Earth's demise likely in 1 billion years, not 5 billion, as solar brightening threatens plant life

Long before the sun swells into its final red giant phase five billion years hence, Earth faces a quieter, more certain end — one already set in motion by the slow brightening of our star. Within roughly one billion years, rising solar luminosity will collapse the atmospheric conditions that plants require to survive, triggering a cascade that strips the oceans and renders the planet barren. This is not a catastrophic surprise but a trajectory written into the physics of stellar aging, a deadline that reframes humanity's place in deep time and the urgency of imagining futures beyond this world