ld think we were blind if we had
not just seen the stars and sun.

Groping our way along to an electric lamp, we turn it on. It shines
brightly, but it does not make anything around it light; everything
stays absolutely invisible. It is as if all things in the world except
the lights had put on some sort of magic invisible caps.

We can strike a match and see its flame. We can see a fire on the
hearth. We may feel around for the invisible poker, and when we find
it, we may put it in the fire. When it becomes hot enough, it will
glow red and become visible. We can make a match head glow by rubbing
it on a wet finger. We can even see a firefly, if one comes around.
But only those things which are glowing of themselves, like flames,
and red-hot pokers, and fireflies, will be visible.

The reason why practically everything would be invisible if there were
no reflection of light is this: When you look at anything, as a man,
for instance, what you really see is the light that hits him and
bounces back (reflects) into your eyes. Suppose you go into a dark
room and turn on an electric light. Instantly ripples of light flash
out from the lamp in every direction. As soon as they strike the
object you are looking at, they reflect (bounce back) from it to your
eyes. When light strikes your eyes, you see.

Of course, when you look at an electric lamp, or a star, or the sun,
or anything that is incandescent (so hot that it shines by its own
light), you can see it, whether reflection exists or not. But most
things you look at do not shine by their own light. This book that
you are reading simply reflects the light in the room to your eyes;
it would not give any light in a dark room. The paper reflects a
good deal of light that strikes it, so it looks very light; the print
reflects practically none of the light that strikes it, so it looks
dark, or black, just as a keyhole looks black because it does not
reflect any light to your eyes. But without reflection, the book would
be entirely invisible. The only kind of print you could read if
there were no reflection would be the electric signs made out of
incandescent lamps arranged to form letters.

WHAT THE RING AROUND THE MOON IS; WHAT SUNBEAMS ARE. The reason you
sometimes see a ring around the moon is that some of the moonlight
reflects from tiny droplets of water in the air, making them visible.
In the same way, the dust in the air of a room becomes visible when
the sun shines t