Question about Paradoxes

egon spengler

Its a fairly stupid question but how do we know paradoxes cant exist just because our brains have evolved not to understand them as bio logic machines? x and not x being one and the same thing at the same time, I mean its ad hoc conjecture but is there some form of un-logic that is more powerful than logic which would make this possible to conceive of that we dont have built in? I dont know, but the schrodingers cat experiment, wouldnt that be an example of a real life paradox, the cat is both alive and dead until it is observed to be either alive or dead? Or firing electrons through one slit while they are passing through the other slit, isnt that paradoxical? The universe operates by laws of logic I gather, but if we can nominate the concept of a squared circle we can conceptualize it indirectly, we cant understand it nor envisage it but we can still name it which means we can invoke it from abstraction. It may not exist except in this form, does this mean that it lies outside the universe as matter and information if the universe only operates by logic?

Ghost Rider

I can't follow everything you've said and I don't know about Schrodinger's cat, but I agree with you about the squared circle. We can have a concept of it even if we cannot imagine it. The same is true of infinity: we can't imagine it but we can conceive of it perfectly well (to the extent that we can use it in mathematics). Kant would also have added to that list what he called ideas of reason, including freedom and justice.

Paradoxes, like ideas of reason, may well teach us more about the limits of our frames of reference - whether that be a natural language or, say, propositional logic - than they do about the nature of world outside of those frameworks.

To take it a step further, and in a Wittgensteinian direction, paradoxes may be of interest because they're akin to bumping up against the structure of a frame of reference. Thus, linguistic paradoxes tell us something about the structure of language, while logical paradoxes tell us something about the structure of logic.

The general lesson of all this is that we shouldn't treat problems in our frames of reference as if they were problems with the world. It is we who seek understanding of the world; the world doesn't seek it of us!

egon spengler wrote:

Its a fairly stupid question but how do we know paradoxes cant exist just because our brains have evolved not to understand them as bio logic machines? x and not x being one and the same thing at the same time, I mean its ad hoc conjecture but is there some form of un-logic that is more powerful than logic which would make this possible to conceive of that we dont have built in? I dont know, but the schrodingers cat experiment, wouldnt that be an example of a real life paradox, the cat is both alive and dead until it is observed to be either alive or dead? Or firing electrons through one slit while they are passing through the other slit, isnt that paradoxical? The universe operates by laws of logic I gather, but if we can nominate the concept of a squared circle we can conceptualize it indirectly, we cant understand it nor envisage it but we can still name it which means we can invoke it from abstraction. It may not exist except in this form, does this mean that it lies outside the universe as matter and information if the universe only operates by logic?

egon spengler

Ghost Rider wrote:

I can't follow everything you've said and I don't know about Schrodinger's cat, but I agree with you about the squared circle. We can have a concept of it even if we cannot imagine it. The same is true of infinity: we can't imagine it but we can conceive of it perfectly well (to the extent that we can use it in mathematics). Kant would also have added to that list what he called ideas of reason, including freedom and justice.

Paradoxes, like ideas of reason, may well teach us more about the limits of our frames of reference - whether that be a natural language or, say, propositional logic - than they do about the nature of world outside of those frameworks.

To take it a step further, and in a Wittgensteinian direction, paradoxes may be of interest because they're akin to bumping up against the structure of a frame of reference. Thus, linguistic paradoxes tell us something about the structure of language, while logical paradoxes tell us something about the structure of logic.

The general lesson of all this is that we shouldn't treat problems in our frames of reference as if they were problems with the world. It is we who seek understanding of the world; the world doesn't seek it of us!

Here schrodingers cat if your interested

Wiki wrote:

A cat is placed in a sealed box. Attached to the box is an apparatus containing a radioactive atomic nucleus and a canister of poison gas. This apparatus is separated from the cat in such a way that the cat can in no way interfere with it. The experiment is set up so that there is exactly a 50% chance of the nucleus decaying in one hour. If the nucleus decays, it will emit a particle that triggers the apparatus, which opens the canister and kills the cat. If the nucleus does not decay, then the cat remains alive. According to quantum mechanics, the unobserved nucleus is described as a superposition (meaning it exists partly as each simultaneously) of "decayed nucleus" and "undecayed nucleus". However, when the box is opened the experimenter sees only a "decayed nucleus/dead cat" or an "undecayed nucleus/living cat."

