Some scientists argued, based upon the sources of energy of the sun that were known at a time, that the sun was at most a few tens of million years old. Many geologists and biologists concluded that the sun must have been shining for at least several hundreds of millions of years in order to account for geological changes and the evolution of living things, both of which depend critically upon energy from the sun. But how old is the sun? As many scientists have found from using radiation over the lifetime or something like that that the sun is about 4.6 billion years old.. As I have learned that nothing is permanent, I believe that the sun will expand to a red-giant which means the sun will disappear. As you know that the sun ejects its mass which is carbon and oxygen to burn out, and gives us light. You don’t believe it burns permanently, right? Then I believe one day, the sun will be gone, and another planets would exist. We won’t be here to worry about it though. You can sleep well tonight and tomorrow. It will take few more billions year from now on.