How much does the Earth weigh? About six ronnagrams

For the first time in more than three decades, the metric system adopts new prefixes.


The General Conference on Weights and Measures (CGPM) on Friday adopted two new prefixes, Ronna (R) and Quetta (Q), to express tiny or gigantic orders of magnitude, increasingly common in modern science .

It is the first time in more than three decades that the International System (SI), established in 1960 and more commonly called the metric system, adopts new prefixes.

Although everyone knows the kilo , which expresses, for example, a number of meters or grams in a thousand -with three zeros after the unit-, only scientists use the terms Zetta (Z) and Yotta (Y), which express, respectively, a quantity with 21 and 24 trailing zeros.

They were introduced in 1991, when the chemical community needed to express numbers of molecules of this magnitude.

But even the Yotta cannot meet the need to express larger and larger orders of magnitude due to the explosion of digital technologies, explains Richard Brown, head of Metrology – the science of measurement – at Britain’s National Physics Laboratory.

“We are very close to the limit to express data in yottabytes, which is the highest prefix available,” the scientist told AFP , at the initiative of this change.

These prefixes will not only refer to the infinitely large. They will also apply to the infinitely small, for example in “quantum science – particle physics – where you measure very, very small things,” adds Richard Brown.

The new prefixes and the letter that represents them

The new Ronna (R) and Quetta (Q) prefixes express quantities with 27 and 30 zeros after the unit, respectively.

Symmetrically, the ronto (r) and the quecto (q) express quantities whose unit is located, respectively, in the 27th and 30th position behind the comma.

With these prefixes, “the Earth weighs about 6 ronnagrams,” that is, a 6 followed by 27 zeros, observes Dr. Brown.

Conversely, something weighing 6 rontograms would be equivalent to a decimal number and the 6 would be placed in the 27th position to the right of the comma.

The British scientist wanted to create new prefixes due to the appearance of fanciful names used for data storage, such as +brontobytes+ or +hellabytes+.

But it was necessary to satisfy the requirement of the International System and use single letter prefixes.

On the other hand, 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, will be able to meet very large number measurement needs for at least the next 20 to 25 years, according to the metrology specialist.