Adrian Dening's Stars Over Somerset

    Gibbous Moon

    Monday 3rd to Sunday 9th May 2021

    It's almost the first anniversary of our Stars Over Somerset features, so I thought I would cover something a bit different this time!

    Around late afternoon last week, it was possible to see a Gibbous Moon in the east while it was still daylight and this reminded me of a couple of questions I am often asked on my astronomy courses - why is the sky blue and why can we only see stars at night?

    Firstly, the Sun produces "white light" which is actually made up by a combination of all the colours of the rainbow. All the different colours have different wavelengths - red light has a longer wavelength than blue. Because the shorter blue waves are more easily scattered by the tiny molecules of gas in our atmosphere, this makes the blue much more obvious to our eyes.

    A rainbow occurs when spherical droplets of rainwater, which are larger, do a more efficient job of scattering all the different light wavelengths and so you see all the colours.

    You can't see stars during the day simply because the light from the Sun is far more powerful than the faint light radiating from the stars.

    Did you spot the daytime Moon last week? That is because the Moon is relatively close to us and so the powerful sunlight was reflecting off its surface.


    Copyright Adrian Dening and Radio Ninesprings 2021

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