On May 20th, the 26th General Conference on Weights and Measures instituted a new standard for the kilogram mass. A metal block kept in a hermetically sealed vault in Paris had been the mass standard for 130 years. New standards were also introduced for the unit of current (Ampere), temperature (Kelvin), and the mole.

It used to be the case that standards for the basic units used in science had been defined in terms of macroscopic objects like this and thus could be easily understood. But the need for increasingly precise and unvarying standards meant that these were no longer suitable and standards have increasingly shifted to using the fundamental constants of nature and getting from those to the familiar quantities involves quite a long chain of reasoning. The kilogram is the last remaining physical object to be so displaced.
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That is a blatantly clickbait-and-switch post title. Anyone expecting to read about the origins of romantic outings involving two people will have to look elsewhere. What this post is about is how the idea of assigning consecutive numbers to the years originated.

We now routinely assign a numbered year to events in recorded history, so that I can write that Bishop Ussher’s year of the creation of the Earth was 4004 BCE or that the American revolution was in 1776 CE. This sequential numbering of the years enables us to immediately fix an event in relation to other events. The system seems so natural that one feels that it must have always been in place and did not have to be invented at all, let alone have a definite beginning. But classicist Paul J. Kosmin says that there was a time when this system of numbered years did not exist and that events were placed in a historical sequence using various circumlocutions that had only local validity.
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We have all seen migrating birds traveling in a V-formation. It has long been speculated that this pattern is chosen because it reduces the energy required for flight in the birds that are at the back. But so much fine-tuning of positions was required to save energy by this method that some researchers doubted that this could be the reason and suggested alternatives, such as that the better navigators were in the front for others to follow or that this formation reduced the risk from predators.

But scientists were able to attach devices to a flock of birds and noticed that the birds were not just locating themselves precisely with respect to the lead birds as predicted by the aerodynamics of fixed wing aircraft, but that they were even synchronizing the flapping of their wings to achieve maximum energy savings.
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Some time ago, I discussed how a car’s differential works to allow the outer and inner wheels to rotate at different speeds when going around curves. Along with that I discussed how trains manage to go around curves even though they do not have differentials and the two wheels rotate at the same rate. Via Mark Frauenfelder, I came across this video demonstrating it even more clearly.

There is something fascinatingly contradictory about carnivorous plants. This close up video by the BBC shows how one of them, the Venus Flytrap, works. I have to admit, I was fascinated to learn how the plant captures its prey but saddened by the sight of hapless flies succumbing to its wiles.