Time is a slippery thing: lose hold of it once, and its string might sail out of your hands forever.
How do you ever know for certain that you are doing the right thing?
Open your eyes and see what you can with them before they close forever.
What do we call visible light? We call it color. But the electromagnetic spectrum runs to zero in one direction and infinity in the other, so really, children, mathematically, all of light is invisible.