Questions and Answers about Theories of Everything

joke hollywood star of brian greene Sometimes the journalists and editors get it right. In fact, they get it right a lot of the time, but you hear more about the complaints (sometimes from me, sometimes elsewhere) about them getting it wrong, when it comes to things like science coverage especially. What am I talking about? I’m talking about the set of questions and answers that are in a new article on MSNBC that a number of people pointed out to me yesterday and today. It starts out as an article about Brian Greene’s science outreach efforts (books, and tv and movie appearances, including a new one), with some discussion of how this is regarded by his colleagues, the value it has had in raising public awareness of physics (and fundamental science in general, I would argue), and so forth. All that is interesting, but not nearly as interesting to me right now as the later parts of the article which is simply a question and answer session. (Picture above right is from a fun joke I carried out last year that you can read here – be sure to read the comments too.)

Alan Boyle, the science editor, asks Brian a series of very thoughtful questions, and Brian gives some very thoughtful answers. The topics include research in string theory (of course), hopes and possibilities for experimental and observational results (such as from the LHC and Planck) that can inform and ultimately test the ideas coming from string theory and open up new vistas in fundamental physics, research on issues such as the landscape, the idea of multiple universes, research on better developing our understanding of string theory (to the point where we can, it is hoped, extract firm predictions from it), and many other things. (I wrote an introduction to aspects of the landscape issue here – see also the comments – and talked a bit about a Tom Siegfried article on the discussion amongst researchers here.)

It is nice to see an honest, non-inflammatory and non-hyped conversation about the issues, and read Brian’s personal take on some of these matters. The bottom line is, of course, that we (the community that is working on string theory) don’t know the answers, but we are working on some of the tools and ideas that we regard as very promising directions to follow. There’s a great deal to do, and progress continues to be made.

Other people are free to make the case for other directions of research. There’s value in multiple approaches. Nobody is wedded to string theory for its own sake. If something demonstrably better or more promising is presented as an alternative, lots of people will work on it and help it develop further, and it may well strengthen into the dominant approach to finding the answers we seek about nature. This is the way it has always been in research. We just want to know what works. With regards to those who don’t like string theory, make overly strong (and sometimes just plain wrong) public statements about and against research in that area, you’ve read my writing here and the writing of others here and elsewhere on why science simply does not and has not ever worked that way. Here is a comment from UCSB’s Mark Srednicki earlier today on just this point (follow the link for the full comment:

We see that the big issue for Brian, and for just about all scientists (though with the apparent exceptions of Lee Smolin and Peter Woit), is what is TRUE. Not what corresponds to some philosophy of what science is or is not. Lee writes that the landscape must be rejected because “it would mean the end of our field” (page 165). It should be obvious that this is not the basis that is traditionally used for accepting or rejecting a theory! Peter’s (essentially the same) argument that string theory must be rejected because (at the moment) it does not appear to be sufficiently predictive (for Peter) is also irrelevant to the question of whether or not string theory is TRUE.

Well, I’ll let you read the article, but will end with one of the questions and its answer, which echoes things I keep saying here. Before I quote it, I’d like to say one more thing. I’ve found that different people have different takes on what it means to have a “theory of everything”. There is a popular idea (perhaps the most common) that this somehow means that this theory will describe (at least in principle) all known basic physical phenomena (constituents and their interactions, if you like) once and for all. Others mean something less ambitious, a theory that consistently describes the four fundamental forces and the things that interact with them, achieving a unification of all the forces and phenomena that we currently understand. I personally think that the first idea of a theory of everything is rather naive, and my personal hunch (and bias from what I’ve learned about the history of science) is that there is simply no such thing. There’ll always be new layers, new questions we simply have not even thought of. I find it hard to believe that it is possible to write something down that can answer all questions, about everything, for all time. (I think I’ve said this at greater length in a comment elsewhere, but I can’t find it, so I will update later with a link to it, perhaps.)

What do you think?

Anyway, in reading the question below, I find myself wondering which definition the questioner is using, and which definition the answerer is using, and also which definition Hawking (who is referred to) is using. Interesting to wonder. Well here it is:

Boyle: Hawking has said that there could be a “theory of everything” produced in the next 20 years, or by 2020. Do you get that same sense? Or will there ever be a theory of everything?

Greene: Well, I always find it difficult to make predictions that are tied to a specific time frame, because as we all know, one of the exciting things about science is that you don’t know when the big break is going to happen. It could happen tomorrow, it could happen 10 years from now, it could happen a century from now. So you just keep pressing on, making progress, and hope that you reach these major milestones — ideally in your own lifetime, but who knows? So I don’t know if 2020 is the right number to say. But I would say that string theory has a chance of being that unified theory, and we are learning more and more about it. Every day, every week, every month there are fantastically interesting developments.

Will it all come together by 2020, where we can actually have experimental proof and the theory develops to the point that it really makes definitive statements that can be tested? I don’t know. I hope so. But hope is not the thing that determines what will actually happen. It’s the hard work of scientists around the world.


(Thanks Tameem, Sean, and Mark!)

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