Earth and Sky:Black and White 黑与白

Black and White黑与白

Sometimes you hear it said that white is a combination of all the colors of the rainbow -- and that black is the absence of color. Find out more about whether black and white are colors -- today on Earth and Sky.

JB: This is Earth and Sky. A listener wants to know, "Are black and white really colors?"

DB: Color isn't a physical quality. It's a phenomenon of light and perception. Matter and energy are colorless. It's really our eyes and brains that make a fire-engine red or chickens white.

JB: Colors are defined by their hue¹, saturation², and value. Hue is what we think of as making blue blue, and not orange or grey. Saturation refers to a color's vividness -- it's what makes a pale blue sky different from one that's deep blue -- or pink different from red. Value refers to a colored object's lightness, darkness, and brightness -- that's the contrast between, say, the shining moon and a glass of red wine.

DB: It gets pretty complicated to talk about what makes a color a color -- because colors can only be talked about in terms of themselves -- and how they differ from one another. Black is black precisely³ because it has no redness or greenness or any other hue. But, to answer your question, black and white -- and grey, for that matter, too -- are colors. They're neutral colors -- different from each other only in terms of their darkness and lightness. Like all colors, black and white are products of our visual processes -- they exist only because we're there to sense them.

JB: To ask us your question, come to earthsky.org. With thanks to the National Science Foundation, we're Block and Byrd for Earth and Sky.

1 hue   

n.色度；色调；样子

参考例句：

• The diamond shone with every hue under the sun.金刚石在阳光下放出五颜六色的光芒。
• The same hue will look different in different light.同一颜色在不同的光线下看起来会有所不同。

2 saturation   

n.饱和(状态)；浸透

参考例句：

• The company's sales are now close to saturation in many western countries.这家公司的产品销售量在许多西方国家已接近饱和。
• Road traffic has reached saturation point.公路交通已达到饱和点。

3 precisely   

adv.恰好，正好，精确地，细致地

参考例句：

• It's precisely that sort of slick sales-talk that I mistrust.我不相信的正是那种油腔滑调的推销宣传。
• The man adjusted very precisely.那个人调得很准。