Why Do We Seem to See Red Light When We Close Our Eyes Under the Sun?

When you look at the inside of your eyelid you will notice it is red. This is because the inside of your eyelid is covered with many, many blood capillaries through which blood runs. The eyelid is very thin. When you close your eyes under strong light, some of the light will go through the eyelid. As the eyelid is full of blood, it makes the light red, too.