The Making of Earth: From the first particle to a finished planet, element by element

Every atom in Earth was made somewhere else, at a particular time, by a particular process, and then sorted into its present place by a second sequence of events that took a few hundred million years. This paper tells both stories in order. The first runs over nine billion years: protons and neutrons in the first microseconds, hydrogen, helium and lithium in the first twenty minutes, the first atoms at 373,000 years, the first carbon, oxygen and iron in the first stars a hundred million years later, and then nine billion years of stellar generations in the Milky Way that built up the oxygen, magnesium, silicon and calcium of rock, the iron and nickel of the core, and the gold, platinum, uranium and thorium of the trace inventory. The second story begins 4,567.3 million years ago, when the first solids condensed from the cooling gas around the young Sun. It follows the condensation sequence that set which elements a rocky planet could hold, the growth of planetesimals heated by aluminium-26, the descent of iron into the core within about thirty million years, the Moon-forming impact, a magma ocean and steam atmosphere, the first oceans and continental crust by 4.4 billion years ago, the late addition of gold, platinum, water, carbon and nitrogen, the start of the geodynamo, and the radioactive heat engine that still drives the planet. A timeline (Figure 1, Table 2) and an element ledger (Table 3) record what arrived when and where it now resides. The arc is the history of the universe from creation to crunch in the Euler Cosmos, measured by the phase θₜ = H₀t, which runs from 0 at creation through 0.881 now to about 3.95 at the crunch. On the arc, Earth’s material is gathered by θₜ ≈ 0.59, and the planet is finished in outline by θₜ ≈ 0.62, before the first trace of life. Every number in the paper is imported from nuclear physics, astronomy, cosmochemistry and geology. The contribution is the ordering: a single continuous record from the first particle to a planet ready for chemistry.