EXCERPT

John Ellis: The candidate we have for the grand, final theory of everything is string theory and it is a bit of an embarrassment. Nobody in the 40 years that followed its formulation has been able to come up with a way to test the string theory as a potential grand theory of unification.

Nicholas Maxwell: I think that science has already established that there is a unified theory of everything. Insofar as science can ever establish something theoretically.

Frank Close: We have seen successful ways of bringing apparently opposing energies together. The interaction between the moon and our planet for example is remarkable. We take it for granted but it is remarkable.

Chair: Going from the sub-atomic to the pan-galactic, from the infinitesimal to the infinite, from the unifying to the universal. Instead of a sales offer “everything must go”, the motto here is “everything must come together”. But must it?

Why is it that some physicists are so certain that across every scale, from the microscopic to the macroscopic there is “one thing to bring them all and in the darkness bind them”.

Even if there is, how near might we be to formulating or unscrambling such grand theory? Is it possible that there may be something out there but that it will be forever beyond our grasp? And what do we mean by everything? How all-encompassing is it?

Let's start with John Ellis, the first to introduce the theory of everything in serious debates in the mid-80s and one of the key figures at CERN.


John Ellis:

Physics has been in the unification business for a long time, going back as far as Newton. Modern theories of unification got going with Maxwell – 150 years ago – a professor at King’s College, London who unified electricity and magnetism. Since then we’ve unified quantum theory and special relativity, we’ve got a unified theory of the radioactive force together with electricity and magnetism.

Going further than that there are grand unified theories (GUTS), with the shining castle on the hill: combining all that with the quantum theory of gravity. That would be the ultimate theory of everything. As long as the string theory hasn’t been tested, in a way, it isn’t much of a theory. People have been beavering away on that problem but there is no way to test it so far.

See the article: “String theory: theory of everything or nothing?”


Nicholas Maxwell:

In order to better understand our problem here we need to improve our ideas about science itself. There is this orthodox idea - that many scientists pay lip service to - that in science theories get accepted or rejected based on evidence. In the end it’s evidence that decides what’s accepted as knowledge

This in my view is untenable. In theoretical physics at least, what goes on is that there are two requirements a theory has to satisfy in order to be acceptable: it has to be sufficiently empirically successful and it has to be unified. That is, it has to say that the same laws apply to all the possible phenomena that the theory applies to. You can’t have a theory that says one set of laws over here, another set of laws over here etc… You can’t have a patchwork of theories like that in science. In my view that means that the whole scientific enterprise makes a whole assumption about the nature of the universe, at the very least that the universe is such that all grossier disunified theories are false. This is a metaphysical assumption and untestable assumption of course. Then the question becomes: what should this assumption be? And how can we improve it? Because since it’s an assumption about the ultimate nature of the universe… we can’t get it wrong.


Frank Close:

Yes physics is in the business of unifying things and looking for a theory of everything. But physics is also in the business of approximations, thanks to nature. Scientists are always working at their own level (chemistry, astrophysics, biology) without having to know about the very specifics of other fields their colleagues are working on. Quantum gravity, which certainly would require to be understood, has yet to be experimented. We may have a theory but is it nature’s theory? We won’t know until we can test it and experiment it.

Having a theory of everything and how useful it is in practice to our understanding of the world are two different things. Or at least they might be two different things. We already have a theory of quantum gravity in the string theory but whether it is the right theory of it… time will tell.