The question is: when does the system stop existing as a mixture of states and become one or the other (see basis function)? The purpose of the experiment is to illustrate a paradox; as Schrödinger wrote:

"The [wavefunction] for the entire system would [have] the living and the dead cat (pardon the expression) [sic] mixed or smeared out in equal parts."[1] Because we cannot get along without making classical approximations, quantum mechanics is incomplete without some rules to relate the classical and quantum descriptions. One way of looking at this connection is to say that the wavefunction collapses and the cat becomes dead or remains alive instead of a mixture of both.

The assertion that this thought experiment most clearly refutes is that the laws of physics are fundamentally different for an act of observation than for other situations. This makes the selection of which laws of physics apply to the cat, between the nuclear decay and the opening of the box, depend on whether or not one considers a cat to qualify as an "observer".

The original article appeared in the German magazine Naturwissenschaften ("Natural Sciences") in 1935: E. Schrödinger: "Die gegenwärtige Situation in der Quantenmechanik" ("The present situation in quantum mechanics"), Naturwissenschaften, 48, 807, 49, 823, 50, 844 (November 1935). It was intended as a discussion of the EPR article published by Einstein, Podolsky and Rosen in the same year. Apart from introducing the cat, Schrödinger also coined the term "entanglement" (German: Verschränkung) in his article.

Albert Einstein was impressed; in a letter to Schrödinger dated 1950 he wrote:

You are the only contemporary physicist, besides Laue, who sees that one cannot get around the assumption of reality - if only one is honest. Most of them simply do not see what sort of risky game they are playing with reality - reality as something independent of what is experimentally established. Their interpretation is, however, refuted most elegantly by your system of radioactive atom + amplifier + charge of gun powder + cat in a box, in which the psi-function of the system contains both the cat alive and blown to bits. Nobody really doubts that the presence or absence of the cat is something independent of the act of observation.
Today, the mainstream view is that the thermodynamically irreversible triggering of the device acts as if it were an observation, in that the triggering apparatus generates decoherence that appears to "collapse" the wave function. This may be the best way to describe this experiment, but it is of little help in the EPR case mentioned above, rendering the last sentence in the Einstein quote above no longer true.

and the full link, there are a lot of links in the page linked to really interesting stuff, as always with quantum mechanics.

http://en.wikipedia.org/wiki/Schrodingers_cat

Say with mathematics, wouldnt paradoxes within it have a bearing on possible paradoxes in real life given that it is a very powerful and general tool which can be used to describe phenomena? Also Im not sure on this completely but I think the universe is a self contained system operating on laws of logic. Now its not infinite, so would that not infer that something exists outside or beyond/before it even though by definition the universe is all there is!, which could include paradoxes? Evidence seems to indicate, and Im recalling very sketchily, that the universe will continue to expand until all the energy in it is expended thereby resulting in it having a zero state of energy which means it will tunnel in on itself, it wont have anything to exist with. I also recall, and this is probably distorted by memory and the passing of time that everything that has, is and will happen informs what has happened in the universe in its infant state which in turn informs what has, is and will happen after this state, like a river shaping a valley and vice versa. No doubt this is arseways and probably vastly inaccurate but thats how I remember it anyway. So in that case wouldnt the universe be all there is as a self contained system (obviously contradicting the idea that it will die), in a platonic forms kind of way?

