Quantum Mech incompatible with Relativity

In summary, standard quantum mechanics does not include a description of gravity, making it incompatible with general relativity. While special relativity has been integrated into QM, relativistic QM is mathematically complicated and not typically covered in undergraduate courses. The reason for this incompatibility is that gravity cannot be quantized in the same way as other interactions due to the lack of a mediating particle. Additionally, while there is evidence for the quantization of electromagnetism, there is currently no experimental evidence for quantized gravity.
  • #1
Pjpic
235
1
Is there a consise, yet accessible, description of how quantum mechanics and relativity are incompatible?
 
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  • #2
Yes, standard quantum mechanics does not include a description of gravity, which is why it is not "compatible" with general relativity (which is basically the theory OF gravitaty).

Note that special relativity was integrated in QM a long time ago, the only "problem" with relativistic QM is that it is mathematically quite complicated which is why it is not covered in undergraduate courses etc.
 
  • #3
f95toli said:
Yes, standard quantum mechanics does not include a description of gravity, which is why it is not "compatible" with general relativity (which is basically the theory OF gravitaty).

Note that special relativity was integrated in QM a long time ago, the only "problem" with relativistic QM is that it is mathematically quite complicated which is why it is not covered in undergraduate courses etc.

Thanks for the answer. Is there a (understandable) reason QM does not include a description of gravity?
 
  • #4
Every tuesday on the history channel a show called The Universe comes on and details cosmic quandaries in great detail. One episode talked about the incompatibility of general relativity and quantum mechanics. The episodes can be purchased on itunes as well.
 
  • #5
Pjpic said:
Thanks for the answer. Is there a (understandable) reason QM does not include a description of gravity?

From a mathematical point of view the problem is that you can't quantize gravity in the same way that you can quantize e.g electromagnetic radiation (which is mathematically actually quite easy to do).
Now, the reason we can quantize electromagnetic interaction is because it is mediated by particles (i.e. photons) and the same is true for all other interactions as well, except for gravity -which as you know- according to GR is just curved spacetime: i.e. in "classical" GR there is no mediating particle (and introducing the graviton doesn't really solve the problem either).
 
  • #6
But classical E&M also doesn't have particles (photons). The photons come from the quantization process.
 
  • #7
jtbell said:
But classical E&M also doesn't have particles (photons). The photons come from the quantization process.

Yes, but the quantization procedure is quite straightforward and can be done by starting from classical EM and introducing a few concepts that are at least "reasonable".
Also, if is usually possible (albeit complicated)to use quantized EM (QED) for ordinary EM problems as well, there is no contradiction between QED and classical EM in limits where they both are useful. But we do not have a quantized theory of gravity that agrees with the predictions of GR.

Moreover, there is plenty of experimental evidence showing that EM really IS quantized, i.e. the photon is "real"; at least to the extent that a single photon detector will register discrete events (not to mention HB&T experiments etc).
But we do not yet -as far as I know- have any experimental evidence for quantized gravity.
 

1. What is the main difference between Quantum Mechanics and Relativity?

The main difference between Quantum Mechanics and Relativity is that Quantum Mechanics deals with the behavior of particles at a subatomic level, while Relativity deals with the behavior of objects at a macroscopic level. Quantum Mechanics focuses on the probabilistic nature of particles, while Relativity focuses on the relationship between space and time.

2. How are Quantum Mechanics and Relativity incompatible?

Quantum Mechanics and Relativity are incompatible because they have different sets of rules and principles that govern the behavior of particles and objects. For example, Relativity states that the speed of light is constant, while Quantum Mechanics allows for particles to exist in multiple states simultaneously.

3. Can Quantum Mechanics and Relativity be unified?

Many scientists have attempted to unify Quantum Mechanics and Relativity into one overarching theory, but so far, no single theory has been able to fully explain all phenomena at both the subatomic and macroscopic levels. This remains an important area of research in physics.

4. How does the incompatibility between Quantum Mechanics and Relativity affect our understanding of the universe?

The incompatibility between Quantum Mechanics and Relativity challenges our current understanding of the universe and the fundamental laws that govern it. It also highlights the limitations of our current scientific theories and the need for further research and exploration.

5. Are there any experiments that have demonstrated the incompatibility between Quantum Mechanics and Relativity?

There have been several experiments that have demonstrated the incompatibility between Quantum Mechanics and Relativity, such as the Bell test and the double-slit experiment. These experiments have shown that particles can behave in ways that cannot be explained by either Quantum Mechanics or Relativity alone.

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