Why do we have headache and nausea while we go on a bus, car, boat, flights etc.?

Our brain has two types of motion. Of that, one is running and walking. Because when we move, our brain also moves. Same goes for running. But while riding on a car, bus, planes on a long travel, our body is relaxed. So our eyes and ears moves and hence our brain becomes confused. Therefore we feel nauseated or headache. Many signals that reach our brain from our body parts and overtime, the signals are continuous and our brain gets used to it while traveling. After that, it turns to normal stage.