The solar eclipse on April 8th doesn’t come alone; it will be accompanied by a couple of scientific phenomena promising to captivate both children and astronomy enthusiasts alike. One of them will ‘change’ the way we perceive colors: this is the scientific explanation behind the phenomenon known as the Purkinje effect.
On April 8th, the American continent will witness the great solar eclipse, with Mexico being the country with the best conditions to observe this astronomical spectacle. One notable feature of this eclipse is its extensive path of totality, spanning between 173 and 196 kilometers wide, covering more ground along its route than other similar phenomena, but that’s not the only relevant aspect.
What Is the ‘Purkinje Effect’ and Why Will It Affect the Solar Eclipse on April 8th?
During the eclipse, it’s possible that what scientists refer to as the Purkinje effect may occur, a visual phenomenon where there is a “natural change in color perception caused by fluctuating light levels,” according to the specialized magazine Scientific American. This causes colors like red and orange, which appear rich and vibrant to the human eye under bright light, to become dark and muted under low light conditions. Conversely, colors like violet, blue, and green light up when subjected to these same conditions.
To understand this, we first need to know that our retina (part of the eye) has two types of cells: cones and rods. Under bright light conditions, we perceive colors primarily through cones; however, when light becomes dim, rods take over. Rods are more sensitive to light but less sensitive to color, leading to a shift in color perception. Unlike humans, the Purkinje effect of the April 8 solar eclipse can be more intense, as in the case of birds, while dogs may lose stunning visual changes because “their retinas contain only two types of cones: blue and yellow.”
All of this is a consequence of the rapid and dramatic decrease in sunlight during a total solar eclipse, which can intensify this phenomenon, making these events even more surreal. Conditions like twilight or the totality of a solar eclipse cause our eyes to enter mesopic vision, where the rods and cones of the retina work together.
How Is This Change Possible During the April 8th Solar Eclipse?
Let’s remember that human retinas have three types of color-sensing cones: red, green, and blue. Combinations of these cones allow us to see all the colors of the rainbow in broad daylight. But in the mesopic period, signals from red cones (which detect longer, redder wavelengths of light) are lost, while those from shorter wavelengths detected by green and blue cones persist. That’s why greens and blues are notably vibrant during twilight and a solar eclipse. At the peak sensitivity of our rods, there’s a wavelength that appears cyan or the color of the ocean, and that’s the color that truly penetrates and is probably most beautiful during [a solar eclipse].
This story was written in Spanish by Perla Vallejo in Ecoosfera.
