The Magic Cloth

Now, let’s go back to a red star and examine a piece of cloth (or color pattern on paper).
Space travelers call it “the mystery cloth” because they have a hard time agreeing on the colors they see on it.

Make sure only the red light is on. While you talk, start unrolling the multicolored cloth or handing out paper color patterns so that everyone will have it in front of them. With rolled-up cloth, once you start, let the audience continue unrolling.

Will someone please describe the pattern on this cloth for us?

[Stripes of the same width; colors.]

Does everyone agree with that description?

[Accept a few opinions.]

Perhaps we can agree that there is a bright stripe that reflects red light (or looks bright under red light) and a dark stripe or two that absorbs it (or looks dark under red light).

Let’s take the cloth to a different star, a green star perhaps, to see if we can get some more information about the colors of this cloth. Please fasten your safety belts again.

DIGITAL EFFECT: Green Light
Red lights off; Fill the entire dome with green light.
Expect gasps of astonishment from your students.

Wow! What happened!!? Could this be the same piece of cloth?

Would someone please describe this new pattern for us?

[There’s a new thin zig-zag line, so there are three stripes of different widths. Colors?]

Does everyone agree with this new description?

[Listen again to a few opinions.]

We want to discover the true colors of each of those stripes, and to do this we can use what we learned when we looked at our clothes under different color lights.

Does that zig-zag look bright or dark? [Dark.]

That is because it must be absorbing the green light.

Is it possible that the zig-zag could be green?

[No. If so, it would look bright.]

What about the background stripe that the zig-zag is on, does it look bright or dark?

[Bright.]

It looks bright because it is reflecting the green light.

Is it possible that the background could be green? [Yes.]

Could it be another color? [White.]

Now keep track of that zig-zag by putting your finger on it while we return to the red star to see what happens.

DIGITAL EFFECT: Red Light
Turn green light off; red light on.

The zig-zag disappeared! Where did it go? I told you to keep track of it!

Now, does the area where the zig-zag is supposed to be look bright or dark? 

[Bright.]

The zig-zag and its background are two different colors but they are reflecting red light equally.

Is it possible the zig-zag could be red? [Yes.]

Now its background looks bright, too.

Could it be red, also? [No.]

It looks bright with both red and green, so it probably is white, yellow, or some other color that reflects both red and green. Now, put your finger on the dark stripe.

Could this be red?

[No, because it absorbs red light.]

Let’s go to a green star.

DIGITAL EFFECT: Green Light
Red light off; Fill the entire dome with green light.The stripe looks bright.

What color do you think it could be?  

[Green; or maybe, blue.]

If it is blue it should look brighter near a blue star: let’s see.

DIGITAL EFFECT: Blue Light
Green light off; Fill the entire dome with blue light.

It looks darker, therefore it’s not blue, it’s probably green.
So far we have guessed a wide green stripe, and a red zig-zag on a white or yellow background.

What color light do you think we could shine on the cloth to see its real colors? 

If they say: red, blue, green, respond: “We already looked at it with those colors.” When they say any other color: “I only have red, blue and green.” When they suggest white or a combination…

Let’s see what happens when we combine colors.
Look at the ceiling as I mix the colors: We have blue light, now we add green.

DIGITAL EFFECT: Green/Blue Light
Fill the entire dome with a mix of green and blue light (i.e., cyan), as a color combination.

We get aqua (or turquoise, cyan, or plain blue-green). Let’s add red to blue.

DIGITAL EFFECT: Red/Blue Light
Fill the entire dome with a mix of red and blue light (i.e., magenta), as a color combination.

We get pink (or purple, or magenta).

Let’s add green to red.

DIGITAL EFFECT: Red/Green Light
Fill the entire dome with a mix of red and green light (i.e., yellow), as a color combination.

We get yellow! 

This is usually a surprise for most people.

And finally let’s have red, green and blue together

DIGITAL EFFECT: Red/Green/Blue Light
Fill the entire dome with white light, to demonstrate “white light” as a combination of red, green, and blue combined.

We get nearly WHITE!!
White light is made from all colors mixed together.
Look at your clothes now.

Do they look their normal color again? [Yes.]

Now we can see the “true” colors of the cloth and we find that we were correct in our guesses.

Please roll-up the cloth that is not-so-mysterious anymore.

Collect cloth once it is rolled up…or collect the Magic Cloth paper handouts.

DIGITAL EFFECT: Red Light
Fill the entire dome with of red light.

In summary, we can say that an object looks brightest when illuminated by light of the same or nearly the same color (because the object reflects the light), and looks dark when illuminated by a light of very different color (because the object absorbs the light). 

Pale colors and white look bright in any color light, and dark colors like black, or brown, look dark in any color light. The red zig-zag and its pale background looked equally bright in the red light. In fact we could not tell they were different and that’s what made the zig-zag disappear.

On the other hand, in blue or green light the red became very dark, while the pale background remained bright. This is because light striking an object is either reflected into our eyes, or absorbed.

Objects reflect mostly the color light that they appear to be, and absorb all other colors.