12.4 Universal Forces

If you could travel to a distant planet in another galaxy, what would you expect to find? The scene shown in Figure 18 is one possibility. Although this world looks so different from the one you know, some things on this distant planet would be familiar—the forces.

Observations of planets, stars, and galaxies strongly suggest four different forces exist throughout the universe. These forces are known as universal forces. The four universal forces are the electromagnetic, strong nuclear, weak nuclear, and gravitational. All the universal forces act over a distance between particles of matter, which means that the particles need not be in contact in order to affect one another. In addition, each of these forces is affected by the distance between the particles of matter.

Figure 18 An artist's depiction of a planet's surface shows a world very different from Earth. Regardless of location, however, certain universal forces are present.

Table of Contents