Has Dark Energy Been Debunked? Probably Not.

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The galaxy cluster Abell 1689 is famous for the way it bends light in a phenomenon called gravitational lensing. Study of the cluster has revealed secrets about how dark energy shapes the universe.
The galaxy cluster Abell 1689 is famous for the way it bends light in a phenomenon called gravitational lensing. Study of the cluster has revealed secrets about how dark energy shapes the universe. (Image credit: NASA, ESA, E. Jullo (JPL/LAM), P. Natarajan (Yale) and J-P. Kneib (LAM))

A new study suggests that dark energy might not be real after all. But other scientists have found major flaws with this bold claim.  

Dark energy is a mysterious and hypothetical form of energy that is used to explain the accelerating expansion of our universe. One way that scientists have provided evidence of dark energy and its influence on the universe comes from measuring the redshift (a phenomenon in which the light coming from objects moving away from us appears red) of type Ia supernovas (SN Ia). 

In other words, by measuring how the light that these supernovas emit changes as they move away from us, scientists can show how far they are and therefore how the universe is "pushing out" or expanding over time. This evidence depends on the assumption that supernova luminosity, or brightness, doesn't evolve with redshift, or vary over cosmic time.

Related: The History & Structure of the Universe in Pictures

If dark energy is real, as many scientists expect it to be, the universe will continue to expand faster and faster. But, if it turns out that dark energy doesn't exist after all, the expansion of the universe will eventually slow down and the universe could even start shrinking. 

A bold claim

In a new study, published to the pre-print server arXiv and accepted for publication in The Astrophysical Journal, researchers from Yonsei University in Seoul, South Korea, along with collaborators at Lyon University and the Korea and Space Science Institute claim that they have found proof that dark energy might not exist at all. They studied a small sample of galaxies hosting about 30 type Ia supernovas and claim to have disproven the assumption that supernova luminosity evolves.

"Quoting Carl Sagan, extraordinary claims require extraordinary evidence, but I am not sure we have such extraordinary evidence for dark energy. Our result illustrates that dark energy from SN cosmology, which led to the 2011 Nobel Prize in Physics, might be an artifact of a fragile and false assumption," professor Young-Wook Lee of Yonsei University, who led the study, said in a statement. 

"Taken at face values, our result suggests that ~100% of the evidence for dark energy simply goes away. This will be confirmed by future observations," Lee and co-author Yijung Kang told Space.com in an email.

To come to such a bold conclusion, the researchers observed the spectra — bands of colors that can be produced when matter interacts with or emits electromagnetic radiation — of the stars in nearby galaxies that host these supernovas. Studying the light coming from these galaxies helped them to determine the ages of the stars in those galaxies.

The team found what they reported as a significant correlation between the luminosity of these supernovas and the ages of the stars in these galaxies. They found that supernovas in younger galaxies are fainter than in older galaxies, which would upend the assumption that supernova luminosity doesn't evolve over cosmic time. So, because they found fault with one of the main pieces of evidence for dark energy, they concluded that there is a likelihood that dark energy may not exist at all. 

Flawed science

Taking this study at face value, it seems probable that, if the researchers' work is correct, it could throw a huge wrench into our understanding of dark energy. However, in speaking with Adam Riess, a professor of physics and astronomy at Johns Hopkins University in Baltimore, and looking a bit closer at the study, it became clear that this study likely does not discredit the existence of dark energy. 

"I think that it's flawed," Riess said about Lee's study. The findings from Lee's team are "at odds with what's been seen with larger samples of supernovae," he added.

Riess pointed out a few inconsistencies with the figures that the researchers published. For instance, one figure (below) plots galaxies with their brightness on the y-axis and their stellar population age on the x-axis. The green line (added by Riess) shows the beginning of our universe. So the figure plots galaxies as older than our universe.

"Some models overestimate ages for older galaxies," Lee and Kang said.

This figure from Lee's study with additional markings from Riess. These marking point to a few potential flaws within Lee's study.  (Image credit: Lee et. al, with additional analysis from Adam Riess.)

