[MUSIC] What color is the moon? I asked you all this question and got some
very interesting answers. Silver like aluminum white, like the color of clouds Chalky, like ash silver, kind of like an old coin gray like pavement silver like your mother’s hair milky chalk gray like a used eraser white, like a diamond But among all the varied responses and interesting
comparisons, you all pretty much agreed: The moon is a very light color, something
like this. But what if i told you it was actually more like this [MUSIC] When our brains are trying to figure out what color something is the first thing we do is try to figure out how bright it is. This side of the apple looks like a brighter color than the side away from the light, we can see that is so, but our brains are able to take this lighting into account and we know that the whole apple is the same red. If a car drives out of a dark tunnel, we don’t assume the car magically changed color, because our brains correct
for differences in all the light in whatever scene we’re looking at. But that doesn’t always work so well. Here’s a white square No, here’s a white square. No, here’s a white square Wait a second, what is going on here? All these squares are the same. And you may have seen this famous illusion before.
The two lettered squares are actually the same color. Even when the light in a scene doesn’t change,
the colors surrounding an object can also trick our brains. If you stare at the center
of this image, between the yellow and blue bars, the tiny squares look like different
colors, but they’re not. If our brains could make an absolute measurement
of light passing through our pupils, maybe we wouldn’t be tricked by these illusions.
But we can’t do that, our eyes aren’t cameras or light meters or that little eyedropper
tool in Photoshop. As far as our brains are concerned, it’s
not what color something is, it’s what color something appears to be. Which brings us back to the moon.
The full moon gives enough light that it can even cast shadows on the ground on a dark night here on Earth. But it only looks so blindingly bright in the night sky because there’s
nothing else nearby it to compare to, except the night sky itself. Instead of measuring the absolute number and wavelength of photons the moon gives off, our eyes and brains compare the relative amounts of light given off by two or more objects
within our field of view. Consider these shapes. The smaller rectangles
in the center are the same color, but since the *relative* difference between the two
top shapes is greater, the small rectangle *appears* brighter up top. The lightest object in a scene becomes a sort
of anchor, our brains say “that’s white”, So how bright is the moon? Not that bright. The moon only reflects about
13% of the light that hits its surface. But in the night sky, against the dark blackness of space, it’s the brightest thing we can see, so our brains tell us “that’s
white”. But if we viewed the moon next to Earth, under
the same illumination, it would be a very dark gray, almost like an asphalt road. In
fact, you can see this dark gray color in photos taken on the Moon during the Apollo
missions. Compared to a white spacesuit, suddenly the moon doesn’t seem as bright, does it? I hope you’ve enjoyed this little mind-bender,
and that next time you look up at the moon, you don’t see it in exactly the same light. Remember, the eye and mind work together
in mysterious ways, and… “Colours, seen by candle-light
Will not look the same by day.” Stay curious.