Dark matter: a cosmic mystery
The dark matter is one of the greatest mysteries of the universe. Discovered indirectly thanks to its gravitational effects, it constitutes approximately 85% of the total mass of the cosmos. Yet, unlike the “ordinary” matter that makes up stars, planets and ourselves, it remains invisible. Dark matter does not glow, does not emit light, and does not react to electromagnetic radiation, making its direct observation impossible.
Historically, the concept of dark matter originated in the 1930s Around this time, astronomer Fritz Zwicky observed that galaxies in clusters appeared to be moving much faster than expected, suggesting that a large amount of hidden mass was exerting an additional gravitational pull.
In the. detail, according to Newton's law of gravitation, the speed of rotation or movement of an object (such as a galaxy) depends on the mass of the object around which it rotates. In a galaxy cluster, one would expect galaxies on the outskirts to move more slowly than those closer to the center, because they would feel less gravitational pull.
Zwicky observed, however, that galaxies in clusters, such as the Coma Cluster, moved at very high speeds, suggesting that they were attracted by a much greater mass than could be observed.
The evidence for the existence of dark matter then strengthened in the following decades. By studying the rotation curves of galaxies, astrophysicist Vera Rubin showed in the 1970s that stars located at the edges of galaxies also moved at speeds that could not be explained solely by visible matter.
< p>The presence of this mysterious material is now accepted, but its exact nature still remains an enigma.
Credits: titoOnz/istock
Theories on the nature of dark matter
To try to explain this phenomenon, several theories have been proposed. The most popular is that of WIMPs (Weakly Interacting Massive Particles), massive particles which interact very weakly with normal matter, making their detection extremely difficult. Although several experiments have been carried out to detect these particles, none have yet produced conclusive results.
Other hypotheses include axions, even lighter and hypothetical particles, or theories modifying gravity itself, such as modified gravity, which seek to explain observations without the need for dark matter.
Despite decades of intensive research, however, none of these hypotheses has yet allowed to solve the mystery. This is causing some scientists to consider alternative ideas. One of the most intriguing and recent theories is that of primordial black holes.
These black holes, still hypothetical, would have formed in the very first moments of the universe from dense pockets of matter. Unlike astrophysical black holes, which are created from the collapse of massive stars, these objects would also be much smaller, some as small as an atom, but with significant mass.
These objects would have remained hidden throughout cosmic history, traversing the universe without interacting with ordinary matter or emitting light. If these black holes still exist today, they could therefore be the key to explaining dark matter. At least that's the idea.
An illustration of a cavalcade of primordial black holes. Credits: NASA Goddard Space Flight Center
Mars as a detector?
That being said, according to recent analyses, primordial black holes could pass through our solar system approximately once every ten years. Researchers liken these primordial black holes to cosmic “bullets,” fired through the universe at incredible speeds. According to calculations, these tiny objects could travel through the solar system at more than 8 million km per hour. By passing close to a planet, such as Mars, such an object could then cause a slight deviation in the planet's orbit.
Mars is an ideal candidate for these observations, because its orbit is well documented, and there are few gravitational disturbances compared to planets like Jupiter or Saturn. Additionally, telemetry tools that measure the distance between Mars and Earth are extremely accurate, with a margin of error of only about 10 centimeters. So, although the “oscillations” in its orbit caused by the passage of a primordial black hole are tiny, they could possibly be detectable.
An illustration shows dark matter causing a “wobble” in the motion of Mars. Credits: Robert Lea (created with Canva)
The challenges of discovery
The concept of monitoring the effects of primordial black holes on Mars is still in the development phase , but it is promising. The next step for the researchers is to continue refining their simulations and collecting observational data from the Red Planet. They will also have to develop methods to differentiate between disturbances caused by asteroids or other objects in the solar system, and those caused by primordial black holes.
If the researchers manage to detect such a disturbance in Mars' orbit, this could provide strong evidence for the existence of primordial black holes. This discovery would then have profound implications for our understanding of the universe. Not only would it provide an answer to one of the greatest mysteries of cosmology, namely the nature of dark matter, but it would also reveal new aspects of the formation of the universe in its earliest moments.
Source: Physical Review D.
With an unwavering passion for local news, Christopher leads our editorial team with integrity and dedication. With over 20 years’ experience, he is the backbone of Wouldsayso, ensuring that we stay true to our mission to inform.
