The Times Australia
The Times World News

.
The Times Real Estate

.

Astronomers see ancient galaxies flickering in slow motion due to expanding space

  • Written by Geraint Lewis, Professor of Astrophysics, University of Sydney
Astronomers see ancient galaxies flickering in slow motion due to expanding space

According to our best understanding of physics, the fact space is expanding should influence the apparent flow of time, with the distant Universe appearing to run in slow motion.

But observations of highly luminous and variable galaxies, known as quasars, have failed to reveal this cosmic time dilation – until now.

In a new study[1] published in Nature Astronomy, we use two decades of observation to untangle the complex flickering of almost 200 quasars. Buried within this flickering is the imprint of expanding space, with the Universe appearing to be ticking five times slower when it was only a billion years old.

This shows quasars obey the rules of the cosmos, putting to bed the idea they represented a challenge to modern cosmology[2].

Time is a funny thing

In 1905, Albert Einstein, through his special theory of relativity, told us the speed of clocks’ ticking is relative, dependent on how the clocks are moving. In his 1915 general theory, he told us gravity too can influence the relative rates of clock ticks.

By the 1930s[3], physicists realised the expanding space of the cosmos, which is described in the language of Einstein’s general relativity, also influences the universe of ticks and tocks.

Read more: Timeline: the history of gravity[4]

Due to the finite speed of light, as we look through our telescopes, we are peering into the past. The further we look, the further back into the life of the Universe we see. But in our expanding Universe, the further back we look, the more time space has had to stretch, and the more the relative nature of clock ticks grows.

The prediction of Einstein’s mathematics is clear: we should see the distant universe playing out in slow motion.

Tick-tock supernova clock

Measuring this slow-motion universe is difficult, as nature does not provide standard clocks across the cosmos whose relative ticks could be compared.

It took until the 1990s for astronomers to discover and understand the tick of suitable clocks[5]: a particular kind of exploding star, a supernova. Each supernova explosion was surprisingly similar, brightening rapidly and then fading away over a matter of weeks.

Supernovae are similar, but not identical, meaning their rate of brightening and fading was not a standard clock. But by the close of the 20th century, astronomers were taking another look at these exploding stars, using them to chart the expansion of the Universe[6]. (This expansion turned out to be accelerating, leading to the unexpected discovery of dark energy[7].)

Read more: From dark gravity to phantom energy: what's driving the expansion of the universe?[8]

To achieve this goal, astronomers had to iron out peculiarities of each supernova, putting them on an equal footing, matching them to a standard intrinsic brightness and a standard clock.

They found the flash of more distant supernovae was stretched precisely in line with Einstein’s predictions. The most distant observed supernovae, exploding when the Universe was half its present age, brightened and faded twice as slowly as more recent supernovae[9].

The trouble with quasars

Supernovae are not the only variable objects in the cosmos.

Quasars were discovered in the 1960s[10], and are thought to be supermassive black holes, some many billions of times more massive than the Sun, lurking at the hearts of galaxies. Matter swirls around these black holes on its journey to oblivion inside, heating up and glowing brightly as it does so.

Quasars are extremely bright[11], some burning furiously when the Universe was an infant[12]. Quasars are also variable, varying in luminosity as matter turbulently tumbles on its way to destruction.

Because quasars are so bright, we can see them at much greater distances than supernovae. So the impact of expanding space and time dilation should be more pronounced.

However, searches for the expected signal have turned up blank. Samples of hundreds of quasars observed over decades definitely varied, but it seemed that the variations of those nearby and those far away were identical.

Some suggested that this demonstrated that the variability of quasars is not intrinsic but is instead due to black holes scattered through the Universe, magnifying some quasars[13] by the action of gravity. More outlandishly, others have claimed that the lack of the expected cosmological signal is a clear sign that we have cosmology all wrong[14] and need to go back to the drawing board.

New data, new approaches

In 2023, a new set of quasar data was published[15]. This presented 190 quasars originally identified in the highly successful Sloan Digital Sky Survey but observed over two decades in multiple colours – green, red and infrared light.

The data sampling was mixed, with lots of observations over some times, and less over others. But the wealth of this data meant the astronomers, led by graduate student Zachary Stone at the University of Illinois[16], could statistically characterise each quasar’s variability as what is known as a “damped random walk[17]”. This characterisation assigned a time scale, a tick, to each quasar.

Like each supernova, each quasar is different, and the observed variability can depend upon their intrinsic properties. But with this new data, we could match similar quasars with each other, removing the impact of these differences. As had been done for supernovae before, we had standardised the tick-tock of quasars.

The only remaining influence on the observed variability of quasars was the expansion of space, and we unambiguously revealed this signature. Quasars obeyed the rules of the Universe exactly as Einstein’s theory predicted.

