It was once thought that the universe would keep expanding forever until it evaporated away into frozen nothingness in many trillions of years’ time. However it could actually meet a much more dramatic fate far sooner than we thought.
The universe is already 41 per cent of the way through its lifespan and will collapse back on itself to meet its death in an implosion called the “Big Crunch” in just 19.5 billion years’ time, a study has concluded.
This is only a fraction of the time we thought the universe had left, although one scientist remarked that there would be “no need to cancel your summer holiday plans” as it was still longer than the 13.8 billion years that had passed since the Big Bang.
The research suggests our cosmos is not a newborn infant in cosmological terms, but has entered its thirties if converted into an average human lifespan. The entirety of the cosmos as we know it will meet its end at the tender age of 33.3 billion years old, according to the study, which was undertaken by scientists at Donostia International Physics Center in Spain and published in pre-print form. Some cosmologists raised eyebrows at the highly specific nature of the estimated date.
If the expansion of the universe was slowing down, it would suggest that the cosmos might ultimately stop expanding altogether and start collapsing back inwards to a single point.
The concept of this Big Crunch had largely been dismissed because data appeared to show that the expansion of the universe was accelerating, with theories that mysterious “dark energy” was pulling galaxies apart at a growing rate. It was thought that dark energy retained a constant density, even when spread over a larger volume as the universe expanded.
More studies are now suggesting, however, that we may need to rethink this and that dark energy may behave differently than we expected, based on data from tools such as the Dark Energy Survey Instrument.
Ed Macaulay, a cosmologist at Queen Mary University of London who was not involved in the research, said that the science of cosmology was currently on an exciting “knife edge” between theories over whether the universe would expand forever or collapse inwards.
Ed Macaulay
In the recent study, researchers from Spain, China and the United States used a theory called the “axion dark energy model”, based on the theorised existence of ultra-light — but as yet undetected — particles called axions. They also suggested that the “cosmological constant” once thought to keep the universe at a constant size may actually be negative.
They concluded: “Using the best-fit values of the model as a benchmark, we find the lifespan of our universe to be 33 billion years.”
Willem Elbers, a cosmologist at Durham University who was not part of the research, said: “If the finding of evolving dark energy is confirmed in the coming years, it would mean that the fate of the universe could be very different from what we currently expect. However, the specific value of the lifespan, and whether a Big Crunch will happen at all, is still subject to enormous uncertainty.”
Macaulay said that it was “an interesting piece of work” and a novel way to “to highlight some of the interesting cosmological developments of recent years”. He said that the Nancy Grace Roman Space Telescope due to launch in the next year could provide exciting new data.
Asked about the sooner-than-expected demise of the universe, he reassured people by saying: “If you’ve got plans for the bank holiday, proceed as usual.”