Six rungs. They work on a paper from a national laboratory, a passage from a two-thousand-year-old text, a
line of dialogue in a film, and a backyard experimenter with a shed full of coils. Same six, same order, every time.
The order matters: the numbers come before the argument, and the argument comes before the verdict nobody
needs to reach.
1
The story
Tell it the way the person telling it meant it. No wink, no sneer, no quotation marks doing work a
sentence should be doing. If the story has a shape, the shape is the first piece of data you have.
1768 to 1772 · Lucé, France
Farmers across Europe reported stones falling out of the sky, and had been reporting it for as long
as there were records to keep. One landed at Lucé, near Le Mans, in September 1768. A committee of
the Académie des Sciences examined it, Antoine Lavoisier among them, and reported in
1772 that it was ordinary sandstone struck by lightning. That was a careful reading by a careful
chemist, and it was wrong. The reports kept arriving anyway, because people kept picking the stones
up and putting them on the kitchen table.
2
The claim as a spec
Pull the numbers out and give them units. How heavy, how hot, how fast, how long, how far. A claim with
numbers in it can be wrong, which is the useful part, because wrong is a thing you can go and check.
1794 to 1803 · Leipzig and Normandy
Ernst Chladni, a German physicist better known for what sand does on a ringing plate,
published a short book in 1794 arguing that the iron masses people kept turning up came from beyond the
Earth. He gave the claim edges you could grab. The masses carry nickel, which the local ores do not.
They arrive with fireballs, and the fireball accounts and the finds line up in place and in time. A body
coming in fast would melt its own skin, which is why the crust is dark and glassy and the inside is not.
Every one of those is checkable by someone with a balance and a notebook. On 26 April 1803 about three
thousand stones fell at L'Aigle in Normandy, Jean-Baptiste Biot went out for the Institut de France to
collect the stones and the eyewitness accounts, and the list came back checked.
3
The physics it would need
Name the mechanism the claim depends on, then put a number on how far away it sits. A gap is not a
verdict, it is a length. A factor of two and a factor of fifty million are both gaps, and they call
for completely different next moves.
1912 to 1963 · Frankfurt, Cambridge, the sea floor
Alfred Wegener set out continental drift in a lecture in January 1912, and his evidence
was good: coastlines that fit, fossils that match across an ocean, rock sequences that carry on where
the other continent begins. The mechanism was the weak part. He had continents ploughing through the
ocean floor, shoved along by tidal drag and by a slow drift away from the poles. Harold Jeffreys ran
the sums in 1924 and found those forces far too small for the job, and on that point he was right. The
claim survived anyway, because the gap was in the engine and not in the evidence. Wegener died on the
Greenland ice in 1930 without an engine. It arrived in September 1963, when Fred Vine and Drummond
Matthews read the magnetic stripes running either side of a mid-ocean ridge and worked out that the
sea floor itself is spreading. Today the number is routine surveying: Australia travels north-east
about 7 centimetres a year, fast enough that the country's official map grid was
shifted about 1.8 metres to catch up, a change published in 2017.
4
The nearest built thing
Find what already exists that rhymes with the claim, and lead with it. Of the six rungs this is the one
that pays. A claim you cannot settle still points at a bench you can visit, and the bench is usually more
interesting than the argument. Mercury ion drives really flew. The push of empty space is really measured.
Sand really does find the still places on a ringing plate.
1787 to 1816 · brass plates, a bow, and a prize
Chladni again, the same man who argued the meteorite case. In 1787 he was scattering sand on brass
plates and drawing a violin bow down their edges. The sand slides off the parts that move and piles up
along the lines that hold still, so each note draws its own figure in the grains. He published the
drawings, took the plates on tour, and demonstrated them to Napoleon in Paris in 1809, who put up a
prize of 3,000 francs for anyone who could write the mathematics of a vibrating plate.
Sophie Germain won it in 1816, on her third attempt, having taught herself the calculus from books she
was not supposed to be reading. Two hundred years on the same demonstration runs in school labs with a
speaker and a shake of salt, and it is still the fastest way to see what a vibrating surface is
actually doing. There is a plate you can drive over on the cymatics page.
5
What would have to be true
State the conditions plainly, as things that either hold or do not. Written out this way a claim stops
being a position somebody is defending and becomes a list, and a list can be worked through one line
at a time by anyone who feels like it.
1979 to 2005 · Royal Perth Hospital
In 1979 Robin Warren, a pathologist at Royal Perth Hospital, kept finding curved
bacteria sitting on stomach linings where the textbooks said nothing could live. For the claim to work,
one thing had to be true: a bacterium would have to survive acid running near pH 2, about as sharp as
lemon juice and often sharper. It turns out one can. Helicobacter pylori makes an enzyme that splits
urea into ammonia and wraps itself in the result, buffering its own little patch of stomach. Barry
Marshall put the condition to the sharpest test on offer in 1984 by drinking a broth of the stuff, and
had gastritis within days. He and Warren shared the Nobel Prize in Physiology or Medicine in 2005, and
a stomach ulcer became a fortnight of antibiotics instead of a life sentence.
6
What you would measure
Finish on an instrument. Which one, pointed at what, returning which quantity, and what it would read if
the claim were wrong. That is the only ending that moves anything, and it is a much better place to stop
than an opinion.
2012 to 2014 · Qinghai plateau, China
Ball lightning had been reported for centuries with no measurement attached, because it turns up for a
second or two and never where anyone is waiting with gear. On a night in July 2012 a group from
Northwest Normal University in Lanzhou was out on the Qinghai plateau filming ordinary lightning with
slitless spectrographs, instruments that spread light into its colours without needing
a narrow slit aimed at the source. A strike hit the ground, a ball of light about five metres across
formed and drifted, glowing for roughly one and a half seconds, and the spectrum landed in the data by
accident. The bright lines were silicon, iron and calcium: the elements of the soil where the bolt came
down. Published in Physical Review Letters in January 2014. The instrument was already built, already
running, and pointed at something else entirely.