Week 3 [09-15.11.20] The dark side of the universe

The dark side of the universe

The mysterious name and confusing description of dark matter have been inspiring works of fiction for a long time. When mentioned in literature, films or computer games it is usually described as a source of almost magical or extraordinary physical behaviour and even as material from which you could craft weapons. But what exactly is dark matter from a scientific point of view?

The answer is that even certified researchers still don’t know it well. As scientific research is based on things we can observe and measure, it’s difficult to define it comparing it to the matter that we encounter and experience on a daily basis. A common element, which includes atoms and provides them with mass, is called the Baryonic matter and it doesn’t interact with dark matter. Furthermore, the dark matter is entirely invisible to light and other forms of electromagnetic radiation, making it inaccessible for detection. Because of its gravitational effects on celestial bodies such as galaxies, planets and stars, scientists are certain that it exists. It also explains optical illusions seen by astronomers in the deep universe, known as gravitational lensing.

NASA, ESA, M. J. Jee and H. Ford et al. (Johns Hopkins Univ.)

Due to those reasons, we can’t be certain of what dark matter actually is, but there is evidence of what it isn’t. From the observations of the universe, scientists concluded that it’s not in the form of celestial bodies that we see. It is not in a form of dark clouds of Baryonic matter, as we are unable to detect their absorption of radiation passing through them. Additionally, from the lack of production of unique gamma rays, it was ruled out as antimatter and massive black holes. Some scientists speculate that dark matter is made up of more unfamiliar particles such as axions or WIMPs (Weakly Interacting Massive Particles).

Another side of the mystery is dark energy. It appears that as dark matter makes up about 27% of the universe, it is dominated by the dark energy that makes up 68% of the universe's total composition. In the past, physics presumed that the universe expansion would slow down over time due to the attractive force of gravity. However, more recent research has proved them wrong, and the expansion is actually speeding up. Existence of dark energy neatly explains this phenomenon of space stretching, but yet again it leaves us with more questions than answers.

Questions:

If we get closer to a more specific description of dark matter, do you believe there could be something like anti-dark matter? And if so, what would be its characteristics?
As the dark matter causes the universe to expand rapidly, and we don’t exactly know how it behaves. Do you think it might actually shrink someday as expected by the researchers in the past?
The topic of dark matter inspires many works of fiction; Have you seen any worth recommending?

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