1963 (or 1021): nuclear tests left a date stamp in your cells

Part IOne dial in the sky

Chapter 1Nineteen sixty-three

How can a cell in your brain, or a plank in a Viking camp, know what year it was made? Neither carries a label. Both carry carbon, and a tiny part of that carbon is carbon-14, whose share in the air has changed from year to year in ways we can read.

The biggest change was made by people. In August nineteen sixty-three, the carbon-14 in the air north of about 40° latitude peaked: its ratio to ordinary carbon, as a laboratory measures it, was 1.948 times that of the old standard (+944.6‰ in the units of Chapter 2).¹ The air of 1950–52, before the hydrogen-bomb tests, had stood at 0.974 on the same scale. So the peak was exactly twice the pre-bomb air: 1.948 / 0.974 = 2.00 (this page's arithmetic). Every cell born since the mid-1950s has built its DNA from carbon that came, through plants and food, from air somewhere on that curve. Read the carbon-14 in a tissue's DNA, find it on the curve, and you learn when that tissue's cells were made.

The other date was written by the Sun. In 993 a storm of energetic particles from the Sun added a sudden step of carbon-14 to the air, and every tree alive took it into that year's ring. In 2021, a team led from Groningen found the step in three pieces of wood cut with metal tools at L'Anse aux Meadows, the Norse site in Newfoundland. In all three, the step sat 28 rings inside the bark: the trees were felled in ten twenty-one.²

The two kicks differ enormously in size. In yearly means, the bomb tests raised northern air about 870‰ above its pre-bomb level; the storm of 775, the larger of the two medieval storms, raised it by about 12‰.^1,3 The human kick was some seventy times the solar one (this page's arithmetic). Yet one simple model of the carbon cycle, a set of linked reservoirs that swap carbon, explains the shape of both fingerprints, and this page uses it for both.

And the dial is moving again, the other way. Carbon from coal, oil and gas holds no carbon-14, and it is diluting the air faster than the bomb excess is draining away. In 2024 the air over the Swiss Alps measured −12.7‰, below the old standard and at about the level of the air of 1921.^4,5

The page follows the dial in order. Part II is the Sun's storms in the trees, and the Viking date. Part III is the bomb pulse and what it revealed about the ages of your cells. Part IV is the present: why the air has slipped below the standard, why the cell clock is slowing, and how, under high emissions, a shirt grown in 2050 could carry the carbon-14 of wood from about 1050.

Chapter 2A dial set by the sky

Cosmic rays, mostly protons from beyond the Solar System, strike nuclei in the upper air and set off showers of secondary particles, among them neutrons. Slowed by collisions, a neutron is captured by nitrogen-14, the commonest nucleus in air, which gives up a proton:

¹⁴N + n → ¹⁴C + pThe same reaction made the bomb carbon-14 of Part III: nuclear explosions in the air released huge numbers of neutrons, and nitrogen captured them.

A 2012 calculation puts the global production at 1.64 atoms per square centimetre of the Earth's surface per second in the modern era and 1.88 averaged over the Holocene before industrial times; the difference comes from the Sun's activity and the Earth's magnetic field, not from industry.⁶ Over the Earth's 5.1 × 10¹⁸ cm², that is about 6 to 7 kg of carbon-14 a year (this page's arithmetic). Production is higher near the poles, where the Earth's magnetic field shields less, and when the Sun is quiet, because the solar wind's magnetic field then keeps out fewer cosmic rays. The same rain of cosmic rays has a rare, extreme tail; Nº 7 uses its fastest protons to test the speed of gravity.

A new carbon-14 atom is soon oxidised to carbon dioxide and mixes into the air. Plants take it in by photosynthesis; animals eat the plants. So every living thing holds carbon-14 at about the level of the air it has been feeding from, roughly one carbon atom in a trillion. The carbon cycle can be pictured as a few reservoirs that swap carbon: the stratosphere and the lower air, plants and soils, the surface ocean and the deep ocean. A sudden injection of carbon-14 into the air spreads through them over years and decades. Chapter 3 turns this picture into a model.

Carbon-14 decays back to nitrogen-14 by beta decay, with a half-life of 5,700 ± 30 years.⁷ That is unusually long for so light a nucleus. The decay is strongly hindered by the structure of the two nuclei; with a normal strength, as Walter Kutschera puts it, the half-life would be only a few days, useless for dating. At 5,700 years, a sample loses about 0.12‰ of its carbon-14 a year, and 1% in 80 years (this page's arithmetic). Willard Libby won the 1960 Nobel Prize in Chemistry for using that slow decay to date ancient material.⁸ A nucleus can keep time in a faster way too: Nº 9 follows the thorium-229 nucleus that a laser can now make tick.

Today carbon-14 is mostly measured by accelerator mass spectrometry (AMS), which counts carbon-14 atoms directly against the stable isotopes carbon-12 and carbon-13. The best laboratories reach ±1.5 to 2.5‰ per sample, which is about 12 to 20 radiocarbon years.² Two quantities appear on this page:

F¹⁴C = (¹⁴C/C)_sample / (¹⁴C/C)_standard
Δ¹⁴C = [ F¹⁴C · e^{(1950 − y)/8,267} − 1 ] × 1000 ‰Both ratios are corrected for isotope fractionation using carbon-13. y is the year the sample grew. 8,267 years is the mean life for a half-life of 5,730 years, the value this convention uses. F¹⁴C is what the laboratory measures; Δ¹⁴C states the sample's carbon-14 at the time it grew, so that air, rings and cells of different years can be compared directly.^9,10

Radiocarbon ages use yet another half-life. By a convention fixed in 1977, a conventional age is t = −8,033 ln F¹⁴C years before 1950, with Libby's original half-life of 5,568 years (mean life 8,033 years), so conventional ages understate the true decay time by about 2.3%.⁹ They are turned into calendar years with a calibration curve built from tree rings and other records, currently IntCal20.¹¹ On this scale 1‰ is about 8 radiocarbon years.

One point about the zero matters throughout this page. Δ¹⁴C = 0 is the level of wood grown before industry, not the air of 1950. In 1955 Hans Suess showed that tree rings of the industrial era carry less carbon-14, because the carbon from burning coal is so old that its carbon-14 has decayed away.¹² This dilution is called the Suess effect. By 1950–52, northern air had already fallen to −26‰.¹ Keep that number: Part IV depends on it.

