system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do people get incredibly nauseous reading or looking at a phone in a moving car but not on a moving train or airplane? what makes the car so unique?
gpt
Motion sickness comes from your sense of balance detecting movement, but your eyes insisting that nothing is moving (because you're focusing on an immobile object). If your brain can't reconcile receiving both "we're moving" and "we're not moving" signals at the same time then it freaks out, and for many people the brain's default reaction is "sensory input is all fucked up, we've been poisoned, expel everything". 

It's more obvious in cars because your sense of balance detects *changes* in motion, and cars speed up and slow down and change lanes all the time. People can also be affected on trains and planes as well, though, depending on the person.