Physics

6 breaks

Forces, light, time and the odd behaviour of the very small.

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Why a small ball on a big ball shoots up nine times higher: the two-step bounce Drop a tennis ball on top of a basketball and the small ball can fly far above the height it fell from. Nothing is cheating: it is a two-step bounce. The floor… Physics4 min read Why the sky is blue and the sunset red: Rayleigh scattering and the length of the air The sky is blue and the sunset is red, yet the sunlight is the same. Air scatters short blue waves about four times more strongly than long red ones, a… Physics4 min read Why light bends in water: the lifeguard's shortest-time path (Fermat's principle) A lifeguard runs faster than she swims, so the quickest route to a swimmer is not a straight line. It bends at the shoreline, and the bend follows one tidy… Physics4 min read Why soap bubbles swirl with colour, then turn black just before they pop Soap has no dye, yet bubbles shimmer with magenta, gold and green. The colour comes from thickness: light bounces off both the front and the back of the film… Physics5 min read Why the sky is blue and sunsets are red: it's the same light The blue sky and the red sunset are the same effect, seen from two angles. Air molecules scatter short, blue wavelengths far more than long, red ones: about… Physics4 min read Why a rainbow is always a circle 42° around your shadow Every rainbow is part of a circle centred on the shadow of your head, with its red edge about 42° away. That number comes from inside a single raindrop… Physics5 min read