If someone were to ask “What do physicists do?”, a good answer might be: “Physicists discover and create knowledge about the universe.” We label the category "Discovering and Creating Knowledge" as item number “∞” because it is a never-ending pursuit. In a 1945 report to the president of the United States*, Vannevar Bush called science “the endless frontier”; the report then laid the foundation for broad public support of scientific investigation. Centuries of evidence support the idea that knowledge pursued for its own sake is hugely valuable to humanity, because this knowledge inevitably becomes a resource for meeting our needs and addressing our practical concerns. Fundamental research by physicists is part of the larger spectrum of scientific investigation across many disciplines. By posing questions that are as deep and fundamental as the human mind can conceive, physics creates a foundation for all of science. It also gives humanity a better sense of its place in the universe. Fortunately, physics as a fundamental pursuit for its own sake need not conflict with physics as a base for applications. One might see these as two sides of the same coin, the body of which consists of common methods of analysis, computing and experimentation. Physics often progresses through metaphorical thinking and real-world experience can trigger insights into deep questions. Conversely, fundamental theories demand new types of experiments and these, in turn, push the limits of our technologies in ways that inevitably translate into practical use.
*See https://www.nsf.gov/od/lpa/nsf50/vbush1945.htm