#485

July 31, 2016

How Do I Interpret General Relativity Theory?

Dear Dr. Craig,

Thank you for your ministry. The content on your website and mobile app is an incredible resource. I absolutely love it and can't seem to get enough!

I have a question, Dr. Craig. An atheist with whom I'm in dialog with claims that you reject General Relativity (GR). I hadn't ever heard this so I asked what caused him to believe this, he says that because you interpret special relativity in neo-Lorentzian fashion that this interpretation does not allow a pathway to GR and thus no theory of gravitation.

Additionally, he says that it is impossible to have a derivation of GR without using the principles of Einsteinian SR.

From reading some of your work, it is clear that you prefer the Lorentzian approach to SR due to your commitment to the A-Theory of time. What I'm not able to figure out is whether the assertion is true that GR needs to be rejected as a result. Would you mind clarifying this?

Enrique


United States

It’s disheartening, Enrique, when critics misrepresent my positions on various issues. In this case I commend to you my book Time and the Metaphysics of Relativity (Dordrecht: Kluwer Academic Publishers, 2001), for a clear explication of my views on time and special and general relativity.

It is true that because I am persuaded that a tensed theory (or so-called A-theory) of time is true (according to which temporal becoming is real and there is an objective difference between past, present, and future), I hold to a neo-Lorentzian interpretation of special relativity (according to which absolute simultaneity and length exist, even if we are unable to measure them due to the effects of uniform motion upon our measuring instruments). For the same reason, I reject four-dimensionalism or spacetime realism (a so-called B-theory of time, according to which all events in time are on an ontological par). But that leads me to reject, not general relativity, but a four-dimensionalist interpretation of general relativity. I see gravitation, not as spacetime curvature but as a force, just like the other forces of nature such as electromagnetism.

Your friend has evidently bought uncritically into presentations of general relativity in terms of spacetime as a literalistic piece of metaphysics, rather than taking spacetime as a heuristic device for expounding the theory. This is simply naive. Indeed, some prominent physicists, such as Stephen Weinberg, have complained that presentations of the theory in terms of spacetime geometry, rather than in terms of a force, have actually impeded the advance of physics by hindering gravitation’s integration into a unified theory of the four fundamental forces of nature.

Your friend’s assertions that “it is impossible to have a derivation of GR without using the principles of Einsteinian SR” and so a neo-Lorentzian interpretation of special relativity “does not allow a pathway to GR and thus no theory of gravitation” makes it evident that he mistakenly believes that general relativity is an extension of special relativity. It’s true that Einstein tried to extend his principle of relativity to cover not only uniform motion (special relativity) but accelerated and rotational motion as well (general relativity). But this is the part of Einstein’s paper that is generally recognized to be a failure. He did not succeed in enunciating a general principle of relativity or in relativizing all motion. What he did do was discover a new theory of gravitation to replace Newton’s. The name “general theory of relativity” is thus recognized to be a misnomer, a historical vestige. It is a gravitational theory, not a relativity theory. That Lorentz’s interpretation of special relativity is not incompatible with general relativity should be evident by the fact that Lorentz, long after Einstein’s publication of his general theory, continued to lecture on both theories while never abandoning his commitment to absolute time and space.

Indeed, you can be a spacetime realist and a neo-Lorentzian if you want to. Just add a preferred foliation of spacetime into successive temporal slices, and you can have absolute simultaneity and all the rest. Although general relativity does not impose a way of slicing up spacetime into successive temporal slices, once you marry general relativity with empirical cosmology, a natural slicing of spacetime emerges, along with a cosmic time which is independent of space and which records the proper time or duration of the universe in an observer-independent way right back to the beginning of time about 13.7 billion years ago. That discovery features prominently, as you must know, in my defense of the kalām cosmological argument.

For examples of prominent physicists, like Franco Selleri and Antony Valentini, who advocate neo-Lorentzian interpretations of general relativity, take a look at the volume of essays edited by Quentin Smith and me, Einstein, Relativity, and Absolute Simultaneity (London: Routledge, 2007).