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Scientists Declaration about The Holy Quran and Islam-Professor Emeritus
Dr. Moore was a former President of the Canadian Association of Anatomists, and of the American Association of Clinical Anatomists. He was honoured by the Canadian Association of Anatomists with the prestigious J.C.B. Grant Award and in 1994 he...
Space Pollution
I bet you haven’t ever wondered about pollution of space. Yes, man started polluting space ever since Yuri Gangarin (first man in space) saw Earth in its entirety. Earth is not only orbited by satellites but also by paint particles, pieces of glass...
The Nos Feratu
The Caduceus has the pine cone representing the Pineal Gland which it looks like. Clearly the Edwin Smith Codex alone should be enough to tell us that the Egyptians knew a great deal about the human anatomy. But like the Rhind Papyrus which was...
The Stalker as Antisocial Bully
Stalkers have narcissistic traits. Many of them suffer from personality disorders. The vindictive stalker is usually a psychopath (has Antisocial Personality Disorder). They all conform to the classic definition of a bully. Before we proceed to...
Walls can cool themselves!
I always start my column with a question. So why break away with tradition now? Would you believe that walls can cool themselves when they get hot? (Actually that’s 2 questions at the beginning of this column!) Many of you, if not all of you will...
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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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