Our planet's personal space heater is incredibly efficient. Our sun is a fairly average star in the Milky Way—not the brightest, not the biggest, and only 4.5 billion years old. It’s only unique in that its light and heat sustains all the life on the only inhabited planet we know of in the universe. Luckily for us, it didn’t burn out before we showed up a … [Read more...] about Why hasn’t the sun burned out yet?