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Hot answers tagged theory-of-everything

44

The answer is no, because although a "Theory of Everything" means a computational method of describing any situation, it does not allow you to predict the eventual outcome of the evolution an infinite time into the future, but only to plod along, predicting the outcome little by little as you go on. Gödel's theorem is a statement that it is impossible to ...

33

I think Conway's Game Of Life is a great example here. We have the "Theory of Everything" for Conway's Game Of Life--the laws that determine the behavior of every system. They're extremely simple, just a few sentences! These simple "rules of the game" are analogous to a "theory of everything" that would satisfy a physicist living in the Game Of Life ...

27

One thing that stops us from having a theory of everything is actually quite simple. Gravity as we understand it, thanks to the strong equivalence principle, is not a force. It is entirely geometrizable because there is actually no coupling constant between a physical object and the "gravitational field". This means that there is no a priori way to ...

23

Because the "theory" you write down doesn't exist. It's just a logically incoherent mixture of apples and oranges, using a well-known metaphor. One can't construct a theory by simply throwing random pieces of Lagrangians taken from different theories as if we were throwing different things to the trash bin. For numerous reasons, loop quantum gravity has ...

22

While NKS came out with much hype, and with a lot of skepticism from scientists, the scientific ideas there are not completely trivial. I just think they are not foundational for the science of physics (at least not as we know it so far), rather they are foundational for the science of biology. The main discovery made by Wolfram (although with an important ...

20

Wolfram's early work on cellular automata (CAs) has been useful in some didactical ways. The 1D CAs defined by Wolfram can be seen as minimalistic models for systems with many degrees of freedom and a thermodynamic limit. Insofar these CAs are based on a mixing discrete local dynamics, deterministic chaos results. Apart from these didactical achievements, ...

16

As with many discussions about string theory, it is sometimes good to recall some reality: It was over 50 years ago that the Higgs mechanism was proposed. Compared to fully-fledged theories such as string theory, the Higgs mechanism is a tiny add-on to the observed standard model (as it was then). It took 50 years for experiment to get to the point of ...

16

The principle of stationary action is what you're looking for. You can construct a quantity called the Lagrangian, which is kinetic energy of the system, minus the potential energy of the system, namely: $$\mathcal{L} = T-V$$ It is a function of position and velocity and for example, for a particle on a line, with a force acting on it, such that $F = ... 14 People tend to take Gödel's theorem and bend it, stretch it, misstate it, misapply it, and generally do things to it that, if you did them to a cockroach in Texas, would get you arrested for animal cruelty. But there is a book, Franzén (2005), that should be enough to inoculate any responsible adult against such naughty behavior. Some points made by Franzén: ... 14 Shortly after NKS came out, I wrote a review in which I tried to explain why the answer to your excellent question is yes. A deterministic model like Wolfram's can't possibly reproduce the Bell inequality violations, for fundamental reasons, without violating Wolfram's own rule of "causal invariance" (which basically means that the evolution of a CA ... 13 The idea which is being challenged, though certainly not disproved yet, is that there are new particles, other than the Higgs boson, that the LHC will be able to detect. It was very widely supposed that supersymmetric partners of some known particles would show up, because they could stabilize the mass of the Higgs boson. The simplest framework for this is ... 11 If you go back to the origins, the difficulty in merging gravity with the other forces mostly stems from general relativity being a purely geometric theory -- again, that's in its original form -- and all the other forces being quantum, by which I mostly mean they are conveyed by well-defined force particles. The photon as the particle that conveys the ... 11 The Standard Model is a quantum field theory that explains almost everything we know about except gravity, and you can do very precise computations using it (even more precise, now that we know the mass of the Higgs). However, there are good reasons to believe that gravity cannot be incorporated into a quantum field theory. String theory attempts to ... 10 It will all depend on what the Theory of Everything will be, no? We can only look back at the technological progress that appeared once we mastered electromagnetism, and then quantum mechanics and nuclear physics. Maxwell unified electricity and magnetism in his theory, in the middle of the nineteenth century. His work in producing a unified model of ... 8 The unifying theories of the three non-gravitational forces are known as GUT, Grand Unified Theories. The only known consistent unification of all forces including gravity (plus the known matter species) is string/M-theory. The relevant energies or temperatures where the unification become crystal clear are very high – de facto experimentally inaccessible ... 8 From my cursory overview of the stuff these people have online, there are a few really glaring problems: First and foremost, it doesn't appear that the electric universe model makes any quantitative predictions. I don't see any models for how stars and galaxies are supposed to form and behave, just a bunch of words about how gravitational models make too ... 8 Unfortunately, no physically reasonable detector could ever detect gravitons. For example, a detector with the mass of Jupiter placed in close orbit around a neutron star would only be expected to observe one graviton every 10 years (see the below paper). The few that would be detected would be indistinguishable from the background 'noise', i.e. neutrinos. ... 8 This is perhaps best summarized by a review that was left on his book's amazon site: I bought the book, because I am a graduate student in string theory and was curious about "new" ways of thinking in ten dimensions. I knew the author of the book was actually a musician (some research with google was required for that), but so is Brian May of Queen, and ... 8 I think I will add my two bits as an experimentalist. The Standard Model is not the result of brilliant physicists thinking deeply and coming up with a theoretical self consistent formulation that miraculously fitted the data. It is the result of strong interplay between experiments and tentative models that coalesced to what is now the standard model. In ... 8 First regarding: Is there any appreciation for how the Incompleteness Theorems might apply to physics? To put this in perspective, image Newton said "Oh, looks like my$F = m a\$ is pretty much a theory of everything. So now I could know everything about nature if only it were guaranteed that every sufficiently strong consistent formal system is complete." ...

