The nature and properties of dark matter remain largely unknown to scientists. Dark matter does not interact with electromagnetic radiation, making it difficult to directly observe or study. Our understanding of dark matter comes from its gravitational effects on visible matter and its impact on the large-scale structure of the universe.
To visualize what the universe would look like if it were made entirely of dark matter, we rely on computer simulations and theoretical models. These simulations use our current understanding of dark matter's behavior and distribution, along with the known properties of normal matter, to create hypothetical scenarios.
In these simulations, dark matter is represented as a diffuse and invisible substance that forms massive halos around galaxies and clusters of galaxies. These halos provide the gravitational scaffolding for the visible matter to collect and form structures like galaxies and galaxy clusters.
Based on these simulations, if the universe were made entirely of dark matter, we would expect to see a similar large-scale structure to what we observe in the visible universe. However, the distribution and dynamics of the dark matter structures would be different because dark matter interacts only through gravity.
Keep in mind that our knowledge of dark matter is still incomplete, and there are ongoing efforts to understand its true nature. Scientists are conducting experiments in particle physics and astrophysics to detect and study dark matter directly, which could provide more insights into its properties and help refine our understanding of its potential impact on the universe.