Vishnupurana 2.8.21

2.8.21

prabhā vivasvato rātrāv astaṃ gacchati bhāskare
viśaty agnim ato rātrau vahnir dūrāt prakāśate //

The radiance of the solar orb, when the sun has set, is accumulated in fire, and hence fire is visible at a greater distance by night than by day: during the latter a fourth of the rays of fire blend with those of the sun, and from their union the sun shines with greater intensity by day. Elemental light, and heat derived from the sun or from fire, blending with each other, mutually prevail in various proportions, both by day and night. When the sun is present either in the southern or the northern hemisphere, day or night retires into the waters, according as they are invaded by darkness or light: it is from this cause that the waters look dark by day, because night is within them; and they look white by night, because at the setting of the sun the light of day takes refuge in their bosom.