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Dark matter is one of the most intriguing mysteries in modern astrophysics. It is a hypothetical form of matter that does not emit, absorb, or reflect light or other forms of electromagnetic radiation, making it invisible to telescopes and other instruments that detect light.
Despite its invisible nature, dark matter is believed to be present throughout the universe, making up approximately 85% of its total matter content.
In this article, we will explore what dark matter is, why it is important, and what scientists know about it so far.
What is Dark Matter?
Dark matter is a form of matter that does not interact with light or any other form of electromagnetic radiation. This means that it cannot be seen directly by telescopes or other instruments that detect light. However, dark matter is believed to exist because of its gravitational effects on visible matter. The presence of dark matter can be inferred from its gravitational influence on stars, galaxies, and other astronomical objects.
One of the most compelling pieces of evidence for dark matter comes from observations of galaxy clusters. These are groups of galaxies that are bound together by gravity.
By measuring the motion of the galaxies in a cluster, astronomers can estimate the total mass of that cluster. However, the mass estimated from visible matter, such as stars and gas, isn’t enough to account for the observed motion.
Therefore, there must be some additional, invisible mass that is contributing to the gravitational pull. This is where dark matter comes in – it is believed to make up the majority of the mass in galaxy clusters, and its gravitational influence is responsible for the observed motion of the galaxies.
Why is Dark Matter Important?
The discovery of dark matter has profound implications for our understanding of the universe.
One of the most significant is its impact on the large-scale structure of the universe. The distribution of dark matter is thought to have played a key role in the formation of galaxies and other structures. It is believed that dark matter began to clump together due to its gravitational pull shortly after the Big Bang, eventually forming the scaffolding on which galaxies and other structures could be built.
The existence of dark matter also has important implications for our understanding of the nature of matter and the fundamental forces of the universe.
The current standard model of particle physics, which describes the behaviour of matter and the fundamental forces, cannot account for dark matter. This suggests that there may be new, undiscovered particles that make up dark matter.
The search for these particles is one of the most active areas of research in particle physics today.
What do we know about Dark Matter?
Despite decades of research, scientists still do not know what dark matter is made of. However, they have made some progress in ruling out certain types of particles.
For example, dark matter cannot be made up of any of the known particles of the standard model of particle physics, such as protons, neutrons, or electrons. It also cannot be made up of any of the known particles that make up light, such as photons.
One of the leading candidates for dark matter is a type of particle known as a WIMP, or weakly interacting massive particle.
WIMPs are hypothetical particles that are thought to interact with normal matter only through the weak nuclear force and gravity. This would make them very difficult to detect directly, as they would interact very weakly with detectors.
Another possibility is that dark matter is made up of axions, which are hypothetical particles that were originally proposed to solve a problem in particle physics known as the strong CP problem. Axions are much lighter than WIMPs and interact even more weakly with normal matter. They are also difficult to detect, but there are experimental efforts underway to search for them.
The discovery of dark matter particles would be a major breakthrough, not only in our understanding of the universe but also in our understanding of the fundamental nature of matter and the forces that govern it.
I’m the founder of The Average Scientist and also an Astrophysicist, a passionate Science Communicator and elected Fellow of the Royal Astronomical Society.
I regularly speak at various events, including our TAS Talks and theatre shows on subjects such as Astrophysics, Planetary Science and the Evolution of the Universe.