Finally, why the cells of Part III are not "carbon-dated". Over a human life, decay removes about 1% of the carbon-14, far too little to time anything. Dating a cell uses the opposite idea: not how much carbon-14 has decayed since the cell was made, but how much the air held when it was made, read off a curve that changed fast.

Part IIThe Sun's storms in the trees

Chapter 3The year the sky jumped

In 2012, Fusa Miyake and colleagues at Nagoya University measured carbon-14 ring by ring in Japanese cedar. Between the rings of 774 and 775 they found "a rapid increase of about 12‰", about 20 times larger than the changes caused by the ordinary solar cycle.³ No known process had made such a jump in a single year. The authors weighed a solar flare and a nearby supernova and found problems with both; the solar explanation came with later work. A second, smaller jump, between the rings of 993 and 994, followed in 2013, matched by peaks of beryllium-10 in an Antarctic ice core, and there the authors called solar activity "a plausible cause".¹³

The test of a global event is that it appears everywhere at once. In 2018, Ulf Büntgen and 66 co-authors measured 484 single rings from 44 tree-ring records on five continents. The excursions started "in the boreal summer of 774 and the boreal spring of 993" in every record, and historical reports of red auroras support a strong burst of solar protons.¹⁴ Beryllium-10 and chlorine-36, made by the same particles in the air and stored in polar ice, give an independent check on such events.^15,16

How big was the storm of 775? Models of the carbon cycle turn the ring values back into a production of extra carbon-14. A commonly used value is about 1.9 × 10⁸ atoms per square centimetre, roughly three years of normal production at once.^14,17 Over the whole Earth that is about 22 kg of carbon-14 (this page's arithmetic). The first estimates had been too large; in 2013 Ilya Usoskin and colleagues traced that to an unsuitable carbon-cycle model and showed that the 775 event matched the measured solar particle event of 23 February 1956 scaled up about 45 times: in their words, "strong, but not inexplicably strong".^17,54

Why does a burst of a year or less leave a fingerprint that lasts decades? Because the carbon-14 it makes does not stay in the air. This page's teaching model has seven reservoirs: the stratosphere and the troposphere (the lower air, which trees breathe), which swap air in about two years; a fast biosphere of leaves, roots and litter, and a slow one of wood and soils; and the surface ocean, the ocean beneath it down to about a kilometre, and the deep ocean. Each reservoir i holds carbon C_i with a carbon-14 ratio R_i relative to the standard, and the exchanges are linear:

dN_i/dt = Σ_j F_ji R_j − Σ_j F_ij R_i + P_i − λN_i, N_i = C_iR_iF_ij: the gross flow of carbon from reservoir i to j, in billions of tonnes a year; P_i: carbon-14 production entering reservoir i; λ = ln 2 / 5,700 per year. The exchange rates were fitted to the measured bomb curve, averaged over the two hemispheres (Chapter 8). Δ¹⁴C of the troposphere is (R_T − 1) × 1000.

In the model, a storm the size of 775's, injected in mid-774 with 70% of its carbon-14 into the stratosphere, raises the 774 ring by 6.5‰ (only part of that growing season came after the storm), the 775 ring by 14.2‰, and the 776 ring by 15.3‰, the peak, because the stratosphere keeps feeding the lower air for a year or two. Then the excess leaks into plants and the sea: the rings fall below half the peak after about 13 years and are still about 4‰ high after 30 (this page's model). The model's peak is a little above the 12‰ measured in the Japanese cedar, a reminder of how much the answer depends on the model. Figure 1 draws the seven reservoirs as tanks above the rings they write: send the storm in, watch it spread, then change the world it falls on (Chapter 6 explains why that matters).

Figure 1🌞 Try it

One storm, seven tanks of carbon

Press play, then flip the world

Years after the storm

Storm size, × the storm of 775

Biggest ring jump

Biggest ring

Down to half after

Carbon-14 made

This page's seven-box carbon model (stratosphere, troposphere, fast and slow biosphere, surface, upper and deep ocean; exchange rates fitted to the measured bomb curve averaged over the two hemispheres, Chapter 8), forced by a storm of 1.88 × 10⁸ carbon-14 atoms per cm² injected in mid-774 (70% into the stratosphere). Dots: tree-ring values (May to August means) above the pre-storm level; the line is the air. Tank colour shows each reservoir's excess, on a square-root scale set by the stratosphere's peak; tank sizes grow with the carbon each holds (area as the square root of the carbon) above a minimum size that keeps the labels legible, so the smaller tanks look alike. "Ice age" lowers CO₂ to 190 ppm, a full-glacial value: by 12350 BCE the air had partly recovered, so the switch shows the largest the CO₂ effect could be. "Weaker field" multiplies production by 1.3, an assumption standing in for geomagnetic shielding; with both switches on, the storm that gives the 30‰ measured for 12350 BCE (Bard et al. 2026), about 1.2 times 775's, illustrates the 18 ± 11% stronger storm found with a full chemistry-climate model (Golubenko et al. 2025) rather than testing it. Published models turn the same 775 rings into 1.1 to 2.2 × 10⁸ atoms per cm² (Cliver et al. 2022): sizes are model-dependent, timing is not.Press play to fire a storm of particles from the Sun into the air. The carbon-14 it makes (about 22 kg) flows from tank to tank: up high, into the air, then into plants and the sea. The dots are tree rings: a jump in a ring or two, then a slow fade. Now switch to the ice age, turn on the weaker magnetic field, and find how big a storm makes the 30 per mil jump seen in 12350 BCE.

Notice the asymmetry. The jump arrives within one or two rings, but the tail outlives a human generation, because the deep ocean, which holds most of the Earth's exchanging carbon, takes centuries to catch up. The same arithmetic explains a fact that troubles anyone who wants to know how strong these storms were: published models turn the same 775 rings into productions from 1.1 to 2.2 × 10⁸ atoms per square centimetre.¹⁷ In this page's model, 1.1 and 2.2 × 10⁸ give peaks of 8.9 and 17.9‰. When the storm happened is fixed by the rings to the year. How big it was depends on the model.

Chapter 4Twenty-eight rings to 1021

A step that appears in the same calendar year in every tree on Earth is a time stamp. Tree-ring scientists can already count rings exactly, but a piece of wood whose rings cannot be matched to a dated sequence floats in time. If it contains the 993 step, it is anchored to the year.

