Dizziness and Office Chairs

22 October 2006

It's absolutely fascinating to hear about how our ears detect and process sound, but our ears also have another really important function, which is helping us to balance and know which way's up. So to have a look at how balance works, we're now off to Hunsbury Park Primary School in Northamptonshire, where Derek and Dave are with Sim, Alex and a rather innocent looking office chair…

To do this experiment, you will need:

Swivel office chair A wide open space with nowhere to hit your head or hurt yourself One person to sit on the chair and another person to do the spinning!

How to do the experiment:

1 - Put the chair in a safe place away from anywhere you might hurt yourself.

2 - Sit on the chair with your ear on your shoulder. Your head should be bent right over.

3 - Stick your legs out and prepare to be spun round and round by your friend. You don't need to go too quickly - just keep going for about 30 seconds.

4 - Stop the chair, stand up immediately and slowly try to walk forwards. What happens?

What's going on?

You should find that you either fall forwards or backwards. This is different to when you spin yourself round on a chair with your head upright, when you tend to wobble off sideways.

The reason you feel dizzy at all is due to fluid moving around in three tubes in your inner ear. These are called the semicircular canals. In normal life (ie: when you're not spinning around on a chair) these help your brain work out which way up your head is pointing and moving. When you move your head, the liquid in the tubes stays still and your head moves round it. Your brain can measure how far it's moved past the liquid and thus how far forwards, backwards, up, down or side-to-side your head has turned.

So why do you feel dizzy? If you spin round and round for a long time, such as on an office chair, the fluid starts moving around within the tubes rather than staying still. When you stop spinning, the fluid carries on moving, making you feel like you're still spinning on the chair. The conflicting information confuses your brain and makes you feel dizzy.

But in our experiment, we found that our unsuspecting victims always fell either forwards or backwards. This is all due to the fact the semicircular canals are made of three different tubes in different orientations: one of them is going round your head in the same orientation as a halo; one goes round your head making a loop from ear to ear; and the third goes round as if through your nose and chin and back round the back of your head. This last tube helps detect how far your head is moving backwards and forwards. However, if you turn your head on its side, that tube is now in the position the first tube would normally be in. Spinning the chair makes the fluid swirl in that tube. When you stand upright, the tube with the spinning fluid is now in its normal position, and makes you feel as if you're spinning forwards.

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