Sabine Hossenfelder reviews Shell Beach: the Search for the Final Theory by Jesper Grimstrup
Jesper Grimstrup is a Danish theoretical physicist who received his PhD in 2002. His life’s mission is to find a theory of everything. In Shell Beach: the Search for the Final Theory, Grimstrup explains how he had a brilliant idea on a trip to China two months after his PhD defence, and how he has since tried to convince other physicists of it. He calls his approach “Quantum Holonomy Theory”. I believe I’m not giving away too much when I say that other physicists have not been convinced.
Originally published in Danish in 2019, the English version of Shell Beach is a self-published book that Grimstrup released this year. He promised to write it for the supporters who financed him after he failed to obtain research grants to pursue his passion. It is not so much about the search for the final theory, but about his search in particular. The reader learns little about this pursuit in general, about its scientific history, or indeed what reason we have to believe that there should be such a theory to begin with. Grimstrup does away with the question of whether he is chasing ghosts in little more than a sentence, arguing that the laws of nature seem to have a minimal length scale and that settles the case.
It’s an untypical book for the non-fiction genre. Half of it is an attempt to convey the mathematics that Grimstrup believes matches his 2002 idea. It is a combination of loop quantum gravity and the theoretical physicist Alain Connes’ non-commutative geometry. I think that most readers, even those with a PhD in physics, will find these parts difficult to follow. The other half of the book comprises diary entries from Grimstrup’s numerous kayaking, skiing, camping and hiking trips in different countries. The book has neither figures nor references.
Grimstrup does not tell his story chronologically. A childhood recollection from 1988 is followed by a trip to Germany in 2008, a 2011 conference in India, a memory from Iceland dated 2006, and then another visit to Germany in 2009. It is confusing and does not create a coherent narrative. The tales from Grimstrup’s outdoor adventures, while possibly entertaining for some readers, do little to advance the scientific explanations. They do, however, illustrate that Grimstrup sees himself as an adventurer, proud of taking risks – he once very nearly broke his neck jumping off a cliff – and his quest for a final theory is a challenge for him, just like, say, paddling down a waterfall.
Reports from research visits and conferences likewise add little to the reader’s comprehension of the science, but rather shed light on Grimstrup’s struggle to find a place in academia. According to him, the field is fractured into the tribes that are the large research programmes, and if one wants to survive, one needs to join a tribe. Those who are in the system don’t welcome dissenters. He believes he is onto a great revelation but – besides his long-term collaborator Johannes Aastrup – no-one is interested. He does not seriously consider, at least not in his book, that this lack of interest might have scientific reasons. When a well-known German professor (who is not named but is easy to identify) calls Grimstrup’s approach “obviously wrong”, Grimstrup neither comments nor explains the situation. Instead, the next paragraph skips to one of his travel adventures.
Along the way, Grimstrup chides physicists who, on encountering non-commutative geometry, ask “whether this formulation involves more or fewer free parameters than the ordinary formulation”. Grimstrup thinks this is “tedious nitpicking” because “there is beauty here, I assure you”. He complains about the lack of attention he gets because he believes “that the mere possibility of a link, the idea itself, is worthy of discussion since it is one of the only existing candidates for a final principle”. He doesn’t discuss other existing candidate theories of everything, aside from briefly mentioning string theory, and the two approaches that he himself works with.
This book does not clarify for me what problem Grimstrup believes he has solved
In the end he explains that he found his theory, but it is “empty” because gravity remains a non-quantum force. The name of the book Shell Beach refers to the place sought by the protagonist of the 1998 movie Dark City that, when he finds it, turns out to be empty. This book does not clarify for me what problem Grimstrup believes he has solved. He does not explain how, if gravity remains unquantized, his idea solves the problem that the measurement update in quantum mechanics is instantaneous and hence incompatible with relativity. Indeed, the measurement update isn’t even mentioned in the book. (Please note that I am reviewing his book, not his scientific papers.)
But many of the accusations that Grimstrup raises against the current academic system and its culture deserve to be taken seriously. The difficulties he has faced are familiar to me, and I am heartened by the support he received through crowdfunding. However, I also think Grimstrup is too quick to put all the blame on others.
What does physics look like, and does it matter?
I have met many physicists – some young, some not-so young – who believe their sense of mathematical beauty allows them to recognize whether an idea will describe nature well. Like Grimstrup, they don’t care that, historically, this approach to theory development has worked badly. Like Grimstrup, they’re on a personal search for meaning, an “intellectual search for something that lies outside of the intellectual”, as he puts it. And since the societal relevance of such a personal endeavour is highly questionable, I think research funding bodies are right in refusing to spend tax money on it.
Be that as it may, Grimstrup has managed to present a topic that’s been written about too much already – the search for a theory of everything – in a new and original way. Shell Beach goes a long way to illustrate what’s wrong with the foundations of physics. You’ll not learn much physics from it, but I’m sure it’ll become an important case study in the sociology of science.
- 2021 Self-published £23.99pb 276pp