L'Anse aux Meadows, at the northern tip of Newfoundland, is the only confirmed Norse site in the Americas outside Greenland. Margot Kuitems, Michael Dee and colleagues chose three pieces of wood from it, each from a different tree (two firs, possibly balsam fir, and a juniper or thuja), each with its bark edge (the last ring grown before felling), and each cut with metal tools, which the Indigenous inhabitants of the area did not make at the time.² They measured carbon-14 in single rings, 127 measurements in all, with precisions better than ±2.5‰.

Number the rings inwards from the bark ring, ring 0, as −1, −2 and so on. Ring −29 grew in 992, and the jump sits in the next ring outwards, ring −28, which therefore grew in 993. From there, 28 rings lead to the bark: 993 + 28 = 1021. (Reports of "29 rings" count to ring −29, the last ring before the jump, grown in 992.) All three trees gave a best fit of 1021, with 95% ranges between 1019 and 1024. The last ring even told the season: one tree was felled in spring, one in summer or autumn.² The paper was published online on 20 October 2021 and in print in 2022. Figure 2 is a schematic timber with illustrative values: find the ring with the jump, then count to the bark.

Figure 2🪓 Try it

Count the rings to 1021

Find the jump, count to the bark

Ring, counted in from the bark

Rings in from the bark

Carbon-14 vs. the rings before

This ring grew in

A schematic timber with 41 rings and illustrative carbon-14 values: the shape of the 993 step from this page's box model (a spring storm scaled to the measured step of about 9‰), with noise like that of real measurements (±1.5‰; error bars ±2‰). The dating logic is that of Kuitems et al. (2022): in three pieces of wood from three different trees, cut with metal tools at L'Anse aux Meadows, the step sits 28 rings inside the bark edge, so all three were felled in 1021 (95% ranges 1019–1024). Ring widths are invented; the real pieces had different ring counts and were measured at Groningen and Mannheim (127 measurements).Each band is one year of growth, with the bark on the outside. Slide along the rings and watch the carbon-14 dots: one ring jumps. That's 993, the year of the solar storm. Press play to count from there to the bark: 28 rings, so the tree was cut in 1021. Try the other two trees: same answer. (The ring values are made up to look like real ones.)

The step stands out only because many rings were measured and because three different trees agree. The date says that people with metal tools were cutting wood at L'Anse aux Meadows in 1021. It does not say when Europeans first arrived. In the authors' words it is "the only secure calendar date" for Europeans across the Atlantic before Columbus, and the earliest known year by which human migration had encircled the planet.²

The method has been used on other events. At Dispilio, a Neolithic lake village in northern Greece, a 303-ring juniper chronology contains the step of 5259 BCE; its last ring grew in 5140 BCE, 119 rings after the event (this page's arithmetic on the published dates).¹⁸ Not every step is so sharp, though. A 2024 study found that the event of 664–663 BCE shows "a 12‰ rise over two years" in some trees, and its authors caution against using it for single-year dating.¹⁹ A 2026 review lists the other traps: the season in which a short-lived sample grew, the smoothing of calibration curves, and regional differences in the air.²⁰

Chapter 5Six storms in fifteen thousand years

How many such storms are known? As of 24 October 2026, this page counts six large ones, each a sharp rise in tree-ring carbon-14 replicated in more than one tree:

12350 BCE (14,300 years before 1950): a jump of about 30‰ in subfossil pines from the Drouzet River in the southern French Alps, the only region so far. Carbon-cycle runs forced by the beryllium-10 record of the GRIP ice core in Greenland are "compatible" with it, which is consistency, not a year-by-year confirmation in ice.^21,22
7176 BCE: a rise of about 2% (20‰) in tree rings, confirmed by beryllium-10 and chlorine-36 in Greenland and Antarctic ice.^23,16
5259 BCE: also about 2% in trees, and confirmed in Greenland and Antarctic ice in 2026, similar in size to 7176 BCE.^23,24
664–663 BCE: first seen in 2017 as a jump of about 10‰ in tree rings, then in ice-core beryllium-10 and chlorine-36 as an event "comparable" to 774/775. It is spread out: a 12‰ rise over two years in larch from Siberia, and in 2026 trees from Finnish Lapland showed the rise starting in the late summer of 665 BCE and nearly complete by 664 BCE, while trees at lower latitudes peak later.^25,15,19,26
774–775: about 12‰ in the Japanese cedars, seen in 44 records on five continents.^3,14
993–994: about 9‰ in the Japanese cedars; across the worldwide network about half the size of 775, and in a carbon-cycle model about 0.55 of its extra carbon-14.^13,14

Around them sit suspects. A rise of about 6‰ in 5411–5410 BCE was found in trees from California, Switzerland and Finland in 2021, smaller than the others and left out of some lists.²⁷ Smaller increases around 1052 and 1279 were reported in 2021 from a millennium-long annual record.²⁸ A 2024 remeasurement in tree-ring-dated northern European oak found "effectively no increase" in either year.⁵⁵ In a Royal Society theme issue on these events, published on 10 September 2026, new measurements of 1279–1280 found no significant single-year spike, only "a small but significant" rise around 1279–1280 whose cause, solar particles or a change in galactic cosmic rays, could not be decided.²⁹ The same issue added a "likely Miyake-type event" around 1532 BCE, about half the size of the smallest confirmed one, and possible ones around 1814 BCE (moderate confidence) and 1111 BCE (low confidence).³⁰ Smaller events are turning up too. In April 2026 a Japanese team, testing medieval records of red auroras against buried cypress from northern Japan, found no rise at the Kyoto auroras of 1204 but a possible "sub-extreme" storm between the winter of 1200 and the spring of 1201; storms of that class are about 10 to 30% of the size of the largest.³¹

So the count depends on who is counting. Cliver, Hudson and Fletcher write that in the last 15,000 years "six such events have been confirmed".³² Other groups count six to eight, and not always the same ones: lists made before 2023 could not include 12350 BCE, which was published that year.^33,34 A 2026 review calls the study of these events "an entirely new and interdisciplinary subfield".³⁵ Figure 3 shows the list two ways, as the jump in carbon-14 and as the strength of the storm: tap an event, then switch the view.

Figure 3🧊 Try it

Fifteen thousand years of solar storms

Twice the carbon, not twice the storm

Bars show

confirmedstrong, one region so farsuspect

Storm

Carbon-14 jump

Strength vs. 775

The next storm: odds for an assumed rateWhen is the next one?

