Quetta and Ronna are listed as new prefixes for the SI measurement


It can now be said that the earth weighs about six ronagrams instead of 6,000 yottagrams. Jupiter can be described as having a mass of about 1.9 quettagrams instead of just 1.9 million yottagrams. And the weight of an electron is a rontogram, or 0.001 yoctogram.

The ability to more succinctly describe the weight of our planet and the particles of our visible world emerges from a meeting of scientists and officials on the outskirts of Paris that ended Friday. Participants at the 27th Session of the General Conference on Weights and Measures agreed to introduce ronna, quecto, ronto, and quecto as prefixes to the International System of Units, better known as the metric system.

It was the first time since 1991 that scientists approved expanding the prefixes used in the global measurement system.

Ronna refers to the use of 27 zeros after a first digit – or 1,000,000,000,000,000,000,000,000,000 – and quetta means there are 30 zeros. Ronto is the opposite of Ronna, making it 0.00000000000000000000000001 while quecto is the inverse of quetta. The newest members of this prefix club join the more well-known kilo (1,000), mega (1,000,000), milli (0.001), and micro (0.000001).

“At first glance, this might not sound like a particularly exciting change,” wrote Oliver Jones, a professor of environmental chemistry at Australia’s RMIT University, in an email. But “standardized prefixes that are the same around the world help us say what we mean and help others understand us.”

The recent additions have been “driven by the growing demands of data science and digital storage, already using prefixes at the top of the existing offering,” Britain’s National Physical Laboratory said in a statement. All of the world’s data will be about 175 zettabytes (21 zeros), or about 0.175 yottabytes, by 2025, forecasts market research firm IDC.

Scientists are changing what a kilogram is. That’s massive.

Richard Brown, head of metrology or measurement at NPL, presented the four new prefixes for approval by delegates representing the 64 countries, including the United States, that are members of the International Bureau of Weights and Measures.

The new terms are necessary as the amount of digital data increases, Brown told the Associated Press. “Over the past 30 years, the datasphere has grown exponentially, and data scientists have realized they will run out of words to describe the level of storage,” he said.

Jones, the RMIT professor, said the new units “help us manage the digital infrastructure, advance science and sustain society, and that’s why this change is important.”

Ronna, Ronto, Quecto and Quecto were chosen because the letters R and Q are not used for existing prefixes, Brown added. The symbols for ronna and quetta are R and Q, respectively, while those for ronto and quecto are r and q.

Regular use of the latest additions to the measurement system will likely be limited to scientists and data professionals. However, participants in the conference said that the prefixes needed to be introduced pre-emptively to discourage the adoption of unofficial prefixes.

Delegates also agreed not to add leap seconds to official clocks until 2035. These were used to compensate for the difference between atomic time and the slowing of the Earth’s rotation. Leap seconds can “create discontinuities that can cause serious malfunctions in critical digital infrastructure,” including those that dictate global telecommunications and power transmission systems, the conference said.

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