• Science in the Bath

    March 1st, 2012ImogenUncategorized

    Noble, gaseous air. Can’t live without it, can’t walk over it. If you’re not an Olympic swimmer then you probably spend most of your waking hours moving through air. Therefore, as well as serving a perfunctory functional purpose, a bath can be a bit of respite. A change of scene- or state, if you will. However, next time you have a bath, there’s no need to just sit there! Did you know that there is a whole host of micro-experiments you can try out, all from the comfort of your lavender scented water? Here are my top 3 favourites.

    1. Wave Interference

    Unless you are some sort of bath-drawing pro, there’s always some essential water mixing to be performed. This is a perfect opportunity to make something constructive. Or destructive, if you so wish. Make some waves travel down the bath then watch as they are reflected by the end of the bath and travel back on themselves. Where two peaks intersect you will get constructive interference and the wave will be bigger and splashier. If a peak and a trough meet then they will cancel each other out and you’ll get a ‘node’, or flatness.

    This is exactly how noise cancelling headphones work: the headphones listen to the ambient noise around you and play you a sound wave that is the exact opposite to the noise. The ambient sounds are cancelled out by the new wave and so you don’t hear it. This is why these devices work better for environments with constant noise levels- when you are on an aeroplane, for instance.

    2. Manual Airfoil

    Technically a waterfoil, but that sounds like a duck or something. If you make a cupped shape with your hand under the water and sweep it along your leg, you will feel a suction pulling your palm towards your lallies. This works best if you hold your hand as close as possible to your leg without actually touching it.

    Your hand is moving through the water like the wing of an aeroplane moves through the air. As the water moves over the curved back of your hand it has to travel faster than it does under your flat palm. The slow moving water under your hand creates a region of lower pressure, effectively sucking your hand in that direction. So really, planes don’t fly, they’re just suckers.

     self portrait

    3. Living on Jupiter

    Ok so you’ve made waves, swooshed your hands around, splashed lots of water on the floor, and maybe got a bit cleaner too. Before you turn into a complete prune it’s time to get out, but you’re just so relaxed and comfy. Instead of arising abruptly and possible getting a head rush and falling and hitting your head on the sink and having a brain haemorrhage (don’t say I didn’t warn you), try number 3 instead. Lie in your bath and take the plug out. As the water line drops further, you will start to feel strangely heavy. Your muscles have had a bit of a holiday, aided by the buoyancy of the water. Now the water’s gone there is no upthrust, only a force of approximately 1 Newton per Kilo pulling you towards the centre of the Earth. Now, don’t you feel like you’ve just come back from the moon?


    If you like to take some refreshment at bathtime then be sure to check out my other blog post Slurpy Bath Tea, it’s essential reading on the topic.

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