Today, Earth is a very accommodating and hospitable place for us to live. Temperatures are just about right. There is more than enough oxygen for us to breathe. Pure drinking water falls from the skies. Food grows on trees. For what more could we ask? These near-ideal conditions are dependent upon our nearest star, the sun. Our understanding of solar physics and astronomical observations of other stars tells us that since its formation the sun has grown 30 percent brighter. Over the course of time this increase in brightness will continue. It is projected that when it becomes only 10 percent brighter than today the increased radiant energy reaching Earth will have vaporized the oceans, creating H2O greenhouse conditions that will raise temperatures by several hundred degrees, killing off all plant and animal life. Because the sun burns through 600 million tons of hydrogen per second, it has already consumed almost half of its hydrogen stockpile. Further down the road, after this supply of hydrogen has become depleted, the sun will become a red giant star, rapidly burning through its limited accumulation of helium. The brightness of the sun will dramatically increase in nearly a dozen outbursts over the course of a few thousand years, peaking at 10,000 times its current brightness and ballooning out to more than 250 times its current diameter, swallowing all of the inner planets, including Earth.
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