7

I can only speak from my personal experience (which seems fair enough since this question is subjective). Most physicists I know, including myself, are much more humble on what physics knows now and will know in the future compared to the "celebrity physicists" you mentioned. It's fairly easy to see from history of the field that whenever we think we ...

6

Disclaimer: I am not a phenomenologist. ... Having said that, I think there are two issues that are conflated here: The first is that SUSY is more or less necessary for the mathematical consistency of string theory, yes. The other is that if nature is supersymmetric at LHC-accessible energy scales, then we might have a solution to the Hierarchy ...

6

The equation is not literally correct. The single terms labeled Maxwell-Yang-Mills, Dirac, and Yukawa, are standing in for whole families of terms from the standard model lagrangian, a version of which you can see on page 1 here. The "F^2" term, which comes from electrodynamics, should really be more like "trace(G^2) + trace(W^2) + B^2", where G is for ...

6

The idea that nature is described by a nonlinear system of equations was the idea that Einstein had in the 1920s, and motivated his search for a unified field theory. It doesn't work, and it's philosophically less worthwhile than current theories anyway, so even if it did work, it wouldn't be simpler than string theory, or as elegant. The idea that you can ...

6

I don't agree with your statement of Gödel's theorem. Gödel's incompleteness theorem says that in any formal language that is strong enough to do arithmetic (i.e., you can write down Peano's axioms) there will always be a true statement that cannot be proven. What Gödel did to prove this was to construct something like the liar's paradox in any such ...

6

If a "Theory of Everything" means a computational method of describing any situation, and true arithmetic formulas exist (as Gödel has shown) which cannot be proven, true arithmetic formulas exist which are necessary to describe some situation which cannot be discovered computationally, or if discovered incidentally, can not be proven true. So for example ...

5

Yes, our Universe is approaching the empty de Sitter space – we are already pretty close to it, actually, because the cosmological constant dominates the vacuum energy (68% of it). It has a cosmic horizon (the boundary behind which we can't see) and the degrees of freedom are formally living on that surface. Via the holographic principle (in a somewhat less ...

5

Let's look at the forces in nature, there are four of them as far as we know (note that I am not very precise in the numbers I give, but for the comparison I make this is enough): the strong force is very strong, it's coupling constant (which is a measure for its strength) is about 0.1 the weak force is not actually all that weak. It can be unified with ...

5

I think it may have been Witten (perhaps somebody can correct me) who suggested that a TEO might not actually exist. Just as we might never, even in principle, posses the mathematics that can interpolate between the strongly coupled and free limits of QCD, it might not be possible to write down one set of equations that describes one corner of a TEO, say, ...

5

Lee Smolin doesn't mean that the most fundemental physical theory can have no symmetry. What he means is that symmetry shouldn't be the guiding principle in discerning fundemental physical theories. While symmetry is mathematically useful, it doesn't provide a sufficient reason to accept a theory, this goes back to Leibniz's principle of sufficient reason. ...

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