On October 31, the world celebrates Halloween, but there is another mysterious event that is also worth celebrating: “Dark Matter Day.” Since 2017, scientists have celebrated this day by researching the most enigmatic materials in the universe. This year, more than 350 events will be held around the world to highlight this invisible substance that we cannot observe directly. However, despite the fact that most of the matter we see around us is composed of baryonic matter, it is believed that 85% of the universe consists of dark matter, the nature of which we still do not understand. In this article, we will explore this cosmic mystery in detail and review some scientific hypotheses about what dark matter is, from heavy non-interacting particles to primordial black holes. Let us begin our journey into the world of dark matter to uncover some of its exciting secrets.
What is Dark Matter and Why is it Considered a Scientific Mystery?
Dark matter refers to the invisible form of matter that makes up a large part of the universe and is considered one of the biggest mysteries in astronomy and physics. Although dark matter accounts for about 85% of the cosmic mass, scientists have yet to detect it directly. The difficulty lies in the fact that it does not interact with light or with the electromagnetic forces that make the rest of the universe visible to us. The familiar objects we see, such as planets, stars, and cosmic dust, are all made of “ordinary matter” that represents less than 15% of the total content of the universe. Thus, dark matter remains hidden and invisible, making the search for it a significant challenge for all scientists.
Evidence for the existence of dark matter comes from its gravitational effects. For instance, when we observe the motion of galaxies, we find that they move at speeds greater than what can be explained by the visible mass within them, indicating the presence of additional invisible mass that pulls them with its gravity. Additionally, the presence of dark matter is considered pivotal in the formation of galaxies and the cosmic web, as it is viewed as the mass around which other elements gather.
Main Candidates for Dark Matter
Scientists are searching for various bodies that could make up dark matter, among which prominent candidates are “WIMPs” and “Axions.”
WIMPs (Weakly Interacting Massive Particles) represent one of the leading theories in this field; they are massive particles that interact weakly with ordinary matter. Many models suggest that WIMPs should be electrically neutral and possess specific characteristics that allow them to concentrate around galaxies. The “Large Hadron Collider” (LHC) experiment is one of the projects seeking to discover these particles, but so far, no strong evidence supporting their existence has been found.
On the other hand, there are “Axions,” hypothetical particles that are not only lighter than WIMPs but also interact less with light, making them invisible. Axions were initially proposed to solve a problem in the standard model of particle physics and have since been considered a strong candidate for dark matter. Similarly, scientists are still searching for evidence to confirm their existence.
Current Events and Projects Related to Dark Matter
Dark Matter Day involves global activities and events aimed at raising public awareness about the significance of this mysterious phenomenon. For example, more than 350 events have been organized worldwide including seminars, lectures, workshops, and information-sharing sessions, all aimed at enhancing awareness of dark matter and its importance in shaping the universe.
Projects that are working to explore dark matter include new systems for imaging celestial bodies and long-term studies that rely on ongoing research and data analysis from observatories such as the “Hubble” and “Chandra” observatories. Modern physics laboratories are also conducting experiments on hypothetical particles, in an effort to develop new theories applicable to the behavior of the universe.
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Recent scientific studies suggest that we need to be more formal in our efforts, as effective strategies must be developed to attract more funding for investments in this opportunity-filled field. It is important for scientific research to continue until we truly understand what dark matter is and how it affects the structure of the universe and everything around us.
Effects of Dark Matter on the Universe
The impact of dark matter on the universe cannot be overstated; it plays a crucial role in the formation of galaxies and the structure of the cosmos. Without dark matter, there would not be enough gravitational forces to stimulate the formation of galaxies or the attraction between them. The existence of dark matter forms an important unit that enhances the stability of gravitational formations.
Clearly, dark matter plays a key role in the movement of galaxies. According to astronomers’ theories, dark matter helps organize the movement of planets and stars within galaxies, giving them their dynamic structure. These gravitational effects play a role in how the universe has evolved over billions of years, including how galaxies and stars have formed.
