What is the “geodynamo”, and what is believed to be the cause of it?

Our planet's magnetic field is believed to be generated deep down in the Earth's core. ... This flow of liquid iron generates electric currents, which in turn produce magnetic fields.

Ithink that its like 15 mph.

Essential for a scientist to do for credibility

evidence and logical support is essential for a scientist to do in order to maintain credibility. this is because no one can believe without any logic and without any evidence.hence a scientist can maintain credibility by proving himself and by answering logically so experiments prove very beneficial. logical hypothesis give conclusion which is acceptable. therefore, there are two main factors to maintain credibility by a scientist is evidence and logical support.