system
Given the following post, respond as if you're commenting on Reddit:
human
How do we differentiate the Earth's magnetic field weakening due to a pending reversal instead of a complete shutdown like is suspected to have happened to Mars?

From my understanding, it is suspected that Mars once had a magnetic field like ours, but because of its smaller size, the core eventually cooled and stopped its movement, causing the field to "turn off".

How do we know the current weakening of Earth's field is not a similar process, but instead just a reversal?
gpt
Loss of magnetic field is a gradual process which results from the cooling and solidification of the liquid outer core. We know from seismic studies we are nowhere near that point - it is still large and molten.  Turning off of the magnetic field is *not* a rapid on-off process.

The reason we're so far from it happening on Earth is the much bigger volume of our planet in comparison to Mars, hence the cores are bigger, better insulated, and the much higher volume to surface area ratio which means that cooling is less quick.