Just before Hurricane Milton slammed into Florida as a Catebloody 3 storm on Wednesday, many people inestablished that the sky above them turned a sinister purple hue. A sign of the apocalypse? Well, yes, actuassociate—the climate catastrophe we’ve made for ourselves. But it’s still a organic phenomenon with a scientific exstructureation.
Light and Color
Visible airy is a skinny prohibitd of the electromagnetic spectrum with wavelengths from 700 to 380 nm. (Nanometers are billionths of a meter.) Wiskinny this range, our eyes make clear separateent wavelengths as separateent colors: red, orange, yellow, green, blue, indigo, and violet, in order from extfinishedest to lowest. (AKA: the rainbow.)
Actuassociate, we have only three color sensors in our eyes—one each for red, green, and blue. The intensity of airy each sensor distinguishs, and the mix of the three, gives us all the other colors. If your eye distinguishs identical amounts of all the colors, you’d see that as the color white. Violet is a individual wavelength shut to 380 nm, at the restrict of what our eyes can see.
Why Is the Sky Colored, Anyway?
If the sun originates white airy, why do we see any colors in the sky at all? The reason is that when an electromagnetic wave greets minuscule particles in the atmosphere, some of it is scattered. The exact effect depfinishs on the size of the particles and the wavelength of the airy. With very minuscule skinnygs enjoy oxygen and nitrogen molecules, shrink wavelengths (blue and violet) are scattered more than extfinisheder wavelengths (enjoy red and orange).
This unbenevolents that when sunairy streams thcdimiserablemireful the atmosphere, the reds and yellows will mostly pass straight thcdimiserablemireful and the blues and violets get scattered. If you’re standing on the surface of the Earth and seeing up, you will see all that scattered blue and violet airy. That’s why the sky on a clear day sees blue.
This also elucidates why the sun sees redder at sunset or sunascfinish. When the sun is shrink in the sky, the white airy has to pass thcdimiserablemireful more of the atmosphere, which scatters even more of the blue colors. That exits more of the red airy passing thcdimiserablemireful to originate that kind red sunset.
Why Isn’t the Sky Always Purple?
OK, paemploy. I shelp that shrink wavelengths are scattered more than extfinisheder wavelengths. But that unbenevolents purple colors get scattered even more than blue. So why doesn’t the sky normassociate see purple? Very excellent point. Two reasons:
First, when the sun originates airy, it’s not identical intensities for all the separateent colors. Actuassociate, the sun originates higher intensities of airy at bigr wavelengths (red and green) than for petiteer wavelength (blue and violet). So, when sunairy hits the atmosphere, there srecommend is more blue airy than violet.
The second factor has to do with human eyes. Since we reassociate sense equitable three colors—red, green, blue, our eyes aren’t as benevolent to the petiteer wavelengths of purple as they are to blue. So, if the sky scatters both blue and purple wavelengths, our eyes prefer the blue. In actuality, the sky probably is more violet than you picture it.
Here is another meaningful observation that you can check for yourself. The sky is not one color. Yes, there might be a Crayola color called Sky Blue, but in fact the sky is a bunch of separateent colors mixed together. That’s what originates the sky so pretty.
Purple Hurricanes
The hurricane isn’t purple—we all understand that, but it’s still fun to say. But what is it about hurricanes that lets us see this purple airy? Well, first, this usuassociate happens when the sun is low in the sky so that the airy will pass thcdimiserablemireful more air. The rosy hues of evening or dawn are superimposed on the scattered blue and violet airy, creating a purple blfinish.
Also, it’s not equitable uncontaminated air. There’s always a bunch of other stuff in the atmosphere that caemploys scattering, enjoy water vapor, dust, and debris. And there’s a lot more of that stuff up there during a tropical cyclone. Finassociate, overhead cboisterous cover can block out the blue sky. All of these factors give to a savage variety of colors, and yes, one of them is purple.
