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Carl Jung
Carl Jung wondered if he might be crazy when he had visions of the World War before the first of these conflagrations in the 20th Century came to pass. This made him a lot more desirous of understanding from whence his prophetic visions might have...

Crop Circles and Genetic Knowledge
CROP CIRCLES: The crop circle enigma is not always a hoax. I am not able to see how someone could do a massive design overnight in the cases where the plants have their stems broken from within. Yes, that is the case in what I consider the real...

God v. Gods
Aristotle referred to happiness as the most we can achieve. Demons and gods were interchangeable in the time of Homer when people had far less institutionalized manipulation of their thoughts and soulful understandings. What is the ‘anima’ referred...

Major landmarks on the moon
This article lists some of the more well-known and interesting landmarks on the moon. The moon is the second brightest object in our nighttime sky. Our moon is also known as Luna and is our nearest neighbor. It takes 27 and 1/3 days for the...

The future of the Human Species - Part 1: Are we in danger?
The sun, that celestial body which has always fascinated the human species, which differentiates night and day, which when angry, produces the fascinating auroras, is father to us all: humans, animals and plants. The sun is the father of life on...

 
How strange! The sky is blue!

Look up! Just do it. What do you see? Stupid question, eh? You see the ceiling of course. When you look upwards during a sunny day while picnicking however, you see the blue sky. Ever wondered why the sky is not green nor but blue?

Before answering this question, let’s go back to the basic physics of light. Sorry, but here I go…

Light is a kind of energy, which travels in waves. In fact, light is a wave of vibrating electric and magnetic fields. Light forms only one small part of a larger range of vibrating electromagnetic fields called the electromagnetic spectrum. Electromagnetic waves travel through space at an amazing 300 00km/s. Therefore this is also the speed of light.

When you see white light from the bulb, you are actually seeing the seven colours of the rainbow! This is because white light consists of a combination of these seven colours.

Each of these colours has a different wavelength, frequency and energy. Wavelength is the distance between the crests of the waves. The frequency is the number of waves that pass by each second. Note that the longer the wavelength, the lower the frequency and the less energy it contains.

·Violet: Shortest wavelength, highest frequency and energy
·Red: Longest wavelength, lowest frequency and energy

Now back to our main topic. That blue colour of the sky is due to an effect known as the Rayleigh scattering. As light from the sun moves towards Earth’s atmosphere, not all the colours are actually able to pass through that atmosphere. Most of the longer wavelength colours do pass (red, orange and yellow for sure) but


the shorter wavelength ones however are mostly absorbed by gas molecules found in the atmosphere. Absorbed blue light is then bounced back (radiated would be a better word) in all directions. This makes the shy to appear blue!

You would however ask me why it’s the blue rays, which get scattered, and not the indigo nor the violet rays (the other colours pass through the atmosphere remember – there’s also blue that pass through but it then gets scattered). Well in fact, the shorter the wavelength, the more the colour gets scattered. Violet, which has the shortest wavelength of all colours of the rainbow thus gets scattered more than blue rays do. Our eyes however are much more sensitive to blue than to violet and the sky therefore doesn’t appear to be violet but blue (in reality the sky is violet-indigo!).

Now do take the time making the following:
Take a look at the horizon (if you’re at the seaside) and note the sky’s colour there. No, it’s not as blue as the rest of the sky, is it? It’s much paler. This is because for the blue light to reach your eye, it has to travel more. Blue light will thus pass through more air consequently getting scattered more. Conclusion: less blue light reaches your eyes than compared to blue light from just above you.

About the Author

K.A.Cassimally is the editor in chief of Astronomy Journal and Astronomy Journal Ezine. He is also the co-founder of the RCPL Astronomy Club. K.A.Cassimally is best known for his article 'Harry Potter and the Moons of Jupiter'.
He is also Senior Columnist at BackWash.com where he writes 'Not Scientific Science'.

 

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