Motion sickness is a nausea caused by the body perceiving motion of its surroundings. The inner ear detects this motion and sense signals to the brain that the body is off balance. The brain then tries to balance the body, which is already in balance. The resulting hyper-correction causes nausea.
Common forms of motion sickness include:
- car sickness (false perception of body movement, resulting from car moving horizontally on the ground)
- air sickness (false perception of body movement, resulting from air vessel moving vertically in the air)
- sea sickness (false perception of body movement, resulting from sea vessel moving sinusoidally along the waves).
- vertigo (perception of body falling when body is still)
- gravity sickness (perception of body falling experienced by astronauts returning from weightlessness)
- decompression sickness (colloquially known as the bends) (perception of body flying away, experienced by deep sea divers relieved from heavy pressure)
It is not clear if motion sickness is genetic and evolutionists cannot explain its evolutionary advantage. Scientific tests are inconclusive whether animals without ears, such as fish and amphibians, suffer from motion sickness, despite being very sensitive to motion.