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.
