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The Earth now weighs 6 ronnagrams. What does that mean?

The International Bureau of Weights and Measures, based near Paris, helped organize the conference that led to the new prefixes being created. (Michel Euler/AP)

The Earth can now be said to weigh about six ronnagrams, 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 an electron’s weight is one rontogram, or 0.001 yoctograms.

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

It was the first time since 1991 that scientists approved the expansion of 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 inverse of ronna, making it 0.000000000000000000000000001, while quecto is the inverse of quetta. The newest members of this prefix club join the more familiar kilo (1,000), mega (1,000,000), milli (0.001) and micro (0.000001).

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

The latest additions were “driven by the growing requirements of data science and digital storage, which is already using prefixes at the top of the existing range,” Britain’s National Physical Laboratory said in a statement. All the data in the world will total about 175 zettabytes (21 zeros), or about 0.175 yottabytes, by 2025, predicts market intelligence company IDC.

Scientists are about to change what a kilogram is. That’s massive.

Richard Brown, NPL’s head of metrology, or measurement, 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 grows, Brown told the Associated Press. “In the last 30 years, the datasphere has increased exponentially, and data scientists have realized they will no longer have words to describe the levels of storage,” he said.

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

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

Regular use of the most recent additions to the measurement system is likely to be limited to scientists and data professionals. But the conference’s participants said that the prefixes needed to be introduced preemptively, to prevent the adoption of unofficial prefixes.

The delegates also agreed to stop adding leap seconds to official clocks by 2035. These had been used to make up the difference between atomic time and the Earth’s slowing rotation. Leap seconds can create “discontinuities that risk causing serious malfunctions in critical digital infrastructure,” including those that dictate global telecommunications and energy transmission systems, the conference said.

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