Review of 'The Grand Design' by Stephen Hawking and Leonard Mlodinow - part 3: M theory and multiverses
'The Grand Design' by Stephen Hawking and Leonard Mlodinow is full of philosophical speculation disguised as science. They talk about M-theory without ever explaining what it is, and invite us to believe in its truth on their authority as scientists.
In 'The Grand Design' Hawking and Mlodinow use their authority as scientists as a platform to advance philosophical speculations that go way beyond science.
M-theory plays a starring role in their efforts to answer the big questions:
‘String theorists are now convinced that the five different string theories and supergravity are just different approximations to a more fundamental theory, each valid in different situations. That more fundamental theory is called M-theory, as we mentioned earlier. No-one seems to know what the ‘M’ stands for, but it may be ‘master,’ ‘miracle’ or mystery.’ It seems to be all three.’ (p. 116-117)
As Hawking and Mlodinow say that no-one knows what the M stands for, I suggest that - at least in ‘The Grand Design’ - it stands for ‘Mystification.’
Mystification is the art of appearing to say something profound, without actually saying anything at all. And that’s what Hawking and Mlodinow do. They say
‘We will describe how M-theory may offer answers to the question of creation.’ (Page 8.)
But they don’t deliver on this promise. Nowhere in this book is there anything explaining what M-theory is.
So this becomes an appeal to authority: ‘Believe me; I’m a scientist.’
One of the central claims of Dawkins and others, is that science - unlike religion - does not rely on authority. It doesn’t say ‘believe this because I tell you.’ Rather it says ‘do the experiment and check this out for yourself.’
This is exactly what Hawking and Mlodinow don’t do. Instead they use their authority as scientists to make their philosophical speculations sound more authoritative than they really are. All they’re doing with M-theory is to throw sand in our eyes so we can’t see the lack of substance behind the words.
Not only that, but they claim as matters of scientific fact things which are only philosophical speculations, and which not all scientists would agree on.
Cracks and contradictions
Although they make a big thing of M-theory, if you read carefully you can see some of the cracks in their arguments. On one hand, they say that M-theory is the only possible ultimate theory:
'M-theory is the only candidate for a complete theory of the universe.' (Page 181)
But on the other hand:
It could be that the physicist’s traditional expectation of a single theory of nature is untenable, and there exists no single formulation. It might be that to describe the universe, we have to employ different theories in different situations. Each theory may have its own version of reality, but according to model-dependent realism, that is acceptable so long as the theories agree in their predictions whenever they overlap, that is, whenever both can be applied.’ (p. 116-117)
‘There seems to be no single mathematical model or theory that can describe every aspect of the universe. Instead, as mentioned in the opening chapter, there seems to be the network of theories called M-theory. Each theory in the M-theory network is good at describing phenomena within a certain range. Wherever their ranges overlap, the various theories in the network agree, so they can all be said to be parts of the same theory. But no single theory within the network can describe every aspect of the universe – all the forces of nature, the particles that feel those forces, and the framework of space and time in which it all plays out. Though this situation does not fulfil the traditional physicists’ dream of a single unified theory, it is acceptable within the framework of model-dependent realism.’ (p. 58).
Notice the huge implication of what they are saying here: for a generation or more, physicists – including Hawking - have been searching for a unified theory - a ‘Theory of Everything.’ But now, they’re saying that such a theory may not exist. This sounds like an admission of defeat. I think most practising scientists wouldn’t agree with it. They might be pessimistic about finding a theory of everything anytime soon, but I think most scientists still hope that there is such a theory out there, because there is only one reality, and only one ultimate truth.
Hawking and Mlodinow play on Richard Feynman’s ‘sum over histories’ approach to quantum physics.
'According to Feynman, a system has not just one history but every possible history.’
The sum over histories is an accepted scientific way of understanding quantum physics. But Hawking and Mlodinow extend this to some murky philosophical meanderings. From it they develop the traditional idea of multiple universes:
‘Some people make a great mystery of this idea, sometimes called the multiverse concept, but these are just different expressions of the Feynman sum over histories.’ (Page 136)
‘In this view, the universe appeared spontaneously, starting off in every possible way. Most of these correspond to other universes. Most of these correspond to other universes. While some of these universes are similar to ours, most are very different. They aren’t just different in details, such as whether Elvis really did die young or whether turnips are a dessert food, but rather they differ even in their apparent laws of nature. In fact, many universes exist with many different sets of physical laws. Some people make a great mystery of this idea, sometimes called the multiverse concept, but these are just different expressions of the Feynman sum over histories.’ (p. 136)
So starting from the sum over histories approach, they get to the multiverse, and from the multiverse they get to ‘no need for God:’
‘According to M-theory, ours is not the only universe. Instead, M-theory predicts that a great many universes were created out of nothing. Their creation does not require the intervention of some supernatural being or god. Rather, these multiple universes arise naturally from physical law.’ (pages 8-9)
I’ve written about the problems with the multiverse idea elsewhere. I won’t repeat it here. All I want to do is to underline that everything they are talking about here is speculation. Not only that, it is speculation that goes beyond their competence as scientists, into the realm of philosophy, where they are not so competent. As the review in 'The Economist' says:
Once upon a time it was the province of philosophy to propose ambitious and outlandish theories in advance of any concrete evidence for them. Perhaps science, as Professor Hawking and Mr Mlodinow practice it in their airier moments, has indeed changed places with philosophy, though probably not quite in the way that they think.
Because Hawking and Mlodinow are respected as scientists, we are inclined to take their philosophical musings more seriously than they deserve to be taken. Don’t be mystified by what they say about M-theory. Before you take as gospel anything in this book, please read an alternative view, for example Lee Smolin’s excellent book ‘The Trouble with Physics,’ which shows just how speculative and controversial some of the ideas in 'The Grand Design' are.
More reactions to 'The Grand Design.'
And an interesting video response...