a little look into the wonderful blue sky!
By zteve t evans
On a clear day you look up to the sky and high above and all around is a beautiful shade of light blue which ever way you look. The Sun is a pale yellow so bright that you cannot and should not look at it. As you look towards the horizon the blue gently pales to white. You may be over come with a feeling of wonderment and awe as you gaze around the seemingly limitless pale blue skies.
Why is the sky blue?
Why is it that the sky is blue and not green, or brown or yellow or any other color, or even one big rainbow? To answer that question you need to know a little bit about the atmosphere surrounding the Earth, a little bit about light and a little bit about something called Rayleigh scattering. To be satisfied with the answer you may to think a little about something else.
The atmosphere
The atmosphere surrounding the earth contains trillions of minute particles. Most of these are far too small for the human eye to see but they still have an influence on what we see. The very tiniest of these particles by chance happens to be of equal length with the wavelength of blue light.
Light through a prism
Most, but not all of our light comes from the Sun. Light from the Sun to humans looks white. In fact it is really made up of all of the colors of the rainbow. This can be seen when light passes through a crystal called a prism. When light passes through a prism it becomes separated into its constituent colors which can then be seen to the human eye.
Light waves
Light is made up of different wave lengths. Red light waves are longer than blue light waves. Light waves travel from the Sun to the Earth in straight lines until something interferes with them in some way.
For example, light can be reflected by some thing such as a mirror. It can be bent in a prism. Or it can become scattered when it passes through tiny particles such as the molecules of gas and dust particles in the Earth’s atmosphere.
When light from the Sun travels through the atmosphere it passes through the molecules of gas and dust and becomes scattered in all directions. This is known as the Rayleigh scattering after Lord Rayleigh who first discovered it.
Why is it that the sky is blue and not green, or brown or yellow or any other color, or even one big rainbow? To answer that question you need to know a little bit about the atmosphere surrounding the Earth, a little bit about light and a little bit about something called Rayleigh scattering. To be satisfied with the answer you may to think a little about something else.
The atmosphere
The atmosphere surrounding the earth contains trillions of minute particles. Most of these are far too small for the human eye to see but they still have an influence on what we see. The very tiniest of these particles by chance happens to be of equal length with the wavelength of blue light.
Light through a prism
Most, but not all of our light comes from the Sun. Light from the Sun to humans looks white. In fact it is really made up of all of the colors of the rainbow. This can be seen when light passes through a crystal called a prism. When light passes through a prism it becomes separated into its constituent colors which can then be seen to the human eye.
Light waves
Light is made up of different wave lengths. Red light waves are longer than blue light waves. Light waves travel from the Sun to the Earth in straight lines until something interferes with them in some way.
For example, light can be reflected by some thing such as a mirror. It can be bent in a prism. Or it can become scattered when it passes through tiny particles such as the molecules of gas and dust particles in the Earth’s atmosphere.
When light from the Sun travels through the atmosphere it passes through the molecules of gas and dust and becomes scattered in all directions. This is known as the Rayleigh scattering after Lord Rayleigh who first discovered it.
Rayleigh scattering
Blue light travels in shorter wave lengths than other colors. By coincidence blue wave lengths happen to be the same, or similar in length as those of the gas molecules and dust particles in the atmosphere. This causes more blue light than other colors to be scattered around the atmosphere. This is why the sky appears to be blue for much of the time in daylight.
The pale horizon
If we look towards the horizon the blue becomes paler or even white. This is because light reaching our eyes has passed through more atmosphere than light from directly above us. This has caused the blue light to repeatedly scatter and re-scatter and the surface of the Earth has also reflected it again scattering it in all directions. The light becomes remixed again with all of this scattering so that we see more white than blue near to the horizon. It is Rayleigh scattering that causes the sky to look blue and the Sun to look yellow.
Coincidence or design?
As we look around enjoying the blue sky spectacular maybe we say to ourselves, “Is it really all a great big, amazing, coincidence that the materials and scientific principles combine to provide such beautiful and spectacular results?
Or we may say, “Is it all by design? Did this come from the mind of someone? When we look into the blue sky are we looking into the mind of some great designer?”
What do you think?
© 10/07/2013 zteve t evans
Blue light travels in shorter wave lengths than other colors. By coincidence blue wave lengths happen to be the same, or similar in length as those of the gas molecules and dust particles in the atmosphere. This causes more blue light than other colors to be scattered around the atmosphere. This is why the sky appears to be blue for much of the time in daylight.
The pale horizon
If we look towards the horizon the blue becomes paler or even white. This is because light reaching our eyes has passed through more atmosphere than light from directly above us. This has caused the blue light to repeatedly scatter and re-scatter and the surface of the Earth has also reflected it again scattering it in all directions. The light becomes remixed again with all of this scattering so that we see more white than blue near to the horizon. It is Rayleigh scattering that causes the sky to look blue and the Sun to look yellow.
Coincidence or design?
As we look around enjoying the blue sky spectacular maybe we say to ourselves, “Is it really all a great big, amazing, coincidence that the materials and scientific principles combine to provide such beautiful and spectacular results?
Or we may say, “Is it all by design? Did this come from the mind of someone? When we look into the blue sky are we looking into the mind of some great designer?”
What do you think?
© 10/07/2013 zteve t evans
References and Attributions
Copyright 19th of July 2013 zteve t evans
Copyright 19th of July 2013 zteve t evans