Dizziness most commonly occurs when a person who has been moving around with speed stops suddenly. The sensitive liquid in the inner ear, which mainly controls balance, continues to move around for a time after the body has stopped. So the surroundings appear to be still in motion. However, it takes only a few seconds for the fluid and balance to settle.
This sensation, which is also called vertigo, may also occur to someone looking down from a height or on board ship. Here the cause is probably not so much physical as a nervous reaction which affects the fluid in the inner ear.