Even though about 70% of the energy in the universe is made up of dark energy, it remains one of the biggest unsolved mysteries of modern physics. At present, humankind's understanding of dark energy is still in the period of basic scientific exploration; it is far from reaching the level where practical applications can be discussed. Any idea about "harnessing" dark energy currently lacks scientific basis and is more like a science fantasy. It may even mislead people and cause people to ignore truly feasible and urgent energy solutions.
What exactly is dark energy and why it cannot be utilized so far?
A hypothetical component introduced to explain the accelerated expansion of the universe is dark energy. Its essential physical properties are completely unknown to us. Scientists can only indirectly infer its existence through its macroscopic effect, which is to accelerate galaxies away from each other. A key parameter describing the properties of dark energy is its equation of state, that is, the ratio of pressure to energy density. However, the scientific community has been in fierce debate about its specific value and whether it changes.
The fundamental reason why we cannot use dark energy is "unknown". We don't know whether it is some kind of particle field, whether it is a characteristic of space-time itself, or whether it is caused by flaws in the current gravity theory. For such a thing whose basic appearance is not clear, capturing, storing or using it is like inventing a perpetual motion machine. All current rigorous scientific research is focused on "detecting and understanding" dark energy, without involving utilization.
How dark energy's equation of state challenges existing theories
In the past standard cosmological model, dark energy was simplified into a "cosmological constant" whose state equation was constant and equal to negative one. This model succinctly explained many observational phenomena. However, the latest observational data are challenging this traditional understanding. Results from the Dark Energy Spectroscopic Survey show that dark energy's equation of state may evolve over time, and there are signs that its value may cross the critical dividing line of minus one.
This discovery is of extremely great significance because whether the equation of state is equal to -1 is the key to distinguishing different theoretical models. For example, the "Elf" dark energy model proposed by Chinese scientist Zhang Xinmin's team in 2004 predicted that the equation of state can cross -1. DESI's observational data provides preliminary support for this type of dynamic dark energy model. This has shaken the theoretical foundation that regards dark energy as constant, indicating that there may be a more complex physical mechanism behind it. However, it also makes us realize that we are still very far away from revealing its essence.
What are the current main scientific methods for detecting dark energy?
Today, scientists around the world use large-scale international cooperation projects to detect dark energy. The core method is to draw a three-dimensional map of the universe. The most representative one is the DESI project. This project uses the 4-meter telescope installed at the Kitt Peak Observatory in the United States and uses 5,000 optical fibers to simultaneously collect the spectra of distant galaxies. By analyzing the red shift of the spectrum, scientists can set the distance of celestial objects and then construct a three-dimensional distribution map of the large-scale structure of the universe.
The DESI project released its first year of data in 2025, containing information on nearly 18.7 million galaxies, quasars and stars. This is the largest three-dimensional map of the universe to date. Scientists use the statistical characteristics of the distribution of matter in the analysis map, such as baryon acoustic oscillation, also known as BAO, to reversely deduce the expansion history of the universe, thereby limiting the characteristics of dark energy. In addition, cross-verification of multiple independent observation methods such as cosmic microwave background radiation, supernovae, and weak gravitational lensing is also a key method to improve the reliability of research.
What are the latest breakthroughs in dark energy research?
In recent years, the most eye-catching breakthrough in dark energy research has occurred, which stems from the search for evidence of "dynamic dark energy". In 2025, the DESI international collaboration team led by Zhao Gongbo of the National Astronomical Observatory of the Chinese Academy of Sciences published a paper in Nature Astronomy, announcing that it had discovered proof of the evolution of the dark energy equation of state over time, with statistical significance exceeding 4 standard deviations. This strongly suggests that dark energy is not a constant "cosmological constant."
What is particularly worthy of attention is that the data show that the parameters of the state equation of dark energy show the characteristic of "crossing -1" in its evolution process, which is consistent with the prediction of the "Elf" () model mentioned earlier, although the confidence of this evidence has not yet reached the 5σ confirmed discovery in physics. The gold standard, but this is undoubtedly a key step towards uncovering the nature of dark energy. This result has also received positive evaluations from international colleagues and is regarded as potentially heralding a new standard cosmological model.
Why is it said that dark energy has extremely low energy density and is difficult to collect?
A common misunderstanding is that because dark energy accounts for nearly 70% of the total energy in the universe, it should be a powerful energy source with high density. However, the opposite is true. The energy density of dark energy is indeed quite large when accumulated on the scale of the observable universe, but its density in local space is so low that it is almost impossible to detect its existence in the laboratory or even within the solar system.
Some views vividly show that at a local microscopic level, dark energy is already "weak to the point of being completely useless". If we want to collect such diffuse and weak energy within the scope of the earth or solar system where we live, the efficiency will be so low that people feel desperate when considering the actual physical principles. This is even more fundamental in the field of engineering. It does not have any feasible properties, and there is absolutely no way to compare or measure it with the density corresponding to the power of any energy tool that we humans have fully mastered (including solar energy). To place expectations on such a very illusory and unrealistic concept to solve energy problems is completely inconsistent with the real practical situation.
What is the focus and development direction of future dark energy research?
Future research will undoubtedly continue to focus on basic science, which is to accurately measure the characteristics of dark energy and then develop new physical theories that can explain its causes. With the DESI project continuing to carry out sky surveys and accumulating more data, it is possible to prove that the dynamic dark energy phenomenon has a higher degree of confidence. During the same period, next-generation sky survey projects such as the Euclid Space Telescope will start observing activities.
Chinese scientists are also exploring unique research paths. For example, Ali's original gravitational wave detection experiment is designed to explore the possible interaction between dark energy and photons by measuring the polarization of the cosmic microwave background radiation. This provides a new potential window for understanding the dynamic properties of dark energy. These cutting-edge explorations are without exception, and their primary goal is to "understand the universe" rather than "utilize energy." Only by achieving a breakthrough in understanding first can we talk about the philosophical possibilities of its application in the distant future.
After understanding that the exploration of dark energy is entirely an exploration of basic science, we should probably reflect on whether we should indulge in unrealistic daydreams when faced with a majestic but distant scientific fantasy, or should we focus more on promoting the advancement of energy technologies that are currently feasible? What are your views on dark energy?
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