String theory (superstring, M-theory , F-theory ) is currently the most promising and, in fact, the only candidate for the theory of everything. Loop quantum gravity, spin networks, and other “alternative theories” are no longer seriously considered by the scientific community.
String Theory of Science
There are some good non-fiction books on the subject. The "Elegant Universe" by Brian Green is recalled.
But for one good book there are several, to put it mildly, not quite objective. The books of Lee Smolin or Peter Voight fit that definition.
Recently, in connection with the “problems” of gender inequality and various kinds of minorities, alternatively thinking representatives of these categories have received increasing attention. Suffice it to recall the recently published book by Sabina Hossenfelder , criticizing string theory for (you will not believe) the complexity of the mathematics used in it.
Indeed, in order to proceed to the study of string theory, one must first master the quantum field theory. To understand the ideas of quantum field theory, it is necessary to study relativistic quantum mechanics (Dirac equation, spinors, etc.). But first of all, it is necessary to understand the mathematics of ordinary quantum mechanics (Hilbert space, Hermitian operators, unitary operators, etc.) and its postulates.
Already at this first step, many are eliminated. Even the mathematics of the basic tenets of quantum mechanics is unbearable for the majority. With each subsequent step, mathematics is complicated by an order of magnitude. The number of people able to master it is reduced by an order of magnitude. As a result, string theory experts now have a maximum of several hundred in the world. Moreover, most authors of non-fiction books (Lee Smolin, Peter Voight, Sabina Hossenfelder and others) are not included.
The fact that the new physical theory requires more complex mathematics is a regularity. Theories are becoming more abstract. So it was with special and general theories of relativity, with quantum mechanics, quantum field theory. String theory is no exception.
There is no turning back. No one in the future will cancel the differential and integral calculus or tensor analysis. Replace with something even more complicated - please cancel or replace with a simpler one - no.
Arguments of Opponents of String Theory
Consider a few more popular arguments against string theory, in addition to the logic “If I don’t understand, then this is not true.”
String theory makes no predictions. It can be adjusted to any results. It is not falsifiable and is not a scientific theory by Popper's definition.
This is not true. There are ingredients without which string theory cannot do, for example, supersymmetry . If it is experimentally discovered that supersymmetry is absent in our Universe, then string theory will be refuted.
String theory has already provided some useful predictions. So in the framework of it, the formula of the entropy of a black hole was obtained from the first principles. String theory also resolved the black hole information paradox formulated by Stephen Hawking himself. Within the framework of string theory, it is shown that it is not lost.
The standard argument for the thesis that string theory can be adapted to any experimental data is the presence of order solutions, each of which gives its own physics. The so-called landscape .
Indeed, string theory is a metatheory. By analogy with how the solutions of the Maxwell electrodynamics equations give different phenomena depending on the initial conditions (light wave, static Coulomb electric field, etc.), different solutions of string theory give different physics - effective quantum field theories. Why we have such fields, and not others, really remains an open question.
But string theory doesn't exactly say that it can describe anything. On the contrary, it has many limiting criteria. For example, it forbids universes in which electromagnetic (and any other) interaction is weaker than gravitational . See also swampland .
Well it's not such a big number. If we assume that our Universe is one of this set, then its "coordinates" in this large mathematical structure will occupy only 500 decimal places. Less than a kilobyte of data fully identifies our Universe among hypothetical others. Agree, not a lot.
String theory requires additional measurements.Here is another example of how string theory provides predictions. If it is discovered that there is only one temporal dimension and three spatial ones, then string theory will be refuted!
String theory is the only physical theory that dictates the number of dimensions. Newtonian mechanics can work in any number of spatial dimensions, string theory - no. She explains why the measurements should be 10, 11 or 26. I agree that the question of why only 4 of them have macro sizes remains open.
There is no exact definition of string theory, so this is not even a theory.Yes, due to the complexity of the mathematics used, there is no strict definition yet. However, it has been shown that different versions of string theory describe the same mathematical structure from different angles (M-theory). Different versions of string theory are connected by duality .
Well, my favorite argument:
What does a string consist of?The question is a person who is far from quantum mechanics and thinks of a string as a guitar string, as well as an electron - a small ball or Newtonian material point, at best a classical wave of matter or the distribution of electric charge.
Such people usually show the greatest activity in discussions, with foam at the mouth in the comments proving the fidelity of the world-wide interpretation of quantum mechanics and the fallacy of string theory.