Given two identical satellites, which one has a lower orbital radius?

The correct choice reveals that the satellite at 4 Earth radii has a lower orbital radius compared to the one at 6.6 Earth radii. In orbital mechanics, the term "orbital radius" refers to the distance from the center of the Earth to the satellite.

When comparing the two satellites based on their given distances from the center of Earth, 4 Earth radii (which equals four times the Earth's radius) is a smaller distance than 6.6 Earth radii. The satellite at 6.6 Earth radii orbits at a greater distance from the center of Earth, thus has a higher orbital radius.

Understanding these distances is critical in determining the characteristics of orbits such as period and speed, where objects closer to the Earth have faster orbital speeds and shorter orbital periods compared to those further away. This fundamental principle of orbital mechanics makes it clear that the satellite at 4 Earth radii will indeed have a lower orbital radius compared to the one at 6.6 Earth radii.