There are many truths in the world. In 2002 Donald Rumsfeld said there are known knowns, known unknowns, unknown knowns, and unknown unknowns. This is an interesting way to view the world and the category of unknown unknowns is likely the largest. There are so many things out there in the world that we don’t even know that we don’t know. It makes the mind do summersaults to think that we have so much to discover that we don’t even know where to start. Today we want to discuss an unknown-unknown for many people. The color of mirrors.
This may make you stop and question for a moment. The color of mirrors? Do mirrors even have a color? Well of course they do – everything in life has a color. Many of you are now nodding your head and saying ok sure, then the color of a mirror is white or silver? Close but not quite right. The truth is that mirrors are green.
To be exact mirrors are soda-lime colored with a silver backing. This put basically is a light shade of green. When we look at mirrors we don’t see this color because they are reflecting all the light that is around them, so we only see what is around us. Yet if we could look at them in isolation – we would see this green shade.
Scientists have managed to do this too. To look at the color of mirrors they put two mirrors facing each other in an enclosed tunnel. The experiment took place in Grenada Spain in 2004 and the mirrors are still on display today. The scientists put two peepholes into the tunnel so that viewers could look inside. When they did they saw a lot of green. The mirrors were bouncing the reflection of the other mirror again and again, back and forth until the green wavelength becomes so clear that it can be seen by the naked eye.
The obvious next question is why? Why did the mirror creators make them with green glass instead of white glass? The answer is, of course, science. If people used white glass for mirrors then they would not reflect surfaces correctly. As you may know from high school science class white reflects light in all directions. This means that as light hits a white-based mirror it is then reflected in every direction. That is not very useful as a mirror. When light hits a glass that has a color, like green, it reflects it back directly at the source it came from. If you held up your phone number to a mirror you would see it in the mirror reflected backward. If you held it up to a white-based mirror, you would not see the number at all.
Mirrors are ever-present in our society today. We use them when we first wake up in the morning to fix our hair, put on our makeup, and brush our teeth (isn’t it strange how weird it is to do that without a mirror). We use them when driving to make sure that we can see all around us and we use them as decorative pieces to make rooms look larger. Consider how many mirrors you walk past every day. Have you ever asked the question of what color they are? Well, now you know. Mirrors have color. Only a little bit but they have it and it just so happens to be green. The next time you are trying to tell your friends about unknown unknowns, talk to them about the color of mirrors which is now a known-known to you.