Age of the Solar System.

If you go to the link below, you will find the basic theory to calculate
the age of the Sun and the solar system. A resume of the theory is that
the solar system is expanding according to the overall expansion in the
universe, and the planets are pushed outwards. It also implements that
the planets are created as the sun shrink and it has to get rid of some
mass. It takes about a billon years to create a planet, and if we
calculate with 10 planets including the Moon and no more planets outside
Pluto, we get an age of 10 billion years. This is less than the current
opinion of the age of the universe today which also have increased
during the years. You should skip the equations and read the summary and
the chapter about how the sun is pulsating, when you visit the site.

http://home.no.net/knutove/gravity/indexg.html