Additionally, while the study already uses a small sample of galaxies, you can see points in the same figure (above); the empty points were galaxies not included in the overall conclusion. So, just off the bat, there are a few things that seem strange about this study, as Riess pointed out. 

Riess explained further how the data collected by other studies that have used much larger samples and seem to have delved deeper into the issue, is in direct contrast with what Lee and Kang's team found. Riess pointed to the study "Think Global, Act Local: The Influence of Environment Age and Host Mass on Type Ia Supernova Light Curves," which was led by astrophysicist Benjamin Rose. In a figure from that study (below), Riess added a red circle where a plot point from Lee and Kang's figure would fall, and it is clear that in Rose's study, that point would not exist. 

The additional analysis of this figure, from a study led by Benjamin Rose, highlights a data point (in red) that exists within Lee's study but not other studies (like Rose's) with larger sample sizes.  (Image credit: Rose et. al with additional analysis from Adam Riess.)

It can be kind of confusing to get "into the weeds" of studies like this, but it's important that extraordinary claims provide extraordinary evidence, as Lee noted. 

Lee's team does acknowledge that their claims require further observations to prove, but it seems, as Riess described, that their conclusion has some flaws. 

Alternative explanations

In addition to the possible errors in this conclusion is the fact that the luminosity and changing distance of supernovas is not the sole evidence for dark energy. 

While Lee's team asserts that the redshift of these supernovae is the strongest evidence for dark energy (and that additional evidence for dark energy is flawed), it is not the only evidence. 

Two other main sources of evidence are cosmic microwave background (CMB) and baryon acoustic oscillations (BAO). 

According to scientists, a universe without dark energy would have a lot of structure, which would change the way that CMB photons act. However, observations of CMB have remained consistent with predictions about what CMB would look like in a universe with dark energy.  Observations of BAO also align with the current understanding of what the universe would look like with dark energy. 

Follow Chelsea Gohd on Twitter @chelsea_gohd. Follow us on Twitter @Spacedotcom and on Facebook.

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Chelsea Gohd
Chelsea Gohd
Senior Writer

Chelsea “Foxanne” Gohd joined Space.com in 2018 and is now a Senior Writer, writing about everything from climate change to planetary science and human spaceflight in both articles and on-camera in videos. With a degree in Public Health and biological sciences, Chelsea has written and worked for institutions including the American Museum of Natural History, Scientific American, Discover Magazine Blog, Astronomy Magazine and Live Science. When not writing, editing or filming something space-y, Chelsea "Foxanne" Gohd is writing music and performing as Foxanne, even launching a song to space in 2021 with Inspiration4. You can follow her on Twitter @chelsea_gohd and @foxannemusic.

40 Comments Comment from the forums
  • rod
    Admin said:
    Researchers claim to have found serious fault with the existence of dark energy, but not everyone is buying into it.

