Air Pressure Curriculum

Section 1: Overview—Explanation of Photograph

This section addresses students' tendency to focus on obvious causes. It introduces students to the concept of non-obvious causes. Non-obvious causes are often overlooked when people generate explanations. Air pressure is typically non-obvious, and historically its effects were attributed to other causes.

Explanation of Photo

What causes a sunset? Again, the cause is non-obvious. When sunlight travels through the atmosphere to Earth, its rays are scattered by the molecules that make up the air. Higher frequencies of light, such as blue and green, are scattered more than lower frequencies, such as red. When the sun is directly overhead, its light travels the shortest distance possible through the atmosphere to an observer on earth, and not much scattering occurs. But at sunrise and sunset, sunlight travels the longest path through the atmosphere to earth, given the sun's position in the sky, and this causes increased scattering, letting only redder frequencies of light reach earth. Particles in the atmosphere, such as air pollution, smoke, or ash from a volcanic eruption, scatter the sunlight even more, resulting in redder and more dramatic sunsets.