What’s a 100-year flood? Do they really occur only once in 100 years?

What's a 100-year flood? Do they really occur only once in 100 years?

What’s a 100-year flood? Do they really occur only once in 100 years? ENLARGE Diagram: DNR. The name is misleading: a “100-year flood” does not happen only once every 100 years. The name describes the estimated probability of that particular… More »

Why does the sun look flat near the horizon?

Why does the sun look flat near the horizon?

This flattening of the sun on the horizon is an example of a mirage. Mirages are not illusions; they are images formed as light bends on its passage through the atmosphere.

This bending, called refraction, explains many everyday phenomena. For example, refraction causes objects partly immersed in water More »

How does fog form?

How does fog form?

How does fog form? Photo: NASA Fog is a cloud in contact with the ground. When the relative humidity approaches 100 percent, water vapor condenses on tiny particles suspended in the air to form a suspension of small water drops.… More »