Sunday, 27 August 2017

Chelsea's speech

Topic - Why is the sky blue? - and that is that


The sky is blue and that is that. Have you ever wondered why the sky is blue? I mean why can’t it be purple, or green, or even yellow? That's why I’m here, to tell you what makes the sky blue.


An irish physicist called John Tyndall took the the first steps towards correctly explaining the colour of the sky in 1859.


Now remember, the sun is earth’s light source, and light from it travels in waves.


John said the sky is blue because blue light is scattered in all directions by the tiny molecules of the airs atmosphere. Blue is scattered more than other colours because it travels as shorter, smaller waves. This is why we see blue most of the time.


So, Why does the sky turn black at night?
As earth turns on its axis, the part of the planet you're standing on turns for a time so that you face into earth’s shadow. While we are in the earth’s shadow the light from the sun is unable to reach us and reflect off the molecules in the sky this means we can not see colours in the sky. When you face into the shadow, it’s night. When earth turns so that you face the direction of the sun it is day.


And, Why does the sky change colour at night and morning?
When we look towards the sun at sunrise or sunset, we see orange and red colours because the blue light has been scattered out.


you face into the shadow, it’s night. When earth turns so that you face the direction of the sun it is day.


Why does the sky change colour?
Scattering affects the colour of light coming from the sky, the colour we see is determined by the wavelength of the light and the size of the particle. Molecules and small particles in the atmosphere change the direction of light rays, causing them to scatter, this is called refraction.


Why do we see rainbows?
Rainbows are created as light from the sun meets a raindrop, the raindrop acts the same as a triangular prism to separate the light into different wavelengths allowing us to see all the colours in the rainbow. The beams of sunlight are separated into the colours of the rainbow as they make contact with a raindrop.

So there you have it, according to John Tyndall the sky is blue because tiny molecules in the earth’s atmosphere scatter blue light more than other colours.The sky is blue and that is that.

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