Can We Survive the Death of the Sun?

In a few billion years the sun will turn into a red giant star

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Adapting to the whims of a star is no small task, however.

The sun may appear to be constant from day to day, but let time stretch out for millions or even billions of years, and things will change—a lot. And not always for the better.

For example, in its thermonuclear-driven core, the sun fuses about 700 million tons of hydrogen into 695 million tons of helium every second. The missing five million tons are converted into energy (via everyone's favorite equation, E = mc²). This energy is enough, it turns out, to power a star. If you like mind-boggling numbers, the sun produces 4 × 1026 watts of power— 400 trillion trillion watts. In other words, the energy our star emits in a single second is sufficient to satisfy humanity’s total consumption for about 650,000 years.

It’s also enough to warm our planet to its current comfy clime. In fact, by using some basic physics principles, it’s possible to mathematically calculate how warm Earth should be given the sun's energy-emission rate. That solar energy flows into space in all directions around the sun, and a tiny fraction (about half of one billionth) of it is intercepted by Earth, heating our planet. Just how much heating takes place is a bit complicated and depends on the actual radiant flux from the sun, Earth's distance from it and reflectivity, and more. When we run the numbers, Earth's average calculated temperature today is approximately -15 degrees Celsius, colder than the freezing point of water.

Actual measurements of Earth's temperature, however, give an average that's much warmer: about 15 degrees C. The difference exists because greenhouse gases in the air essentially trap heat from the sun, warming Earth above the calculated temperature.