地球の重さは「６ロナグラム」　計量単位に接頭語４種追加

【パリＡＦＰ＝時事】仏パリ近郊のベルサイユ宮殿で開催された第２７回国際度量衡総会で１８日、メートル法を基本とする国際単位系（ＳＩ）に「ロナ」や「クエタ」などの新たな接頭語４種を追加することが決まった。（写真は地球。資料写真）
　一般になじみが深い「キロ」や「ミリ」と同じ接頭語に新たに加えられたのは、１０の２７乗を表す「ロナ」、１０の３０乗を表す「クエタ」、１０のマイナス２７乗を示す「ロント」、１０のマイナス３０乗を示す「クエクト」の四つ。
　ＳＩに新たな接頭語が追加されるのは３１年ぶり。これまで最大だったＳＩ接頭語は１０の２４乗を示す「ヨタ」で、１９９１年に制定されていた。
　新たなＳＩ接頭語制定を推進した英国立物理学研究所の度量衡学責任者リチャード・ブラウン氏によると、その「ヨタ」でさえも、世界で増大し続けるデータ量に対応する上では不足しつつあるという。
　ブラウン氏はＡＦＰに対し、「現在最高位の接頭語であるヨタバイトでデータを表すのは、ほぼ限界に達している」と説明。上位の接頭語の数に合わせて下位の接頭語も追加することは理にかなっており、最小単位は量子科学や素粒子物理学で極小の物体を測定するときに役に立つと指摘した。
　同氏によると、新たなＳＩ接頭語を用いて地球の質量を表すと約６ロナグラムで、これは６の後に０が２７個続く数となる。木星の質量は２クエタグラム（２の後に０が３０個）になるという。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2022/11/21-10:43）

Say hello to ronnagrams and quettametres: International scientists gathered in France voted on Friday for new metric prefixes to express the world's largest and smallest measurements, prompted by an ever-growing amount of data.
It marks the first time in more than three decades that new prefixes have been added to the International System of Units (SI), the agreed global standard for the metric system.
Joining the ranks of well-known prefixes like kilo and milli are ronna and quetta for the largest numbers -- and ronto and quecto for the smallest.
The change was voted on by scientists and government representatives from across the world attending the 27th General Conference on Weights and Measures, which governs the SI and meets roughly every four years at Versailles Palace, west of Paris.
The UK's National Physical Laboratory, which led the push for the new prefixes, confirmed that the resolution had passed in a statement.
The prefixes make it easier to express large amounts -- for example, always referring to a kilometre as 1,000 metres or a millimetre as one thousandth of a metre would quickly become cumbersome.
Since the SI was established in 1960, scientific need has led to a growing number of prefixes. The last time was in 1991, when chemists wanting to express vast molecular quantities spurred the addition of zetta and yotta.
A yottametre is a one followed by 24 zeroes.
But even the mighty yotta is not enough to handle the world's voracious appetite for data, according to Richard Brown, the head of metrology at the UK's National Physical Laboratory.
In terms of expressing data in yottabytes, which is the highest prefix currently, we're very close to the limit, Brown told AFP.
At the bottom end, it makes sense to have a symmetrical expansion, which is useful for quantum science, particle physics -- when you're measuring really, really small things.
- New weight of the world -
The new prefixes can simplify how we talk about some pretty big objects.
If we think about mass, instead of distance, the Earth weighs approximately six ronnagrams, which is a six followed by 27 zeroes, Brown said.
Jupiter, that's about two quettagrams, he added -- a two followed by 30 zeros.
Brown said he had the idea for the update when he saw media reports using unsanctioned prefixes for data storage such as brontobytes and hellabytes. Google in particular has been using hella for bytes since 2010.
Those were terms that were unofficially in circulation, so it was clear that the SI had to do something, he said.
However metric prefixes need to be shortened to just their first letter -- and B and H were already taken, ruling out bronto and hella.
The only letters that were not used for other units or other symbols were R and Q, Brown said.
Convention dictates that the larger prefixes end in an A, and the smaller ones in an O.
And the middle of the words are very, very loosely based on the Greek and Latin for nine and 10, Brown said.
The new prefixes should future proof the system and satisfy the world's need for higher numbers -- at least for the next 20 to 25 years, he added.