The sky with its varying colours throughout the day, leaves most of us awestruck. But have you ever wondered why the sky changes colours? Why we see a blue sky in the day and black at night? Here’s Why!
To us, from earth, when we look at the sun, it appears as yellow, however, the colour of the sun is white. The light emitted by it is also white, when sunlight enters the earths atmosphere we see the light as yellow due to the scattering of light. White light is nothing but a result of the combination of the following colours of different wave lengths: violet, indigo, blue, green, yellow, orange and red.
As mentioned earlier, sunlight scatters when it enters the earths atmosphere, this is because it collides with the air particles in the atmosphere. As we know that all colours have a different wave length. Colours with a shorter wavelength usually scatter more on collision as compared to colours with a longer wavelength. As a result, violet light is scattered the most. However, violet is a colour that the human eyes do not see very well. Blue after violet light is the most scattered light. Human eyes being very sensitive to the colour blue, easily see the colour and therefore we see a blue sky.
We know that the moon does not have a light of its own and reflects the suns light. If sunlight, even though indirectly, is scattered at night, why does the blue sky then change its colour and appear as black?
The light that the moon reflects is not as powerful as actual sunlight. It is the overpowering, extremely strong nature of sunlight that conceals outer space. The sunlight that is reflected by the moon is not as powerful as direct sunlight, therefore not leading to scattered light reach the eyes of the observer. Outer space is black in colour with its planets, moon and stars, which is visible to us in lack of sunlight at night; changing the colour of the blue sky to black.
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Also, read about our previous blog Tell Me Why: Interesting Food Facts
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