General Relativity VS Quantum Theory

[Stargazer]

No, and that's because it's not possible. One or both need to change first.

[TINNY]

why? are they mutually exclusive? or is there a fundamental law underlying the two?

[Stargazer]

As far as I understand, there have been some success in uniting the forces of the quantum mechanics, at least the electromagnetic and the weak force. However according to general relativity, gravity is not described as a force. I'm not sure if this is the only thing that makes it so different, but I suppose there is place for the graviton in the standard model, but it's never been detected. Also, the wave aspect has not been detected either. I am sure I'm wrong somewhere, but this is how I understand it.

[Bo]

quantum theory and general relativity do indeed 'bite' each other. In principle quantum mechanics gives a formalism which allow you to rewrite a known theory to a quantum theory. With the weak, strong and electromagnetic this has been achieved, and there exists a good quantum formulation of these theories. However with gravity (which is described by general relativity) this cant be done. (i'm quite sure this was recently discussed in more detail on this forum, dont know where exactly....)

 

Bo

[infamous]

At what point in current theory do quantum effects and gravitation diverge. Or is there no relative simularity between the two to begin with. And if gravitation should not be described as a force, how can we explain it's effect on universal mass. I've read that gravity causes space it'self to warp, what do we know about the reason for this effect.

[lindagarrette]

In the era around one Planck time, 10-43 seconds, it is projected by present modeling of the fundamental forces that the gravity force begins to differentiate from the other three forces. This is the first of the spontaneous symmetry breaks which lead to the four observed types of interactions in the present universe. Prior to one Planck time, there was essentially one force but the energy level needed to recreate that condition will probably never exist in a laboratory.

[infamous]

If I'm correct in my understanding that takes us back to 1E-43 sec. after the Big Bang. Am I right to assume this result?

[Freethinker]

At what point in current theory do quantum effects and gravitation diverge. Or is there no relative simularity between the two to begin with.

I'm not sure about at which level you are asking this. One fairly surface level answer is size or scale. Just as Newtonian physics works fine on a simple level, say to calculate the trejectory of a cannon ball, it does not work on a larger scale, especially wherre relative momentum is involved. But bother are still based on gravity as a major player.

 

But gravity has little effect on the smaller particle scale. There QM takes over.

 

Each has a functional value in working with physical laws at it's own level of interaction. Now we need the TOE (Theory of Everything) to tie them all together.

And if gravitation should not be described as a force, how can we explain it's effect on universal mass. I've read that gravity causes space it'self to warp, what do we know about the reason for this effect.

Perhaps it is better to understand that gravity does not CAUSE space to warp. Mass CAUSES the warping, gravity IS the warping of space.

[infamous]

Thanks Freethinker; you are right about mass causing the warpage. I stand corrected. If I may ask another question here; as mass gives rise to the gravitational infleunce, what do we know about this interaction, and can we define the term mass in a way that draws a fundamental difference between itself and energy. I realize the the equation E=mc^2 does reveal the equivlent nature of both, but because mass represents itself to us in such a different way, is there something that we are missing in our understanding? Forgive me if this is a stupid question, I don't pretend to be an expert in this field of investigation.

[Tormod]

Mass is just concentrated energy.

[infamous]

Yes Tormod, I understand the principle. I quess my question is more in terms of state. Let me give you an example; H2O can exist in three different physical states, water, ice, and gas as in vapor. The difference between water and ice is quite evident for the observer, both being states of the same chemical composition, however temperature is responsible for the difference. With matter and energy, what is the responsible agent for the different states. I don't understand how one could define energy as an agent because it is one of the two states, thus requireing it to be two different things. On the one hand, it's a component in the reaction, and on the other hand its the cause. Straighten me out on this.

[Tormod]

temperature is responsible for the difference.

Actually, temperature is just a measurement of the available heat content in a body, or molecular motion if you want, so it represents the energy level of a macroscopic object. So it's the same thing. When water heats up, it gets energy from the source that heats it, and at the boiling point the energy is high enough to make water vaporize. At freezing point it will melt or freezem depending on whether energy is being absorbed or emitted. These are just phase changes.

