Scientists used to believe that chemical reactions fueled the sun. Why did this lead them to believe that the sun was very young? What kind of reactions do we now think are responsible for the energy released by the sun, is it nuclear fusion or nuclear fission. In two sentences, explain your reasoning.

Answer 1

Scientists used to believe that chemical reactions fueled the sun because they knew that chemical reactions release large amounts of energy, like combustion. However, chemical reactions would only provide enough energy to sustain the sun for a relatively short period of time, leading them to conclude that the sun must be young.

Now, we know that the energy released by the sun is a result of nuclear fusion, where hydrogen atoms combine to form helium. This is because nuclear fusion can generate much greater amounts of energy than chemical reactions, and it is capable of sustaining the sun's energy output over billions of years.