What are Crepuscular Rays?

Crepuscular rays can be seen as the bright lines that lead away from the sun in the photo above.

We see sunlight when it travels directly into our eye and hits our retina. If a light beam travels on a different path we will not see it directly.

But most of the time we see sunlight indirectly. That is why the sky is blue. Light from the sun scatters off the molecules in the atmosphere and bounce around. We see that effect as a blue sky. If there was no atmosphere, the sky would look black, it would appear the same during the day as it does at night, but with a bright fiery ball of the sun there too.

In the picture above we can see the sun’s light in lots of different ways.

  1. It bounces off the molecules in the air giving us a blue sky.
  2. It bounces off the water giving us a glitter path.
  3. It bounces off the clouds giving us reflections and shadows.
  4. It bounces off the land giving us dark greens.
  5. It also bounces off particles in the air, forming straight lines called crepuscular rays. The particles are often made of dust, water or salt.

Crepuscular rays form straight lines that stretch away from the sun. But as navigators we can look at this differently: the rays always point to the sun. This is especially useful when the sun is hiding behind lots of clouds. They are giving us a way to see the sun, even when it’s hiding.

A simulation of what daytime would look like with no atmosphere. Image Credit: Stellarium

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