Question: how long will the sun still burn

Keith Brain answered on 17 Jun 2010:

It seem that we have about 5 billion more years left before that happens, although well before then things would get pretty hot on the earth, as the sun is slowly expanding as it loses its mass (due to its radiation of particles and nuclear fusion reactions – mass is conserved in chemistry, but not in nuclear physics!). As it expands the earth will get uncomfortably hot, but we still have a few billion years.