In conclusion, dark matter remains one of the greatest scientific mysteries awaiting resolution by scientists. Ongoing research and experimentation open up vast spaces for a deeper understanding of this dark aspect of the universe, which may allow us to uncover previously unimaginable truths. Scientists’ and laboratories’ efforts to develop new models and deeply examine comprehensive data will be central to future discovery processes.
Concept of Dark Matter and Its Importance in the Universe
Dark matter is one of the most mysterious and interesting topics in modern physics, constituting about 27% of the total mass of the universe, yet it cannot be seen or measured directly. Dark matter has been found to influence the movement of galaxies and the distribution of matter in the universe as a whole. Scientists have proposed the existence of dark matter as a result of studies showing that there is additional mass affecting the movement of stars in the galaxy. By analyzing the orbital motions of stars in nearby galaxies, astronomers observed that the speed at which these stars orbit the center of the galaxy is much faster than expected based on the amount of visible distant matter, indicating the presence of unseen matter acting as a guide.
Since then, several models have been proposed to explain dark matter, including remaining concepts such as WIMPs (Weakly Interacting Massive Particles), axions, and MACHOs (Massive Compact Halo Objects). Each of these concepts has its unique characteristics that make it a potential candidate, but none have been conclusively proven. The search for dark matter is an essential part of efforts to better understand the universe, as understanding it may help reveal the nature of gravity and the origin of the universe.
Possibility of Massive Compact Halo Objects (MACHOs)
Among the common candidates for dark matter are MACHOs, or Massive Compact Halo Objects. These objects include red dwarf stars, brown dwarfs, neutron stars, and solar-mass black holes. MACHOs are considered suitable for Occam’s razor theory, which assumes that there is no need to impose new entities to explain complex hypotheses. However, current estimates suggest that the proposed objects are not sufficient to explain all dark matter, as they may only represent about 20% of it.
Interestingly, many scientists have abandoned the idea of MACHOs over time. The most notable of these was through statements by physicists such as John Ellis, who stated that MACHOs are “dead.” This is partly because there is a need for more entities to explain the remaining proportion of dark matter, indicating that research needs to focus on new options like WIMPs or axions.
Black Holes
Primitive Black Holes and Their Relationship with Dark Matter
The other candidate for dark matter comes from primitive black holes, which are believed to have formed in the early moments of the universe after the Big Bang. These black holes are characterized by their small sizes compared to the supermassive black holes found in galaxies. The mass of primitive black holes can range from the mass of a planet to very intermediate masses. These black holes spark controversy due to the lack of strong evidence for their existence so far, but some argue that they could account for dark matter.
However, the hypothesis of primitive black holes is often criticized due to the thermal radiation proposed by Stephen Hawking, which suggests that black holes leak thermal radiation, which should lead to their evaporation. If primitive black holes are small and hot, it is expected that they have evaporated long ago, meaning they cannot explain the current dark matter. Nevertheless, some scientists are still exploring means to sustain or preserve these ancient black holes.
Rethinking Gravity Theories: MOND
The Modified Newtonian Dynamics (MOND) theory was proposed in 1982 as an alternative to the idea of dark matter, suggesting that gravity itself may need to be modified under certain conditions. Proponents of this theory claim that altering Newton’s laws can explain phenomena related to the motion of stars in the galaxy without the need for dark matter. However, this hypothesis has not been able to explain many other recorded phenomena, such as cosmic background radiation variations.
Unfortunately, most scientists have overlooked this theory due to its inability to explain some phenomena that have long been considered evidence for dark matter. Nevertheless, some scientists still believe there is hope for new discoveries that may reconsider the nature of gravity, keeping the case open and emphasizing the importance of ongoing scientific research.
Source link: https://www.space.com/dark-matter-day-suspects-axions-black-holes
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