Final answer:
Large bodies cool more slowly and retain internal heat due to their size and heat capacity. For example, giant planets can still retain primordial heat from their formation and cool more slowly than smaller objects.
Step-by-step explanation:
The reason behind the phenomenon of large bodies cooling more slowly and retaining internal heat is primarily due to their size and mass. Larger bodies have a higher heat capacity, which allows them to retain internal heat for longer periods of time. For example, giant planets like Jupiter were heated during their formation by the collapse of surrounding material onto their cores, and they can still retain some of this primordial heat. Additionally, the larger the planet or moon, the more slowly it cools, similar to a hot baked potato cooling more slowly than a small one.