Why is the sky blue? And other surprisingly difficult questions.

If you have ever encountered a magnet and thought about it for a few minutes you will have undoubtedly wondered how the damn things work. Why, when I bring my souvenir photo of Yosemite National Park, encased in plastic, near a fridge does it decide to stick? How does it know to move in that direction? What information is communicated by a seemingly inert piece of rock and metal that should make them move towards each other? And why sometimes do they want to move apart?

Before we answer that, here’s another question: why is the sky blue? Easy, you might say. Rayleigh scattering. Next question. I read that on Wikipedia years ago.

Whilst technically correct, the two-word answer “Rayleigh scattering” does omit a few minor details. That being said, it’s a cool sounding answer which, last time I checked, is what physics is largely all about. However, the persistent amongst you might follow up with “well, how does Rayleigh Scattering work?” Another good question.

There are two important factors that make the sky blue. The sunlight and air. Sunlight comprises lots of different colours of light which, combined together, give the white colour we perceive when we look at the sun (disclaimer: don’t look at the sun). We’re able to see these colours when we hold a prism up to sunlight or there’s a…