Assumed rate: one storm every

Within the next

Chance of at least one

Storms expected

Even odds within

What one would do now: the ground stays safe under the atmosphere, but a burst of high-energy protons upsets and ages satellite electronics and solar panels, and raises the radiation dose of aircrews and passengers, most on high-latitude and polar routes, where the magnetic field shields least.What one would do now: nothing to you on the ground, but satellites would glitch and wear out faster, and crews on polar flights would take an extra dose of radiation.

Solar particle events in tree-ring carbon-14, as of 24 October 2026. Solid: confirmed in several regions and by beryllium-10 and chlorine-36 in ice; half-filled: strong but so far from one region (12350 BCE); hollow: suspects (5410 BCE, Miyake et al. 2021; 1052 and 1279–1280, Brehm et al. 2021, not replicated by Scifo et al. 2024, with 1279–1280 rechecked by Miyake et al. 2026; about 1532 BCE, Frank et al. 2026). "Carbon-14 jump": the published rise in tree-ring Δ¹⁴C (approximate; 664–663 BCE rose over two years). "Storm strength": the particle fluence relative to 775 from one three-dimensional model fitted to seven events, each corrected for the CO₂ and geomagnetic field of its time (Golubenko et al. 2026; 12350 BCE from Golubenko et al. 2025; ratios and errors are this page's arithmetic); 1532 BCE, 1052 and 1279–1280 have no estimate. The bomb row is the northern air's rise to 1964 (Hua et al. 2022) and, as a count of atoms, about 65 times 775 (Naegler and Levin 2006; this page's arithmetic). Annual carbon-14 measurements cover only parts of these 15,000 years, so the list is incomplete; different groups count six to eight events.Each row is one solar storm found in tree rings. Full dots are confirmed, the half-filled one (12350 BCE) is strong but so far seen in one region, and empty ones are suspects that might not survive. Tap a storm to read about it. Then switch to "Storm strength": the ice-age storm that left the biggest jump was only a little stronger than the one of 775. And look at the last row: the bomb tests are off the scale.

Switch the view and the order changes. In carbon-14, 12350 BCE stands far above the rest; as a storm, it is only a little stronger than 775. The next chapter explains why. And the last row, the bomb tests, does not fit on either scale.

Chapter 6Twice the carbon, eighteen per cent more storm

The event of 12350 BCE left a jump of about 30‰ in the Alpine pines, "nearly twice" the peak of 775 as many trees record it (about 15‰; 12‰ in the Japanese cedars).^22,34,25 Read naively, it was a storm twice as strong. It was not, because the same burst of particles makes a bigger signal in a different world.

Two things were different 14,300 years ago, at the end of the last ice age, and Bard and colleagues name both: lower carbon dioxide in the air and a weaker geomagnetic field.²² With less carbon in the air, the same number of new carbon-14 atoms is a larger fraction of it, so the ratio jumps further. With a weaker magnetic field, more solar particles reach the atmosphere, so the same storm makes more carbon-14.

Kseniia Golubenko, Ilya Usoskin, Eugene Rozanov and Edouard Bard worked this out in 2025 with a three-dimensional chemistry-climate model of the atmosphere that follows carbon-14. They found the storm of 12350 BCE "stronger by 18±11%" than that of 775, probably in the first months of the year.³⁴ Twice the carbon-14, about a fifth more storm; and the error bar is large. In 2026 the same group fitted one model to seven events, each corrected for the carbon dioxide and magnetic field of its time, and got the same 18%. 775 stays the strongest storm since the ice age: the two 20‰ events of 7176 and 5259 BCE come out at 0.85 and 0.93 of it, 664–663 BCE, "comparable" in ice, at 0.55, and 993–994 at 0.47 (this page's ratios of the published strengths).⁶⁰ The title of their paper calls it "the record-strong extreme solar storm", and Bard et al. call it "the most powerful ESPE evidenced so far" (an ESPE is an extreme solar particle event), much stronger than the largest particle event seen by instruments in the last 80 years.^34,22 As of 24 October 2026 it is still seen in one region only.

Figure 1 shows the effect with this page's simpler model. Its "ice age" switch lowers the carbon dioxide to 190 ppm, a full-glacial value; by 12350 BCE the air had already recovered part of the way towards pre-industrial levels, so the switch shows the largest that the carbon dioxide effect could be. Alone, it makes the same storm's peak about 1.26 times taller (1.17 to 1.36, depending on how the exchanges with plants and sea are scaled; this page's model). The "weaker field" switch is not physics but an assumption: it multiplies the production by 1.3. With both on, a storm 1.18 times the size of 775's gives about the measured 30‰ (1.26 × 1.3 × 1.18 ≈ 1.93 times the model's 15.3‰ peak for 775, or about 29.5‰; this page's model). The lesson is the one the full model gives: a jump in carbon-14 measures the storm only after the world it fell on is modelled.

Chapter 7A storm the Sun should not make

Most researchers attribute these events to the Sun. The ratios of beryllium-10 and chlorine-36 in ice point to solar protons with a hard spectrum, rich in high energies, and candidate records of red auroras from the 770s fit a solar storm.^16,15,14 But "solar" raises a problem of size.

Cliver, Hudson and Fletcher estimate that the flare behind the 774 event would have been of soft X-ray class X430. Extrapolating the size distribution of flares observed from 1975 to 2022, they get a return time of a million years or more for each of the six Miyake events, yet six appeared in 15,000 years. They conclude that the most likely explanation is "a yet unknown Dragon-King type mechanism", something that boosts the high-energy proton output of certain events by one to two orders of magnitude.³² Other stars point the other way. In Kepler observations of 56,450 Sun-like stars, a 2024 study found 2,889 superflares and estimated that flares above 10³⁴ erg, more energetic than any recorded on the Sun, occur roughly once a century on each such star.⁵⁶ Whether such flares come with particle storms big enough to leave a Miyake event is not known, so the two numbers frame the puzzle rather than solve it. The 2026 seven-event fit of Chapter 6 sees no clear sign yet of a ceiling on the storms' size, against earlier suggestions of one; its authors read that as the Sun probably not having reached its limit, while saying the data cannot yet settle it.⁶⁰

Other clues do not fit a simple picture either. The events "do not show a consistent relationship to the solar cycle", and several seem to last more than a year.³³ The 7176 BCE event happened near a solar minimum; the 5410 BCE rise came during a period of high solar activity.^16,27 For the weak rise of 1279–1280, solar particles and a change in galactic cosmic rays cannot yet be told apart.²⁹ The event of 664–663 BCE builds up over two years or more, starts earlier in high-latitude trees than in low-latitude ones, and a carbon-cycle box model fits it with either one burst of carbon-14 or two.^19,26

