# The weight of the Earth? 6 ronnagrams

Earth from space .

Welcome to ronnagrams and quettameters: the General Conference on Weights and Measures (CGPM) on Friday adopted new prefixes to express minute or immense orders of magnitude, which have become ever more common in modern science.

This is the first time in more than three decades that the International System, introduced in 1960 and more commonly known as the metric system, has adopted new prefixes.

If everyone knows the kilo, which expresses for example a number of meters or grams in thousand, with three zeros behind the unit, only the scientists use the zetta or the yotta, which express a quantity with respectively 21 and 24 zeros behind.< /p>

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

But even the yotta cannot satisfy the need to express ever-increasing orders of magnitude because of the explosion of digital technologies, says Richard Brown, head of metrology, the science of measurements, at the UK's National Physical Laboratory.

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“We are very close to the limit for expressing data in yottabytes, which is the highest prefix available.

— Richard Brown, UK National Physics Laboratory

This change is not just about the infinitely large: it also applies to the ;infinitely small, when you study quantum science, particle physics, where you measure very, very small things, adds Richard Brown.

The new prefixes ronna (R) and quetta (Q) express quantities with 27 and 30 zeros respectively behind the unit. Symmetrically, the ronto (r) and quecto (q) express quantities whose unit is respectively the 27th and the 30th behind the comma.

With these prefixes , the Earth weighs about 6 ronnagrams, or a 6 followed by 27 zeros, notes Dr. Brown.

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

These changes were adopted Friday at the Palace of Versailles (west of Paris) by scientists gathered at the CGPM, which is held every four years.

The British scientist wanted to create new prefixes by noting the appearance of fanciful denominations used for data storage, such as brontobytes or hellabytes.

But the requirement had to be met of the International System to use single-letter prefixes. The only letters not to be used for other units or symbols are R and Q, he says.

Convention also dictates that prefixes 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 satisfy the measurement needs of very large numbers for at least the next 20 to 25 years, says the metrology specialist.

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