Final answer:
Motion sickness occurs when there is a conflict between the motion signals received by the visual and vestibular systems. Our bodies have adapted to the Earth's motion over time, which is why we do not experience motion sickness from its movement around the sun.
Step-by-step explanation:
Motion sickness occurs when there is a conflict between the motion signals received by the visual and vestibular systems in our body. It is not solely related to motion in vehicles, as it can also occur in other situations where there is a disconnect between what our eyes see and what our inner ear senses. When we are on Earth, our bodies have adapted to the Earth's motion over time, which is why we do not experience motion sickness due to its movement around the sun. The Earth's motion is relatively slow and constant, so our body adjusts and perceives it as the norm.