# How Long Life on Earth Would Survive Without the Sun
The sun's disappearance would trigger a cascade of catastrophic changes, but Earth's survival timeline depends critically on which organisms you track and what conditions they could exploit.
In the first hours, surface temperatures would plummet. Earth would lose its primary heat source, and the planet would radiate its stored thermal energy into space. Within about a week, average surface temperatures would drop below freezing. Within a year, the planet would reach roughly minus 73 degrees Celsius. Most photosynthetic life, which depends on solar radiation for energy, would die within days.
But not all life would vanish immediately. Extremophiles, particularly those thriving in Earth's deep subsurface and around hydrothermal vents, might persist for decades or even longer. These organisms derive energy from chemical processes rather than sunlight. Chemosynthetic bacteria near ocean vents consume hydrogen sulfide and other minerals, requiring no solar input. Deep subsurface microbes, which live kilometers underground in pores within rock, could theoretically continue metabolizing without sunlight for extended periods.
The deeper layers of the ocean would remain warmer longer than the surface. Hydrothermal vent ecosystems pump heat directly from Earth's interior, meaning these zones could sustain microbial life for years or possibly centuries. The planet's geothermal energy, generated by radioactive decay and residual heat from planetary formation, would become the sole energy source. However, even this reserves have limits.
Larger organisms would perish much faster. Animals depending on plants for food would starve within weeks. Mammals and birds, which require constant metabolic activity to maintain body heat, would succumb to freezing and starvation simultaneously. Fish in shallow waters would experience shock as temperatures crashed, while deep-sea creatures adapted to stable, cold conditions might show more resilience initially, though food chains would collapse without photosynthesis at higher trophic levels.
The atmosphere itself would change. Without solar heating, atmospheric circulation would cease. Clouds would freeze and rain, potentially falling as snow indefinitely. The water cycle would largely halt. Over time, carbon dioxide would accumulate in the atmosphere as organisms stopped photosynthesizing and released trapped CO2 through respiration and decomposition.
Researchers at New Scientist have explored reader responses to this scenario, finding that while most recognize surface extinction would be swift, many point to deep biosphere survival as a genuine possibility. Some readers noted that even if chemosynthetic bacteria survived geothermal-powered ecosystems, their populations would eventually decline as chemical nutrients depleted and the heat source gradually diminished.
The geothermal argument has scientific merit. Earth's internal heat will remain active for billions of years, driven by long-lived radioactive isotopes. Small populations of extremophiles could theoretically persist in protected subsurface zones for centuries, though at dramatically reduced scales compared to current life.
Practically speaking, complex multicellular life would be extinct within months. The biosphere as humans know it would cease within days. Only in Earth's most isolated, chemically rich deep zones would any life persist, existing as sparse microbial communities in conditions utterly alien to surface experience.