Alternate theory: the material scooped and dumped to cover the pyramid has different thermal characteristics than the pre-existing soil surrounding the site. That is, it's not the pyramid that stands out, it's the covering.
I don't know, just formulating another hypothesis for the fun of it.
alternate alternate theory: the ancient pyramids, created and dropped there by aliens, are superconducting - they cool the ground above them in a characteristic square gradient.
I don't know, just formulating another hypothesis for the fun of it.