Report | Science and Technology Daily reporter Gan Xiao
Will Einstein also make mistakes? On April 9, a significant result released by the National Astronomical Observatory of the Chinese Academy of Sciences in Beijing indicates that Einstein's idea about dark energy might be wrong.
Illustration of major results in testing the dynamical properties of dark energy by the National Astronomical Observatory team. (Image courtesy of the National Astronomical Observatory; background image source: DESI official website)
The research team led by Zhao Gongbo from the National Astronomical Observatory has confirmed through data related to the "Dark Energy Spectroscopic Instrument (DESI)" project that dark energy is not constant as Einstein assumed the "cosmological constant" to be, but is very likely to have dynamic attributes.
This achievement provides a new perspective and key evidence for exploring the physical mechanism behind the universe's accelerated expansion, while suggesting the possible existence of new physics beyond the standard cosmological model. On April 8, the relevant research results were published on the arXiv preprint server.
"The biggest mistake of my life"
Current studies have found that our universe is accelerating its expansion. Theoretically, this may be caused by dark energy, which accounts for approximately 70% of the total energy density of the universe and has negative pressure.
What exactly is the nature of dark energy? This question has troubled the scientific community for over 20 years and still lacks a definitive answer.
In the press conference, Zhao Gongbo introduced the history of dark energy from general relativity. In the early 20th century, when Einstein applied the equations of general relativity to the entire universe, he unexpectedly discovered a shocking conclusion — the universe cannot remain stationary, it either expands or contracts. This result contradicted Einstein's belief that "the universe is static and eternal," leaving him perplexed.
Thus, in 1917, Einstein forcibly introduced the cosmological constant (Λ) into general relativity, attempting to counteract gravity with repulsive force to keep the universe stationary. However, in 1929, the discovery of the universe's expansion overturned everyone's understanding. "Introducing the cosmological constant was my greatest error." Einstein scratched out the "Λ" in his equation.
Another reversal occurred in 1998 when cosmic acceleration was discovered. This meant that there indeed exists some unknown repulsive force opposing gravity, acting as the "hidden hand" driving the universe's accelerated expansion. Scientists re-examined Einstein's equations, reintroduced the "Λ" term, and assigned it specific values, perfectly explaining the observations.
Looking back at this history, researchers believe that it was Einstein's "mistake" that gave new life to the cosmological constant. This once-abandoned "error" has now become the key to explaining approximately 70% of the universe's unknown components.
Nearly "confirmed"
Over the more than 20 years since scientists "reclaimed" the "Λ" in Einstein's equations, the standard cosmological model (ΛCDM) has successfully explained a large amount of cosmological observational data and is widely considered the simplest and most effective theoretical framework today.
Zhao Gongbo introduced: "The physical properties of dark energy are reflected in its 'equation of state.' In ΛCDM, dark energy is usually regarded as a vacuum energy that does not evolve over time, with an equation of state constantly fixed at -1."
However, with the development of cosmological observation technology and the continuous improvement of data accuracy, people gradually discovered that different types of observational data showed a certain degree of inconsistency under the ΛCDM model. This posed a new challenge to the ΛCDM model.
In this latest study led by Zhao Gongbo, the research team developed a new method for reconstructing and analyzing dark energy. Using this tool, they measured the universe's expansion rate based on the latest data from DESI and combined it with observations of supernovae and cosmic microwave background radiation, providing crucial data support for exploring the essence of dark energy.
Their new finding is that the equation of state of dark energy evolves with cosmic evolution. Data analysis shows that the confidence level of this conclusion reaches 4.3 sigma. In particle physics, the golden standard for determining whether a discovery is "definitive" is reaching 5 sigma, meaning the probability of error is only 0.0001%, making the result almost certainly true and valid.
In other words, the latest research results nearly "confirm" that Einstein's initial assumption about the cosmological constant "Λ" had a deviation — it is not constant but evolves over time.
"This study confirms the conclusions obtained by the DESI international collaboration group using different analytical methods, namely, 'dark energy is likely to have dynamic attributes.'" Zhao Gongbo emphasized that this poses a challenge to the traditional cosmological constant model, implying more complex evolutionary behavior.
"The study of dark energy has entered a new phase, with great potential in terms of observations and theoretical explanations." At the press conference, Academician Chang Jin, president of the University of Science and Technology of China, highly praised this achievement.
Large Scientific Facilities + International Cooperation
Zhao Gongbo stated that in the next step, his research team will continue to use subsequent DESI observation data for more refined analysis and collaborate with international peers, striving for more precise measurements and more complete theoretical models to comprehensively and rigorously test the dynamical properties of dark energy.
Expert in dark energy research and researcher Zhang Xinmin from the Institute of High Energy Physics of the Chinese Academy of Sciences said: "With the accumulation of data, we have reason to believe that the confidence level value will definitely increase in the future and eventually reach 5 sigma."
In the eyes of experts, astronomical large scientific facilities and international cooperation were crucial to achieving this result.
The DESI project is one of the most important dark energy observation programs globally, jointly involving more than 70 research institutions worldwide to form an international collaborative team. Relying on a 4-meter aperture optical telescope, DESI performs high-precision measurements of the redshifts of tens of millions of celestial bodies, finely mapping the three-dimensional structure of the universe's large-scale structure, aiming to deeply reveal the physical properties of dark energy.
Zhao Gongbo's team and Professor Zou Hu's team from the National Astronomical Observatory have been participating in the DESI project for over ten years. Zhao Gongbo's team leads the consortium in systematic research on the nature of dark energy using self-developed analysis methods. Zou Hu's team actively participates in the scientific operations of DESI, contributing important added-value star catalogs to DESI data releases, promoting the progress of new scientific discoveries.
Today, countries around the world are actively deploying large astronomical observation equipment. Internationally, there are telescopes such as the 4-meter Multi-object Optical Spectrograph Telescope (4MOST), the 6.5-meter MegaMapper Telescope, and the 10-meter-class Monakai Spectral Survey Telescope (MSE). In China, there are telescopes like the 2-meter China Space Station Telescope (CSST), the 6.5-meter Wide-field Survey Telescope (MUST), and planned projects including the second phase of the Guo Shoujing Telescope (LAMOST) survey and the 10-meter-class Extremely Large Spectral Survey Telescope (ESST).
"We hope everyone supports the development of astronomical facilities!" For this, Chang Jin called out, "Of course, having a large facility, how to achieve world-class results through this advanced tool is also a problem worth considering for astronomers."
Relevant paper information:
https://arxiv.org/abs/2504.06118
Original article: https://www.toutiao.com/article/7492426287157264923/
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