Final answer:
Uranus does not emit much internal heat, leading to a cooler atmosphere, while Neptune, though further from the Sun, has some internal heat contributing to a relatively warmer atmosphere, demonstrating the complexity of planetary environments.
Step-by-step explanation:
The differences in internal heat between Uranus and Neptune are intriguing and suggest complex dynamics at play. Uranus is notably colder and doesn't emit a measurable amount of internal heat, resulting in an atmosphere that is cooler than might be expected for a planet of its size. Neptune, despite being further from the Sun, emits some internal heat, which contributes to its warmer atmospheric temperature. This heat may originate from the planet's core or radioactive decay, though the exact sources are not well understood. The surprising fact that Uranus and Neptune have similar atmospheric temperatures, regardless of Neptune's additional internal heat source, underscores the complexity of planetary atmospheres and the mechanisms that drive their circulation and temperature distributions.