Can Physics Coherently Deny the Reality of Time?

Summary

Introduction

The conceptual and technical difficulties involved in creating a quantum theory of gravity have led some physicists to question, and even in some cases to deny, the reality of time. More surprisingly, this denial has found a sympathetic audience among certain philosophers of physics. What should we make of these wild ideas? Does it even make sense to deny the reality of time? In fact physical science has been chipping away at common sense aspects of time ever since its inception. Section 1 offers a brief survey of the demolition process. Section 2 distinguishes a tempered from an extremely radical form that a denial of time might take, and argues that extreme radicalism is empirically self-refuting. Section 3 begins an investigation of the prospects for tempered radicalism in a timeless theory of quantum gravity.

How Physics Bears on the Reality of Time

Let me begin with a quotation:

Time by itself does not exist. Time gets its meaning from the objects: from the fact that events are in the past, or that they are here now, or they will follow in the future. It is not possible that anybody may measure time by itself; it may only be measured by looking at the motion of the objects, or at their peaceful quiet.

This quote is from Lucretius's De Rerum Natura. It illustrates the fact that, for a long time now, there have been philosophers who have doubted the reality of time.