 

With matter and energy, what is the responsible agent for the different states.

Energy is always conserved. Matter is not. Any conversion of energy into matter (for example fusion) requires energy, any conversion of matter into energy (for example fission) releases energy.

 

The latter is the easy part - it needs only matter to work. That's why we can make practical use of fission reactors, because they work by matter decay. Fusion reactors, however, require enormous amount of energy to work - like the inside of a star. But they would be much more useful than the fission reactors, because they would not leave enormous piles of lethal waste products.

 

http://www.iter.org/ITERPublic/ITER/fr_text.html

 

I don't understand how one could define energy as an agent because it is one of the two states, thus requireing it to be two different things. On the one hand, it's a component in the reaction, and on the other hand its the cause. Straighten me out on this.

Well, it's particle physics and not my field but I have read quite a few books on the subject. But why can an agent not also be a cause? Energy and matter come in many forms and shapes. It is in the nature of energy to lump together and form matter. The forces behind this are the nuclear forces (weak and strong) and electromagnetism. These are all specialized forms of energy.

[infamous]

Thanks Tormod; I think it's time for me to do some more research. I appreciate your willingness to take the time and help with these questions. It is just much easier to get a question answered by someone you trust than to do the study yourself. I have to admit that I'm a little guilty in this respect. Thanks again.

[maddog]

I think Tormod's description at the beginning of this thread stated the case the closest.

Also to reiterate these are two different theories that are very accurate in there respective

distance scale (QT & GR). When either attempt operate among the other scale, contradictions

arise.

 

excuse me, what's the difference between QT and QM? :)

 

To help Tinny here.

 

QT = Quantum Theory

QM = Quantum Mechanics

 

QT basically incorporates both QM and QFT (Quantum Field Theory). QFT is basically

QM mixed in with Special Relativity (SR).

 

So a consistent QFT description of a gravity field would then incorporate GR and this

at current does not work. Something is missing/wrong or broken.

 

Currently M-Theory is hacking at it from QFT side and Loop Quantum Graivty is doing

the same from GR. Yes, the book by Lee Smolin was an exellent book! Hope this helps.

 

Maddog

[TINNY]

Mass is just concentrated energy

how is energy concentrated? what is the level of concentration for energy to be mass? i don't understand how photons becomes massive. It is something like slowing it down right?

Am I too ridiculous?

[infamous]

Tinny; This may be too simplified an answer for those of us with our heads buried in string theory, but in basic terms, mass is energy that has taken on a geometric from. Energy will propagate in straight line form unless acted upon by external influence. This might be gravity for one example, or the influence of another competing energy. I could however, be somewhat in error with this explaination, defining mass is still a difficult task.

[maddog]

how is energy concentrated? what is the level of concentration for energy to be mass? i don't understand how photons becomes massive. It is something like slowing it down right?

Am I too ridiculous?

 

Let's see where do I start ?.... Regarding concentration. It goes like this. You think of

concentration of anything like thinking about a distribution of the something over a range.

With respect to either mass or energy, you could think of this distribution over a range of

space. For instance the earth has a certain mass which can be thought of as the avg density

times the volume equals the mass. For the earth, the actual density increases as the depth

increases so you can think of an equation for the mass density of the earth and integrate over

the volume to get the mass. The same would be true if mathematically we were to convert

the earth into energy.

 

Your statement get funny when you imply that photon changes its value for mass

("gets more massive")... The fact is a Photon NEVER changes its mass. It is ALWAYS 0 (ZERO)!

A Photon is a massless particle of spin 1 (Boson). This does not mean the same for it's

Energy which is never 0. I think the connundrum here is both Fermions and Bosons both

can convert energy to mass (and vis versa). However, they do so differently. Energy for a

photon converts to its momentum (mv) which is dependent on a photons wavelength. Also

a photon doesn't slow down ever; it is ALWAYS going the speed of c. Time also does exist

for a photon either. GR does show light (photon) being bent around the neighborhood of a

massive object. One could use energy density as well here. Where you have a concentration

of energy, you can also perceive it as mass. End of story.

 

Maddog