We learn in high school science classes that scientific progress comes brick-by-brick. We learn that scientists form hypotheses, devise experiments to test them, collect data, form conclusions, wash-rinse-repeat. Their conclusions are bricks that get added to the wall of science, a wall that gets built higher and higher over time with each generation of scientists.
That is not how science really advances, argued Thomas Kuhn The Structure of Scientific Revolutions (1962). Using historical examples, he showed that the model I just laid out describes how science works sometimes, for some periods. Yet the real rhythm of science, Kuhn said, is different: on occasion results come along that do not fit into the brick wall that everyone else has built. These anomalies do not fit the reigning paradigm (a word Kuhn popularized), and so they get set aside.