The universe might be younger than we think, galaxies' motion suggests

News
By Keith Cooper
published

We think the universe is 13.8 billion years old, but could we be wrong?

a swarm of galaxies varying in size paints a scattering across black space.
An example of a galaxy group, in this case the Copeland Septet. Do the motions of smaller satellite galaxies in such groups imply that the universe is younger than we think? (Image credit: DESI Legacy Imaging Surveys/LBNL/DOE & KPNO/CTIO/NOIRLab/NSF/AURA)

The universe could be younger than we think, based on the motions of satellite galaxies that reveal how recently they have fallen into a galaxy grouping.

According to measurements of the cosmic microwave background radiation (CMB) by the European Space Agency's Planck mission, the universe is about 13.8 billion years old. This calculation is based on what's known as the Standard Model of cosmology, which describes a flat universe dominated by dark energy and dark matter and which is expanding at an accelerating rate. 

The Standard Model is then used as a basis for supercomputer simulations that can depict the growth of large-scale structure in the universe — galaxies, galaxy clusters and huge chains and walls of galaxies. 

However, these models have now run afoul of new measurements of the motions of pairs of galaxies that don't tally with what the simulations are telling us.

Related: How old is the universe? 

In a new study, astronomers led by Guo Qi from the National Astronomical Observatories of the Chinese Academy of Sciences studied pairs of satellites in galaxy groups.

Galaxy groups are small collections of galaxies, such as our own Local Group, in which a few large galaxies are joined by a swarm of smaller ones. Like larger galaxy clusters, these galaxy groups form where filaments in the cosmic web of matter that spans the universe meet, with smaller galaxies moving along the filaments before falling into a group. 

Using observations made by the Sloan Digital Sky Survey (SDSS) of 813 galaxy groups within about 600 million light-years from Earth, Qi's team focused on the most massive galaxy in each group and measured how pairs of satellites on opposite sides of that galaxy moved.

They found that the fraction of satellite galaxies that were counter-rotating with respect to each other — in other words, orbiting the large galaxy in opposite directions — is higher than predicted by computer simulations of large-scale structure, such as the Millennium Simulation and the Illustris TNG300 model, which are both based on the Standard Model as described by the Planck mission.

This is a natural state of affairs if the satellites have just fallen into orbit around the larger galaxy of the group. But over time, galaxy groups and clusters should reach a dynamically relaxed state, with most satellites co-rotating. If galaxy groups and clusters coalesced when the Standard Model suggests they should have, then the fraction of counter-rotating satellites should be smaller. The fact that they are a greater fraction of satellites is a problem for the Standard Model.

“We found in the SDSS data that satellite galaxies are just accreting/falling into the massive groups, with a stronger signal of ongoing assembly compared to simulations with Planck parameters,” Qi told Space.com in an email. 

In other words, it seems that the satellite galaxies have only recently fallen into their respective groups.

“This suggests that the universe is younger than that suggested by the Planck observations of the CMB,” said Qi. “Unfortunately, this work cannot estimate the age of the universe in a quantitative manner.”

This is because there is still too much leeway in the motions of the satellite pairs and models of how groups form to be able to place a firm figure on how much younger than 13.8 billion years these results suggest that the universe is. 

If correct, then the new findings imply that something is amiss in the Standard Model, and that some of our assumptions about the universe must be wrong. In fact, one cosmic paradox that scientists are currently investigating could be the answer.

Related: Our expanding universe: Age, history & other facts

The expansion rate of the universe is defined by a number called the Hubble constant. Planck measured the Hubble constant to be 67.8 kilometers per second per megaparsec — in other words, every megaparsec volume of space is expanding by 67.8 kilometers (42.1 miles) every second. (One megaparsec is about (3.26 million light-years.) Based on this expansion rate, cosmologists are able to calculate the universe's age as 13.8 billion years by rewinding the clock.

However, observations of the redshift of Type Ia supernovae, which are exploding white dwarfs, give the value of the Hubble constant as 73.2 kilometers (45.5 miles) per second per megaparsec. With this expansion rate, rewinding the clock would give a younger age of 12.6 billion years.

Both measurements of the Hubble constant are considered to be unimpeachable, and yet they differ drastically. This paradox has become known as the "Hubble tension."

“This of course could be related to the Hubble tension problem,” said Qi when asked whether the younger age suggested by satellite pairs in galaxy groups is support for the faster rate of expansion from the supernova measurements.

However, there are other hurdles to overcome. If we lower the age of the universe too much, then astronomers will find themselves in the awkward position of having stars that are known to be older than the universe itself. 

RELATED STORIES:

— What is the Hubble constant?

— What is the Big Bang theory?

— What is dark energy? 

Perhaps the explanation lies with other aspects of the Standard Model. For example, the model is heavily dependent upon dark matter, but so far scientists do not know what dark matter is. Other researchers argue that dark matter does not exist at all, and that its gravitational effects can be explained by a modification of the laws of gravity at low accelerations, such as those experienced by satellite galaxies orbiting at greater distances. Qi's team did find that satellite pairs at larger orbital radii are more likely to be counter-rotating.

