Fascinating Meteorology Terms: Jacob’s Ladder

Crepuscular rays spreading out from behind a cloud

One of the most beautiful additions to a sunset, Jacob’s Ladder, also known as crepuscular rays, sunbeams, light shafts or God’s fingers can be seen quite often in the sky. Usually on a cloudy day when the sun peeks through, near twilight, beams of light will flow from the clouds to the ground or spread out into the sky. It delivers a dramatic experience to the onlooker as they gaze at the display of light. Many describe this scene as something out of a bible, as if angels were ascending to heaven from earth on beams of light or that the sun was drawing up water from the ocean. 

Jacob's Ladder is an optical phenomenon made by sunlight that is scattered by particles of haze or dust in the sky. The dust, tiny water droplets or haze scatters the light making a certain area of the sky appear brighter. Light scattering is when a beam of light hits an object of imperfect shape and gets redirected or reflected back in many different directions. Most of the time, the beams of light scattered from the cloud are a blue or yellow tint. This is due to the type of particle that is scattering the light. Some particles are selective scatterers, meaning that when a beam of light hits them, they tend to absorb certain wavelengths of that light and scatter the other wavelengths. Different colors of light have different wavelengths. For example, reds, yellows and oranges have larger waves then blues, purples and greens. So, if you spot Jacob's ladder, and the beams of light are yellow, you can tell that the particles scattering them are absorbing shorter wavelengths and scattering longer wavelengths of light.      

The name Jacobs ladder originates from a biblical story about a patriarch that had a dream about a stairway to heaven. Although it has many versions, the story is simplified. During a quarrel with his brother over their birthright to the family inheritance Jacob fled from his brothers rage. During his escape, he stopped for the night and slept on a rock. When he slept he had a dream about a ladder or stairway to heaven shrouded in golden light where he saw God at the top and angels ascending it from earth. It's easy to see where this optical phenomenon may resemble the description in Jacobs dream. Most of the time, crepuscular rays that shine down and touch the earth are so golden and breathtaking that they look as if they are coming from the open doors of heaven.

© 2020 Meteorologist Alex Maynard 

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Sources:

Ahrens, C. Donald., and Robert Henson. Meteorology Today: an Introduction to Weather, Climate, and the Environment. Cengage, 2019.

Ancient-Origins. “Stairway to Heaven: The Story of Jacob's Ladder.” Ancient Origins, Ancient Origins, www.ancient-origins.net/myths-legends-europe/stairway-heaven-story-jacobs-ladder-006173.

Baker, Jess. “Science Behind the Optical Illusion of Crepuscular Rays (PHOTOS).” The Weather Channel, The Weather Channel, 4 Aug. 2015, weather.com/news/news/fingers-of-god-crepuscular-rays-20130220.