Today, across the dailies
Three daily surfaces I run, each on its own audience — a word and where it came from, a U.S. patent worth looking at, a paradox worth re-reading. Three independent rotations; this page is the editorial home that pulls today's pick from each. The dailies live where their readers find them; this is where they sit together.
rehearse
To rehearse is to go over a thing again before its real performance — to run the lines, walk the blocking, practice the speech. The word is, at the root, agricultural: Old French <em>rehercier</em>, "to harrow again," from <em>herce</em>, a harrow — the spiked frame dragged across a plowed field to break the clods and even the soil. To rehearse is to drag the rake back over ground you have already worked: a second pass over the same earth. The funeral <em>hearse</em> is the harrow's sibling — it began as a harrow-shaped frame of spikes set with candles over a coffin. And the farm implement called a <em>harrow</em> in English is, despite being the same tool, a false friend: a separate Germanic word. The word for practice is a word for re-tilling — working the same field a second time until it lies right.
Process for Amplifying Nucleic Acid Sequences
PCR — the technique that made forensic DNA, prenatal genetic testing, and the COVID-19 PCR test possible. Mullis said he conceived the entire method on a Friday-night drive up California Highway 128 in 1983, while his girlfriend slept in the passenger seat. He had to pull over to write down the doubling math. PCR copies a target DNA sequence one billion-fold in a few hours; before it, sequencing required laboriously cloning DNA in bacteria. Mullis won the 1993 Nobel and spent the rest of his life championing scientifically marginal positions (HIV/AIDS denial, astrology). The technique stands regardless.
Simpson’s Paradox
A trend that appears in groups of data can disappear or reverse when the groups are combined.
The classic instance: in 1973, UC Berkeley’s graduate admissions appeared to favor men. Broken down by department, almost every department favored women. Women were applying disproportionately to departments with low admit rates. The aggregate trend was real; the per-department trend was real; both were correct, and they pointed in opposite directions. The paradox is most often presented as a statistical curiosity, but the deeper problem is that almost every “controlled for” claim in observational data depends on choosing the right grouping — and the data alone cannot tell you which grouping is right. The choice is causal, not statistical, and you cannot make it without a theory of how the world works. Simpson published the canonical 1951 paper; Pearson and Yule had stumbled into the same structure half a century earlier without naming it.