Issues in the Physics and Philosophy of Space and Time
Spring 1997

1. What is the relationship between mathematical or theoretical models and experiential reality? [Zeno et al. see Q13 below]

2.Empiricism is the view that our knowledge of the physical world is based* on experience. But, "based on" has meant [1] has its source in, or [2] is validated by. Pure geometries are empirical in the first sense but not in the second. [Cf Q 14 below]

3.Does the universe have a temporal origin?

4.Are space and time [or - in relativity physics, spacetime] "realities" independent of physical objects, processes and events?

5.If so, what is their nature? Are they substances? What sort of properties do they have? [Plato's "receptacle"]

6.Are there any empirical (or epistemic or metaphysical) tests relevant one way or the other? [Newton's bucket and globes]

7.Are space and time discrete or continuous? [Zeno]

8.Are spatial and temporal continua "pointlike"? If so, what is the relationship between the size of an interval and the number of points that it contains? [Zeno, Aristotle, Cantor]

9.What is the nature of infinity? What is the difference between infinite divisibility and infinite extendibility? What is the difference between potential infinities and actual infinities? Are any infinities actual? [Aristotle thought no; moderns think yes]

10.Can we make sense of the notion that some infinities are "larger" than others? [Cantor]

11.Do physical space and time have an "intrinsic structure", I. e., a "natural" geometry?

12.If so, what is it? How would we go about trying to experimentally or experientially determine what it was? [Gauss, Poincare - this question presumes that there are viable alternatives to Euclid, see Q14 below]

13.What is the role of convention in testing the applicability of theoretical models to experiential reality? How does one determine, e. g., that two temporal intervals are congruent? How about two spatial intervals (at a distance)? [Cf Q1 and Q2 above]

14.In the nineteenth century, it was discovered that there were alternatives to Euclidean geometry. This led to the distinction between "pure" and "applied" geometries. How are they related? Is it a matter of fact that the geometry of the physical world is what it is or is it a matter of convention?

15.Does nature abhor a vacuum? If not, what are vacua?