You are given a sentence and your task is to generate another sentence that supports the given input.

All objects moving toward the earth do so because of two distinctly different forces, one pushing the object and one pulling the object.
Objects on earth have two forces acting on them at all times.

For example, the sun transfers heat to the earth through radiation.
Heat energy from the sun is transferred to earth primarily by radiation.

Examples of primary pollutants are exhaust fumes (gas) from cars, soot from smoke, dust storms and ash from volcanic eruptions (as seen in the picture on the left).

Ash that enters the air naturally as a result of a volcano eruption is classified as a primary pollutant.