Life, love and a finite universe

Most children find it impossible to explain their work to their parents. So spare a thought for theoretical physicist Janna Levin, whose research addresses some of the most profound questions about the cosmos. How the Universe Got its Spots is a collection of unsent letters written to Levin's mother that attempts to explain her research as well as charting the nomadic and sometimes lonely life of an academic. Over two years the letters have grown into a sporadic diary that Levin has edited - a sort of Brief History of Time meets Bridget Jones' Diary .

But Levin is no Bridget Jones. Sassy, ambitious and intelligent, her ideas on the shape or "topology" of the universe are at odds with those of most of her scientific colleagues. Most cosmologists believe that the universe is never ending: in principle, a rocket launched into space would journey for ever to infinity and beyond. Levin thinks that the universe is finite and that the fabric of space wraps back on itself. Flying in a straight line without stopping, Levin's rocket would eventually return to Earth.

Her book is not intended to be a historical treatise of modern cosmology. However, Levin skilfully gives enough background on the abstract ideas of relativity, quantum mechanics and topology for the general reader to understand her arguments. Einstein's general theory of relativity has been remarkably successful at explaining the nature of space, time and gravity. It even led to the predictions of black holes and the big bang that gave birth to the universe some 15 billion years ago. Yet relativity says nothing about the shape of space as a whole, nor explains why space is three dimensional.

Levin uses analogies to explain how a branch of mathematics called topology might help. While it is second nature for mathematicians to explore multi-dimensional worlds using equations, Levin helps readers to visualise these concepts by first describing life in a two-dimensional "flatland". The rectangular fabric of space in this flattened universe can be rolled up in different ways to form three-dimensional shapes, such as the cylinder, the doughnut and the Mobius strip. Someone living in a finite flatland could tell these topologies apart by looking at the way light travels as it follows the curvature of space and reflects from the edges. The reflections and spatial connections would reveal themselves as a pattern of ghostly images.

Some 300,000 years after the big bang, the universe filled with light that has been travelling through the cosmos ever since. In the 15 billion years since then, the universe has expanded, galaxies have formed, and stars have come and gone. Yet this cosmic background radiation has imprinted on it the earliest record of the universe.

Satellite experiments have measured the temperature of this radiation and found that it is almost identical in every direction. Crucially, however, it is peppered with hot and cold spots - regions that are just one part in 100,000 times hotter or colder than the average temperature. By looking for repeat patterns among the universe's spots, Levin believes that one day we may find that the universe is finite and discover its shape. Maps of the cosmic background radiation have provided information about the early universe but are not detailed enough to answer the topology question.

What makes Levin's account compelling is the insight into her life with musician boyfriend, Warren, who follows her around the world from one research grant to the next. It is a situation that many physicists' wives would recognise, but the gender switch is effective at revealing the pressures of academic life. Sadly the relationship does not survive, although there are hints that the couple might reunite.

I hope Levin is writing a sequel. Her female perspective is refreshing, and her personal account is firmly aimed at non-experts, such as her mother, yet avoids patronising readers. Scientifically there is ample opportunity for a follow-up: a more advanced satellite is currently mapping the skies in even greater detail and cosmologists are drooling in anticipation of the results. If they match expectations, Levin's conviction that the universe is finite may prove true. And I hope that Warren will be there to savour the moment.

Valerie Jamieson is a former particle physicist, now a features editor at New Scientist .