Since the stars, galaxies, and other cosmic bodies are too far from Earth to visit, scientists must find ways to answer this question, by examining what we see from Earth. We use the laws of physics, as we know them here on Earth, to interpret the electromagnetic radiation emitted by these objects.

"Seeing" can be done in many ways. Our eyes see colors and shapes. Binoculars and telescopes make the images bigger, so we can see more definition and color.

In order for us to see, light has to enter our eyes. This means that our eyes and brains interpret the light into images. Without light, we could not see anything. We know that a lamp is lit because we see the yellow light of the bulb, even though it might not be bright enough to cast a shadow. We know when it is off, because we see light reflected off it from other sources.

When we look up in the sky at a star, we are seeing the light coming directly from it into our eyes. Since stars are very far away, the light we see, actually left the star long before we were born. Even long before the dinosaurs were born! Know what? This means we are looking back in time, and we can never observe the Universe as it is today - only as it was! WOW! Maybe it isn't there anymore???

The colors that we can see are only a very small range of what actually is shining from an object!

Let's think, for a minute, about sounds. Sometimes we hear something that a person beside us doesn't hear, right?

Or, how about those dog whistles that make sounds that a dog can hear, but we can't? Guess what! The same thing happens with seeing!

Now, most people do see the same range of colors. Sure, some people are color blind, but for this lesson, let's assume we all see the same colors. Red to me is red to you, OK?

Light, as we know it, is part of something called electro-magnetic radiation (EMR). That is the really fun stuff, and I can't wait to tell you about it, but before that, I need to remind myself, How do we know what the objects in the universe are made of?