Which is a “big idea” of physical science? motion cannot be altered by forces. most of the mass of the earth consists of solid matter. the universe is getting smaller. energy can be transferred but it can never be destroyed.

some think that theories become laws, but theories and laws have separate and distinct roles in the scientific method. a law is a description of an observed phenomenon in the natural world that hold true every time it is tested. it doesn't explain why something is true; it just states that it is true.

d. air pressure decreases as altitude increases.