Short answers, pulled from the story.
Physics is the scientific study of matter, its fundamental constituents, and its motion and behavior through space and time, together with the related ideas of energy and force. It is one of the most fundamental scientific disciplines, and a scientist who specializes in it is called a physicist.
Physics is called the fundamental science because all branches of natural science, including chemistry, astronomy, geology, and biology, are constrained by the laws of physics. It aims to describe the phenomena of nature in terms of simpler phenomena and to connect observable things to their root causes.
Physics became a separate science during the Scientific Revolution of the 17th century, when early modern Europeans used experimental and quantitative methods to discover what are now considered the laws of physics. Before that, for much of the past two millennia, physics, chemistry, biology, and parts of mathematics were all part of natural philosophy.
Aristotle, who lived from 384 to 322 BCE, wrote a substantial treatise titled Physics in the 4th century BC, and his approach remained influential for about two millennia. He explained motion and gravity using the theory of four elements, air, fire, water, and earth, though his approach is entirely superseded today.
In July 2012, CERN, the European laboratory for particle physics, announced the detection of a particle consistent with the Higgs boson. With that discovery, all fundamental particles predicted by the Standard Model, and no others, appear to exist.
Classical physics includes branches well developed before the 20th century, such as classical mechanics, thermodynamics, and electromagnetism, and it accurately describes systems larger than the atomic scale moving much slower than light. Modern physics, founded on quantum mechanics and relativity, describes matter and energy under extreme conditions or on very large or very small scales.