The Surfing Scientist › Tricks

DIY Easter jumping beans

Turn your Easter egg wrapper into a colourful critter that jitters like a Mexican jumping bean. Ordinary aluminium foil works too, but will morph into something more Ziggy Stardust than Speedy Gonzales.

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Be an impeccably well-behaved human being for 12 whole months so that the Easter Bunny delivers you an Easter egg. Alternatively, buy an Easter egg. Unwrap your Easter egg and eat the chocolate ovum. Use the back of your fingernail to smooth out the crinkles in the foil. The precise dimensions of your foil aren't super-critical but you want a piece about seven centimetres by 12 centimetres. Roll the foil rectangle around your finger or a thick marker pen or a dowel to make a seven-centimetre-long tube. The tube should be just wide enough for your marble to fit inside. Pinch the ends of the tube firmly shut trapping the marble inside to form an aluminium 'cocoon'. Pop your aluminium cocoon into a small rectangular box. At this stage, it just looks like a crumpled up piece of discarded foil but an amazing metamorphosis is about to unfold right before your eyes. Shake the box side to side so that the bean collides with the walls of the container repeatedly. Every impact does a little more internal 'panel-beating' as the marble pounds the foil from the inside. After sufficient crashing and bashing and smashing, a gorgeous little capsule with beautiful, smooth hemispherical ends has formed. Your jumping bean's transformation is complete. Lay your bean on an inclined surface and it will flip-flop its way downhill in a delightfully surprising way. The heavy marble rolls to the bottom of the inside of the capsule, which makes the capsule flip over, which allows the marble to roll a bit further downhill until it hits the bottom again, which makes the capsule flip over once more and the cycle repeats over and over again.

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What's going on?

This classic little DIY toy is made possible by the twin marvels of 'alfoil' and marbles. Both are surprisingly recent innovations and each is full of surprises.

Aluminium foil really is one of the wonders of the modern world but is now so cheap and ubiquitous that its remarkable physical and chemical properties are often overlooked. Most people have no idea, for example, that the aluminium in their 'alfoil' is made of is actually a violently reactive metal used to propel fireworks into the night sky. Powdered aluminium is so explosive, in fact, that it was NASA's fuel of choice for the Space Shuttle's solid booster rockets. Kerpow!

Don't panic now. A roll of aluminium foil won't blow your kitchen to smithereens because it is coated with a thin layer of clear aluminium oxide (Al 2 O 3 ) which forms naturally the instant 'alfoil' is made. The aluminium reacts immediately with the oxygen in air, but the veneer formed is so thin that it is invisible and yet thick enough to prevent further reactions between the aluminium atoms in the foil and the oxygen atoms in the air or water.

Aluminium is the most common metal in the Earth's crust but, unlike gold, pure aluminium is nowhere to be found in nature. All of the aluminium on the Earth's surface occurs as silicates or oxides. Corundum is aluminium oxide that is so hard we use it to make sandpaper.

Persuading aluminium atoms to abandon their silicon or oxygen companions is so difficult that pure aluminium was once more expensive than pure gold. Legend has it Napoleon Bonaparte (1769 - 1821) served his most honoured guests' food on aluminium plates while the lowlife had to make do with boring old gold. The Washington Monument is capped with a pyramid-shaped lightning rod cast in pure aluminium by Frishmuth's Foundry and displayed at New York's Tiffany & Co before the placement ceremony in 1884.

Danish scientist Hans Christian Ørsted (1777 - 1851) is credited with 'discovering' pure aluminium in 1825. That's just five years after he stumbled onto the fact that electricity and magnetism are not two separate and independent forces but actually two sides of the coin making him one of the biggest overachievers you've probably never heard of. Pure aluminium melts at 660°C, boils at 2519°C (yes, it can boil), and is now used to make a bazillion things including aeroplanes, window frames, soft drink cans and that amazing foil you can make jumping beans with.

Cheap, mass-produced marbles are a fairly recent innovation too. The ancient Egyptians, Aztecs, Greeks and Romans apparently all enjoyed flicking small round objects at other small round objects but they used naturally occurring things like acorns or nuts.

Glassblowing was invented in the 1st century BC but the first mass-produced marbles were made of clay. In 1890, Samuel C. Dyke patented a machine that rounded precut slugs of clay. His clay marbles quickly became so common that kids started calling them "commies."

These days, perfectly spherical glass and ceramic marbles can be found in just about every kids' toy box. Since 1932, the World Marble Championship is held on Good Friday, every year, in the car park of a pub in the town of Crawley, England called The Greyhound. The version of marbles played is 'Ring Taw' or 'Ringers' and you can find all the fantastically convoluted rules of that game.

Last year's winners were from Germany. I am waiting with baited breath to see this year's champion will be and I hope they remember to make a Mexican jumping bean with their winning 'tolley' when the Easter Bunny pops by the following Sunday.

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