Astronaut singing (“I was strolling on the moon one day.”) What do..
you see?
No, its not the astronauts singing on the moon, but the sky in the moon
is black.
The sky on Earth is blue, 
Why is that so?
There is an important difference between the earth and the moon.
The moon doesn’t have an atmosphere.
The atmosphere is a thin layer surrounding the earth.
This layer mainly consists of nitrogen and oxygen.
The nitrogen and oxygen make up the air that we are surrounded by.
The reason that the sky looks blue is due to the atmosphere.
How can the white light from the sun be responsible for the blue sky?
We show this
with a simple experiment.
The experiment consists of a bright lamp and a prism.
The lamp represents the sun.
The prism splits the light into its colour components.
White light consists of many different colours.
The same colours that you can see in a rainbow.
A second prism combines the colours back together and we get white light again.
The theory is explained by
Prof. Dr. Ansgar Reiners of the University of Göttingen.
the light of the sun, which seems white to us,
is in fact not white, but composed of 
many different colours, for example, blue, green and red. Blue light has..
short wavelength and high energy,
and the red light is on the other side of the spectrum.
The blue light, due to its high energy, is dispersed much more..
when the white sunlight passes through the Earth’s atmosphere
most of the blue light is diffracted to the side.
So, if we were to get away from the sun, and look at the atmosphere, 
it would look more blue than other colours. 
Why the atmosphere is blue in all directions,
we can conduct an experiment to illustrate the effect. 
We first mix a tincture of Myrrh to water,
and this mixture represents our atmosphere.
The Myrrh particles diffract the light from the lamp,
just like the molecules in the atmosphere diffract the light from the sun.
One can also use milk, 
to get the same effects from the experiment.
If you use an aquarium, please take out the fish before the experiment.
We shine the light from the lamp sideways into the aquarium.
Now the liquid turns blue just like our atmosphere.
That’s the blue that we see in the sky.
OK.
The light that is shone directly through the liquid,
seems yellow like the sun.
Why is the light now yellow?
This can be shown with the prisms. If we filter the..
blue colour,
the remaining colours make up yellow.
The same thing happens if we look at the Sun from the Earth,
because in the atmosphere, the blue light is scattered to the side..
and only the other colours remain.
That is why, we see the sun as yellow.
But we don’t always see it as yellow. During sunrise and sunset,
the light from the sun seems bright red and 
orange.
How can one explain that?
We again ask Prof. Dr. Ansgar Reiners of the 
University of Göttingen.
When the
sun is directly on top, we look through the Earth’s atmosphere,
which is about 8 kilometers thick.
This is not particularly much.
Some of the light is diffracted, but a high proportion of it reaches us directly. That is why the sun appears white.
Not much is happening. When the sun is closer to the horizon, 
the short 8-kilometer atmosphere now becomes longer
because we now have to look through much more of the atmosphere towards the light. 
This is about 300 kilometers and in that distance, 
a large amount of light is scattered towards the blue spectrum. 
The blue light is diffracted a lot more than the red light and therefore we see the sun red.