Would such a storm matter today? Its carbon-14 would be harmless, but its particles would be a hazard for satellites, aircraft crews and astronauts. A 2026 paper estimates the radiation doses at aviation altitudes and in space, worst cases that assume each carbon-14 spike was a single event.³⁶ How often to expect one is not settled. Six large events in about 14,400 years would be one per 2,400 years if the record were complete, and it is not: annual carbon-14 measurements cover only parts of the last 15,000 years. The same 2026 fit, which also counts 5410 BCE, gives roughly one clearly detectable storm in two thousand years (one in one to three thousand, at 68% confidence) and one as strong as 12350 BCE in about ten thousand; it too treats the record as complete.⁶⁰ For illustration, a rate of one per 2,400 years gives a 4% chance of at least one in a century, and one per 400 years gives 22% (this page's arithmetic, assuming the storms come at random). The honest answer is a range, not a number. The authors of the 1532 BCE study call for replicating tree-ring measurements "50–100x" more, which they call "a big-science approach".³⁰

Part IIIThe bombs' pulse in you

Chapter 8Two centuries of carbon-14 in a few years

Above-ground thermonuclear testing "from 1952 through 1962 nearly doubled the concentration of radiocarbon" in the air.³⁷ The explosions released vast numbers of neutrons, and nitrogen in the air captured them by the reaction of Chapter 2. The largest test series came just before the Partial Test Ban Treaty, signed in Moscow on 5 August 1963 and in force from 10 October 1963, which ended tests in the atmosphere, in space and under water for the states that joined it.³⁸ Smaller series went on in the air for years afterwards, by France until 1974 and by China until 1980, states outside the treaty.

Tobias Naegler and Ingeborg Levin balanced the global budget and found that the tests between 1945 and 1980 produced 598 to 632 × 10²⁶ atoms of carbon-14.³⁹ That is 1.4 to 1.5 tonnes, about 200 years of natural production at the pre-industrial rate, and 62 to 66 times the storm of 775 (this page's arithmetic). It did not double the world's carbon-14: the natural inventory, production times mean life, is about 50 to 60 tonnes, most of it in the deep ocean (this page's arithmetic). It doubled the share of carbon-14 in the air of the north, for a few months.

The record of that pulse is the compilation of Quan Hua and colleagues, which gives monthly values for five zones of latitude from 1950 to 2019.¹ In the northernmost zone, north of about 40°, the air peaked at +944.6 ± 3.2‰ in August 1963 (2.00 times the pre-bomb air, Chapter 1). The southern hemisphere lagged by one to two years and peaked lower, at about +660‰ in 1965. Most of the bomb carbon-14 was injected into the northern stratosphere and came down through gaps in the tropopause in spring, so the zones kept different levels into the early 1970s. Yearly means in the north peak in 1964 rather than 1963, because the air of early 1963 was still rising while that of 1964 stayed high all year. In annual means, northern air stood at +846‰ in 1964, about 870‰ above the pre-bomb air, against about 12‰ for the jump of 775: seventy times in the air, a little more than the 62 to 66 times counted in atoms (this page's arithmetic).

Then the pulse drained away. The excess above the pre-bomb air fell with an e-folding time of about 16 years from 1966 to 1980 and about 21 years from 1980 to 2000 (this page's arithmetic on the annual means). The seven-box model of Chapter 3, whose exchange rates were fitted to the average of the northern and southern curves, reproduces that average to about 10‰ rms from 1975 to 2018; it does worse in the 1960s (about 25‰ rms over 1955–2018 as a whole), because it has a single troposphere and no hemispheres (this page's model). In the model, about half of the bomb carbon-14 was in the ocean by 1995, and the decline slows because plants and soils, which took up bomb carbon in the 1960s, hand it back as they decay.

None of this is a health story. Every body has always carried natural carbon-14: a few thousand decays a second in an adult (this page's estimate, taking an adult to hold about 16 kg of carbon). The bomb pulse at most doubled the share in tissue made in the mid-1960s. What it did give biology was a time stamp.

Chapter 9Birth certificates for cells

A cell copies its DNA when it divides, and the new DNA is built from carbon in the food of the time. A cell that never divides again keeps that DNA, and its carbon-14, for life. In 2005, Kirsty Spalding, Jonas Frisén and colleagues at the Karolinska Institutet showed that the carbon-14 in genomic DNA "closely parallels atmospheric levels" and used the bomb curve to date cells retrospectively.⁴⁰ Their first headline: neurons of the visual cortex, at the back of the brain, "are as old as the individual", while the non-neuronal cells around them are exchanged.⁴⁰ That is a result about the visual cortex, not about all neurons; Chapter 10 has the rest of the brain.

The amounts are tiny. A diploid human genome has about 6 billion base pairs, with about 20 carbon atoms per pair, so about 1.2 × 10¹¹ carbon atoms. At the standard carbon-14 level of about 1.2 × 10⁻¹², that is on average 0.14 atoms of carbon-14 per cell: one cell in seven holds a single carbon-14 atom in its DNA, and at the 1963 peak about one in four (this page's arithmetic). So the method cannot date one cell. It sorts millions of nuclei of one cell type, pools their DNA, and measures the average.

The curve has two arms, and a reading can sit on either. Northern air held about +134‰ in 1958, on the way up, and again in 1992, on the way down.¹ For a person, the known birth year usually decides: cells made after birth must lie on the curve after it. Decay plays almost no role: between 1963 and 2026 it removed less than 1% of the carbon-14. It matters only when comparing values decades apart (Chapter 11).

Most tissues are mixtures of cells made at different times. If cells are replaced at random at a rate r per year, the DNA of a tissue sampled in year T by a person born in year b is

Δ_DNA(T) = e^−R(b,T) A(b) + ∫_b^T r(s) e^−R(s,T) A(s) ds, R(s,T) = ∫_s^T r(u) dur(u): the replacement rate, per year, at time u; A(s): Δ¹⁴C of the air in year s. The first term is the cells that have survived since birth; the integral is the cells born later and still present. The published studies fit richer versions (rates that change with age, cells that copy their DNA without dividing) to the measurements.^41,42

Take a person born in 1970 and sampled in 2026. In this page's model, with the published rates, visual-cortex neurons sit at +536‰, the air of 1970; heart muscle, about 40% replaced since birth, at +376‰; fat cells, renewed about 10% a year, at +19‰, the air of about 2014; and the cells lining the heart's blood vessels, renewed more than 15% a year, at +3‰. One person, four tissues, spread over the whole curve. Figure 4 puts them on the bomb curve: drag the birth year and change the tissue.

