For billions of years, Earth lacked the oxygen-rich atmosphere that sustains life today. A new study reveals a surprising truth about the Great Oxidation Event (GOE), the pivotal period when oxygen began to accumulate in our planet’s atmosphere. It wasn’t a single, swift event, but a prolonged process marked by fits and starts. Rather than a single on-switch, the GOE lasted at least a staggering 200 million years. During this time, oxygen levels shot up only to be pulled back down by geochemical processes that absorbed the free oxygen from the atmosphere. This was an incredibly long chemical t…