Why is the Sky Blue?

World's Most Asked Questions: Why is the Sky Blue?

 

It’s the mother of all questions! Well, except maybe What’s the Meaning of Life? -- which we actually have our own scientific answers to … Or What Is Love? -- We have some thoughts on that, too. But one of the most googled questions in the English-speaking world is the one that kids are famous for asking -- and grown-ups are notorious for avoiding, because they just don’t know.

Why is the sky blue?

Just give me a couple minutes and I'll let you know why.

This is the World’s Most Asked Questions!  

The sky is blue because of three things: light from the sun, particles in our atmosphere, and the fact that you’re a human. I’ll get to that last part in just a minute. But let’s start with how sunlight interacts with particles in the sky. I’m not talking about dust or water droplets or other big particles, which are sometimes mistakenly used to explain the sky’s blueness .

Instead, it’s the very small particles in our atmosphere that make the sky look blue. I’m talking about molecules of the air itself ,mostly molecular oxygen and nitrogen -- O2 and N2. These molecules are super-abundant in our atmosphere and so small that they’re even smaller than wavelengths of visible light! And that’s the key. Visible light consists of a range -- or spectrum-- of different wavelengths. Light with the longest wavelengths are at the red end of the spectrum, and light with the shortest wavelengths are at the blue and violet end. Since the blue wavelengths of light are shorter, they’re more likely to strike those tiny molecules of oxygen and nitrogen more often ,and when they do, they get scattered in all directions.

 This effect is known as Rayleigh scattering ,because it was first described by John William Strutt, aka the Third Baron Rayleigh, who in 1871 published his mathematical proof that blue wavelengths of light in the atmosphere are scattered 16 times more than red wavelengths. But violet light has the shortest wavelength of all visible light, and it’s scattered even more strongly by tiny particles – so why isn’t the sky purple?

Well, this is where being human comes into play.

 Our human eyes perceive the middle of the spectrum most sharply which is why blue is way easier to see than violet. So even though violet light is being scattered around like crazy, we just don’t detect it as well as we detect the blue. And that’s why the violet band of the rainbow is often the hardest for us to make out.

 So sciencefacthow readers are in luck, because in a survey , the most popular favourite color from the rainbow was blue. 33.55% of survey takers reported blue as their favourite color, while yellow was the least favourite at only 2.8%.

Poor yellow. But, there are other animals that can see all the way into the ultraviolet end of the spectrum, like honeybees and some birds. So may be they like yellow. And maybe the sky looks completely different to them.

Of all the fascinating questions in the world ,what question do you want answered most?

 Thank you for reading and stay tuned for more answers to the World's Most Asked Questions.