Figure 4🎂 Try it

What year are your cells?

Drag to your birth year

Year you were born

Your own rate: cells replaced each year

Scale

Squares show

Air the year you were born

This tissue's DNA in 2026

Cells made since birth

Reads like the air of

Δ¹⁴C of northern air (Graven et al. 2017 before 1941; Hua et al. 2022, zone NH1, the air north of about 40 degrees latitude, annual means; Jungfraujoch 2019 and 2024, Laemmel et al. 2026, with a straight line through them and on to 2026, an assumption) and the DNA of a tissue sampled in 2026, from a one-population renewal model with the published rates: visual-cortex neurons none (Spalding et al. 2005), heart muscle 1% per year at 25 to 0.45% at 75 (Bergmann et al. 2009; childhood rates, higher per Bergmann et al. 2015, are not included), fat cells 10% (Spalding et al. 2008), heart endothelial cells 15% (Bergmann et al. 2015, "over 15%"). Food-chain lag (about a year) and DNA repair are ignored. "Reads like" compares F¹⁴C with decay included, within ±3‰, a typical AMS precision: filled dots are years after birth, hollow dots years before birth, which are ruled out. The squares show 100 cells of the tissue coloured by the air of the year each was made. This page's arithmetic.Drag to the year you were born, then pick a tissue. The line is the carbon-14 in the air, year by year; the dots show where that tissue's DNA sits on it. Your visual-cortex neurons sit exactly on your birth year. Your fat cells sit about ten years ago, whatever your age as an adult. The squares are 100 of that tissue's cells, coloured by the year each was made. Try a birth year from 2020 on: everything starts to look the same.

Neurons ride the curve at the birth year. Fat cells read like the air of about a decade before sampling, whatever the adult's age, because a tissue renewed at 10% a year forgets its past in a few decades. And for anyone born before 1955, any bomb carbon-14 at all in a tissue's DNA proves that the tissue has made new DNA since. Usually that means new cells, but heart-muscle cells also copy their DNA without dividing, so the heart study had to measure and allow for that before it could show that the heart renews (Chapter 10).

The method reaches beyond people. Tissues of animals formed after 1955 can be dated to within 0.3 to 1.3 years of formation, a tool against the illegal ivory trade.³⁷ And the centre of a shark's eye lens is formed before birth and never renewed. In Greenland sharks, the bomb pulse showed up only in the lens centres of the smaller animals, up to 220 cm long, marking them as born after the tests began. With that time marker, the authors estimated that the largest animals were at least 272 years old.⁴³

Chapter 10A body of many ages

The popular claim that the body replaces itself every seven years is wrong in both directions. The bomb pulse showed that tissues differ by orders of magnitude.

Fat. About 10% of fat cells are renewed each year "at all adult ages and levels of body mass index". The number of fat cells is set during childhood and adolescence and stays constant in adults, even after marked weight loss, which shrinks fat cells rather than removing them: a fat cell that dies is replaced.⁴⁴ At 10% a year, the fat cells of a 40-year-old are about 10 years old on average (this page's arithmetic).

Heart muscle. In 2009, Olaf Bergmann and colleagues found that heart-muscle cells renew, slowly: about 1% a year at age 25, falling to 0.45% at 75, so that "fewer than 50%" are exchanged in a normal life.⁴¹ With those rates, about 34% are replaced between 20 and 75 (this page's arithmetic). The 2015 follow-up found that the number of heart-muscle cells is fixed around birth, that renewal is highest in early childhood and below 1% a year in adults, and that other heart cells renew much faster: the cells lining the blood vessels by more than 15% a year, the connective-tissue cells by less than 4%.⁴²

Never renewed. The proteins at the centre of the eye lens form around birth and keep their carbon for life; until then, the authors noted, such permanence was known only for tooth enamel.⁴⁵ The core of the Achilles tendon is formed while we grow and is "essentially not renewed" afterwards.⁴⁶

The brain beyond the visual cortex. The striatum, deep in the forebrain, adds new interneurons in adults.⁴⁷ The hippocampus, a centre of memory, is disputed. In 2013, carbon-14 suggested that about 700 new neurons are added to each hippocampus every day in adults.⁴⁸ In 2018 another group, examining tissue for markers of young neurons, found that their production "drops sharply in children to undetectable levels in adults".⁴⁹ The same year, a group in New York reported "thousands of immature neurons" in the hippocampi of healthy people up to 79.⁵⁷ Later work found that the stain used to spot young neurons weakens when the brain waits long before fixation or stays long in fixative, which may explain part of the clash.⁵⁹ In 2025 the Karolinska group identified dividing neural progenitor cells in adult human hippocampi.⁵⁰ The 2025 result is the latest word, not the last; the question is open as of 24 October 2026.

So a body is not seven years old, or any single age. It is a collection of ages, from cells made last month to neurons as old as you, and the bomb pulse is how we know.

Part IVThe dial swings back

Chapter 11Below zero in 2019

For decades the bomb excess drained into the ocean and plants. Since about 2000, the dominant force pulling the air's carbon-14 down has been something else: the "release of ¹⁴C-devoid CO₂ from combustion of fossil fuels", as a 2026 paper puts it.^51,4 Coal, oil and gas are millions of years old, so their carbon-14 is gone, and each tonne burned dilutes what is left.

In 2015, Heather Graven projected that the air would be "certain to cross below" the pre-industrial level of 0‰ by 2030, "but potentially as soon as 2019".⁵² The northern-hemisphere curve of Hua and colleagues crossed zero early in 2019.¹ At the high-altitude station on the Jungfraujoch, in the Swiss Alps, the annual mean fell from −2.0 ± 3.8‰ in 2019 to −12.7 ± 2.0‰ in 2024, a fitted trend of −2.1 ± 1.9‰ a year (−2.8 ± 1.9‰ in the ICOS measurements at the same station).⁴ (The paper, published on 24 August 2026, is mainly about methane; the carbon dioxide values are a side result, and its conclusions give −12.6 for 2024.) Figure 5 shows the whole record, from the pulse to three possible futures: drag through the years, and switch off the bombs or the fossil fuels in the model.