Also, something that I had a thought about, do all time periods exist with overwhelming probability, in the sense that the universe is near infinite (hence the probability aspect). What I mean to say is that say something happened on earth 100 years ago. A 100 light years away information of that event is just received by aliens, right now actually, but a 100 years ago from where we are observing. A further 100 light years away from the place 100 light years away from where we are, the information is received 200 years from the event on earth by another group of aliens and so pm until aliens at the farthest point in the universe recieve it which will take near infinity? And then the information of their world will take near infinity to reach us (lets assume that the earth will exist for more than 5 billion years when its consumed by the sun). From a birdseye view would all time periods in the universe be seen to be happening simultaneously or would the relativity between them in spacetime, ie what is seen 100 light years away will have happened 100 years ago in our frame of reference, and what we will have seen in that frame of reference will have happened 100 years ago from their frame of reference, negate this (all time periods occuring simultaneously)? If not, would this not grant the universe a platonic immortality such that if it were operating completely on logical grounds there is no such things as paradoxes or would it be the case that the conflation of the past and present is paradoxical in itself? Are these be paradoxes or do they indicate that paradoxes are something deeper which just appear as paradoxes to us?, (just to bring it back on topic), which is kind of what I was saying in the first place.

Goodshape

Just came across this site yesterday, it might offer you some insight :
http://www.tenthdimension.com/flash2.php


...maybe not exactly what you are on about, but I think it's tackling the same question(s).

Ghost Rider

That's excellent.

Goodshape wrote:

Just came across this site yesterday, it might offer you some insight :
http://www.tenthdimension.com/flash2.php


...maybe not exactly what you are on about, but I think it's tackling the same question(s).

pH

Ghost Rider wrote:

That's excellent.

Excellent - if what you want to know is what nonsense a sound engineer can make up in an afternoon about string theory and 10 dimensions.

Presentation 10/10
Meaningful content 1/10 (he gets 1 dimension pretty much right)

The "theory of reality" that I advance on this website and in the book "Imagining the Tenth Dimension" is not the one that is commonly accepted by today's physicists.
http://www.tenthdimension.com/textonly.php

Ghost Rider

Care to elaborate?

pH wrote:

Meaningful content 1/10 (he gets 1 dimension pretty much right)

http://www.tenthdimension.com/textonly.php

Son Goku

Care to elaborate?

The site is just some random idea made up by a sound engineer. It has no reality to it.

Goodshape

Funny - I was going to turn away from that site as soon as the initial "BUY MY BOOK" page came up.. Probably should have gone with my instincts with that one.

Still, I'm confident I have a broader understanding of the dimensions after having watched it.

Don't suppose you want to tell us how it really is, pH / Son Goku?

pH

Goodshape wrote:

Funny - I was going to turn away from that site as soon as the initial "BUY MY BOOK" page came up.. Probably should have gone with my instincts with that one.

*nods*

Still, I'm confident I have a broader understanding of the dimensions after having watched it.

That's interesting, what gives you that confidence?

Don't suppose you want to tell us how it really is, pH / Son Goku?

Nooooooooooooooooooo - not the fibre bundles! - anything but them!

Goodshape

pH wrote:

That's interesting, what gives you that confidence?

My level of understanding was extremely narrow beforehand . At least now I've questions that can be asked and a frame of reference (albeit a somewhat inaccurate and simplified one).

Nooooooooooooooooooo - not the fibre bundles! - anything but them!

Fibre bundles, eh? ...it's like knowing the answer without understanding the question*

And that wiki article reminds me of this. I think I need layman's terms, with plenty of 'real world' similes.


*what do you get if you multiply six by nine?

pH

Goodshape wrote:

Fibre bundles, eh? ...it's like knowing the answer without understanding the question*

And that wiki article reminds me of this. I think I need layman's terms, with plenty of 'real world' similes.[/url]

Excellent example. That video is of course a joke, but it is a great example of what we're talking about here. How can you (or anyone) tell the difference between sense and nonsense?

The fibre bundle is a joke for Son Guko, who is qualified and capable of explaining this to you (I am not).

Ghost Rider

You seem very confident you know the difference.

I repeat, care to elaborate?

pH wrote:

Excellent example. That video if of course a joke, but it is a great example of what we're talking about here. How can you (or anyone) tell the difference between sense and nonsense?

