Book contents
- Frontmatter
- Contents
- Preface to the second edition
- Preface to the first edition
- 1 Preliminaries
- 2 McTaggart on time's unreality
- 3 The Block universe
- 4 Asymmetries within time
- 5 Tensed time
- 6 Dynamic time
- 7 Time and consciousness
- 8 Time travel
- 9 Conceptions of void
- 10 Space: the classical debate
- 11 Absolute motion
- 12 Motion in spacetime
- 13 Curved space
- 14 Tangible space
- 15 Spatial anti-realism
- 16 Zeno and the continuum I
- 17 Zeno and the continuum II
- 18 Special relativity
- 19 Relativity and reality
- 20 General relativity
- 21 Spacetime metaphysics
- 22 Strings
- Notes
- Glossary
- Web resources
- Bibliography
- Index
12 - Motion in spacetime
- Frontmatter
- Contents
- Preface to the second edition
- Preface to the first edition
- 1 Preliminaries
- 2 McTaggart on time's unreality
- 3 The Block universe
- 4 Asymmetries within time
- 5 Tensed time
- 6 Dynamic time
- 7 Time and consciousness
- 8 Time travel
- 9 Conceptions of void
- 10 Space: the classical debate
- 11 Absolute motion
- 12 Motion in spacetime
- 13 Curved space
- 14 Tangible space
- 15 Spatial anti-realism
- 16 Zeno and the continuum I
- 17 Zeno and the continuum II
- 18 Special relativity
- 19 Relativity and reality
- 20 General relativity
- 21 Spacetime metaphysics
- 22 Strings
- Notes
- Glossary
- Web resources
- Bibliography
- Index
Summary
Newtonian spacetime
Newton may be ahead on points, but his account is still blighted by a serious problem. To account for inertial effects Newton recognized absolute acceleration; having recognized absolute acceleration he also had to recognize absolute velocity (change of which constitutes absolute accelera tion), despite the fact that absolute velocity has no physical consequences. In positing absolute velocities, Newtonians expose them selves to the claim that their theory gives rise to empirically indistinguishable states of affairs. Which of the infinite number of possible universes that can be generated by Leibniz's kinematic shift do we inhabit? Which corresponds to the actual world? If Newton's theory is correct, there is no empirical test that could be performed that would reveal the answer.
Since the work of Cartan and others in the 1920s and 1930s, Newtonians have come to see a better way to formulate Newtonian theory, a way that eradicates absolute velocities but retains (in a way) absolute accelerations. The improved formulation involves two steps: first, Newton's theory is formulated in terms of “spacetime”; then this Newtonian spacetime is discarded in favour of neo-Newtonian (or Galilean) spacetime.
Before we can appreciate the difference between these two, we need to know what a spacetime is. We can then consider some of the ways that spacetimes can differ. Before proceeding there are some misconceptions to dispel. On hearing the word “spacetime” one naturally thinks of Einstein and relativity theory.
- Type
- Chapter
- Information
- Time and Space , pp. 194 - 212Publisher: Acumen PublishingPrint publication year: 2010