isn't unification ubsurd

[batmanmg]

i don't see why GR and QM need to be related at all. its like trying to relate the soccer feild to the players on it. are they just trying to find that the building blocks for the feild are the same as the building blocks for the players? I don't see why they can't just live with the fact that the players are the building blocks for the feild. none of this string nonsense. lots of little Q particles make up the feild of GR, nuff said.

(not being a twit with a stick up myself, more like devils advocate)

[houserichichi]

I believe it's the drive of humanity to want to meld everything into one big pot. QM and GR are at odds over eachother when we deal with objects like black holes that need both theories to be described. Since science is supposed to describe everything ultimately, then QM and GR must somehow meet in the middle or meld into something more unified so that black holes and other anomalies can be accounted for and described properly.

[Nick]

You mispelled absurd

[Hugh]

You mispelled absurd

This is too funny to pass... You misspelled misspelled.

[papernuke]

they need to be related because they both can be true, but not with the other one, so finding the theory of everthing that will unify them is important.

[Nick]

Actually, I honestly believed that it was spelled "mispelled"... wow.

[batmanmg]

but thats still misspelling misspelled...

damnit i just lost The Game becuase this is soo off topic...

back on topic... GR doesn't have much of anything to do with QM. They don't effect the same things... they don't even play by similar rules... in fact... the more you learn about one or the other the more differences you find in them...

QM applies ONLY to very small particles. the rules don't have any effect on larger particles / objects.. or is the effects of QM very small for larger objects much like the effects of special relativity are very small for low velocities.

also... GR applies to all objects... large and small... its just that at small sizes, GR has such a small effect its nearly immesurable.

[houserichichi]

or is the effects of QM very small for larger objects much like the effects of special relativity are very small for low velocities.

also... GR applies to all objects... large and small... its just that at small sizes, GR has such a small effect its nearly immesurable.

Yes on all counts. At the macroscopic scale we don't see the effects of QM because QM occurs at the subatomic scale (or near there). The particles that make up the macroscopic are experiencing quantum effects every instant of every day but we don't notice them because we are composed of billions and billions of them. (A quick google search gave me 7x10^27 atoms per body, so break that down into electrons and quarks on your own...so much more than just billions. More like billions of billions.) At any rate, the effects are tiny but everything is shaking. You're shaking. You shake at a measurable frequency...well, predictable frequency. We all do.

What's big doesn't "feel" QM. What's slow doesn't "feel" SR. What's small doesn't "feel" GR. Notice the quotes, but you get the idea of what I'm trying to say.

[batmanmg]

so large objects do (slightly) experiance the effects of QM, but its becuase they are the sum of small parts experiancing these effects. and those effects are extremely small relative to sive of the sum.

but GR folows oppositely... while small objects only experiance the effects slightly becuase they are weak, but when they are parts of a sum the sum is effected greatly. if that made any sense

[houserichichi]

To put it bluntly, QM is the study of the world at the quantum scale. At such small sizes gravity is incredibly feeble and negligible.

GR is the study of gravity and of macroscopic objects. At such large scales, QM effects are incredibly feeble and negligible.

That's exactly what you said and that's exactly right. However, there are times when the two theories are both needed, for instance, with black holes. Black holes are tiny tiny things (QM is needed) but they're incredible massive and exert a monstrous gravitation force (GR is needed). The two theories, then, meet and argue when we talk about things like black holes. The theories maybe be disjoint, but physics is incomplete because sometimes the two need to be used together and they can't yet.

[batmanmg]

why is it that size is the key to entering the world of Quantum physics and not mass? in the world of GR a small object with tremendous mass works the same as a large one... but for QM a nearly massless object that it huge would not feel the same effects as a nearly massless and very small object??

[jinydu]

Perhaps we need a clarification here.

When we say that quantum mechanical effects are "small" for macroscopic objects, what we mean is that the deviation between the predictions of quantum mechanics and classical mechanics are small for macroscopic objects. It does not mean that quantum mechanics gives incorrect predictions for macroscopic objects. However, quantum mechanical calculations do tend to be more difficult than classical mechanical calculations, which is why we often prefer to use classical mechanics when we can.

A similar thing is true for relativity...

Also, if I am not mistaken, quantum mechanical effects are significant when the spacing between energy levels is significant compared to the energy of the system. General relativistic effects are significant when velocities are close to the speed of light or the gravitational field strength is very large.

[batmanmg]

but QM still needs to have spacially small objects to have any significant effect

size is to QM oppositely as speed is to SR (special relativity)
speed is to SR as mass is to GR

spacial size of distance per time for speed and SR
spacial size times denisity for mass and GR
spacial size for size and QM

or would it be
spacial size per density for QM

maby volume (or any dimenstions size) is the binding thread instead of energy?

[houserichichi]

I welcome the addendum from jinydu. I should have worded my QM "argument" more like his.

Boy, where have you been? Are you thesising this year?

[jinydu]

No batmanmg, there are some situations were quantum effects are noticeable on macroscopic scales; for example, superconductivity.

Also, special relativity is a special case of general relativity (hence the names special and general).

Boy, where have you been? Are you thesising this year?

Alas, I haven't reached that stage yet.

I'm still a third-year undergraduate...

[XVX]

The fundamental difference is that QM is quantitized indeterministic and GR is continuous deterministic.

One might say that the continuous nature of GR is because the quantization is so finely spaced, we don't notice it. This is "second quantization" where you quantitize a continuous field into a quantum field theory.

This has been done and that is how they postulate the graviton. If the graviton exists, then QM wins and Einstein is wrong.

If QM wins, then the gravitational force is determined by bosons (gravitons) just like all other quantum field theories. Which means that Einstein's "interpretation" of spacetime geometry determining the gravitational force........is wrong. The success of his theory, almost being reduced to "amazing coincidence".

The theories cannot both be correct. They have ENTIRELY different explanations of the same phenomena. Either spacetime is smooth and continuous as Einsteins Equations predict or its a bubbling sea of gravitons that are quantum mechanically created and annihilated, causing the gravitational force.

What Einstein did was pure genius and quantum field theory has yielded the most accurate results ever. They both stand high on the pedestal and at least, one is wrong.


I tend to think that the graviton is false and thus quantization of Einsteins field equations is inappropriate, since they are nonrenormalizable unlike the EM equations.

QFT has its version of the "Ultraviolet Catastrophe" that becomes very important at high energies, causing the nonrenormalization. This is where string theory comes in and tries to make the connection between QM and GR.

While I tend to think string theory has gotten carried away, this is definitely where new physics will be found.