The theory that the planets formed from a rotating cloud of gas and dust around the young Sun is called what?

• A. Plate Tectonics
• B. The Big Bang Theory
• C. The Nebular Hypothesis
• D. Solar Nebula Theory

Answer: (C)

This question tests how planets are thought to form from a rotating cloud around a young Sun. The Nebular Hypothesis explains that a solar nebula—a spinning cloud of gas and dust—collapsed under gravity. As it collapsed, it flattened into a disk, with the Sun forming at the center and material in the surrounding disk clumping together to become planets. Over time, dust and small bodies stuck together, grown into planetesimals, and then into full-fledged planets. This model also accounts for why planets orbit in roughly the same direction and lie near the same plane.

The other options don’t fit this idea: plate tectonics describes the movement of Earth's lithosphere, not the formation of the solar system; the Big Bang Theory explains the origin of the universe as a whole rather than the formation of our solar system; the term Solar Nebula Theory is related but the traditional, widely taught name for this planetary-formation idea is the Nebular Hypothesis.