However, the sun is slowly changing with more and more of its mass made up of helium and less and less of hydrogen. In the solar core, 37% of the available hydrogen has already been changed into helium. For every 600 million tons of hydrogen fused to helium, 5 million tons are converted into energy and eventually released to space. At this rate, the sun will continue to burn hydrogen for the next 5 billion years.
When we look at the night sky and see the unimaginable number of stars each converting mass into energy, we realize that this is a relatively common process in the universe. Stars are the main engines for changing the mass of the universe into energy. So why doesn't this happen on Earth as well?