Barriers> All sunlight starts in the same place, the sun. But it doesn’t stay there. Instead, it travels. It spreads out in all directions and keeps on going until it hits something.
Some light zooms off to other galaxies. Some light zooms part way through the Solar system, only to get stopped when it runs into the Earth or other planets. The sunlight turns back into heat. We say that the Earth has absorbed the light. And a good thing, too! The light energy it soaks up keeps the Earth warm.
The Earth is solid, and it blocks all the light that runs into it. You certainly can’t see through it. So the half of the Earth that faces away from the sun is always in shadow. The shadow has a special name: “night.”
Objects that block light are <#5640,5113><!opaque>. I’m opaque. You’re opaque. A brick, a rock, and a mirror are opaque too. They absorb light or reflect it (bounce it back). But they don’t let light pass through.
Windowpanes and eyeglasses let almost all light pass straight through. So does a glass of water. These see-through objects are all <#5641,5115><!transparent>.
Some objects let some light through. But they scramble the light. Waxed paper is one example. You can shine a flashlight through it. But hold a piece of up your eyes. What do you see? Just a blur, right? Objects that let some light through but don’t let images through well are <#5642,5114><!translucent>. Many “sheers” in a window are specially designed to be translucent - they let in light, but you can’t really see very much through them. Now try shining a flashlight through a glass of skim milk. Is it opaque, transparent, or translucent?
