes” or even “hellabytes”.
But the international system’s requirement to use single-letter prefixes had to be met. “The only letters you shouldn’t use for other units or symbols are R and Q,” he says.
At least 20 years ahead of them
Furthermore, a convention dictates that prefixes of large orders of magnitude end with the letter “a”, and those of very small quantities with an “o”.
Ronna and ronto, quetta and quecto, should meet the needs of measuring very large numbers for at least the next 20 to 25 years, says the metrology specialist.