    Has Dark Energy Been Debunked? Probably Not. : Read more

    Good report. Dark energy is debated like this recent report, https://phys.org/news/2020-01-evidence-key-assumption-discovery-dark.html or this report from 2016, http://phys.org/news/2016-10-universe-rateor.html Building a database of Type Ia SN spectrums and comparing to support dark energy or debunk - I think is challenging.
    Reply
  • JustOldBobSmith
    Hello Folks,
    I am new here so forgive me if I appear shy.
    Dark Energy and Matter does exist however we seem to be looking for the evidence the wrong way. First, is isn't dark we just cannot see it as it does not come directly into our sensors in the limited forms we are observing with them. Dark Energy and Matter can be explained by the photons we already must know that exist and have existed for at least 13.7 Billion years as they travel in every direction and at every wavelength we can even imagine. These photons carry both an equivalent mass energy and momentum which would account for all of the properties attributed to the "Dark" theory. From the CMB to the acceleration of the expanding of the universe. Simply do the Math, I have and anyone else can if they wish.
    Bob
    Reply
  • Admiral Lagrange
    Have you ever been walking in your house at night without the lights on and run into a door ? If so you just ran into dark matter. Dark matter is called dark matter because we can't see it. Until we develop the technology to see it we can only see it's effect. The bumps on scientists heads proves it's there.
    Reply
  • sgtnos
    rod said:
    Good report. Dark energy is debated like this recent report, https://phys.org/news/2020-01-evidence-key-assumption-discovery-dark.html or this report from 2016, http://phys.org/news/2016-10-universe-rateor.html Building a database of Type Ia SN spectrums and comparing to support dark energy or debunk - I think is challenging.
    Dark energy is not required if you do not believe Relativity. That is why I call relativity a religion, as it seeks to explain the origin of all things, while ignoring observable facts that disagree with the theory. It would also cost a lot of people their job and that is why they keep going at it. It is as if a theory of the creation of the universe is more important than observable fact. I am not making an argument for god or religion, to be clear. Science seems to be trying to prove God wrong with the Big Bang and they cannot let go of their beliefs, even willing to the point of violence (just like a religion that they hate for its unproven belief).
    Reply
  • rod
    sgtnos said:
    Dark energy is not required if you do not believe Relativity. That is why I call relativity a religion, as it seeks to explain the origin of all things, while ignoring observable facts that disagree with the theory. It would also cost a lot of people their job and that is why they keep going at it. It is as if a theory of the creation of the universe is more important than observable fact. I am not making an argument for god or religion, to be clear. Science seems to be trying to prove God wrong with the Big Bang and they cannot let go of their beliefs, even willing to the point of violence (just like a religion that they hate for its unproven belief).

    Dark energy is based upon Type Ia supernovae spectrum studies, their light curves as standard candle and redshifts documented along with their distances obtained. Relativity as Einstein defined it is very specific. "According to the theory of relativity, action at a distance with the velocity of light always takes the place of instantaneous action at a distance or of action at a distance with an infinite velocity of transmission.", p, 48., Relativity, The Special and the General Theory, A Clear Explanation that Anyone Can Understand by Albert Einstein, Crown Publishers, inc., 1961.

    Type Ia SN spectrums do not show the supernovae violating Relativity.
    Reply
  • sgtnos
    A lot of that was done using light measurements and we did not discover we were in a cloud of interstellar gas until 1970. Einstein also said we could not violate the speed of light and acted as if space is a perfect vacuum (which his theories require).
    https://www.scientificamerican.com/article/particles-found-to-travel/https://bigthink.com/dr-kakus-universe/what-travels-faster-than-the-speed-of-lighthttps://phys.org/news/2019-04-researchers-develop-way-to-control.htmlhttps://bigthink.com/surprising-science/astrophysicists-gamma-ray-jets-speed-of-lighthttps://futurism.com/the-byte/scientists-make-light-travel-fasterAlso I keep forgetting how much of a big deal the low energy transmutation seen in SAFIRE is and how much it actually breaks, seriously look into it.
    DTaXfbvGf8E:1471View: https://www.youtube.com/watch?v=DTaXfbvGf8E&t=1471s
    Reply
  • rod
    Einstein did not claim an unlimited domain like quantum mechanics and velocities that may be observed at the quantum level. Astronomers across the universe measure that c is finite velocity like the discovery of the finite speed of light in the 1670s while observing the Galilean moons. Before that, light was considered infinite velocity. Lunar laser ranging measurements of the distance between Earth and the Moon shows this too, as well as radar measurements and ham radio measurements or NASA space probes like New Horizons transmissions. Light echoes are routinely documented in astronomy that show Special Relativity is correct too. Quantum measurements may vary including index of refraction for a medium and velocity of c in a medium but in the solar system and beyond like binary star orbits, etc., Relativity holds up. The problem is claiming an unlimited domain for Relativity like in quantum mechanics and measurements or claiming quantum mechanics governs how the heliocentric solar system works. Star spectra obtained show alpha, the fine structure constant is not changing and documenting that c is slowing down for example or speeding up. Some tests attempted this but failed. Remember, Newtonian classical physics works like kinetic energy but for a limited domain. Relativity works too in many particle accelerator experiments and across macro measurements in astronomy.

