Time flowed more slowly in the early universe

Scientists have for the first time observed the early universe running in extreme slow motion, unlocking one of the mysteries of Einstein’s expanding universe.

Einstein’s general theory of relativity means that we should observe the distant – and hence ancient – universe running much slower than the present day. However, peering back that far in time has proven elusive. Scientists have now cracked that mystery by using quasars as ‘clocks'.

“Looking back to a time when the universe was just over a billion years old, we see time appearing to flow five times slower,” said Professor Geraint Lewis, a physicist at the University of Sydney.

He collaborated with Dr Brendon Brewer, a senior lecturer in statistics at Waipapa Taumata Rau, University of Auckland, whose research interests include astrostatistcs, statistics applied to astronomical problems. 

“If you were there, in this infant universe, one second would seem like one second – but from our position, more than 12 billion years into the future, that early time appears to drag,” said Professor Lewis.

The research was published in Nature Astronomy.

Professor Lewis and Dr Brewer used observed data from nearly 200 quasars – hyperactive supermassive black holes at the centres of early galaxies – to analyse this time dilation.

“Thanks to Einstein, we know that time and space are intertwined and, since the dawn of time in the singularity of the Big Bang, the universe has been expanding,” Professor Lewis said.

“This expansion of space means that our observations of the early universe should appear to be much slower than time flows today. In this paper, we have established that back to about a billion years after the Big Bang.”

Previously, astronomers have confirmed this slow-motion universe back to about half the age of the universe using supernovae – massive exploding stars – as ‘standard clocks’. But while supernovae are exceedingly bright, they are difficult to observe at the immense distances needed to peer into the early universe.