Have you ever wondered why don’t we see stars and planets in the daytime on earth? One day, a curious kid was asking question after seeing Jupiter in the early hours that where this Jupiter is gone now, why we can’t see it. I was enthralled and at the same time happy to see such curiosity. This is what differentiate us from animals.
Then I thought, is this question valid in space particularly if we are standing on the moon? It becomes more interesting when moon come into the picture. So this question can be divided into two parts.
- Why we can’t see stars in daytime on earth?
- Is this phenomenon only observable on earth, what about the moon?
Firstly, lets understand the reason of this behaviour on earth. As we know, earth has atmosphere with dust particles and other particles which scatter the sun light all over the earth atmosphere and create a blue colour in the sky which has more brightness than stars in the background. But some time we can see moon in the day time, it is because moon is a very bright object and its brightness is still more than earth’s blueish sky.
For explaining the question 2, lets imagine if you are standing on the moon. Do you think the same behaviour will apply on moon? We will find shortly if you are right or wrong.
We should notice that Moon doesn’t have a atmosphere and no particles to scatter light. This results in Sun and stars visible in day time. You can see stars both in day (Figure 1) and night (Figure 2) on the moon. It is really interesting behaviour which is difficult to understand at first but if you understand how light behave, things become easy. We will cover the light/optics in details in coming posts. So, it is the result of light scattering on earth and absence of this process on moon that gives us the answer.
Please comment what do you think of this behaviour and do you know any other place in space which has more strange behaviour than earth and moon.