seven constants given an exact number — and the seven units that follow from them
Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.
Three sizes in one archive — from a sheet on the fridge to a poster on the wall.
In every row a constant is given an exact number and the unit follows from it. The last column names the base units that appear in the constant’s own unit.
Until that day the kilogram was the mass of one platinum-iridium cylinder kept outside Paris. An object can be lost, damaged or changed — the drawback the SI Brochure names.
The number for the Planck constant was chosen so that on the day of adoption the new kilogram equalled the mass of that cylinder to a relative uncertainty of 1 × 10⁻⁸.
So nothing jumped: the definition changed and the mass stayed where it was.
Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 5 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.
convert in your head · without a calculator
the ten largest by surface area — as squares at true scale, each inside the next
the A series · from A0 to A6
how many millimetres each size really is, and how much of the frame goes under the knife