Figure 5🏭 Try it

The dial swings back

Switch off the bombs, or the smoke

Year

Northern air

Compared with the air of 1950

Radiocarbon age of a leaf grown then

Looks as old as wood from

Δ¹⁴C of northern (Hua et al. 2022, zone NH1, the air north of about 40 degrees latitude) and southern (zones SH1–2) air, annual means, 1950–2018; Jungfraujoch 2019 and 2024 (Laemmel et al. 2026); dashed from 2019: this page's straight line through the 2019 and 2024 means, extended to 2026, then the midrange projections of Graven (2015, Table S2) for 2050 and 2100 under three emission scenarios, joined with straight lines (RCP2.6 −20.2 and −16.8‰; RCP4.5 −68.9 and −79.3‰; RCP8.5 −117.9 and −254.5‰). Dashed model curves: this page's seven-box carbon model (one troposphere, no hemispheres) without the bomb tests or without fossil emissions (sizes depend on the model's ocean mixing; the model peaks lower than the northern data because it has no hemispheres). Radiocarbon ages use the conventional Libby mean life from F¹⁴C with the decay correction for the year of growth (Stuiver and Polach 1977; Reimer et al. 2004); "looks as old as" is a crude single-point match to IntCal20 (Reimer et al. 2020) within the curve's error and 20 years, not a calibration. Graven (2015): fresh material in 2050 "could have the same ¹⁴C/C ratio as samples from 1050" under high emissions.The violet line is the carbon-14 in northern air; the brown one is the south. Drag through the years: the bomb pulse, the long fall, and the drop below zero in 2019. Then switch off the bombs, or switch off the fossil fuels, and see which one is pulling the line down now. Past 2026 the line splits into three futures: pick one and see how old a leaf grown that year would look to a radiocarbon lab.

Notice where the cursor sits in 2024: below the standard, but still above the real pre-bomb air of 1950–52, at −26‰ (Chapter 2). At the present pace it should reach that level around 2030 (this page's extrapolation of the 2019–2024 trend, whose uncertainty is almost as large as the trend itself). The north and south curves, far apart in the early 1960s, had merged by the mid-1970s. And in this page's model, the air without fossil fuels would still sit well above zero today; the size of that difference depends on the model's ocean mixing, but its direction does not. The bomb carbon is not gone; the smoke has hidden it.

Where does that leave the cell clock? The air of 2024 had the same carbon-14 level as the air of about 1921 (−12.7‰ in both records).^4,5 That does not make a baby born in 2024 look like a centenarian. The 1921 carbon has since lost 1.2% to decay, about 12‰ in what a laboratory measures, and an AMS measurement resolves 2 to 3‰ (this page's arithmetic). The real problems are two. First, resolution: the curve fell 77‰ a year in 1964–66, so a measurement good to 2 to 3‰ could in principle separate dates about two weeks apart (in real tissue, food-chain lag, seasonal swings and diet limit dates to 0.3 to 1.3 years³⁷); it now falls 2 to 3‰ a year, so the same measurement pins it to one or two years (this page's arithmetic). Second, contrast: for a person born in 2020 and sampled in 2026, fat cells and neurons differ by about 3‰, about the measurement error; for a 2024 birth, by less than 1‰ (this page's model). A reading near today's values also matches a few months of 1953–54, on the rising arm (this page's arithmetic on annual means).

So the honest version of "the clock has stopped" is this: the hand has swung back to the numbers it showed before the tests, and it is slowing down. It would stop only if the air stopped changing. Graven's 2015 strong-mitigation scenario, in which fossil emissions fall after 2020 (so far they have kept rising), does exactly that: the air stays "nearly constant around −15‰" through the end of the century (her table's midrange is −20.2‰ in 2050 and −16.8‰ in 2100, the values Figure 5 shows), and new and old cells would then carry the same carbon-14.⁵² Her 2020 update levels off later and lower: under SSP1-2.6, the milder of its two mitigation scenarios, the air bottoms out at about −38‰ in the 2050s, then edges back up to about −30‰ (Chapter 12).⁵⁸

Chapter 12A shirt from 2050

If emissions keep rising, the hand keeps going. In Graven's high-emission scenario (RCP8.5, in which emissions roughly triple this century, well above current trends), the air is "less than −100‰ by 2050 and reaches −250‰ in 2100". In the middle scenarios it falls to about −80‰ (RCP4.5) or −150‰ (RCP6.0) by 2100.⁵² A 2020 update with the newer SSP scenarios tells the same story: about −290‰ by 2100 under the highest-emission scenario (SSP5-8.5), which would make fresh air look up to 2,500 years old, and a low of about −38‰ in the 2050s under SSP1-2.6, the milder of its two mitigation scenarios; under the deeper one (SSP1-1.9, net zero fossil emissions around 2050) the fall stops sooner and the air then rises again.⁵⁸

Fresh material then looks old. Under high emissions, Graven writes, by 2050 fresh organic material "could have the same ¹⁴C/C ratio as samples from 1050", and the air would approach "a 1,000-y-old radiocarbon age by 2050 and a 2,000-y-old age by 2100".⁵² A cotton shirt grown in 2050 could carry the same carbon-14 as wood from about 1050, a generation after the Viking timber of Chapter 4. The two halves of this page meet there: the Sun's storm that dated the Norse timber, and the smoke that could make a new shirt look as old as that timber.

The exact ages depend on the scenario value and on how the decay since 1950 is handled. Graven's table gives midrange values of −117.9‰ for 2050 and −254.5‰ for 2100 under RCP8.5; with the decay correction of Chapter 2, this page's arithmetic turns them into conventional ages of about 910 and 2,210 radiocarbon years, the values Figure 5 shows (about 750 for air at exactly −100‰). Without that correction the same values give about 1,010 and 2,360 years. Matching a single age to IntCal20 can give several calendar ranges; it is a look-alike, not a calibration.^52,10,11

The consequences are practical. Radiocarbon dating "may no longer provide definitive ages for samples up to 2,000 y old" if emissions keep rising, and elevated carbon-14 will not mark samples as recent "beyond ∼2030".⁵² The bomb pulse that dates ivory and cells is fading as a tool for anything made from now on. The faster we burn, the older new things look. The calibration curves are being rebuilt too: a 2026 paper sets out the challenges for the next IntCal and SHCal.⁵³

What to watch, as of 24 October 2026: a second region for the storm of 12350 BCE; ice-core and southern-hemisphere tests of the 1279–1280 rise and of the new candidates; and the 2025 and 2026 means for the air, which should keep falling by 2 to 3‰ a year.

