Samoa skipped a Friday and paid workers for it

I have started narrating my errands out loud, and the dog has begun to look concerned.

Blue-light glasses rest on real biology and thin evidence

The biology behind blue-light glasses is real and the evidence for the glasses is thin, and it took me an embarrassingly long time to separate the two. Your retina contains ganglion cells that carry light information to the body clock. Their pigment, melanopsin, is most sensitive to wavelengths around 480 nanometres, which is blue. These cells exist in humans, and in mice, removing them abolishes the clock's response to light.

The glasses themselves have been tested less than you might expect. A 2023 Cochrane review assessed 17 randomised trials, each with between five and 156 participants and follow-up ranging from under a day to five weeks. It concluded that there may be no short-term advantage for visual fatigue during computer use, and that whether the lenses change sleep quality is unknown, on very low-certainty evidence. None of the trials evaluated macular health.

A pathway existing shows that the glasses could work. Whether a lens does anything you would notice is a question for trials, and so far the trials are small and short. A plausible mechanism is a reason to run the experiment, which is a smaller thing than a result. The biohacking crowd is right about the pathway and has run ahead of the trials.

A physicist described A4's proportions in a 1786 letter

On 25 October 1786, Georg Christoph Lichtenberg, a physics professor at Göttingen, wrote to Johann Beckmann about the advantages of paper whose sides stand in the ratio of 1 to the square root of two. Cut such a sheet in half across its long side and each half keeps the proportions of the whole. Lichtenberg added that paper of this shape was already commonly available in his day.

France's tax law of 3 November 1798 defined several formats that already match modern A and B sizes, and the series was quickly forgotten. More than a hundred years later Walter Porstmann reinvented it independently, and it was adopted as the German standard DIN 476 in 1922. ISO 216 made it international in 1975.

A0 has an area of one square metre, and four halvings later you are holding A4, at 210 by 297 millimetres.

Samoa skipped a Friday and paid workers for it anyway

On 29 December 2011, Samoa went to bed on Thursday and woke up on Saturday. Anyone who had been rostered to work the Friday that never happened was paid for it, by government decree.

The reason was arithmetic. Samoa's main trading partners sat on the other side of the date line, which left it 21 hours behind Australia and 23 behind New Zealand. Prime Minister Tuilaepa Sa'ilele Malielegaoi put it this way: "In doing business with New Zealand and Australia we're losing out on two working days a week." The move also put the island on the same calendar as the roughly 180,000 Samoans living in New Zealand.

The jump undid a decision from 1892, when Samoa's king was persuaded to align with American ships sailing to San Francisco, and the country had two consecutive Fourths of July that year.

QR codes locate themselves using a ratio printers rarely produce

A QR code has to be found before it can be read, and the three large squares in its corners do the finding. Their black and white bands run in a ratio of 1:1:3:1:1, and the choice came from drudgery. Masahiro Hara's two-person team at Denso surveyed the black and white areas on leaflets, magazines and cardboard boxes, and found this was the ratio that turned up least, so a scanner spotting it was unlikely to be fooled by anything else on the page.

The request came in 1992, when manufacturing sites asked Hara for a scanner that read barcodes faster. The code released in 1994 could be read more than ten times faster than other codes and held about 7,000 digits, where a barcode held around twenty characters.

Denso Wave held the patents, declared it would not exercise them, and kept the trademark.

The first smiley was a fix for jokes people took seriously

On 19 September 1982, Scott Fahlman posted a short note to the general bulletin board of Carnegie Mellon's computer science department, proposing a way to mark jokes. ":-)", he wrote. "Read it sideways." For messages that were not jokes, he suggested ":-(".

The trouble was that text carries no body language or tone of voice, and humour on the board kept being misread. Fahlman later described the note as quite short and casual, part of a discussion involving many people.

He had lost his own copy. In 2002 Jeff Baird and the Carnegie Mellon computer science facilities staff went looking, found an October 1982 backup tape and a compatible tape drive, decoded obsolete formats, and recovered the post. It took twenty years and a small excavation to prove that a sideways face existed, which is a lot of ceremony for a joke marker.

The Samoa Friday is the one I would retell at dinner.