A Law Against Purple!

A few weeks ago, we learned that things around us absorb certain colors of light. So, a tomato is red because some molecules in its skin absorb every color but red. Grass looks green because it contains some molecules that absorb every color but green. But what are these mysterious molecules?

Molecules that have strong colors are called pigments or dyes. There's technically a difference between them, but that's not important right now. There are natural pigments, like the colors found in the tomatoes and grass, and synthetic (artificial) ones. Most of the coloring agents used today are synthetic, because they come in more colors, are stronger, and last longer. But these artificial dyes were first invented in the late 1800's, so for most of human history, people used natural dyes. A lot of these came from plants, such as flowers, nuts, and berries. But some dyes came from surprising places. For example, the dye called Tyrian purple comes from snails that live in the Mediterranean Sea (can you find this sea on a map?). It was very rare and expensive, and in ancient Rome, only the rulers were allowed to wear that color! Can you imagine it being against the law to wear purple?

In the next experiment, you'll learn how to color cloth using natural dyes. But unless you have some Mediterranean sea snails as pets, you probably won't be using any Tyrian purple!