It is normal to watch the sun set in the west, but if you've never turned around and watched what is happening in the east at sunset, you've missed something good.
We all know that the side of the earth that is facing away from the sun is dark, but did you know that the earth blocks the sun and casts a shadow into space? We all can see that a tree or house or anything else can cast a shadow on the ground, but I doubt that most of us have contemplated the idea that if you were to be standing in space you could see that the earth is casting a shadow into the solar system.
We can see a bit of this shadow in the evening at sunset. If you look at the photo above, you will see that the sky at the horizon is dark blue. This is as much of the shadow as we can see from earth. Above it is a thin line of pinkish-red. The sun's rays, since it is just below the horizon, are still shining through our atmosphere. Sunlight is made up of a rainbow of colors, each moving in different wave lengths. Some colors of light easily bounce off dust particles in the air and are refracted in all directions. Red light, however, tends to weave its way through the atmosphere more easily, and it's light is what we see above earth's shadow. This pinkish, reddish line of light is called the Belt of Venus. Sometimes the shadow and belt are very pale; at other times, they are quite noticeable.
So now you know. At sunset, look east.