Is String Theory the Only Solution for Unifying QM and GR?

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In summary, the conversation discusses the need for a theory beyond the standard model as QM and GR equations cannot produce sensible answers when combined. The comparison to QED is mentioned, where infinities were dealt with to produce numbers. It is questioned whether a similar approach could be used for QM and GR, or if string theory is the only solution. The possibility of other approaches is also considered.
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Odysseus
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Hi all, I'm posting this here and not in the Beyond the Standard Model forum because my question is not very precise and I don't know anything substantive about strings or LQG. That being said I will launch into my inquiry.

It's my understanding that the need for a theory beyond the standard model is caused by the fact that we cannot get the equations of QM and GR to work together to produce sensible answers (if we leave aside the question of trying to explain gravity in terms of a force carrying particle). It seems to me that a similar situation occurred during the development of QED, where the equations produced infinities where there clearly shouldn't have been infinities. But, people were able to develop a way of dealing with the infinities to produce numbers that could be compared to experiment. Now, how are we sure that something similar couldn't be done to get QM and GR to agree enough to give us numbers rather than infinities?
 
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Is there a technical reason why this isn't possible? And, if string theory is the only way to solve this problem, does that imply that strings are the only thing that can be used to make sense of QM and GR together? Or, is it possible that some other approach exists?Thanks in advance for any help.
 

1. How do quantum mechanics and general relativity agree with each other?

Quantum mechanics and general relativity are two fundamental theories that describe the behavior of matter and energy on a microscopic and macroscopic scale, respectively. Despite being successful in their respective domains, they are not compatible with each other. It is believed that there is a more comprehensive theory that can unify them, but this theory is yet to be discovered. Currently, there are various approaches, such as string theory and loop quantum gravity, that attempt to reconcile the two theories.

2. What are the main differences between quantum mechanics and general relativity?

The main difference between quantum mechanics and general relativity lies in their assumptions and predictions. Quantum mechanics deals with the behavior of matter and energy at a subatomic level, while general relativity describes the behavior of gravity and spacetime on a macroscopic scale. Quantum mechanics is based on probabilities and uncertainty, while general relativity is based on determinism. Additionally, quantum mechanics is a non-deterministic theory, while general relativity is deterministic.

3. How does the concept of "spooky action at a distance" relate to the agreement between quantum mechanics and general relativity?

The concept of "spooky action at a distance" refers to the phenomenon in quantum mechanics where two entangled particles can affect each other's properties instantaneously, even when separated by a large distance. This concept challenges the principle of locality in general relativity, which states that objects can only be influenced by their immediate surroundings. Reconciling these two theories would require a deeper understanding of the nature of spacetime and how it is affected by quantum phenomena.

4. Are there any experiments that have been conducted to test the agreement between quantum mechanics and general relativity?

Yes, there have been numerous experiments conducted to test the compatibility of quantum mechanics and general relativity. One example is the double-slit experiment, which demonstrates the wave-particle duality of matter. Another example is the gravitational time dilation effect, which has been observed through various experiments and confirms the predictions of general relativity. However, there are still many open questions and areas of disagreement that require further experimentation and research.

5. Is there a definitive answer to the agreement between quantum mechanics and general relativity?

No, there is currently no definitive answer to the agreement between quantum mechanics and general relativity. The two theories have been incredibly successful in describing the behavior of matter and energy in their respective domains, but they are not compatible with each other. Scientists are still searching for a unifying theory that can explain both theories and their limitations. The search for this theory is an ongoing and active area of research in the field of physics.

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