The Sun Also Rises

Sunrise seen from low Earth orbit by the shuttle astronauts can
be very dramatic indeed (and the authors apologize to Hemingway for using
his title!). In this breathtaking view, the Sun is just visible peaking over towering
anvil shaped storm clouds whose silhouetted tops mark the upper boundary
of the troposphere, the lowest layer of planet Earth's atmosphere. Sunlight
filtering through suspended dust causes this dense layer of air to appear red.
In contrast, the blue stripe marks the stratosphere, the tenuous upper
atmosphere, which preferentially scatters blue light.