The fibre bundle is a joke for Son Guko, who is qualified and capable of explaining this to you (I am not).

pH

Ghost Rider wrote:

You seem very confident you know the difference.

I repeat, care to elaborate?

Son Guko already did elaborate (did you read his post?). If you can be a little more specific in your request then I'll do my best.

Son Goku

Essentially, Ghost Rider, the site has no more substance to it than an site which explains how spaceships work in Star Trek.

The guy just picked ten dimensions, simply because that is how many String Theory uses and then proceded to construct a completely random personal cosmology.

Nooooooooooooooooooo - not the fibre bundles! - anything but them!

Goodshape, the correct concept required to understand the notion of the extra dimensions in String Theory is that of Fibre bundles.
Now I could explain them, but it would require a series of lengthy posts with a smorgasboard of analogies......

....or I could simply tell you that String Theory is a very, very technical and hypothetical answer to an already very technical question in physics.
Experimental evidence still supports a universe of only three spatial and one temporal dimension.
So there is no reason to try and understand it, just like one wouldn't try to understand any other current research field, as they aren't solidified or confirmed bodies of knowledge.

Ghost Rider

I did indeed read his post but I don't claim to understand the in jokes, nor do I claim to know anything about string theory. You, on the other hand, in being dismissive, are implicitly making a claim to authority. That's why I'm asking you to elaborate on what you understand to be the "sense" of the ten dimensions of string theory, as distinct from the "nonsense" on that website.

Also, this is supposed to be a philosophy forum, so I think you have more of a duty to explain yourself than you might on some other forum.

pH wrote:

Son Guko already did elaborate (did you read his post?). If you can be a little more specific in your request then I'll do my best.

Son Goku

I did indeed read his post but I don't claim to understand the in jokes, nor do I claim to know anything about string theory. You, on the other hand, in being dismissive, are implicitly making a claim to authority. That's why I'm asking you to elaborate on what you understand to be the "sense" of the ten dimensions of string theory, as distinct from the "nonsense" on that website.

Also, this is supposed to be a philosophy forum, so I think you have more of a duty to explain yourself than you might on some other forum.

The guy, on his site, personally admits that he made it up and one can see that the site is a tool to sell his book.

Regardless of what one understand about String Theory, the fact that the guy states he made it up is enough to dismiss it as nonsense.

Ghost Rider

When you say "there is no reason to try and understand it", bear in mind that this is a philosophy forum. I imagine the people who post here would prefer you to have a go at explaining string theory, or at least the problem in physics which it is supposed to address. I know I would, as I am completely ignorant of the area.

Son Goku wrote:

Essentially, Ghost Rider, the site has no more substance to it than an site which explains how spaceships work in Star Trek.

The guy just picked ten dimensions, simply because that is how many String Theory uses and then proceded to construct a completely random personal cosmology.




Goodshape, the correct concept required to understand the notion of the extra dimensions in String Theory is that of Fibre bundles.
Now I could explain them, but it would require a series of lengthy posts with a smorgasboard of analogies......

....or I could simply tell you that String Theory is a very, very technical and hypothetical answer to an already very technical question in physics.
Experimental evidence still supports a universe of only three spatial and one temporal dimension.
So there is no reason to try and understand it, just like one wouldn't try to understand any other current research field, as they aren't solidified or confirmed bodies of knowledge.

Ghost Rider

That's a fair point. My curiosity has been tickled, though...!

Son Goku wrote:

Regardless of what one understand about String Theory, the fact that the guy states he made it up is enough to dismiss it as nonsense.

pH

Ghost Rider wrote:

Also, this is supposed to be a philosophy forum, so I think you have more of a duty to explain yourself than you might on some other forum.

Right, then let's see ..

"this is the philosophy forum so you have more of a duty to explain yourself than you might on some other forum."

And your explanation/support for the tenthdimension.com was :

Ghost Rider wrote:

That's excellent.

And mine is :

That's rubbish.

They seem equivalent in their fulfilment of their "duty to explain", or possibly you mean this duty applies to others and not to you?