Right now, more data would be welcome. The same phenomenon should hold for larger galaxy clusters, said Qi, but clusters tend to be farther away and the limited sample size and poorer quality of data currently make any measurement inconclusive.

The universe is ancient, whichever age value is correct, but these new results suggest that it may be able to claw some of its youth back.

The new findings were published on Jan. 22 in the journal Nature Astronomy. 

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Keith Cooper
Keith Cooper
Contributing writer

Keith Cooper is a freelance science journalist and editor in the United Kingdom, and has a degree in physics and astrophysics from the University of Manchester. He's the author of "The Contact Paradox: Challenging Our Assumptions in the Search for Extraterrestrial Intelligence" (Bloomsbury Sigma, 2020) and has written articles on astronomy, space, physics and astrobiology for a multitude of magazines and websites.

19 Comments Comment from the forums
  • rod
    Interesting report and reference cited. Perhaps instead of 13.8E+9 age universe it could be 12.6E+9 years old :) Using cosmology calculators varying H0 67 km/s/Mpc to 73 km/s/Mpc or higher, gets a much younger universe age too. We could now enjoy reports on stars older than the universe or globular clusters older than the universe. This problem of dating the age of the universe and dating the oldest objects in it goes way back in science when reviewing past reports. In the past H0 indicated a universe about 1-2E+9 years while rocks were dated 3E+9 years old.
    Reply
  • George²
    The problem begins with the big bang hypothesis, which suggests that the universe has an age. If we get rid of this hypothesis, in favor of the one that the universe is and, has not ceased to be a "black hole", which, due to its size, has a not very high density in most of its volume, and so in fact in these parts , there is matter and conditions that we define as normal. Of course, since in the outer regions the gravity from the center is less and less effective, they expand at an increasingly high rate.
    Reply
  • Helio
    rod said:
    Interesting report and reference cited. Perhaps instead of 13.8E+9 age universe it could be 12.6E+9 years old :) Using cosmology calculators varying H0 67 km/s/Mpc to 73 km/s/Mpc or higher, gets a much younger universe age too. We could now enjoy reports on stars older than the universe or globular clusters older than the universe. This problem of dating the age of the universe and dating the oldest objects in it goes way back in science when reviewing past reports. In the past H0 indicated a universe about 1-2E+9 years while rocks were dated 3E+9 years old.
    Yes, in the early 1930’s the age of older stars showed them to be older than the estimated age of the universe. :). So they knew something was wrong and likely not with their star ages, perhaps due to additional evidence found in the age of old rocks, for instance, as you mention.

    It was later discovered that Cepheid‘s, used to determine distances, don’t just come in one flavor. Hubble was not aware of this and his estimated expansion rate, using the distance to Andromeda, of 500 Kps/Mpc (IIRC) was way off.
    The article‘s video with Adam Riess was a treat. I had never heard him speak. He was the first scientist (Harvard team) to announce that the universe’s expansion is accelerating, which gave us the mysterious DE.

    Since Hubble launched, the improvements to its instruments giving us 10x greater precision was also interesting to learn from the video.

    What puzzles me is why we shouldn’t have two different expansion rates — one at 380,00 yrs. after creation and now? Isn’t that how acceleration works? What good is acceleration if you don’t go faster? ;)
    Reply
  • Helio
    George² said:
    The problem begins with the big bang hypothesis, which suggests that the universe has an age. If we get rid of this hypothesis, in favor of the one that the universe is and, has not ceased to be a "black hole", which, due to its size, has a not very high density in most of its volume, and so in fact in these parts , there is matter and conditions that we define as normal. Of course, since in the outer regions the gravity from the center is less and less effective, they expand at an increasingly high rate.
    Big Bang theory is the leading scientific theory, and the only credible one, that has made predictions that have been confirmed. The CMBR being the most profound.

    Any new theory will need to explain the known observations.

    Big Bang Bullets presents most of the objective-based evidence that show how robust BBT is. Tweaks for such a giant theory, of course, are to be expected.
    Reply
  • George²
    Helio said:
    Big Bang theory is the leading scientific theory, and the only credible one, that has made predictions that have been confirmed. The CMBR being the most profound.

    Any new theory will need to explain the known observations.

    Big Bang Bullets presents most of the objective-based evidence that show how robust BBT is. Tweaks for such a giant theory, of course, are to be expected.
    Since we can't yet measure the distance to even relatively close stars with complete accuracy, isn't it possible for errors to accumulate in the sensing when the parameters are initially inaccurate? The difference may not be large in percentage terms, but enough to cause erroneous conclusions.
    Reply
  • Helio
    George² said:
    Since we can't yet measure the distance to even relatively close stars with complete accuracy, isn't it possible for errors to accumulate in the sensing when the parameters are initially inaccurate? The difference may not be large in percentage terms, but enough to cause erroneous conclusions.
    That's a reasonable question. The accuracy of distances can improve with more and more different lines of evidence. A nearby Cepheid, of the known type, will give an "accurate" value. The reason Cepheid's are known to be useful for distances is due originally to Henrietta Swan Leavitt who studied thousands of variable stars. By using the ones from a fixed, but initially unknown, distance found in the Small Magellanic Cloud, she discovered that certain ones (Cepheids) gave a fixed luminosity for a known period in their varying brightness.