    My recommendation. For those who want to throw out Relativity follow the example of the heliocentric solar system astronomers who won the debate against the geocentric teachers. Develop a better model and better math. However, if you throw out the *math magicians*, you can claim anything about *How the Universe Works* :)
    Reply
  • sgtnos
    Are you missing the stars and other features that should not exist? Seriously. You are ignoring a lot of mistakes and the fact that light can be slowed down. Gravity is not a constant. Again, you ignore the dust cloud and claim that we can get accurate spectra from within a dust storm. The only thing I am not trying to explain is how it came to be. I am trying to explain what it is doing, as every time something that doesn't agree with parts of the original theory all that is done is an exception is created. Some of them are inconsistent with each other. You are unwilling to look at it critically. Next you will say radio waves are not affected, but ignore that ham radio is affected by that and weather. Space is not a vacuum, also show me evidence of gravitational collapse star formation and proof for the Oort cloud. Show me a picture of a comet that is a dirty snowball. Explain the star older than the big bang.
    Actually here I forgot about this.
    http://problemswithrelativity.com/
    Reply
  • sgtnos
    To clarify, I am concerned with explaining what we see, not what happened at the beginning of time. Once you understand what is going on, you can figure out if it is possible to look back in time and see how everything started. In seeking to explain the beginning, based on old theories that came before Einstein, science has erred as he did not have half of the information we have today. We have exponentially progressed technologically, but refuse to update our theories that are disproven in part, acting as if theories that were created with no proof are still otherwise valid. Thought experiments that are taken as being true, just because someone invented an algorithm that produces an answer. If different projects all run into issues with the theory and they keep forcing it, eventually you will build a "religion" that people have to believe in or their life's work is useless and a waste. I think we passed that already.
    Reply
  • rod
    sgtnos said:
    Are you missing the stars and other features that should not exist? Seriously. You are ignoring a lot of mistakes and the fact that light can be slowed down. Gravity is not a constant. Again, you ignore the dust cloud and claim that we can get accurate spectra from within a dust storm. The only thing I am not trying to explain is how it came to be. I am trying to explain what it is doing, as every time something that doesn't agree with parts of the original theory all that is done is an exception is created. Some of them are inconsistent with each other. You are unwilling to look at it critically. Next you will say radio waves are not affected, but ignore that ham radio is affected by that and weather. Space is not a vacuum, also show me evidence of gravitational collapse star formation and proof for the Oort cloud. Show me a picture of a comet that is a dirty snowball. Explain the star older than the big bang.
    Actually here I forgot about this.
    http://problemswithrelativity.com/

    Okay, if there are problems, those who make the experiments, others must be able to repeat too. You said "Again, you ignore the dust cloud and claim that we can get accurate spectra from within a dust storm. The only thing I am not trying to explain is how it came to be."

    The dust cloud does not mean much to me, starlight can have a reddening extinction. If the dust cloud is so bad for astronomy measurements - why do I see so many stars at night, like Orion? :) If the dust cloud was so bad, there would be absorption bands in spectra of starlight too.

    You do not want Relativity to be a factual basis for modern astronomy and measurement and that is the bottom line. Your team needs to follow the heliocentric solar system model example against the geocentric teachers and win the argument. Modern astronomy is founded upon Special Relativity and General Relativity. Do the math and develop a better set of tools for modern astronomy to use - that is a must. When it comes to velocity of c, this can be measured so variations must be documented, others must be able to repeat the claims to verify. That is how the scientific method works. So far I have read various reports involving particle accelerators and measurements in astronomy going back nearly 100 years showing Special Relativity is correct including General Relativity. Exactly how many experiments and measurements show it is wrong, and others repeated the experiments and obtained the same results is upon in the air in my thinking. You cannot have a small group claiming to overthrow Special Relativity without other groups verifying the results. Do the math and replace Special Relativity but the math model must be done to explain the observations astronomers document.
    Reply