Son Guko has already posted a reasonable refutation of the site, so either:

• Ask specific questions,
• or post an argument actually supporting the arguments/theory found on the site

Ghost Rider

I never claimed any authority in saying I thought that site was excellent. I was merely expressing an enthusiastic response. This is not a physics forum, I am not a physicist so how you can assume I speak with any more authority than any other punter, I do not know. If I'd known the content of the Flash animation was a "personal" account of string theory (or what you call "rubbish"), I'd have been a hell of a lot less enthusiastic. I was wrong. I moved on. Is that okay with you?

You, on the other hand, came on to to a philosophy forum making the kind of noises that strongly imply you know your s__t, to put it mildly. Your response was not merely the opposite of enthusiasm, it was that coupled with the strong suggestion that you knew what you were talking about.

I don't like dismissiveness, and I don't think it has any place on a forum like this, especially when it comes from someone who seems unwilling to make any positive contributions. By calling you on your stuff, I was giving you a chance to make a positive contribution. You didn't take that chance, so now that I've explained myself, I'm bowing out of this thread. I don't believe this atmosphere is conducive to philosophical discussion.

pH wrote:

Right, then let's see ..

"this is the philosophy forum so you have more of a duty to explain yourself than you might on some other forum."

And your explanation/support for the tenthdimension.com was :



And mine is :

That's rubbish.

They seem equivalent in their fulfilment of their "duty to explain", or possibly you mean this duty applies to others and not to you?

Son Guko has already posted a reasonable refutation of the site, so either:

• Ask specific questions,
• or post an argument actually supporting the arguments/theory found on the site

Son Goku

When you say "there is no reason to try and understand it", bear in mind that this is a philosophy forum. I imagine the people who post here would prefer you to have a go at explaining string theory, or at least the problem in physics which it is supposed to address. I know I would, as I am completely ignorant of the area.

I wouldn't mind explaining, but with you bowing out of the thread I don't think there'd be anybody else interested. Although I'll leave the offer open.

Playboy

Son Goku wrote:

I wouldn't mind explaining, but with you bowing out of the thread I don't think there'd be anybody else interested. Although I'll leave the offer open.

I'll listen Son Goku, thats if you dont mind posting?

Son Goku

Playboy wrote:

I'll listen Son Goku, that’s if you don’t mind posting?

Of course not.

This will take about three posts and it'll be equal halves history and physics (because the questions themselves have an interesting historical context, which I'll emphasize throughout.)




CM = Classical Mechanics.
QM = Quantum Mechanics.
RQM = Relativistic Quantum Mechanics.
QFT = Quantum Field Theory.
SR = Special Relativity.
GR = General Relativity.

The following box lists a few important points.

The basic ingredients of QM are:
The wavefunction - the basic entity that represented the state of a particle. In classical mechanics there where two entities x(t) and p(t), the position of the particle and the momentum of the particle at a time t. In essence the wavefunction replaced these quantities.

The Quantum Mechanical Hamiltonian - In classical mechanics the Hamiltonian describes the particle's energy. The Quantum Mechanical Hamiltonian does the same.

The Schrödinger Equation - QM's version of Newton's Second Law.
Newton's second law described how classical particles evolved over time, moving from different values of position and momentum as time moved on.
The Schrödinger equation described how the particle evolved into different wavefunctions over time.
The Schrödinger Equation also involved the Hamiltonian, so without a Hamiltonian you had no sensible way of understanding the particle's energy or time evolution.
(This is a very important point).

Also when I say "The mathematics of QM", I mean the extra parts of QM which I haven't listed in the box above.




Now on to the main section.

I'll skip the usual stuff about how physicists realised there was something wrong with classical mechanics and invented quantum mechanics.

I'll pick up after the dust settled on QM and at point where it was becoming an well accepted (although furiously debated) framework.

With the overwhelming success of QM most physicists had begun to see it as the fundamental framework in which to study subatomic physics. Recent work by a physicist named Ehrenfest had also shown that QM scaled up to CM when appropriate, so that included the phenomena described by the old theory.

