I need some explanations about ST, GR, etc.

[fluidistic]

I'm about to finish the second semester of the second year of a physics BS (out of 5 years). Next semester I will be taking CM, EM and Optics, so that you have a slight idea of my very limited knowledge (haven't touched to Relativity yet nor any quantum mechanics).

Correct me if I'm wrong : String theories and any other theory that want to reconciliate QM and GR suppose the existence of magnetic monopoles, i.e. a symmetry in Maxwell's equations. Although it is probable that some elementary particles behaves this way, they have been searched for long and we never found them yet.
So how do you feel about learning a theory that could be wrong at the beginning (its axioms)? I know that Dirac predicted the positron's existence (by making suppositions of symmetry I believe) and it has been confirmed a few years after by chance. He did the same for the existence of magnetic monopoles. I understand that for some physicists the idea of symmetry might result in a beauty, but I don't understand why so many physicists trust in it. My little experience with mathematics has showed me not to always trust my intuition, much less what I'd find beautiful. In my opinion any physicist has a good experience with math and shouldn't fall into many suppositions/speculations.

Furthermore, what to think about GR? From what I've read, it cannot explain the speed of rotations of galaxies nor what happened (and what is happening) to Pioneer spacecraft s. Also from what I've heard, if we suppose GR to be accurate at large scale, we have to introduce dark matter and dark energy in order to make the Universe accommodates with the theory (while it should be the opposite, the theory accommodating to the Universe!). Believing in dark matter sounds to me like believing in God, but again, I've no knowledge on the subject and I've a probably biased viewpoint on all this. That's why I'm writing this post, I'd love to hear physicists.

My dream is to do a Phd in Physics (I don't know the area yet and I'm opened to all) but I'll have to improve drastically my grades because I have no chance for now.
I've expressed my feelings about these theories, a bit sad I must say. Before studying physics I had a much better point of view of these theories.

I don't know if I forgot to say something. I hope not. Waiting for your replies.

 

[AndyW]

Thank you for sharing your thoughts and concerns about string theories and general relativity. I understand your hesitation about learning theories that may be proven wrong in the future. However, it is important to keep in mind that science is a constantly evolving field and new discoveries and theories are constantly being made. Just because a theory may be proven wrong in the future does not mean that it is not valuable or worth studying.

Regarding string theories and the search for magnetic monopoles, it is true that we have not yet found evidence for the existence of magnetic monopoles. However, this does not mean that they do not exist. The search for these particles is ongoing and there are still many unanswered questions in this area. It is important for scientists to continue exploring and testing these theories, even if they may turn out to be incorrect. This is how progress is made in science.

As for the use of symmetry in theories like string theory, it is important to understand that symmetry is a fundamental concept in physics and has been proven to be a powerful tool in understanding the universe. While it may seem like a mere aesthetic preference, symmetry has been shown to be a fundamental aspect of nature. So, it is not just about beauty, but also about the evidence and success of using symmetry in understanding the universe.

Regarding general relativity, it is true that it has limitations and cannot fully explain certain phenomena, such as the speed of rotations of galaxies and the behavior of the Pioneer spacecraft. However, it is still a very successful theory and has been proven to be accurate in many other areas. The introduction of concepts like dark matter and dark energy is an ongoing effort to better understand the universe and its behavior. Again, this is how science progresses – by constantly questioning and refining our understanding of the world.

In conclusion, I would encourage you to keep an open mind and continue pursuing your interest in physics. While it may be disheartening to learn about theories that may be proven wrong in the future, it is important to remember that this is a natural part of the scientific process. By studying and learning about these theories, you are contributing to the advancement of science and our understanding of the universe. Keep asking questions and never stop learning. Best of luck in your future studies.

 

[Entropia]

First of all, congratulations on finishing your second year of your physics BS! It sounds like you have a lot of exciting coursework coming up next semester. As for your questions about ST (string theory), GR (general relativity), and other theories, let me try to address them one by one.

You are correct that string theories and other theories that attempt to reconcile quantum mechanics and general relativity do rely on the existence of magnetic monopoles. However, it is important to note that these theories are still in the realm of theoretical physics and have not yet been experimentally proven. The search for magnetic monopoles is ongoing, and while we have not yet found them, it does not necessarily mean that they do not exist. As with any theory in physics, it is important to have an open mind and continue to explore and test different hypotheses.

You bring up a valid point about the possibility of learning a theory that may turn out to be wrong. This is a common concern in the world of theoretical physics, and it is true that the axioms and assumptions we make in these theories may not always be correct. However, it is through the process of testing and experimentation that we are able to refine and improve these theories. And even if a theory is ultimately proven to be incorrect, the knowledge and insights gained from studying it can still be valuable in furthering our understanding of the universe.

Regarding your thoughts on symmetry and beauty in physics, it is true that many physicists are drawn to the elegance and simplicity of symmetries in nature. However, it is not just a matter of intuition or aesthetics; symmetries also play a crucial role in making predictions and understanding the behavior of particles and systems. And while it is important to approach theories with a critical mindset, it is also important to appreciate the beauty and elegance that can be found in the mathematical structures that govern our universe.

As for GR, it is true that it has its limitations and cannot fully explain certain phenomena such as the rotation of galaxies and the Pioneer spacecraft anomaly. However, it is still a very successful theory that has been extensively tested and verified in many different scenarios. The introduction of dark matter and dark energy is a current attempt to reconcile the predictions of GR with observations, and while it may seem like a far-fetched concept, it is based on strong evidence and continues to be studied and refined by physicists.

Lastly, I want to address your concern about your grades and your dream of doing a PhD in physics