Newton's First Law, the... Law of Inertia, refers only to bodies that are subject to no external forces. It is tempting to say that Newton postulates that such bodies "continue in the same state of motion," but such... would miss the revolutionary aspect... the First Law specifies exactly what counts as "the same state of motion." For Aristotle... a piece of aether in uniform circular motion about [earth,] the center of the universe is always in "the same state of motion," and so there would be no reason to seek out external causes... In Aristotle's physics, external causes are responsible for unnatural motion, such as a rock moving upward instead of down. So for Aristotle, the falling of a stone... requires no external cause, and the continued rotation of a sphere of fixed stars requires no external cause: this what these sorts of matter do by nature.
American philosopher of science (born 1958)
The Theory of Relativity is presented, first and foremost, as a theory of the geometry of space-time. Special Relativity is explained in enough detail to solve specific problems about the behavior of clocks and rigid objects in a relativistic world. General Relativity is presented less rigorously. My aim... make the conceptual foundations of these theories absolutely clear...
[T]he science of thermodynamics... initially aimed at providing a precise account of how heat spreads through an object and from one object to another. But we can discover... detailed equations governing heat flow and still not have an account of what heat is. ...It is a characteristic of contemporary physics education that much more time is spent learning how to solve the equation and get a practical answer... than in... the nature of heat, or the nature of space and time, or the nature of matter. Physics students... fascinated by these foundational questions can find themselves frustrated by... classes that refuse to address them. This volume is dedicated to them as much as it is to philosophers...
[T]he most general question we can ask about matter is what sort of thing it is. ...[W]e might hold that matter is made of point-like particles, or of fields, or of one-dimensional strings, or of some combination of these, or of something else altogether. Given any of these ...there are further, more specific questions ...We will be concerned with the most general questions, rather than the more specific ones.
[T]he experimental verification of Bell's inequality constitutes the most significant event of the last half-century. ...[O]ur basic picture of space, time, and physical reality must change. These results, and the mysteries they engender, should be the common property of all who contemplate with wonder the universe we inhabit.
[P]roblems about the fundamental consistency of our two fundamental physical theories may appear. ...It arises from the remarkable results derived by John Stewart Bell in 1964 ...[C]ertain pairs of particles that are governed by quantum laws... appear to remain "connected" or "in communication" no matter how distantly separated... [T]he connection exists even when the observations carried out occupy positions... which cannot be connected by light rays. The particles communicate faster than light.
The Theory of Relativity has overthrown classical presumptions about the structure of space and time. The quantum theory has provided us with intimations of a new conception of physical reality. Classical notions of causality, of actuality, and of the role of the observer... have all come under attack.
Fundamental conceptual changes occur, but they are always modifications of a previously existing structure. ...[T]actical adjustments are made in order to render the whole consistent. The ad hoc nature of this procedure may leave us with lingering doubts as to whether the whole really is consistent.