The Interpretation of Theory (In the Context of Gravitation)

[εllipse]

About a week back I posted in the strings forum asking about how current theories interpret gravitation and how they differ from general relativity. But the main subject of the thread wasn't how physical theories should be interpreted, so I'd like to pose that question again, in greater detail here. I had wanted to post this in the relativity forum because I am most interested in the opinions of those who are fond of general relativity, but I realize this question may be a little too far into the field of philosophy, so decided to spare the mentors some time and go ahead and post it here .

My question is, how important is the exact interpretation of theories, rather than just their predictions? In particular, is it better to think of gravity in terms of space-time actually, physically being warped, or should one only take the idea of space-time curvature as a model that merely yields accurate predictions to the current extent that we can test with technology?

As Greene points out in The Elegant Universe, Newton found it "inconceivable that inanimate brute matter, should, without the mediation of something else, which is not material, operate upon and affect other matter without mutual contact". Newton, of course, never came to any solutions to what the agent of gravity actually is, and left that to a future generation to decide.

And, as you all know, Einstein found a reason that gravity could act between distant bodies. In Einstein's general theory of relativity, the agent of gravity is space-time itself, as it becomes warped due to the existence of matter. I have to say, I love this interpretation of gravity, and one of the major things I dislike about string theory is that it changes the agent of gravity from space-time to a string vibration. But, string theorists will state that the general theory of relativity is a special circumstance of their equations, just like Newton's theories are special circumstances of Einstein's. This raises a dilemna because, whether or not string theory's equations reduce to Einstein's, they absolutely seem to go against Einstein's belief in what the agent of gravity is.

Thorne seems to prefer the idea that the only important thing about a theory is its predictions, and not the specific way it interprets the world:

When contemplating the above sequence of sets of laws (Newtonian physics, special relativity, general relativity, quantum gravity)--and a similar sequence of laws governing the structure of matter and elementary particles--most physicists are driven to believe that these sequences are converging toward a set of ultimate laws that truly governs the Universe...

One might object that each set of laws in the sequence "looks" very different from the preceding set. (For example, the absolute time of Newtonian physics looks very different from the many different time flows of special relativity.) In the "looks" of the laws, there is no sign whatsoever of convergence. Why, then, should we expect convergence? The answer is that one must distinguish sharply between the predictions made by a set of laws and the mental images that the laws convey (what the laws "look like"). I expect convergence only in terms of predictions, but that is all that ultimately counts. The mental images (one absolute time in Newtonian physics versus many time flows in relativistic physics) are not important to the ultimate nature of reality.

- Kip S. Thorne, Black Holes and Time Warps, pg. 85-86

D'Inverno agrees with this sentiment, stating:

The essential activity of mathematical physics, or theoretical physics, is that of modelling or model building. The activity consists of constructing a mathematical model which we hope in some way captures the essentials of the phenomena we are investigating...

The very success of the activity of modelling has, throughout the history of science, turned out to be counterproductive. Time and again, the successful model has been confused with the ultimate reality, and this in turn has stultified progress. Newtonian theory provides an outstanding example of this. So successful had it been in explaining a wide range of phenomena, that, after more than two centuries of success, the laws had taken on an absolute character. Thus it was that, when at the end of the nineteenth century it was becoming increasingly clear that something was fundamentally wrong with the current theories, there was considerable reluctance to make any fundamental changes to them...

We should perhaps be discouraged from using words like right or wrong when discussing physical theory. Remembering that the essential activity is model building, a model should then rather be described as good or bad, depending on how well it describes the phenomena it encompasses...

- Ray D'Inverno, Introducing Einstein's Relativity, Section 2.1

However, it is also true that physicists are fond of aesthetics and simplicity. There seem to be many who claim to have aether theories that give the same predictions as relativity, but differ mainly in the interpretation of what causes time dilation and length contraction. The difference is they require a luminiferous aether, which Einstein showed to be a useless concept, and, in the spirit of Ockham's razor, the aether has been viewed as extra baggage and discarded. Also, as stated previously, Newton was aware that his theory of gravity wouldn't be the end of the story because it doesn't even have an interpretation. Newton didn't have any ideas about what could cause gravity, but realized that there must be something that causes it. So, on this level, there is some importance to both the predictions of physical theories as well as their unique interpretations of the world.

I'd like to know how some of you feel about this. Should one take the stance that it isn't important what actually causes gravitation in reality as long as we can accurately predict it? Is there even any such thing as a physical agent of gravitation, or is it merely an idea that we've made up to make things easier for us to picture? Or should one take the stance that gravity really is caused by curvature in space-time or a particular string vibration or some other specific mediator?

 

[Pi_314B]

Should one take the stance that it isn't important what actually causes gravitation in reality as long as we can accurately predict it?

One might call this the holy grail. It's most definitely important to explain it with perfect precision.

Is there even any such thing as a physical agent of gravitation?

My answer to this would be no. Thats because my interpretation of the entire universe says that none of it is physical at all.

Or should one take the stance that gravity really is caused by curvature in space-time or a particular string vibration or some other specific mediator?

Gravity wouldn't be caused, but rather just is. Just as matter, antimatter, gravity, weak force, strong force, electromagnetic force, and Big Jims BBQ ribs are all the same thing.

 

[R0man]

The interpretation of theory is a complex and ongoing discussion in the field of physics. While the main focus of scientific theories is to accurately predict and explain natural phenomena, the way in which these theories are interpreted can play a significant role in shaping our understanding of the world.

One argument is that the exact interpretation of theories is not as important as their ability to make accurate predictions. This view is supported by physicists such as Kip S. Thorne and Ray D'Inverno, who emphasize the importance of using mathematical models to describe and understand the natural world. They argue that the success of a theory should be judged based on its ability to accurately predict and explain observed phenomena, rather than the specific way in which it interprets reality.

On the other hand, there are also scientists and philosophers who believe that the interpretation of theories is crucial in understanding the nature of reality. They argue that different interpretations can lead to different understandings of the world and can even shape the development of future theories. For example, the idea of space-time curvature as the agent of gravity in general relativity has significantly influenced our understanding of the universe and has led to further research and discoveries.

Furthermore, the aesthetic and simplicity of a theory's interpretation can also play a role in its acceptance and development. This is evident in the case of the aether theory, which was eventually discarded due to its lack of simplicity and usefulness, despite its ability to explain certain phenomena.

In conclusion, while the main focus of scientific theories is to accurately predict and explain natural phenomena, the interpretation of these theories can also have a significant impact on our understanding of the world and the development of future theories. The debate over the importance of interpretation versus prediction will likely continue, but it is clear that both aspects play a crucial role in advancing our understanding of the universe.