How was Mars' very noticeable change in apparent magnitude explained by the Geocentric Model?
Epicycles: These result in the distance of the planet to Earth changing quite substantially over its orbit (in the geocentric model) and resulting in changes in brightness. With the right choice of epicycles, you can account quite well for the changes in brightness, certainly better than Ptolemy would have been able to measure it.
The less scientifically bent may have assumed it was just &quot;in the nature of a planet&quot; to be brighter at opposition (the god of war, putting out his power making his planet brighter just as it comes to rule the night sky)