A second, in the infant universe right after the Big Bang, would take five of those of the present day universe before it passed, a new research has found, unlocking one of the Einstein's expanding universe's mysteries.
"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 lead author of the study, Geraint Lewis, University of Sydney, Australia.
"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 Lewis.
While Einstein's general theory of relativity says that the more distant the object being observed, such as an ancient universe, the slower it runs than the present day, peering back that far in time has proved elusive.
Examining details of 190 quasars, or hyperactive supermassive black holes at the centres of early galaxies, over two decades, the astronomers rolled back the time horizon to a tenth of its current stage and confirmed that the universe appeared to speed up as it aged. The study is published in the journal Nature Astronomy.
"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.
"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," said Lewis.
Lewis and team combined the observations from quasars taken at different colours to standardise the 'ticking' of each quasar.
Applying statistical analysis, they found the expansion of the universe imprinted on each quasar's ticking.
"With these exquisite data, we were able to chart the tick of the quasar clocks, revealing the influence of expanding space," Lewis said.
Astronomers have previously established this slow-motion universe back to about half the universe's age using supernovae, or massive exploding stars.
But while exceedingly bright, supernovae are difficult to observe at the immense distances needed to peer into the early universe.
"Where supernovae act like a single flash of light, making them easier to study, quasars are more complex, like an ongoing firework display.
"What we have done is unravel this firework display, showing that quasars, too, can be used as standard markers of time for the early universe," said Lewis.
While this study confirmed Einstein's picture of an expanding universe, it contrasted earlier studies failing to identify the time dilation of distant quasars, which led to questions about quasars' cosmological nature and the idea of expanding space.
"With these new data and analysis, however, we've been able to find the elusive tick of the quasars and they behave just as Einstein's relativity predicts," he said.