Final answer:
Juan's professor corrected him by stating that scientific theories are well-substantiated explanations, not mere opinions or beliefs, and they represent reliable facts about the natural world.
Step-by-step explanation:
Juan's professor would likely correct him by saying “Theories are not the same thing as opinions or beliefs.” In scientific context, a theory is a well-substantiated explanation for phenomena, supported by a substantial body of evidence obtained through observation and experimentation. It is not merely a guess or hunch, but a reliable representation of the real world. Scientific theories, such as the theory of evolution, cell theory, or germ theory, are powerfully supported by extensive research and are considered factual despite the common misinterpretation of the term in everyday conversation. While they can be revised with new evidence, changes to established theories are uncommon and result from a rigorous process.