Final answer:
The friction effect in the Earth's atmosphere is greatest in the troposphere, which is the lowest layer, due to the high air density and weather phenomena present in this layer.
Step-by-step explanation:
The friction effect is greatest in the troposphere, which is the lowest layer of the Earth's atmosphere. In this layer, the air density is the highest, which increases the effect of friction. For example, a spacecraft re-entering the Earth's atmosphere, such as the Apollo mission reentry capsule depicted in an artist's impression, experiences significant friction as it moves rapidly through the troposphere. This compression and heating of the air not only slow down the spacecraft but also convert its kinetic energy into heat.
The same layer, extending up to about 12 km high, is also where atmospheric wind and weather occur, contributing further to the friction experienced by objects moving through this area.
Given that the troposphere contains the densest part of the Earth's atmosphere and all weather phenomena, it is the area where frictional forces on moving objects are the most significant. This explains why satellites, upon descending from orbits higher in the atmosphere, where the air is much thinner, eventually encounter increased friction as they reach the troposphere, leading to their gradual deceleration and eventual re-entry or disintegration.