over millions of years, what is happening to: - to (the surface temperature of the sun) - lo (the luminosity of the sun)? to is slowly decreasing, lo is unchanged to is unchanged, lo is slowly decreasing to is unchanged, lo is unchanged to is slowly decreasing, lo is slowly decreasing to is slowly increasing, lo is unchanged to is unchanged, lo is slowly increasing to is slowly increasing, lo is slowly increasing to is slowly increasing, lo is slowly decreasing to is slowly decreasing, lo is slowly increasing