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Why can't scientists link Einsteins theory of relativity with quantum theory?


Samga
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I'm thinking black holes and stuff. Sorry I haven't really got any idea about any of it, I just find it really interesting after seeing a program on TV last night about black holes. Thanks.

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I'm thinking black holes and stuff. Sorry I haven't really got any idea about any of it, I just find it really interesting after seeing a program on TV last night about black holes. Thanks.

 

The short answer: GR and QM are mutually incompatible.

Edited by juanrga
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The short answer: GR and QM are mutually incompatible.

I believe that quite a few theoretical physicists would disagree with you on this issue. A survey in the efforts of physicists to develop "loop quantum gravity" makes for interesting study.

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I believe that quite a few theoretical physicists would disagree with you on this issue. A survey in the efforts of physicists to develop "loop quantum gravity" makes for interesting study.

 

Precisely LQG was developed to try to unify both QM and GR. Searching a bit you would be able to find one of the many criticisms published about LQG.

 

Time ago that I abandoned that line of inquiry, but then the number of theoretical physicists still working in LQG was small, about an order of magnitude less than those working in other approaches to quantum gravity.

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quantum mechanics postulates the existence of a "quantum" of space.

A smallest possible unit of space.

 

this unit of space would not be observer independent.

 

google "double special relativity"

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The short answer: GR and QM are mutually incompatible.

 

Good to point out, that being incapable of unifying two theories may not necessarily mean they inherently incompatible. It may be a point of how people are attempting to unify the theories. Every attempt so far has proven difficult - but on the whole does not mean the two theories cannot be unified.

 

As a I understand it, string theory is also an attempt develop a general theory to include Gen. Rel. and Quantum theory.

 

It's quite an unrealistic approach however. Don't get me wrong, many scientists like Leonard Susskind would bet their life that the world is made of strings... the theory can't convince many however that there really does exist as many dimensions it purports to. Start proving these dimensions exist, all several more of them, and I'm in... otherwise, string theory seems far-fetched.

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Good to point out, that being incapable of unifying two theories may not necessarily mean they inherently incompatible. It may be a point of how people are attempting to unify the theories. Every attempt so far has proven difficult - but on the whole does not mean the two theories cannot be unified.

 

 

 

It's quite an unrealistic approach however. Don't get me wrong, many scientists like Leonard Susskind would bet their life that the world is made of strings... the theory can't convince many however that there really does exist as many dimensions it purports to. Start proving these dimensions exist, all several more of them, and I'm in... otherwise, string theory seems far-fetched.

 

I am as skeptical about string theory as you are. Unfortunately string theory and loop quantum gravity seem to be the only games in town at the moment. I hope that someday physicists will either come up with something better, or else develop one of the above to the point where it can be subject to testing.

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The short answer: GR and QM are mutually incompatible.

 

Good to point out, that being incapable of unifying two theories may not necessarily mean they inherently incompatible. It may be a point of how people are attempting to unify the theories. Every attempt so far has proven difficult - but on the whole does not mean the two theories cannot be unified.

 

Notice that I did not even mention unification.

Edited by juanrga
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However, you replied to a question which was all about ''linking'' the two together. This more or less means unification.

 

I do not consider that "linking" was a synonym for "unification".

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There is a point that is being missed. It is not just linking or unifying. In a stuation where both need to apply at the same time (inside a black hole), you will end up with mathematical nonsense. This implies that it will be necessary to modify one or both theories to make them work together.

Edited by mathematic
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Theories of relativity cannot be linked with Quantum Mechanics because the theories of relativity are fundamentally incorrect as the same has been derived using trickeries. Read

 

OPEN CHALLENGE

 

!

Moderator Note

Mohammad Shafiq Khan you already have a thread on this. Hijacking threads is against the rules. Discussion of your challenge is limited to the existing thread.

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  • 1 month later...

Isn't the biggest stumbling block to the joining of GR and QM gravity?

If you take gravity out of the equation it might be doable.

Since gravity isn't a force but rather a symptom of curved space/time it should be eliminated from the solution.

 

Paul

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As I understand it, quantum mechanics and general relativity are based on fundamentally different views of nature:

 

1) General relativity assumes the universe is deterministic. For example, if you know the location of a particle and its velocity (speed and direction), you can know where it will be in the future (and where it was in the past) -- in principle to arbitrary accuracy.

 

But according to the Uncertainty Principle of quantum mechanics, you cannot know a particle's location and velocity simultaneously to arbitrary accuracy. The lower the uncertainty in one parameter, the higher the uncertainty in the other. Quantum mechanics says all you can do is predict the probability of where a particle will be in the future or where it was in the past.

 

But there is no Uncertainty Principle in general relativity.

 

2) According to general relativity, space and time (spacetime) are warped by mass/energy. There is no such warping of spacetime or spacetime curvature in quantum mechanics.

 

 

These differences are big reason why the two theories are not compatable.

Edited by IM Egdall
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1) General relativity assumes the universe is deterministic. For example, if you know the location of a particle and its velocity (speed and direction), you can know where it will be in the future (and where it was in the past) -- in principle to arbitrary accuracy.

 

So does classical mechanics and classical field theory.

 

 

2) According to general relativity, space and time (spacetime) are warped by mass/energy. There is no such warping of spacetime or spacetime curvature in quantum mechanics.

 

You can formulate quantum mechanics and with lots of technical issues, quantum field theory on curved space-times. The thing is you keep the underlying space classical.

 

 

These differences are big reason why the two theories are not compatable.

 

I would not say that the two theories are necessarily incompatible. The trouble is that standard tools built for the quantisation of field theories on Minkowski space-time do not allow us to directly quantise general relativity, at least not in perturbation theory.

 

The statement is that quantum general relativity in four dimensions is not perturbatively renormalisable. That is one cannot remove the infinities that arise when applying quantisation via perturbation theory, via the path integral formulation.

 

Canonical approaches also have troubles as the Hamiltonian theory has secondary constraints. For example in Loop Quantum Gravity it has not been shown that general relativity (+ small corrections) is the classical limit of the theory. Also, coupling the theory to other fields is problematic. Understanding gravitons is also very difficult.

 

String theory however necessarily contains the graviton in its spectrum and the classical limit here is known to be general relativity.

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The big difference between the theories is granularity.

 

Relativity, in any form, relies on the mathematics of continuous systems and continuous functions.

 

On the other hand QM is inherently about discrete or granular systems and requires discrete or granular maths.

 

This difference has been discussed and worried over at great lenght by many famous people, but never satisfactorily resolved.

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I would not say that the two theories are necessarily incompatible. The trouble is that standard tools built for the quantisation of field theories on Minkowski space-time do not allow us to directly quantise general relativity, at least not in perturbation theory.

 

The statement is that quantum general relativity in four dimensions is not perturbatively renormalisable. That is one cannot remove the infinities that arise when applying quantisation via perturbation theory, via the path integral formulation.

 

Canonical approaches also have troubles as the Hamiltonian theory has secondary constraints. For example in Loop Quantum Gravity it has not been shown that general relativity (+ small corrections) is the classical limit of the theory. Also, coupling the theory to other fields is problematic. Understanding gravitons is also very difficult.

 

String theory however necessarily contains the graviton in its spectrum and the classical limit here is known to be general relativity.

 

Thanks, ajb, for the enlightenment.

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could it not just be this simple.

 

There are "different" laws depending on the "relative" "mass" of said systems.

 

and if this is the case, then systems bigger then the universe, might also have different laws.

 

It is a simplistic approach, I realize that, but could it just be "that simple" ?

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