Just before the hurricane Milton hit Florida as a Category 3 storm on Wednesday, with many people reporting an eerie purple hue to the sky above. A sign of the end? Well, the truth is that climate catastrophe is of our own making. However, it is a natural phenomenon that can be explained scientifically.
light and color
Visible light is a narrow band of the electromagnetic spectrum with wavelengths between 700 and 380 nm. (A nanometer is one billionth of a meter.) Within this range, our eyes interpret different wavelengths as different colors. In order from longest to longest, they are red, orange, yellow, green, blue, indigo, and purple. (Alternative name: rainbow)
In fact, our eyes only have three color sensors: one red, one green, and one blue. The intensity of light detected by each sensor and the mixture of the three gives us all the other colors. When your eyes detect equal amounts of all colors, you perceive it as white. Violet has a single wavelength near 380 nm, which is at the limit of what our eyes can see.
But why is the sky colored?
If the sun produces white light, why do we see color in the sky? The reason is that when electromagnetic waves encounter small particles in the atmosphere, some of them are scattered. The exact effect depends on the size of the particles and the wavelength of the light. For very small objects like oxygen and nitrogen molecules, shorter wavelengths (blue and violet) are scattered more than longer wavelengths (red and orange).
This means that when sunlight passes through the atmosphere, the reds and yellows travel mostly straight, while the blues and violets are scattered. If you stand on the Earth’s surface and look up, you’ll see blue and violet light scattered around. This is why the sky looks blue on a sunny day.
This also explains why the sun appears redder at sunset or sunrise. When the sun is lower in the sky, white light has to pass through more of the atmosphere and more blue light is scattered. This allows more red light to pass through and produces nice red sunsets.
Why isn’t the sky always purple?
Yes, please wait. We said that shorter wavelengths scatter more than longer wavelengths. But that means the purple color is even more scattered than the blue. So why doesn’t the sky usually look purple? Very good point. Two reasons:
First, when the sun produces light, the intensity of that light is not the same for all the different colors. In fact, the sun produces a higher intensity of light at longer wavelengths (red and green) than at shorter wavelengths (blue and violet). Therefore, when sunlight hits the atmosphere, there is simply more blue light than violet light.
The second element has to do with the human eye. Our eyes are not as sensitive to the shorter wavelengths of violet as they are to blue, since we can actually only detect three colors: red, green, and blue. Therefore, if the sky scatters both blue and violet wavelengths, our eyes prefer blue. In reality, the sky must be teeth It’s more purple than I expected.
Here’s another important observation that you can see for yourself. The sky is not one color. Sure, there may be a Crayola color called sky blue, but the sky is actually a mixture of many different colors. That’s what makes the sky so beautiful.
purple hurricane
Hurricanes aren’t purple – everyone knows that, but it’s still fun to say so. But what is it about hurricanes that allows us to see this purple light? First, this usually happens when the sun is lower in the sky and the light passes through more air. The rosy hues of evening or dawn are layered with scattered blue and purple light to create a purple blend.
And it’s not just pure air. There are always a lot of other substances in the atmosphere that cause airborne particles, such as water vapor, dust, and debris. And during tropical cyclones, there are many more like that. Finally, clouds overhead can block out the blue sky. All these elements contribute to different colors, one of which is purple.
(Tag Translation) Dot Physics
