How old are we? Debate over the age of the universe just got a bit more complicated

It's a question that has plagued astronomers for decades: How old is the universe and how will it end? Now an international team of scientists using a telescope in Chile believe their new findings help refine measurements.

Though new data supports an age of 13.77 billion years, the mystery is still unsolved

Using different methods, astronomers are trying to understand how fast the universe is expanding, thus also understanding its current age. But the methods don't agree, leaving them to wonder whether they truly understand the universe or if there's new physics yet to be discovered. (NASA/Hubble)

Another telescope is helping us better understand the age of the universe and its future.

Using the Atacama Cosmology Telescope (ACT) in Chile, a group of astronomers say their observations support an earlier estimate as to the age of the universe: 13.77 billion years, give or take 40 million years. Their paper was released on the pre-print publishing service on Wednesday and submitted to the Journal of Cosmology and Astroparticle Physics.

The estimate supports observations taken by the European Space Agency's Planck space telescope in the early 2010s. 

Over the years, there have been other studies that have disputed that number. For example, in 2019, a study published in the journal Science suggested the universe was 11.2 billion years old.

A portion of a new picture of the oldest light in the universe taken by the Atacama Cosmology Telescope. This part covers a section of the sky 50 times the moon’s width, representing a region of space 20 billion light-years across. (ACT Collaboration)

"For a half dozen years, I'd say even more ... within the past three years, there has been one conference after another all over the world completely focused on this issue where one group comes up and they say, 'Oh, this is what we get,' and the other group comes up and says, 'This is what we get," said Richard Bond, co-author of the paper and director of the Canadian Institute for Theoretical Astrophysics at the University of Toronto.

"We call it the Hubble tension."

Why isn't there a clear-cut answer?

It all comes down to the methods used to calculate the expansion of the universe.

Stars vs. the Big Bang

In 1929, astronomer Edwin Hubble found that the universe is expanding. Ever since, scientists have attempted to calculate just how fast that's occurring. The rate of expansion is called the Hubble Constant.

But the challenge with determining the age of our universe — which in turn helps us better understand not only its past but also its future — is that there are a few methods used to make the calculations.

One involves looking at things that are relatively nearby, cosmologically speaking, such as supernovas (exploding stars) and a particular type of star that varies in brightness, called a Cepheid variable. 

Yet another involves looking far, far back, to a time shortly after the universe came to be — in particular at the cosmic microwave background radiation, or CMB, left over from the rapid birth of the universe, some 380,000 years following the Big Bang.

ACT also used this method, though from a ground-based telescope. But one advantage it had over Planck was the ability to better measure polarization of the CMB, which tells the scientists in what direction the light is moving. This allows it to be more precise.

New physics?

Just how close were their findings to Planck's?

The space telescope put the rate of the expansion of the universe at 67.5 kilometres per second per megaparsec (one megaparsec is 3.26 million light years). The new findings put that at 67.6 kilometres per second per megaparsec.

"What ACT has done is taken away the option that the CMB measurements were just a fluke of some kind," said Mark Halpern, a professor at the University of British Columbia's department of physics and astronomy in Vancouver and co-author of the paper.

This is an important step, the authors say, in trying to determine whether astrophysicists truly understand the universe.

The Atacama Cosmology Telescope in Chile measures the oldest light in the universe, known as the cosmic microwave background. Using those measurements, scientists can calculate the universe’s age. (Debra Kellner)

"If we want the universe to be consistent, then what we need to understand is: [Is] it that we have [something] we haven't accounted for in any of the measurements? Or is there some kind of new physics?" said Renee Hlozek, co-author and a professor of astrophysics at the Dunlap Institute at U of T's department of astronomy and astrophysics.

"Because it could be that we're living in a universe that looks a certain age close to us, but then either the expansion rate changes over time or there's exotic physics that means it's a different age."

Wendy Freedman is an astronomy professor at the University of Chicago's department of astronomy and astrophysics who was not involved in the study. She also researches the expansion of the universe and has used a particular type of star — a red giant — as a method of calculating the expansion.

"I think it's a really superb piece of work," she said of the new paper. "It's a major study — and looking through the papers, they have paid a huge amount of attention to details and possible uncertainties and errors and run tests and checked through their data."

Freedman said while the data supports Planck, there's still something fundamental that we don't understand, something that the authors themselves acknowledge. 

But with the new ground-based findings, they hope that this will be another piece in the puzzle in an attempt to understand what's going on in our universe — in particular how it will ultimately cease to be.

"If we understand the age of the universe now, that can actually help us have a better view of how this is going to end," Hlozek said.


Nicole Mortillaro

Senior reporter, science

Based in Toronto, Nicole covers all things science for CBC News. As an amateur astronomer, Nicole can be found looking up at the night sky appreciating the marvels of our universe. She is the editor of the Journal of the Royal Astronomical Society of Canada and the author of several books. In 2021, she won the Kavli Science Journalism Award from the American Association for the Advancement of Science for a Quirks and Quarks audio special on the history and future of Black people in science. You can send her story ideas at


To encourage thoughtful and respectful conversations, first and last names will appear with each submission to CBC/Radio-Canada's online communities (except in children and youth-oriented communities). Pseudonyms will no longer be permitted.

By submitting a comment, you accept that CBC has the right to reproduce and publish that comment in whole or in part, in any manner CBC chooses. Please note that CBC does not endorse the opinions expressed in comments. Comments on this story are moderated according to our Submission Guidelines. Comments are welcome while open. We reserve the right to close comments at any time.

Become a CBC Member

Join the conversation  Create account

Already have an account?