Why is the sky blue in the day and black in the night? asks Lamar (12)

Lamar – a brilliant question. I will ask my friends to think about it.


Lamar. I hope that you have had the opportunity of passing ‘white light’ through a prism and see the fantastic ‘spectrum’ of coloured light that results. If not then try ‘creating’ white light by using torches and  coloured cellophane (blue, red, green) on each torch and shining them at a white piece of cardboard. Let me know what happens.

Things then get a little difficult. You have to think of the Sun’s white light reaching the atmosphere of the Earth. The two major components of the atmosphere are nitrogen and oxygen. The structure of the molecules of these two components makes them very receptive to the blue part of the white light from the Sun. The air molecules absorb this blue part and then re-emit it in all directions. This is a process called ‘scattering’. Thus the blue sky. The rest of the (white minus some blue) sunlight passes onwards.

At night the Sun is shining on another part of the Earth, so no white light is falling on your part of the Earth. No light ….blackness.

Lamar . An interesting question, a complex answer. Feel free to ask another question.

Natalie’s question was linked to chemicals and what happens when you add a chemical to a chemical.

Natalie, a great question. Before answering it I thought that we needed to think about what was meant by the term ‘Chemical’. So I asked my team.


So the salt that you put on your food is a chemical. The food is made up of chemicals. Water is a chemical and so is Oxygen, the gas that you breathe. Washing up liquid is made of chemicals as is milk and butter.

Sometimes, very, very rarely adding one chemical to another causes an explosion. So there is no need to worry. Please ask another question.

Luie(12) asks ” What is the most deadly gas?”

Luie I asked my friends for help on this question. They had some interesting thoughts.

posinous gases

Luie, it is not quite true that there is only one gas that is not poisonous. Air consists of a variety of gases that are not poisonous, we breathe them in all the time and they don’t poison us. There is however one gas that is used by our body and is more important than the others. What is it? If you know then you could tell me by using the ‘Leave a Reply’ box

Did you know that Hydrogen Sulphide (bad eggs) is more poisonous than Hydrogen Cyanide (almond smell), why ???

Because our nose is much more sensitive to Hydrogen Sulphide than Hydrogen Cyanide. By the time you can smell the almond smell you are dying.

Ira asks about the green flash at sunset,

I investigated the flash on youtube and came up with this excellent video. No need to watch the whole thing the flash occurs very briefly at 1.23. (permission has been granted to copy it).

Ira I think I have an idea about this but I going to ask my friends if they can explain the diffraction of light.

Sunset copy

Amazingly when you see a sunset the Sun is actually quite a way below the horizon. What you are seeing is the light from the Sun refracted. The light from the Sun, during the day it is passing through five different atmosphere levels. At sunset it is just passing through one level – the lowest level and the ‘thickest’ level. This is usually linked to the red sunset …. diffraction by dust of the red part of the spectrum. This also, in very special atmospheric conditions causes the green part of the spectrum to appear at sunset. (will continue to look at this).

Abdur of 6K asked – If you had a solar powered light bulb and you were in a dark room, could you make a circuit with batteries and wires to make it work?

I asked my friends to look at this.

solar cell2

I liked the circuit that my friends made however ….just to let you know, the symbol for a solar cell is:

solar panel
Which one do you like, the one my friends used or the official one? You can vote by clicking on the Reply button below and giving me your answer.

The really testing part of this experiment is where will you put the switch to test that the solar cell, in the dark, is not making the bulb light up? Unsure – then