"The Earth weighs about 6 ronna grams"

Four new prefixes added to international units

Kilobytes, megabytes, gigabytes... How to describe larger data? Millimeters, micrometers, nanometers... How small a number can exhaust the microscopic world? The International System of Units recently introduced four new prefixes for forming decimal multiples and fractional units, respectively expanding the counting units of the largest and smallest numbers to cope with the needs of scientific progress and the surge in data storage.

This rendering released by NASA on July 23, 2015 shows the Earth (left) and the exoplanet Kepler-452b. Xinhua News Agency

According to a report by National Public Radio on the 19th, the four new prefixes are ronna, quetta, ronto and quecto. Among them, ronna means there are 27 zeros after the number, and quetta means there are 30 zeros after the number. Ronto and quecto are used to represent extremely small numbers, indicating 27 and 30 zeros after the decimal point respectively.

The 27th General Conference on Weights and Measures held in Paris, France, adopted the suggestion of Richard Brown, head of metrology at the National Physical Laboratory of the United Kingdom, on the 18th to introduce the above four prefixes into the International System of Units, which will take effect immediately. This is the first time that the International System of Units has added new content since 1991.

Brown told the Associated Press that people are already familiar with the prefix "millimeter" and "milligram", and the four new unit prefixes can represent the maximum and minimum data that have been measured so far.

Previously, the prefix of the largest unit in the International System of Units was "yotta", which means 24 zeros after the number. Previously, the mass of the Earth could be described as about 6000 yottagrams, and after the introduction of ronna, it could be described as about 6 ronnagrams; the mass of the Sun could be described as about 2 billion yottagrams, and now it can be described as about 2000 quettagrams.

This is a photo of the "Sunway TaihuLight" supercomputer installed at the National Supercomputing Center in Wuxi, taken on October 16, 2018. Photo by Xinhua News Agency reporter Li Bo

The National Physical Laboratory of the United Kingdom issued a statement saying that the development of data science and digital storage has reached the largest unit of measurement in the International System of Units, so it is necessary to introduce new unit prefixes. Brown said that the newly introduced unit prefixes will meet the counting needs that will arise in the future. The International Data Corporation, a US market research organization, predicts that by 2025, the world will generate 175 zettabytes of data. Zetta was the second largest unit prefix before, indicating that there are 21 zeros after the number.

The newly added unit prefixes ronto and quecto, which represent extremely small numbers, can meet the research needs of quantum science and particle physics. Previously, "yocto" was the smallest unit prefix, and the mass of an electron could be described as about 0.001 yoctogram, but now it can be described as 1 rontogram.

Brown said that ronna and quetta are abbreviated as R and Q respectively, while ronto and quecto are abbreviated as r and q respectively.

He said that ronna, quetta, ronto and quecto were chosen as new unit prefixes because only the letters r and q had not yet been used as unit prefixes. At the same time, these four words sound like Greek pronunciation and meet the convention that large unit prefixes end with a and small unit prefixes end with o.

Source: Xinhua News Agency

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