On October 31, the world celebrates Halloween, but there is another mysterious event worth celebrating as well, which is “Dark Matter Day.” Since 2017, scientists have celebrated this day by researching the most mysterious substances in the universe. This year, more than 350 events will be held worldwide to highlight this invisible matter that we cannot directly observe. However, despite the fact that most of the matter we see around us is composed of baryonic matter, 85% of the universe is believed to be made up of dark matter whose nature we do not yet understand. In this article, we will explore in detail this cosmic mystery and present some scientific hypotheses about what dark matter might be, 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 intriguing 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 constitutes about 85% of the cosmic mass, scientists have not yet been able 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,” which 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 example, when we observe the movement of galaxies, we find that they move at high speeds that exceed what can be explained by the visible mass within them, indicating the presence of additional invisible mass pulling them with its gravity. Additionally, the presence of dark matter is crucial for the formation of galaxies and the cosmic web, as it is viewed as the mass that gathers other elements.
Main Candidates for Dark Matter
Scientists are searching for different bodies that could constitute dark matter, among which the most prominent candidates are “WIMPs” and “Axions.”
WIMPs particles represent one of the leading theories in this field; they are massive particles with weak interactions with ordinary matter. Many models suggest that WIMPs should be electrically neutral and possess specific characteristics that enable them to concentrate around galaxies. The “Large Hadron Collider” (LHC) experiment is one of the projects aiming to discover these particles, but so far, no strong evidence supporting their existence has been found.
On the other hand, there are “Axions,” which are hypothetical particles that are not only lighter than WIMPs but also less interactive 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 prove their existence.
Current Events and Projects Related to Dark Matter
Dark Matter Day includes activities and global events aimed at raising public awareness of the significance of this mysterious phenomenon. For example, over 350 events have been organized around the world, including seminars, lectures, workshops, and information-sharing sessions, all aimed at enhancing awareness and understanding of dark matter and its importance in shaping the universe.
Projects exploring dark matter involve new systems for imaging celestial bodies and studies that extend over long years, relying on continuous research and analyzing data from observatories such as the “Hubble” and “Chandra” observatories. Modern physics laboratories are also conducting experiments on hypothetical particles in an attempt to develop new theories applicable to the behavior of the universe.
Indicates
Scientific studies have recently indicated 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 that scientific research continues until we clarify what dark matter truly 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 construction of galaxies and the formation of the cosmic structure. Without dark matter, there wouldn’t be enough gravitational force to stimulate the formation of galaxies or their attraction. The existence of dark matter forms an important unit that enhances the stability of gravitational formations.
It is clear that dark matter plays a key role in the movement of galaxies. According to astronomers’ theories, dark matter helps organize the motion 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 formed.
In conclusion, dark matter remains one of the greatest scientific mysteries awaiting resolution by scientists. Ongoing research and experiments open a vast space for a profound understanding of this dark aspect of the universe, which may allow us to uncover facts we never imagined before. The efforts of scientists and laboratories to develop new models and deeply analyze 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 fascinating 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 affect the motion 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 influencing the movement of stars in a galaxy. By analyzing the orbital motions of stars in nearby galaxies, astronomers noted that the speed at which these stars orbit the galaxy’s center is much faster than expected based on the amount of visible distant matter, indicating the presence of an invisible substance acting as a guide.
Since then, several models have been proposed to explain dark matter, including concepts like WIMPs (Weakly Interacting Massive Particles), axions, and MACHOs (Massive Astrophysical 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 a fundamental part of the efforts to better understand the universe, as understanding it may help uncover the nature of gravity and the origin of the universe.
The Possibility of Massive Astrophysical Compact Halo Objects (MACHOs)
Among the common candidates for dark matter come MACHOs or Massive Astrophysical Compact Halo Objects. These include red dwarf stars, brown dwarfs, neutron stars, and solar-mass black holes. MACHOs are considered suitable for Occam’s razor, as it posits that there is no need to introduce new entities to explain complex hypotheses. However, current estimates indicate that the proposed objects are insufficient to account for all dark matter, as they may only represent around 20% of it.
One interesting point is that many scientists have abandoned the MACHOs idea over time. Notably, physicists like John Ellis have stated that MACHOs are “dead.” This is partly due to the need for more entities to explain the remaining fraction of dark matter, indicating that research needs to focus on new options like WIMPs or axions.
Black Holes
Primordial Black Holes and Their Relationship to Dark Matter
The other candidate for dark matter comes from primordial 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 primordial black holes can range from the mass of a planet to very intermediate masses. These black holes stir controversy due to the lack of strong evidence for their existence so far, but some argue that they could compensate for dark matter.
However, the hypothesis of primordial black holes is often criticized due to the thermal radiation proposed by Stephen Hawking, which suggests that black holes leak thermal radiation and should eventually evaporate. If primordial black holes are small and hot, they are expected to have evaporated long ago, which means they cannot explain the current dark matter. Nonetheless, some scientists are still exploring ways to sustain or preserve these ancient black holes.
Rethinking Gravity Theories: MOND
Modified Newtonian Dynamics (MOND) 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 modifying Newton’s laws could explain the phenomena associated with the motion of stars in galaxies without the need for dark matter. However, this hypothesis has been unable to account for many other phenomena that have been recorded, such as variations in cosmic background radiation.
Unfortunately, most scientists have dismissed this theory due to its inability to explain some phenomena that have long been considered evidence for the existence of dark matter. Nonetheless, some scientists still believe there is hope for new discoveries that might 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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