Brian Greene's NYT op-ed

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Let me comment to some extent.

In the decades since, the urgency of finding a unified theory has only increased. Scientists have realized that without such a theory, critical questions can't be addressed, such as how the universe began or what lies at the heart of a black hole. These unresolved issues have inspired much progress, with the most recent advances coming from an approach called string theory. Lately, however, string theory has come in for considerable criticism. And so, this is an auspicious moment to reflect on the state of the art.
Greene is very likely referring to the two books (Woit's "Not Even Wrong" and Smolin's "The Trouble with Physics", and ensuing newspaper/magazine articles that appeared recently, together with the sometimes heated exchanges that have taken place in the past months. I am sure Greene and colleagues have reflected a lot on the "state of the art", but frankly what follows in the op-ed is not much a result of state of the art reflection. Of course, one will read the same stuff that has been repeated on and on since people seriously started asking questions about string theory.

In hindsight, there was almost no way he could have succeeded. He was barely aware that there were two other forces he was neglecting - the strong and weak forces acting within atomic nuclei. Furthermore, he willfully ignored quantum mechanics, the new theory of the microworld that was receiving voluminous experimental support, but whose probabilistic framework struck him as deeply misguided. Einstein stayed the course, but by his final years he had drifted to the fringe of a subject he had once dominated.

After Einstein's death, the torch of unification passed to other hands.
I'm not really sure what this last metaphorical piece is supposed to mean. Given Einstein ignored quantum mechanics, his supposed "torch of unification" could be thought, and quite rightly, as inherently wrong. It wasn't even supposed to light the way to a quantum theory of gravity, since it was not meant to. I guess young physicist serious enough really wanted to grab that kind of torch.

For decades, however, the force of gravity stubbornly resisted joining the fold. The problem was the very one that so troubled Einstein: the disjunction between his own general relativity, most relevant for extremely massive objects like stars and galaxies, and quantum mechanics, the framework invoked by physics to deal with exceptionally small objects like molecules and atoms and their constituents.
I think Greene is wrong here, right? Einstein was not trying to put GR and QM together, hence he could not be concerned by "the disjunction between his own general relativity, [...] and quantum mechanics". Maybe I am not understanding this in the right way, or missing some hint.

To be sure, no one successful experiment would establish that string theory is right, but neither would the failure of all such experiments prove the theory wrong. If the accelerator experiments fail to turn up anything, it could be that we need more powerful machines; if the astronomical observations fail to turn up anything, it could mean the effects are too small to be seen. The bottom line is that it's hard to test a theory that not only taxes the capacity of today's technology, but is also still very much under development.
Then, according to my understanding, the theory of strings is not falsifiable. hmm...

Well, you can read the rest and curse me for quoting what many of you, in general terms, have read and heard so many times now:

Some critics have taken this lack of definitive predictions to mean that string theory is a protean concept whose advocates seek to step outside the established scientific method. Nothing could be further from the truth. Certainly, we are feeling our way through a complex mathematical terrain, and no doubt have much ground yet to cover. But we will hold string theory to the usual scientific standard: to be accepted, it must make predictions that are verified.

Other detractors have seized on recent work suggesting that one of string theory's goals beyond unification of the forces - to provide an explanation for the values of nature's constants, like the mass of the electron and the strength of gravity - may be unreachable (because the theory may be compatible with those constants having a range of values). But even if this were to prove true, realizing Einstein's unified vision would surely be prize enough.

Finally, some have argued that if, after decades of research, the theory is still a work in progress, it's time to give up. But to suggest dropping research on the most promising approach to unification because the work has failed to meet an arbitrary timetable for complete success is, well, silly.

String theory continues to offer profound breadth and enormous potential. It has the capacity to complete the Einsteinian revolution and could very well be the concluding chapter in our species' age-old quest to understand the deepest workings of the cosmos.

Will we ever reach that goal? I don't know. But that's both the wonder and the angst of a life in science. Exploring the unknown requires tolerating uncertainty.
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