Earth’s magnetic field is generated by a conducting fluid in its core. Explain why this is a theory.

It's not a theory, The magnetic pull is from the core of the earth and pulls you down. example: I can jump and fall, Why? because of the core of the earth of me going p and then down. Why do you think that space doesn't have gravity? It's because it doesn't have a core, There are no planets that pull you down enough like earth.