The next important step was obviously to unify Quantum Mechanics and Einstein's Special Relativity.
Special Relativity considered space and time as one entity called spacetime, instead of as two seperate things, which is how they are treated in QM and CM. It also considered Energy and momentum as one thing called four-momentum, again different from CM and QM.

As well as that, it was a big goal to treat not just matter using Quantum Mechanics but also the forces such as electromagnetism.
At that point in the late 1920s when you did Quantum Mechanics you only treated matter in a Quantum Mechanical way, not the Forces, which were fields not particles.
Back then it was considered that the unification with Special Relativity was the way to go at first. Most guessed that making the forces Quantum Mechanical would simply be a technical matter, that could be done at a later date and which would be much easier after the incorporation of Special Relativity.

The first to attempt to construct RQM were Klein and Gordon, who basically changed Schrödinger’s Equation in the smallest possible way, so as to make it Relativistic.

However their equation had a two major problems, it allowed negative energy particles (which don't exist) and unlike QM gave negative probabilities in some situations. As you'll probably understand negative probabilities make very little sense.
(The statement "This has a -13% chance of occurring" is nonsense)

However in most situations the Klein-Gordon version of RQM worked and most physicists accepted it.

Its deep physical problems however worried a young physicist named Paul Dirac. Who wished to get rid of the problems of negative probabilities and negative energy.

While staring into a fire in his office in Cambridge he came upon a solution which involved more complicated mathematics and taking what relativity told us about spacetime more seriously.
His version of RQM didn't use a slightly modified Schrödinger Equation, but a completely new equation called the Dirac Equation.

His new equation also predicted a new type of matter (anti-matter). All-in-all, an improvement from Klein and Gordon.
However there were problems. It seemed that his equation could never be used on a single particle, it always predicted that at high enough energies a single particle system could turn into one with several particles. The number of particles never stayed fixed.

This ambiguity meant that Dirac's equation could never describe a system with a fixed particle, which was a problem, because its interpretation and the ability to use it sensibly rested on it being able to describe a fixed number of particles.

So the unification of QM and SR was riddled with problems.
You either had negative energies and negative probabilities or you had a system where the number of particles could change randomly, all these problems were things QM was not built to deal with. In fact they all made no sense in the framework of QM, particularly the changing number of particles which was something the mathematics of QM didn't "understand".
(Or to put it another way the mathematics of QM couldn't treat systems like this.)

So physicists of the early thirties were left with a large problem of unifying QM and SR. A problem which the next generation would solve and would involve the ignored problem of treating the forces (which were fields) quantum mechanically.

Any questions?:)
(I'll write part 2 after I've dealt with questions, in case there is any misunderstanding)

Playboy

I'm with you so far (I think )

Son Goku

Anyway while the Quantum Theorists were attempting to unify Special Relativity(SR) and Quantum Mechanics(QM), another group of physicists had separated away from the quantum crowd and had begun working on General Relativity(GR), Einstein’s more general theory which explained gravity as the curvature of space. It was basically a step up from SR and required much more advanced mathematics.
These new physicists called “Relativists” had separated away from those doing QM to quite a large degree, often conferences would be for one kind of physicist or the other. Since General Relativity described gravity, which acts on huge distances, they basically study cosmology and things concerned with the universe at large.
General Relativity requires quite a different mindset to QM so physicists tended to be raised in either of these two “schools of thought”. Hawking for instance was trained as a Relativist.
(We’ll leave this group for now because they essentially lived independent of the QM group for a while, practically until the 1980s)

Coming back to the story of QM and SR, Dirac and two other physicists Pauli and Hiesenberg left the question of QM and SR for a while in order to get a quantum mechanical description of the electromagnetic force.
The electromagnetic force is a field and when Dirac got a QM description of it, he noticed that it predicted that the field came in small packets and these packets acted like particles with wavefunctions just like in good old regular “nothing to do with fields or forces” QM.
This was the first Quantum Field Theory (QFT) which stated that particles were nothing more than the smallest “bits” of a field.
The smallest “bit” of the electromagnetic field was called a photon.

