Why does the sun stay hot?
In case you didn’t know, the Sun is in fact a huge nuclear power plant. It runs on hydrogen. The Sun transfers hydrogen atoms into helium by nuclear fusion. It’s nothing like the puny hydrogen bombs humanity finds so impressive. Each second, no less than 400 million tons of hydrogen goes boom. Unfortunately, the amount of fuel inside the Sun is limited. You can’t see it, but in fact, that huge light bulb in the sky we call `Sun’ shrinks and cools down a tiny little bit every second. The Sun is `middle aged’. In another 5,000 million years, it will run out of hydrogen. Long before, we will notice the consequences. On the one hand, the Sun will get brighter and warmer. On the other hand, as the Sun shrinks and becomes less heavy, its gravitational pull on the Earth will loosen. Consequently, the orbit of our planet and all other planets in the solar system will widen. Okay, so an earthly year will be several weeks longer. But don’t mistake, there’s a downside here. It will get colder. An
