BEIJING, March 9 (Xinhua) — The most popular cosmological model believes that behind the accelerated expansion of the universe is a mysterious force we call “dark energy”, and that this undetectable form of energy is constant. However, according to a new study, it is entirely possible that dark energy has changed in the past. Scientists involved in the study suggest that these changes may have led to the universe filling the universe with the conventional material we see every day. From what has been observed so far, something strange has happened in the universe: it is expanding, but it is also full of matter. Over time, the gravitational pull of all these substances should slow the expansion of the universe. However, the expansion of the universe did not slow down, not even at the same rate, but expanded faster and faster.
How does dark energy shape our universe?
Every day, our universe becomes bigger and faster. Cosmologists will cause this accelerated expansion of the energy form called “dark energy”, in part because we have no idea what it is, where it comes from, and what will happen in the future. What we do know is that dark energy has been around 5 billion years ago and has continued to this day.
We also know that the “strength” of dark energy (measured by its density) has remained fairly stable over the past 5 billion years. Dark energy does not seem to weaken or become stronger over time, making it a cosmic constant. However, the early universe was very strange, and something more strange may have happened a long time ago. If these things do happen, they could have a huge impact on the rest of the history of the universe.
Although we hardly know the nature or cause of dark energy, we know that dark energy has no use other than to accelerate the expansion of the universe. This is because, from a cosmological point of view, today’s universe is ancient, cold and near-death.
This widespread silence means that there is not enough energy (dark energy or other) in the universe. If there are some special cases of dark energy, such as changes over time, it will not have a big impact, because it is already very weak. Yes, dark energy is accelerating the expansion of the universe, but it is very slight. That’s why it took scientists so long to determine its impact. This feature limits both the influence of dark energy on the universe and our understanding of it; for cosmologists, there are few dark energy effects that can be measured. In contrast, the early universe was much hotter, denser, more compact, and especially more energetic.
Although dark energy appeared in the universe about 5 billion years ago, it is not necessarily the first time it has appeared. Dark energy may exist in the young universe and push the universe to undergo all sorts of interesting changes that then disappear temporarily into the background. Recently, a group of theoretical physicists were thinking about what such early dark energy might do, and they reported the results in a November 2019 paper and uploaded it to the preprint server arXiv.org.
The researchers found that brief fluctuations in dark energy may have filled the early universe with strange particles such as quarks, gluons and light children, eventually condensing into atoms as we know it today.
According to the researchers, the change must have occurred after the cosmic swell, when the universe became very large in a very short period of time. After the bulge, the whole universe was almost empty; After that, there must be something to “reheat” the universe, bringing a new round of particles to the universe in what we often call the “Big Bang”.
Most theoretical physicists believe that whatever causes the universe to swell, it must have been reheated in itself. But new research suggests that early dark energy may have produced large amounts of particles by losing their own energy. This is an interesting statement, but the researchers’ hypothesis must still match previous observations that have consolidated our understanding of the Big Bang and the cosmic bulge. If dark energy is the cause of the universe’s reheat, then we should see subtle changes in the standard image model of the cosmic microwave background, which in turn affects the patterns of galaxies in the modern universe.
So far, the new model of the reheating of the universe has been consistent with all current observations, even more so than the traditional theory of cosmic bloating. However, we do not have enough information to determine whether this is a statistical coincidence. A new generation of astrophysical tools, such as NASA’s Great Field Infrared Survey telescope (WFIRST), may help scientists better understand dark energy and its role in the early and present universes.
Dark Energy and Evidence of Its Existence
Using current observations, scientists estimate that 70 percent of the universe’s energy is provided by dark energy, about 25 percent by dark matter, and only 5 percent of the ordinary material we see on a daily basis. We now know very little about the nature of dark energy, only that it has a negative pressure force and is almost smooth (i.e. not knotted). The more property of dark energy is described by the ratio of its pressure to energy density, i.e. the parameters of the state equation.
The nature of dark matter determines the fate of the universe. The energy of the vacuum itself is called “vacuum energy”, and if it causes the universe to expand rapidly is vacuum energy, it means that the universe will expand forever, the matter and energy in the universe will become thinner and thinner, the galaxies will move away from each other at an increasingly rapid rate, and new structures will never be formed again. If the dark energy that causes today’s accelerated expansion of the universe is dynamic, the future of the universe will be determined by the dynamics of the dark energies, which may accelerate forever, may re-enter the deceleration, and may even contract.
Understanding the evolution of dark energy state equations over time from astronomical observations is essential to the exploration of dark energy’s function. This is also one of the most important scientific goals of many large-scale sky-touring programs. In 2017, the World’s Largest Galaxy Patrol eBOSS International Science and Technology Program partnered with a significant signal of the sonic oscillation of the heavy son sound waves, using quasars deep in the universe, as yet another independent evidence of the existence of dark energy and yet again evidence that the universe is expanding at an accelerated rate. (Any day)