In 1897, Joseph Thomson discovered that atoms contained electrons. He proposed a change in the atomic theory of that time, and the theory was modified because of his discovery. Since Thomson’s discovery, atomic theory has been further modified. What is the best explanation for why scientific theories are modified?
Theories more than ten years old are usually out of date.
Scientists want to prove that the work of other scientists is wrong.
New evidence that supports a revision prompts scientists to modify earlier theories.
So much information is available today that it is harder to focus research and disprove theories.