After the centimeter and the millimeter, here are the quectometers and ronnamètres!

No more inventing fancy new units for the most extreme measurements.

As its name suggests, the International System of Units, or SI for short, is a standard of measurement used almost everywhere on the planet, with a few exceptions. On a daily basis, ordinary mortals mainly use units such as the litre, the centimeter or the kilogram. But there are plenty of others that are more useful for engineers, scientists, and other technical professions.

At the very top of this scale is the prefix yota-; it corresponds to a quadrillion in the long scale used in France, i.e. 1024 (a 1 followed by 24 zeros), or a million billion billion. For comparison, the radius of the observable universe (in comoving distance) is estimated to be around 435 yottameters.

On the other side, we find the prefix yocto (10-24), which can also be called a quadrillionth or a millionth of a billionth of a billionth. That’s an absolutely tiny distance, about a trillion times smaller than a hydrogen atom. They are generally used to describe the mass of subatomic particles; a neutron weighs for example 1,67 yoctogramme.

A very extensive scale, but still insufficient

These prefixes, adopted in 1991, seem so extreme that one might think that they will be more than enough to frame all scientific work until the end of time. Yet researchers and engineers continue to produce methods and devices that require ever-increasing numbers.

Some are therefore beginning to feel cramped with the current units. This is especially true in computer and data science; at the present time, these are the only disciplines which really urgently need additional units. Indeed, some structures that work in hosting or data processing already think in terms of yottabytes.

For some years now, many of them have therefore been calling for the introduction of a new unit level in the international system. And their wish was finally granted on the occasion of the 27th General Assembly of Weights and Measures, held last week at the Palace of Versailles; the community can now celebrate the arrival of four new prefixes.

© Benjamin Lehman – Unsplash

From the infinitely large to the infinitely small

The first two, quetta- (1030or a quintillion in long scale) and ronna- (1027, or a quintillion on a long scale), settle respectively in 1st and 2nd position on this scale of values. For the time being, they will most certainly be reserved for the computer world (and for amateurs of yo mama jokes of bad taste).

But over time, they might find a niche in other fields that work with colossal numbers. One thinks for example of astronomy. For example, the communiqué published for the occasion by the National Physics Lab (the British institution which manages these standards on the other side of the Channel) indicates that the Earth weighs about 6 ronnagramsand that Jupiter weighs about 2 quettagrams.

On the other side of the spectrum are the prefixes hot and cold (10-30 et 10-27 respectively). If we reason in terms of distance, it begins to approach the scale of the famous Planck length (1.6x 10-35), from which traditional physics simply stops working. These new units will therefore probably be used in the context of fundamental research work that focuses on the infinitely small. We could for example find them in studies on the famous Theory of Everything, which seeks to make the link between Einstein’s relativistic physics and quantum physics (see our article).

With this new update, Specialists will likely be armed for many years, if not decades…unless further dramatic progress leads to the introduction of an even more extreme new tier.

Source: Journal du Geek by

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