HOW long is a piece of string? In this case, as long as the entire universe is wide. But then cosmic strings aren’t your average twine. Thinner than a proton and stretching for billions of light years, they would propagate through space at nigh-on the speed of light, fuelled by – and containing – the barely imaginable energies that existed at the big bang, where they originated.
Or at least that’s the idea. Cosmic strings are among the most extreme phenomena theorists have ever dreamed up, and yet there are sound reasons to consider them. They are “one of the most plausible, testable predictions of unified theories”, says Neil Turok, a physicist at the University of Edinburgh, UK – referring to theories that seek to describe how the fundamental forces of nature were merged, and then diverged, in the very early universe.
We are yet to find any clear evidence for the existence of cosmic strings. But in the past year, astronomers have spotted a slew of anomalies – from inexplicably large galaxies to strangely shaped clusters – that suggest we may finally be within touching distance of these enigmatic threads. What’s more, if one of these hints does hold up, we now have the tools to confirm the existence of cosmic strings once and for all, and even to begin distinguishing between their different forms.
That would count as an “enormous” breakthrough, says Joseph Conlon at the University of Oxford, as it could help theorists decide between the various unified theories on the table. “It would be a fundamentally new…