Carbon-14 is one isotope, nearly all of it made in the sky. The Sun stamped 993 into the trees, and twenty-eight rings later a Norse axe stamped 1021. The bomb tests stamped 1963 into everything that grew, and your cells kept the record. Fossil carbon is now turning that stamp back.

Chapter 13Words and sources

Carbon-14, isotope: Isotopes of an element have the same number of protons and different numbers of neutrons. Carbon-14 has six protons and eight neutrons; it is radioactive, with a half-life of 5,700 years.
Half-life, mean life: The time for half of a sample to decay; the mean life is the half-life divided by ln 2. Radiocarbon conventions use 5,568 years (conventional ages) and 5,730 years (the decay correction in Δ¹⁴C).
Cosmic rays: Energetic particles, mostly protons, arriving from space. Their collisions in the upper air make the neutrons that turn nitrogen into carbon-14.
Δ¹⁴C (per mil): A sample's carbon-14 at the time it grew, compared with the standard of pre-industrial wood, in parts per thousand. 0 is the standard; the air of 1950–52 was −26‰.
F¹⁴C: The measured carbon-14 ratio of a sample divided by that of the standard, without the correction for decay since the sample grew.
AMS: Accelerator mass spectrometry: counting carbon-14 atoms one by one in a beam.
Suess effect: The dilution of the air's carbon-14 by carbon from fossil fuels, which holds none.
Box model: A model of the carbon cycle as a few well-mixed reservoirs that exchange carbon at fixed rates.
Miyake event: A sudden, global, single-year jump in tree-ring carbon-14, most likely from an extreme storm of solar particles.
Dendrochronology, bark edge: Dating by counting and matching tree rings. The bark edge (or waney edge) is the last ring grown before the tree was felled.
IntCal: The internationally agreed calibration curve that turns radiocarbon ages into calendar years; the current one is IntCal20.
Bomb pulse: The rise and fall of the air's carbon-14 caused by the atmospheric nuclear tests, peaking in 1963–65.
Jungfraujoch: A high-altitude research station in the Swiss Alps that samples clean background air.
RCP: Representative Concentration Pathway: a scenario of future greenhouse-gas concentrations, from strong cuts (RCP2.6) to high emissions (RCP8.5).

The list of storms, the air measurements and the papers below are as of 24 October 2026.

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E. Bard et al., "Radiocarbon dating of subfossil trees from the southern French Alps and the extreme solar particle event at ca 14 300 cal yr BP," Phil. Trans. R. Soc. A 384, 20250289 (2026), doi:10.1098/rsta.2025.0289.
N. Brehm et al., "Tree-rings reveal two strong solar proton events in 7176 and 5259 BCE," Nat. Commun. 13, 1196 (2022), doi:10.1038/s41467-022-28804-9.
C. I. Paleari et al., "Ice-core cosmogenic radionuclides support the occurrence of an extreme solar particle storm 5259 BCE (7208 years BP)," Phil. Trans. R. Soc. A 384, 20250347 (2026), doi:10.1098/rsta.2025.0347.
J. Park et al., "Relationship between solar activity and Δ¹⁴C peaks in AD 775, AD 994, and 660 BC," Radiocarbon 59, 1147 (2017), doi:10.1017/RDC.2017.59.
J. Park et al., "Early ¹⁴C increase in high-latitude trees at 665–664 BC," Radiocarbon 68, 382 (2026), doi:10.1017/RDC.2026.10195.
F. Miyake et al., "A single-year cosmic ray event at 5410 BCE registered in ¹⁴C of tree rings," Geophys. Res. Lett. 48, e2021GL093419 (2021), doi:10.1029/2021GL093419.
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F. Miyake et al., "Reassessment of a cosmic ray increase event in 1279/1280 CE using carbon-14 records of tree rings," Phil. Trans. R. Soc. A 384, 20250264 (2026), doi:10.1098/rsta.2025.0264.
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H. Miyahara et al., "Extremely active Sun from 1190 to 1220 in the Medieval Period: intercomparison of historical records and tree-ring carbon-14," Proc. Jpn. Acad. Ser. B 102, 156 (2026), doi:10.2183/pjab.102.011.
E. Cliver, H. Hudson and L. Fletcher, "Tension in the solar energetic proton paradigm for historical cosmogenic nuclide events," Phil. Trans. R. Soc. A 384, 20250291 (2026), doi:10.1098/rsta.2025.0291.
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Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Under Water (the Partial Test Ban Treaty), signed in Moscow on 5 August 1963, in force 10 October 1963; text and status at the Nuclear Threat Initiative.
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K. M. Heinemeier et al., "Lack of tissue renewal in human adult Achilles tendon is revealed by nuclear bomb ¹⁴C," FASEB J. 27, 2074 (2013), doi:10.1096/fj.12-225599.
A. Ernst et al., "Neurogenesis in the striatum of the adult human brain," Cell 156, 1072 (2014), doi:10.1016/j.cell.2014.01.044.
K. L. Spalding et al., "Dynamics of hippocampal neurogenesis in adult humans," Cell 153, 1219 (2013), doi:10.1016/j.cell.2013.05.002.
S. F. Sorrells et al., "Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults," Nature 555, 377 (2018), doi:10.1038/nature25975.
I. Dumitru et al., "Identification of proliferating neural progenitors in the adult human hippocampus," Science 389, 58 (2025), doi:10.1126/science.adu9575.
I. Levin, "Radiocarbon in modern carbon cycle research," EGU General Assembly 2021, EGU21-4268 (conference abstract), doi:10.5194/egusphere-egu21-4268.
H. D. Graven, "Impact of fossil fuel emissions on atmospheric radiocarbon and various applications of radiocarbon over this century," Proc. Natl Acad. Sci. USA 112, 9542 (2015), doi:10.1073/pnas.1504467112.
T. J. Heaton et al., "Challenges and opportunities for the construction of the next IntCal and SHCal radiocarbon calibration curves," Phil. Trans. R. Soc. A 384, 20250265 (2026), doi:10.1098/rsta.2025.0265.
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1963 (or 1021)

1963 (or 1021)

Made in the sky

The year the sky jumped

Count to 1021

Six storms, one puzzle

200 years in a few

Your cells' birthdays

How old is your heart?

Below zero

A shirt from 2050

Nineteen sixty-three (or ten twenty-one)