Monday night's storms dazzle Iowans with 'crepuscular rays'
Many were treated to a spectacular show in the western sky after sunset
Many were treated to a spectacular show in the western sky after sunset
Many were treated to a spectacular show in the western sky after sunset
The setting sun and distant storms provided many Iowans with an especially vivid display of "crepuscular rays" Monday evening.
Crepuscular rays — whose name derives from the Latin word for twilight — are an optical phenomenon caused by sunlight shooting through gaps in clouds or other obstacles.
In the case of Monday after sunset, clouds towered thousands of feet into the air over western Iowa, casting shadows dozens of miles to the east.
The streaks of light and shadow that many saw can actually appear at any time of day, but are most noticeable when the sky darkens at twilight.
The brilliant sunbeams streaking across the sky are visible because of tiny particles like dust, water vapor, or pollen suspended in the air. These particles scatter light, allowing our eyes to see it.
Crepuscular rays are actually parallel, but appear to fan outward from the Sun because of perspective.
That same visual effect makes things like highways and railroad tracks seem to narrow in the distance.
Crepuscular rays can sometimes be accompanied by "anticrepuscular rays." These are usually more subtle and appear in the opposite direction of the Sun due to light backscattering toward our eyes.
Anticrepuscular rays are visible as fainter bands of light and shadow converging toward a point on the horizon.
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