Now a new generation of physicists named Schwinger, Dyson, Feynman and Tomonaga basically came along and said that we could use this reasoning in reverse.
Since we had found that the electromagnetic field came in small packets called photons, why not work backwards and see that electrons could be the smallest packets of some field.

This field became known as the Dirac Field (because he was the one who figured out what it would be like).
The advantage of viewing electrons this way was that it worked with Special Relativity. What previous attempts to unify QM and SR had been missing was this field approach. QM only made sense with SR when you assumed the particles it was describing were the smallest packets of some field.

However the even more powerful aspect of this new field approach was that by just attaching two fields in a very simple way you could explain where the forces of nature come from.
For instance by attaching the Photon (electromagnetic) field to the Dirac (electron) field, you ended up with a theory where electrons emitted and absorbed photons. Quantum Field Theory then showed that electrons emitting and absorbing photons made them move away from each other. Which explains the repulsion of like charges.
It also explained the wierd stuff electrons did as the moved near the speed of light and several other things.
From that point on Quantum Field Theory succeeded in leaps and strides, as the quark field was added and the gluon field, explaining the strong nuclear force. Then the Weak field, which explained the Weak force. Experiments in particle accelerators from the 1950s and until today in CERN confirmed Quantum Field Theory as Quantum Mechanics successor.

However there was one force that hadn’t been accounted for and that was gravity.
In the next part I’ll explain why gravity is such a problem.

Son Goku

Any questions before I continue?

egon spengler

none so far

Son Goku

Essentially all that was left at this point was to explain Gravity in a Quantum Mechanical way. However we run into a few difficulties. First of all, we now have two completely different ways to approach this problem.

First of all, at the classical level, as I said before, gravity is explained by General Relativity which models it as a the curvature of spacetime.

Remember that when we tried to combine Quantum Mechanics with Special Relativity we got Quantum Field Theory. First we could try to combine Quantum Mechanics with General Relativity to get "X theory", lets say.

However in General Relativity gravity is a field, so we could also try to use QFT to say that gravity was a field whose smallest "bits" were particles called gravitons.

So the question is do we :
(a) Improve QM to work with GR, just like we did with SR and get an entirely new framework.

or
(b) Just turn gravity into another QFT with smallest "bits" like the other forces.

Both approaches have the problems. If we use (b) the mathematics completely breaks down and we get infinite answers for everything, gravity "resists" being explained by Quantum Field Theory.

If we use (a) we run into bigger problems. QM and QFT both presume space is smooth. Even in general relativity were spacetime is curved it is still smooth.
If we try approach (a) it basically describes a world where all there is is fundamental entities that I'll just call "nodes". Nodes don't experience time and don't experience space, because they are what makes time and space. It's only when you have enough nodes linked together correctly that space and time emerge.

(Think of a toy train set. If you scatter the pieces of track all over the place, you don't have a sensible "smooth" train track. It's only when you connect them together that the train track emerges.)

Also the mathematics of the other fields (electromagnetic field, Dirac field, e.t.c.) doesn't work at all when you replace smooth space with nodes.
(In fact we don't have a clue how you'd make the other fields work on anything but smooth spacetime)

So with (b) you have Gravity rejecting QFT and with (a) you have QFT saying it doesn't like what you've done with space by making it "nodey".

So we're stuck................

Along comes String Theory in the 1980s which basically says that approach (b) will work if we say that the smallest "bits" of fields are actually string like not particle like. Its only at low energies that the bits look like particles.
So String Theory would basically say that QFT is only a low-energy approximation of String Theory and that is why Gravity refuses to be described by QFT, because it wants to be described by String Theory.

So basically String Theory modifies QFT to make approach (b) work.

Of course there is the tantalising possibility of an, as of yet unknown, approach (c)...............

Son Goku

Again, any questions?

egon spengler

What happens next, I avidly await the next installment