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nargesh
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what is the temperature of cold & hot dark matter?
Dark matter is a hypothetical type of matter that does not interact with light and therefore cannot be directly observed. It is believed to make up about 85% of the total matter in the universe and is thought to be responsible for the gravitational effects observed in galaxies and galaxy clusters.
Cold dark matter is made up of slow-moving particles, whereas hot dark matter is made up of fast-moving particles. This difference in speed affects how they cluster and form structures in the universe, with cold dark matter being better at forming small-scale structures like galaxies and hot dark matter being better at forming large-scale structures like galaxy clusters.
The temperature of dark matter is not directly measured because it does not interact with light. Instead, it is inferred from observations of the large-scale structure of the universe and simulations of how dark matter particles behave. The temperature of cold dark matter is estimated to be around 1 Kelvin, while hot dark matter is estimated to be much hotter at around 10 million Kelvin.
The main evidence for the existence of dark matter comes from observations of the rotation of galaxies, the gravitational lensing of light, and the motion of galaxy clusters. These observations cannot be explained by the visible matter we can see, and therefore suggest the presence of a significant amount of unseen matter, which we refer to as dark matter.
The temperature of dark matter plays a significant role in the evolution of the universe. Cold dark matter's slower speed allows it to form small-scale structures first, which then merge to form larger structures like galaxies. This process is known as hierarchical structure formation. Hot dark matter, on the other hand, would have prevented smaller structures from forming, leading to a different evolution of the universe. The current understanding is that a combination of both types of dark matter is needed to explain the observed structure of the universe.