How much can we rely on theories?

Dammes

Modern physics is trying to understand and describe domains that we cannot observe, therefore we have trust our powers of reasoning, deduction of the mathematical facts.

Im wondering how much we can rely on physics theories created from mathematical models compared to theories created through observations.

Astronuc

Theories and mathematical models are developed from observation in which we attempt to describe (quatitatively as well as qualitatively) a certain phenomenon or behavior in the nature. The validity of the model can then be tested by further observations or experiment, particularly when one can make a prediction about the behavior and then do the experiment to see if the physical system behaves as predicted.

With reliable models we can, with some confidence, design dynamic systems, e.g., cars, planes, spacecraft, buildings, etc, or otherwise, manipulate nature in our presence. Of course, there are limits, and hopefully, the limits are reasonable defined in the models.

harrylin

I think that your question is slightly wrong. The mathematical models have been constructed to match the observations. And such models result in theories for predicting new kinds of observations. The more such predictions are confirmed, the more we rely on such theories to be correct for predicting phenomena.

However, while such a success is suggestive that the models may somewhat correspond to physical reality, it is often found that very different models can provide the same predictions.

Dammes

the mathematical models have been constructed to match the observations, but how much can we see? In quantum physics we are able to observe the affect of the actions of particles, but we can't observe the particle in action itself.

Theories are made from these observations and work well, but we never know if they are truly true.
For example in quantum physics there is no true theory that explains quantum physics. there are multiple theories that explain quantum physics. The theory that most people get taught is the “Copenhagen interpretation”, but when physicist are asked which theory they believe in. only 42 percent choose the “Copenhagen interpretation”.

the “Copenhagen interpretation” works well. As we can see with a lot of our technology, as they are created with “Copenhagen interpretation”. But is it the right one?

another example is the holographic principle. we came up with this theory by looking at black holes. when a object goes into a black hole, the data of the object gets stored on the surface of the black hole and the 3D object is inside the black hole. And because the inside of black holes act the same as our universe (how do we know this if we have never been inside black holes) we assume that we are a projection of the 2D data that is stored on the surface of our universe.

so how much can we rely on these theories?

my knowledge of physics is not that great, but i assume that there are many other well known theories that we use to describe our universe, but cant justify with concrete evidence and need mathematics and reason to fill in the gaps.

Len M

I think your question concerns how much we can rely on physics outside of phenomena, though you may not quite see it framed in that all encompassing way, you were perhaps more thinking of how much we can rely on physics to tell us about that which lay "between" the phenomena (observation) of our measurements and observation. In fact I would say there is no distinction between those two statements because (on the basis that we consider empirical verification to be the bottom and essential line of physics) physics produces its predictive models in terms of phenomena - the verification of theories and models all takes place within our world of phenomena (empirical reality), phenomena is all we ever can have access to in terms of the physical world.

All models in fact suffer from this problem, but some do seem to suffer more than others, especially within the quantum realm. But, for example, even in the classical realm, the model that predicts the trajectory of a cannon ball is a first rate mathematical predictive model that works for everybody all the time within the domain of applicability of that model. But does that model “explain” what lay between or beyond the phenomena? On the face of it, that cannon ball has to replicate itself (Star Trek transporter style) an infinite number of times through a given space and time. That’s just my clumsy personal attempt at trying to "understand" motion in terms of phenomena and I only give it to illustrate that what lay behind phenomena is not addressed by the predictive model simply because the scientific method relies on empirical verification and empirical verification involves observers and observers only have access to phenomena (even instrument readings are phenomena) - we don't get to see what actually lay behind the phenomena of motion (for example), all we have access to is the phenomena involving us and the ball.

We can never know if theories and models are "true" in the sense of accurately representing a reality external to that of phenomena. Each of us has to decide for ourselves what the relationship of a verified model of phenomena is to that which may (or may not) lay between or behind phenomena and that decision involves the adoption of various positions of realism or idealism. I hesitate to use the word, but those positions are philosophical in nature rather than being scientific, by that I simply mean that they are theories that hypothesise that we can say something “true” about independent reality using phenomena or mathematical notions (or both) but that hypothesis cannot be proven. In short realism and idealism rely on trust, belief or induction as opposed to empirical verification which is the hall mark of the scientific method but can only involve phenomena.

Drakkith

This doesn't even make any sense if you think about it. What does "the particle in action itself" even mean? ALL interactions are between two or more particles and the forces between them. To be "in action" would be a change in position, velocity, or some other quantity compared to another particle. We can, and do observe particles all the time, and we see all kinds of actions and interactions take place.
Of course not. Nothing in science is ever "proven true".
It works. Whether it's "right" or not depends on what you define as being the "right" one. I define it as being the theory that holds up the best to scrutiny and makes the most accurate predictions.

It's important to know the distinction between theories that are deemed extremely reliable and are known as "mainstream", and theories which have no supporting observations. Quantum Mechanics and Special Relativity are held up as Mainstream Theories because they have overwhelming evidence supporting them. The holographic theory does not however, and isn't considered "mainstream" as far as I know.

If they make testable predictions that we can actually test with current technology, then we can rely on them a great deal. If not, then we cannot.

ALL theories need mathematics and reason. Mathematics is both a language and a tool that allows us to be specific when making predictions and coming up with explanations. Reason, or logic, is what is needed to combine multiple ideas into one theory and apply it to reality. They do not simply "fill the gap", they are integral to all theories.

phinds

Feynman was fond of pointing out that quantum mechanics gives correct results to a degree that is comparable to measuring the width of the USA and getting a correct answer to within the width of a human hair.

General Relatively is similarly accurate.

I'd call that pretty reliable.

Drakkith

It's almost more reliable than Evo's banhammer.

phinds

Hey, don't be picking on Evo ... she MAY wear high heels and whack you with one.

Drakkith

Oh god...you've discovered what her banhammer actually is! It's more terrible than we ever imagined!!

StevieTNZ

You should replace theory with interpretation.

And the Copenhagen interpretation is wrong. (see, for e.g. the thought experiment by Ghirardi GianCarlo in his book "Sneaking a Look at God's Cards")