Due to their brightness, however, the influence of this cosmic time dilation could be seen much further. The most distant quasars, seen when the Universe was only a tenth of its present age, were ticking away time five times more slowly than today.

At its heart, this is a story about how Einstein is right again[18], and how his mathematical description of the cosmos is the best we have. It puts to rest ideas of a sea of cosmic black holes, or that we truly inhabit a static, unchanging universe. And this is precisely how science advances.

References

  1. ^ new study (doi.org)
  2. ^ challenge to modern cosmology (phys.org)
  3. ^ By the 1930s (articles.adsabs.harvard.edu)
  4. ^ Timeline: the history of gravity (theconversation.com)
  5. ^ suitable clocks (arxiv.org)
  6. ^ to chart the expansion of the Universe (supernova.lbl.gov)
  7. ^ unexpected discovery of dark energy (www.nobelprize.org)
  8. ^ From dark gravity to phantom energy: what's driving the expansion of the universe? (theconversation.com)
  9. ^ twice as slowly as more recent supernovae (arxiv.org)
  10. ^ Quasars were discovered in the 1960s (www.wired.com)
  11. ^ extremely bright (phys.org)
  12. ^ Universe was an infant (phys.org)
  13. ^ magnifying some quasars (arxiv.org)
  14. ^ cosmology all wrong (www.mdpi.com)
  15. ^ published (arxiv.org)
  16. ^ Zachary Stone at the University of Illinois (astro.illinois.edu)
  17. ^ damped random walk (arxiv.org)
  18. ^ Einstein is right again (scitechdaily.com)

Read more https://theconversation.com/astronomers-see-ancient-galaxies-flickering-in-slow-motion-due-to-expanding-space-208621

The Times Features

Best Deals on Home Furniture Online

Key Highlights Discover the best deals on high-quality outdoor furniture online. Transform your outdoor space into a stylish and comfortable oasis. Explore a wide range of d...

Discover the Best Women's Jumpers for Every Season

Key Highlights Explore lightweight jumpers for spring and summer, ensuring breathability and ease. Wrap up warm with cozy wool jumpers for the chilly autumn and winter season...

Uncover the Elegance of Gorgeous Diamond Tennis Necklaces

Key Highlights Diamond tennis necklaces are a timeless piece of jewelry that exudes elegance and sophistication. They feature a continuous line of brilliant-cut diamonds, cre...

Dental Implants vs. Dentures: Which Is Better for You?

When it comes to replacing missing teeth, two of the most common options are dental implants and dentures. Both have their advantages and disadvantages, so choosing between them ...

What Neck Pain Really Means (And Why It’s More Than Just Poor Posture)

Neck pain is often brushed off as something temporary — a tight spot after a long day at the desk or a poor night’s sleep. But when the discomfort keeps returning, it could be a ...

The Work of Gosha Rubchinskiy: Fashion, Culture, and Youth

From Designer to Cultural Architect Gosha Rubchinskiy is not just a fashion designer—he's a cultural force. Born in Moscow in 1984, Rubchinskiy began his career in fashion in t...

Times Magazine

The Essential Guide to Transforming Office Spaces for Maximum Efficiency

Why Office Fitouts MatterA well-designed office can make all the difference in productivity, employee satisfaction, and client impressions. Businesses of all sizes are investing in updated office spaces to create environments that foster collaborat...

The A/B Testing Revolution: How AI Optimized Landing Pages Without Human Input

A/B testing was always integral to the web-based marketing world. Was there a button that converted better? Marketing could pit one against the other and see which option worked better. This was always through human observation, and over time, as d...

Using Countdown Timers in Email: Do They Really Increase Conversions?

In a world that's always on, where marketers are attempting to entice a subscriber and get them to convert on the same screen with one email, the power of urgency is sometimes the essential element needed. One of the most popular ways to create urg...

Types of Software Consultants

In today's technology-driven world, businesses often seek the expertise of software consultants to navigate complex software needs. There are several types of software consultants, including solution architects, project managers, and user experienc...

CWU Assistive Tech Hub is Changing Lives: Win a Free Rollator Walker This Easter!

🌟 Mobility. Independence. Community. All in One. This Easter, the CWU Assistive Tech Hub is pleased to support the Banyule community by giving away a rollator walker. The giveaway will take place during the Macleod Village Easter Egg Hunt & Ma...

"Eternal Nurture" by Cara Barilla: A Timeless Collection of Wisdom and Healing

Renowned Sydney-born author and educator Cara Barilla has released her latest book, Eternal Nurture, a profound collection of inspirational quotes designed to support mindfulness, emotional healing, and personal growth. With a deep commitment to ...

LayBy Shopping