Is the theory of relativity still just a theory ?

I am quite sure that Pauli wasn't talking about relativity.

I think you are muddled about what a theory means. However much confidence we have in it, relativity will always be a theory. This does NOT mean that it is in serious doubt. It simply means that it is not itself an observed fact, but the explanation of observed facts.

Similarly, we talk about quantum theory, which like the theory of relativity has stood up magnificently to every experimental test, or even the mathematical theory of ellipses which is as certain as anything ever can be.

Contrast evolution, which is a phenomenon observed both directly and indirectly, so it counts as a fact not a theory. The explanation of evolution, in terms of natural selection operating on chance mutations, is another example of a highly successful theory, whose basic validity is no longer seriously doubted by serious people, although no doubt it will continue to be improved on and refined.

Labeling something as “just” a theory is simply a lazy way to dismiss any explanation that doesn’t agree with some preconceived notion of “how things ought to be.” Theories are “just” that: explanations of something we can observe.

Several centuries ago, it was commonly believed that objects in the heavens rotated about the earth. Anyone with a pair of eyes could see this was so. And so, elaborate theories were made to “explain” the observations of the motions of the planets, sun, moon, and stars. The theories even “worked” in the sense that most of the observable heavenly motions became predictable. In other words those (we now know to be incorrect) theories were backed up by the twin supports of prediction and experimental evidence.

So, what changed? Better observations. In particular, once the telescope was invented, it was possible to more closely examine the motions of heavenly bodies such as the moons of Jupiter and Mars, certain large asteroids, comets, etc. Such close examination showed that a geocentric theory didn’t fit the observations, but a heliocentric theory did nicely. And eventually (in the 20th century) it became possible to directly observe (from satellites sent far beyond the orbit of Earth) that the Earth did in fact orbit the Sun. However, long before that direct observation, it became accepted as fact, not theory, that the Earth orbited the Sun because of indirect observations that supported the heliocentric “theory”.

Plausible theories must survive the tests of prediction and experiment. A plausible theory will predict the results of an experiment not yet performed, and when performed the experimental results will confirm the prediction of the theory. Both tests are necessary and sufficient to lend plausibility to a theory, but neither nor both can ever “prove” a theory.

Except in mathematics (where theorem means something which can be “proven” based on certain assumptions and logic) there is absolutely no way to prove ANY theory. The best you can do is verify its correctness under specified conditions. There may (or may not) be some other condition, or conditions, that falsify the theory, and these simply haven’t been discovered yet. In the absence of evidence to the contrary, when enough experimental evidence is found that is in agreement with a theory, there is a strong human tendency to accept the theory as being “correct”. That doesn’t “prove” the theory of course, but it allows people to use the theory to solve or explain problems and observations. In other words, it supports a belief system. And everyone needs a belief system, or they must constantly question reality itself.

So, yes, Virginia, the Theory of Relativity remains “just” a theory. It will always be “just” a theory. Even if another theory comes along that explains the real world in a better, more satisfying, way and thereby sets up a new, different, and “better” belief system to replace the Theory of Relativity.

And there will always be holdouts: people who refuse to set aside old belief systems and embrace the new. As you begin to study physics, the first thing you “learn” is Newtonian physics. But isn’t that just a theory? And a disproved one at that, replaced by the better explanation of Einstein’s special relativity theory. Pump that into your observation of high-energy particles. Oh? You are still trying to figure out blocks and planes and pulleys and levers? Well, I guess you can get by with Newtonian theory for THAT. Just don’t push, pull, or accelerate those puppies too hard and fast or the wheels will come off the Newtonian theory.

All theories in science are 'still just theories'. There's a theory that the Earth orbits the Sun. It's not been ticked off as proven for all eternity. Evidence may turn up showing it to be wrong and, if so, then it's been left open for revision or refutation.

There's no special chorum of science druids to meet up somewhere or other by moonlight, to hum and to ha, and then do a little ceremony before announcing that any theory is now beyond dispute.

once theories are proposed it is very difficult for them to become law. Extensive amounts of experimentation must be done in order to prove it in every possible field with incredible exactness. If by any chance something disproves the theory it is rejected.

The theory of relativity is widely accepted but it is still not a law because there are some questions about it and some scientist disagree with it.

Like most things in Physics it remains a theory until disproven.

It's a theory.

Gravity's a theory too.

if its not proven yet means its theory

its a fact

No!