Final answer:
Planets further from Earth are not inherently brighter. Their visibility is influenced by the amount of sunlight they reflect, their distance from the Sun, and their surface and atmospheric properties.
Step-by-step explanation:
The brightness of planets as observed from Earth depends on several factors, including how much sunlight they receive and reflect, their distances from the Sun, and the properties of their atmospheres. Planets that are farther from Earth are not necessarily brighter; in fact, according to the inverse-square law, the light a planet receives from the Sun decreases with the square of the distance from the Sun. For example, Jupiter's moons receive only about (1/5.2)² = approximately 0.037 times (or 3.7%) the sunlight that Earth receives, and Saturn's moons get about (1/9.5)² = approximately 0.011 times (or 1.1%). These bodies are seen from Earth primarily because they reflect sunlight, and their apparent brightness is not only a matter of their distance from the Sun but also factors such as the albedo (reflectiveness) of their surfaces and atmospheres. Hence, a planet's brightness as seen from Earth is not solely determined by its distance from us or the Sun but is a more complex interplay of multiple factors.