How to Survive Doomsday

Let’s be optimistic and assume that we manage to avoid a self-inflicted nuclear holocaust, an extinction-sized asteroid, or deadly irradiation from a nearby supernova. That leaves about 6 billion years until the sun turns into a red giant, swelling to the orbit of Earth and melting our planet. Sounds like a lot of time.

But don’t get too relaxed. Doomsday is coming a lot sooner than that.

The Earth is, in some ways, in a precarious spot in the solar system. There’s a range of orbital distances inside which a planet can have both liquid surface water (which is believed to be necessary for life) and enough atmospheric CO to carry on photosynthesis. This range is called the photosynthesis habitable zone. The Earth orbits barely within the sun’s zone. Some scientists estimate that