Have you ever had that feeling of being barely able to stay on your feet after getting off a spinning fairground ride? Feeling dizzy after experiencing an intense spinning motion is a common sensation, but what causes it? In fact, both an understanding of physics and biology are needed to explain dizziness. One of the fundamental laws of physics states that a body will remain at rest unless an external force is applied to it, and will remain in motion unless it is forced to halt. This resistance to any change to a body’s state of motion is called inertia. This, together with a complex system inside your inner ear, is the reason for dizziness.

Vestibular system

In addition to hearing, your ears also give you a sense of balance. Inside your inner ear are three semi-circular canals, set at right angles to each other. They work together to orientate you correctly in 3D space. Every time your head moves, the flow of liquid within them is picked up by sensory hair cells. These send nerve signals to the brain, which then works out whether the body is upright or lying down and whether it is standing still or in motion—and if so, which direction that movement is. The brain then sends instructions to the muscles to adjust the position of the body if necessary. This is called the vestibular system.

Signals to the brain

The semi-circular canals are tubes filled with liquid, called endolymph. Inside the tubes are tiny hairs, contained inside a cap called a cupula. Each hair is connected to a nerve cell. When the head moves, the liquid sloshes around, causing the the cupula to bend and the hairs inside to sway. As they do so, the nerve cells connected to them send signals to the brain, telling it about that movement.

​​​​​​​When we spin around, the liquid in our semi-circular canals starts spinning around, too. This gives us the sensation of spinning. When we stop spinning, however, the liquid in our ears carries on moving (because of inertia, everything, including liquids, keeps moving until something causes it to stop). Signals of movement are still being transmitted to the brain. You sense that you are moving, but you are not. This feeling is called dizziness. Eventually, the liquid slows down and you return to normal.

Overcoming dizziness

Ballet dancers and skaters are able to perform breathtaking spins without showing even the slightest signs of dizziness. So how do they do it? Dancers keep their eyes fixed on a single point, then whip their heads around rapidly when their necks cannot turn any more. So while the rest of their body keeps spinning, their eyes trick their brain into thinking that they are standing still.

Ice skaters spin much faster than dancers, so it is impossible for them to perform this trick. Instead they fix their eyes on a certain point at the end of each spin. This means the view only spins around one axis—from side to side. The skaters still feel dizzy, but with long hours of practice they can overcome it.