Andrew Pontzen (Jonathan Cape)
GETTING to grips with the enormity of the universe and everything in it has always been the ultimate challenge for scientists.
The universe, as cosmologist Andrew Pontzen notes in his snappily written book, The Universe in a Box, is 13.8 billion years old. It comprises many different kinds of things – from countless atoms, molecules and particles to living things whose actions affect everything around them – so the old butterfly effect idea is actually a fair representation of what is involved.
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Science continues to try to pin the cosmos down, largely through simulations – computer models that attempt to replicate phenomena so enormous they would otherwise defy understanding. Without simulations, many of the ideas informing theoretical physics would remain mere guesswork.
In many ways, Pontzen’s book is a tribute to simulations – which is odd, partly for personal reasons that will soon become clear. Simulations are far from perfect; ask anyone who has looked askance at a forecast predicting a perfectly sunny day while standing in a torrential downpour. Yet the problems with weather forecasting turn out to be useful when it comes to simulating something as vast as the universe.
The factors contributing to changes in weather are minuscule and multiple, so simulations of weather systems can never capture every factor. The work requires educated guesses and making them involves things like aggregating phenomena such as clouds so they represent a group, rather than individual parts of a system.
In such generalisations – which we unknowingly encounter in our daily lives – lie problems, from that unforeseen drenching by a cloudburst to unexpected floods that can cost many lives.
The problems multiply when scaled up to the level of the universe. If we can’t get something as relatively simple as the weather right, how can we know if we are accurately representing the myriad variables involved in the cosmos?
That was something Pontzen thought about earlier in his career. He admits that he was a simulation sceptic, not seeing the point of wasting time creating them. If that famous butterfly’s wing flap is represented by a guesstimate of the actions of 10,000 or 10 million butterflies in aggregate, what are those predictions worth?
Not much, Pontzen thought. As a young researcher, he even asked to be moved away from a PhD project developing a simulation, so pointless did he find the exercise. “I had talked myself into the idea that simulations were hokey,” he writes.
That sentence typifies Pontzen’s ability to weave hard science and dense theory into a gripping narrative. Physicists aren’t often known for their user-friendliness when it comes to explaining their science, but by delving into the history of forecasting and the development of simulations of key things – including the weather, quantum mechanics and black holes – Pontzen makes the complicated comprehensible.
We are lucky to have a sceptic as a guide. Pontzen eventually realised that he had simulations all wrong. They aren’t designed to capture every tiny element of reality in computer code: if we could do that, we would just build a parallel universe. Instead, they provide a way to structure how we think about the world. He says that the best part of his work now is “working with other humans to understand the results that computers produce – we visualise, interrogate, interpret, in an effort to transform simulated worlds into knowledge about our own reality”.
They are guesses, yes, but they are the very best ones we have.
Chris Stokel-Walker is a writer based in Newcastle upon Tyne, UK
Article amended on 15 June 2023
We corrected the age of the universe.
