TECHNOLOGY × ENVIRONMENT

The Nuclear Age

1945 CE

History · Contemporary · Holocene · Meghalayan

In July 1945, in the New Mexico desert, our species detonated the first nuclear weapon; within a month two cities had been destroyed by single bombs. The decades of atmospheric testing that followed dusted the entire planet with radionuclides that nature barely makes: plutonium-239 now lies as a readable layer in lake beds and ice worldwide, while radiocarbon marks the same years in corals and tree rings. The signal is so sharp and so global that geologists have proposed it as the marker for humanity's own epoch.

Why it matters

For the first time, the species acquired the physical means of its own destruction, and the geological record took the date down as it happened. The bomb pulse has an unexpected second life as a dating tool: its radiocarbon spike fixes neurons, teeth and ivory to the year. Whatever geologists finally decide about the Anthropocene, the layer is there, it says 1950s, and it says so in every archive the planet keeps.

Dating & uncertainty

The first nuclear explosion was the Trinity test of July 1945, followed within weeks by Hiroshima and Nagasaki. The stratigraphic signal, though, dates from the atmospheric test series: plutonium-239 appears in sediments worldwide from the early 1950s, peaks in the 1960s and falls away through the 1970s, after atmospheric testing was banned in 1963, with radiocarbon and iodine-129 recording the same pulse in corals, tree rings and ice. Of the three, only iodine-129 has a half-life long enough to keep the record legible in the far future.

Sources

1. Waters et al. (2015), Bulletin of the Atomic Scientists · Can nuclear weapons fallout mark the beginning of the Anthropocene Epoch?doi:10.1177/0096340215581357
2. Yokoyama et al. (2022), Scientific Reports · Plutonium isotopes in the North Western Pacific sediments coupled with radiocarbon in corals recording precise timing of the Anthropocenedoi:10.1038/s41598-022-14179-w
3. Bautista et al. (2023), Science of the Total Environment · 129I in the SE-Dome ice core, Greenland: a new candidate golden spike for the Anthropocenedoi:10.1016/j.scitotenv.2023.164021

Our species’ history as one day

23:59:3722.2 s before midnight

if the 315,000 years of Homo sapiens were compressed into a single day