The body spends a good deal of energy forcing fluids to go up. Otherwise you’d have very big feet. But cerebrospinal fluid has no pump. Instead, after it’s created in the brain, it sinks downward where eventually it’s reabsorbed by your blood vessels (or, some posit, into the lymph system).
Thank you, gravity.
But what happens when there is no gravity? Wouldn’t excess fluid just stay in the brain and create all kind of problems? Interestingly, it seems we’re evolutionarily prepared for space travel (insert ancient astronaut theory here). In conditions of reduced gravity, our brain produces less fluid.
Additional effects of zero gravity include reports of space euphoria akin to Buddhist realization of the interconnectedness of the universe (“It comes through to you so powerfully that you’re the sensing element for Man,” said astronaut Rusty Schweikart).