You don’t need a planet-sized brain to understand that a balloon plus a sharp pointy object equals a big bang. But when you up the ante, the sums don’t always seem to add up, as this entertaining experiment shows…
You will need
- A packet of drawing pins
- An inflated balloon (have one on standby, just in case)
- Scatter a handful of drawing pins evenly over a flat surface, all pointing upwards.
- Push an inflated balloon down onto the bed of pins.
- Be amazed as it doesn’t pop!
What’s going on?
We intuitively think that more spikes mean more damage, but this isn’t true. One drawing pin would burst a balloon easily, but when the balloon is pressed down over many small points, pressure is spread between each one, so you need to push down much harder before any one point has the force to pierce the taut rubber. This principle also explains how circus performers can lie on a bed of nails.
You can even test the theory by walking on eggs without them cracking! Place two large boxes of eggs on the floor, making sure all the eggs are uncracked, about the same size and with their ‘pointy’ ends facing down. Put down some plastic sheeting if you’re worried about making a mess. Take off your shoes and socks and, with someone to help you balance, ease your weight down onto both sets of eggs, spreading your weight as evenly as possible. The lighter you are, the easier it will be, so perhaps this is one just for the kids…
- DIY Science: how to get electricity from coins
- DIY Science: how to create a bottled cloud
- DIY Science: how to make elephant toothpaste
Stuart is a science and medical writer, presenter and educator. He is a trained medical doctor and qualified teacher, and a food scientist for the BBC’s Inside the Factory.