Brett: Eddington’s experiment is an excellent example of what’s called a crucial test, which is sort of the pinnacle of what science is all about.
If we do a test and it doesn’t agree with a particular theory that we have, that’s problematic. But that doesn’t mean that it refutes the theory. If you were to refute the only theory that you have, where do you jump to? You don’t have any alternative.
If we were to do a scientific test tomorrow and it was inconsistent with the theory of general relativity, then what? There is no alternative to general relativity. In fact, there have been experiments over the years that seem to have been inconsistent with general relativity. Guess what? They’ve all turned out to be faulty. If you had to choose between whether or not general relativity has been refuted by your test or your test is flawed, go with the fact that your test is flawed.
In the case of Eddington’s experiment, we had two viable theories for gravity. We had Newton’s theory of universal gravitation on the one hand and we had Einstein’s general theory of relativity on the other.
The experiment you described of how much the light bends during a solar eclipse is the correct way of describing what happened. It is not that we showed that general relativity was correct in some final sense; rather, we refuted Newton’s theory of gravitation. Newton’s theory was ruled out because it was inconsistent with the test, while general relativity was consistent with the test.
This doesn’t mean that general relativity is the final word in science. It means that it’s the best theory we have for now, and there’s a whole bunch of reasons that we might think general relativity ultimately has to be false in the final analysis. This is another aspect of the world view that we never have the final word—and that’s a good thing. That’s optimistic because it means we can keep improving, we can keep making progress, and we can keep discovering new things. There is no end of science.
People have feared that one day progress will come to a halt, that science will end. In fact, we are at the beginning of infinity, and we will always be at the beginning of infinity precisely because we can improve our ideas.
We’re fallible human beings. None of our theories is perfect, because we aren’t perfect. The process by which we create knowledge isn’t perfect, either. It’s error-prone.