    With modern space telescopes, parallax measurements have greatly improved the "distance ladder" to the closer stars. These improvement measurements, in turn, tweak the Cepheid accuracies as well.

    For distant galaxies, there are several methods used to help produce a confluence in the same, or close, results. Certain galaxies of a certain size have about the same brightness. But they know this could be fooling them, so when you have millions of galaxies cataloged, better use of them are possible for distances.

    The Type Ia supernova are considered reliable for the very distant galaxies, which, of course, helps confirm, or improve, the accuracy of the other galactic methods. And vice versa, no doubt. But how accurate is still a question, IMO. There are debates on just how accurate they are, or whether or not they are all the same type of explosion. The more they get studied the better the accuracy. This may have something to do with the "paradox" mentioned in the Hubble tension.

    So, it's fair to say, IMO, that a grain of salt is needed when we claim one distance or not. But these grains are far smaller than they used to be. You will find astronomers are careful in determining their margin of error, based on a standard deviation analyses.

    What makes any scientific hypothesis or theory appear solid is how well it holds up to scrutiny. No theory is proveable, but they must, by requirement, be falsifiable, else they're just suppositions. Subjective opinions can be helpful, but objective evidence is required for the basis of the theory itself, and objective evidence must be what is later found from the predictions of the theory.

    When the priest, Georges Lemaitre, introduced what we now call the BBT he based it on Einstein's theory, which he learned from Edington and MIT in getting his doctorate in physics, but also it was based on objective observations from two astronomers.: Vesto Slipher, who discovered the first nebulae (galaxies) redshift values; and Hubble, who had the earliest galaxy distance measureents (using the wrong Cepheids for some). Lematire and Einstein knew each other, at conferences at least, and Einstein called his theory fine for the math, but "abominable" for its physics. To him, and mainstream science, the universe was static.

    My point is that BBT had to prove itself as it was not desired by the scientific community initially. Fortunately, Eddington and deSitter and others soon realized how important it was. Subsequent observations have helped it greatly, but it didn't rule on top until the predicted cosmic microwave background was discovered. That sealed the deal.
    Reply
  • Helio
    I don't know if Space.com did an article on this, though I did a quick look for one, but I think it's quite interesting and it applies to this subject.

    S&T, March 2024, issue has a page on the "Largest-ever Computer Simulations of the Universe". This latest model produces a simulation of the early formation of the large scale cosmos. They use 300 billion "particles", representing the small galaxies in the early period. Each particle has a baryonic mass of 130 million solar masses. All this was within a 9.1 billion lyr on each side of a cube.

    To produce an accurate result, it had a run-time for 50 million hours! On a single processor, this would equate to something over 5000 years! But they used 30,000 processors, cutting the time to 69.5 days, if simple division works for this estimation.

    The program considers DM and neutrinos, etc. But is it perfect? Nope. As we learn more, and computers get faster, better simulations will produce better results. Their work seems to have helped explain why the universe appears to be clumpier than what the simulations suggest, but their work only reduced the problem. Thus, this more advanced simulation is both helpful to this issue but also brings more attention to it since it didn't resolve it.
    Reply
  • George²
    Yes, this looks like it was set up on purpose. Nothing else works, well it's relic radiation, which may be of a different origin than the big bang-friendly interpretation.
    Reply
  • Atlan0001
    So you have the overcurrent observed and well drawn. Me, I also believe in and work with the always equal but opposed undercurrent unobserved (unobservable) and most usually dismissed by the 1-dimensional-only among us. The universe is always relentlessly, inexorably, attempting to return to its frontier youth . . . and succeeding!

    Complexity builds and collapses. Always in building, thus always building to collapse. Thus always a collapse basing the build. The past is the future and the future is the past.

    Arthur C. Clark sort of drew up an illustration in the beginning and ending of his '2001: A Space Odyssey'. Not to get religious but the Christian Bible, as old as it is, does exactly the same in the wrap around of its 'Genesis' and 'Apocalypse'/'Revelations' (new beginnings (endless beginnings)). Will Durant, the chronicler of Western Civilization, does the same thing in saying history always repeats in large even if never, or rarely if ever, repeating in small detail.

    Stephen Hawking lamented the tearing separation in "physics"(particularly cosmological physics) that occurred in the 19th through 20th centuries between "theoretical Physics and Cosmology" and the wider rest of the knowledge base evolved and built up over thousand of years (knowledge of the currents of the world and universe, and, thus, applicable natural laws).

    The 'Horizon Universe' is NOT a one-way street!
    Reply
  • George²
    Helio said:
    the predicted cosmic microwave background was discovered. That sealed the deal.
    Have too big anisotropy and seen universe in microwaves is granulated in last maps.
    Reply