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Every eye has a hole in its vision, and your brain paints over it Every one of your eyes has a hole in its vision, about ten Moons wide, and you have never seen it. It is where the optic nerve leaves the retina, a patch with… Mind3 min read3 Oct Earth is closest to the Sun in January. So why is that winter? Summer can't be caused by being closer to the Sun: Earth makes its closest pass around 3 January and is farthest around 4 July. The distance changes by only… Earth & Space4 min read29 Sep 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 read28 Sep How chameleons change colour: they stretch a mirror made of crystals A chameleon doesn't change colour by mixing pigments. Under its skin sit cells packed with tiny guanine crystals, arranged in a lattice that works like a… Biology4 min read28 Sep Why one more candle lights a dark room but vanishes in a bright one Add one candle to a dark room and everything changes. Add one to a room with a hundred and nobody notices. Your senses don't measure differences in amounts… Mind5 min read27 Sep 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 read27 Sep How computers fake grey using only black and white dots Old Mac screens, cheap printers and some modern games can only show two colours: black and white. Yet they still draw soft shadows and smooth skies. The trick… Computing5 min read26 Sep 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 read26 Sep Why traffic jams appear out of nowhere Sometimes a motorway grinds to a halt and then clears up with no crash, roadworks or merge in sight. That's a phantom traffic jam, and it starts with one… Engineering4 min read26 Sep