Final answer:
Scientists change their scientific theories when new evidence conflicts with old ideas, in order to accommodate the new evidence and improve our understanding of the natural world.
Step-by-step explanation:
When new evidence conflicts with old ideas, scientists change their scientific theories. They do not change experimental results or experimental variables because these are based on the specific experiments conducted. Similarly, they do not change scientific methods because these are the processes used to conduct experiments and gather evidence.
Scientists change their theories because a theory is a well-substantiated explanation of the natural world, but it is not set in stone. Theories must stand up to scientific testing, and when new evidence arises that contradicts the current theory, scientists revise or discard the theory to accommodate the new evidence.
For example, the theory of evolution is continuously updated as new fossil evidence, genetic studies, and other scientific discoveries emerge. Scientists modify the theory to incorporate new findings and improve our understanding of how species change over time.