The four forces of the universe are the strong nuclear force, the weak nuclear force, electromagnetism and gravity. These forces are theorised to have been part of a single superforce in the early universe. When the universe cooled, the four forces split off in stages to become the ones we see now. This all happened in the first billionth of a second after the big bang.
None of these forces should be confused with The Force, which is only accessible to Jedi Knights.
If the universe cooled very quickly, it's possible it was 'fractured' when the forces split up. The popular analogy is with an ice cube when it gets a crack in it. It is these fractures that created the cosmic strings.
Cosmic strings were first proposed by a theoretical physicist called Tom Kibble in the 1970s, just before he went on to invent the dog food that bears his name. Cosmic strings would be extremely thin — about the diameter of a proton — but they'd also be very long, stretching right across the universe. It's all very topological if you want to get into it (and I certainly don't).
They'd still be in existence too, which means they're discoverable. In theory.
Before we get to the point of this article, we need to describe another astronomical phenomenon: pulsars. Pulsars are small, compact stars (usually neutron stars) with a strong electromagnetic field. They rotate very quickly — often at sub-second intervals — and beam electromagnetic radiation out of their poles. We can see that radiation when they're pointed towards us, rather like a lighthouse.
The consistency of a pulsar's rotation and its emission of radiation makes it very handy as a clock for measuring time and distance in the universe.
There is a group of astronomers who watch pulsars, which is understandable as they're more entertaining that most things on television these days. Sometimes these astronomers see distortions in the blips of radiation from pulsars. These distortions can be caused by gravitational waves, and the gravitational waves are caused by things like two black holes colliding.
If that's the case, you'd expect the gravitational waves to be distorted in a different way for each pulsar because the distortion would depend on the masses of the black holes in question. But what one experiment purports to have found is that the distortions all look similar, suggesting a common cause.
One candidate for that common cause is cosmic strings.
But let's not jump the gun. The paper is still being peer reviewed and there could be other causes of the distortions: faulty instruments, skewed analyses or maybe someone was microwaving a pie at the time they took the measurements.
It's an intriguing thought, though, that we might be able to detect something from fractions of a second after the big bang; something as bizarre as a cosmic string too.