Quasar blinks reveal time was five times slower in early universe

Quasars have been used for the first observations of time dilation showing time running in “slow motion” soon after the Big Bang.

The Theory of Relativity suggests that looking at the early universe should show – from our existing position – time running much slower than it does in the present day. But examining how time flowed billions of years ago has been difficult.

Read more: JWST identifies the earliest strands of a quasar’s web

Now a team of astronomers, including researchers at the University of Sydney, have made headway into this puzzling aspect of the cosmos using quasars. Their results are published in Nature Astronomy.

Quasars are among the most brilliant objects in the universe. This makes them a prime candidate for observing far off ancient structures of the universe. Quasars are the hyperactive supermassive black holes, often found at the centres of galaxies, which can be observed because they shoot out huge amounts of radiation into the universe through the swirling shroud of cloud, dusk and stars which orbit them.

Using data from 190 quasars, the team was able to measure the effects of time dilation – one of the effects of relativity which emerges from the stretching of space time.

“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,” says lead author Professor Geraint Lewis from the University of Sydney.

“Looking back to a time when the universe was just over a billion years old, we see time appearing to flow five times slower,” Lewis says.

Man in white collared shirt stands in doorway next to maths white board
Lead author Professor Geraint Lewis from the School of Physics and Sydney Institute for Astronomy at the University of Sydney.

Lewis adds that, if a person travelled back to the early universe, time would appear to flow at the same rate. “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.”

For example, a human blink takes about one third of a second. That’s what it would be like for a person one billion years after the Big Bang.

But that blink, viewed from our present position 12 billion light years away, would appear to take 1.5 seconds due to time dilation.

Read more: Einstein and Euler foundational theories scrutinised using time distortion at the edge of the universe

The constant emitting of a quasar acts like that blink and it can be measured.

The team examined the different wavelengths of light from the quasars to standardise their “tick.” Using a statistical technique called Bayesian analysis, they found the rate of expansion of the universe imprinted in each quasar’s tick.

Quasars are the supermassive black holes at the centres of early galaxies. Professor Geraint Lewis at the University of Sydney has unlocked their secrets to use them as ‘clocks’ to measure time near the beginning of the universe. With this tick-tock of the quasar clock, we can now chart time across the life of the cosmos.

The results further confirm Einstein’s picture of an expanding universe.

“With this 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,” Lewis says.

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