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Published on Jul 23, 2013
When the Cheltenham Science Festival asked if I had any experiments I'd like to do outside I jumped at the chance, with the caveat that this wasn't the type of experiment you see in a science show where you know it's going to work. This is more like an experiment you might see in a lab where you don't know what the outcome will be!
Thomas Young performed an incredible experiment in 1801. He shone sunlight though two holes and found that the beams of light coming out the other side were interacting with each other. This shouldn't happen because light is made of lots of little particles called photons (it's these particles that hit the back of our eyes and enable us to see). We know that these particles don't interact with each other, so how can two beams made up of these particles interact?
That got me thinking, is there some other kind of wave I could use to show this kind of interference? Then it hit me, I could use sound! So instead of two holes or two slits, I'd use two speakers. And instead of a tank of water I'd use an audience of people!