system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What makes one’s head spin when they are drunk?
gpt
Inside your ear is a canal filled with a liquid and lined with tiny hairs. When you move your head the liquid moves about and pushes the hairs around, like tree branches in the wind. Your brain can sense the movement of the hairs and this is a large part of how you sense "movement" of your body, it's also how you balance yourself.

Your brain also takes input from your eyes and compares it to the movement. When these inputs disagree, like when you're sitting a car (eyes say not moving) and getting carsick (ears are feeling the bumps and twists and turns) the outcome is often nausea. This is because your brain assumes this disagreement is causes by poisoning and it's trying to eliminate the poison.

In the case of when you're drunk, the alcohol changes the way the fluid in your ears behaves (it becomes "thinner" like water vs maple syrup) which basically makes the hairs much more sensitive. To basically even the slightest movement if your head sends a HUGE MOVEMENT signal to the brain. So your brain is desperately trying to balance your body as if you're flying about the room, although you obviously aren't. And both efforts are in disagreement with what your eyes are seeing. So, basically, you're a spinny, off-balance mess.