Question
What is dark matter?
Answers
GPT-4o mini
Dark matter is a form of matter that is thought to make up about 27% of the universe's total mass-energy content. Unlike ordinary matter, which includes atoms and is responsible for the structure of the visible universe (like stars, planets, and galaxies), dark matter does not emit, absorb, or reflect electromagnetic radiation, such as light. This makes it invisible and detectable only through its gravitational effects.
Key characteristics of dark matter include:
1. **Gravitational Effects**: Dark matter's presence is inferred from its gravitational influence on the motion of galaxies and galaxy clusters. Observations show that galaxies rotate at such speeds that they should fly apart if only visible matter were present. The additional mass provided by dark matter helps account for the observed gravitational binding.
2. **Cosmic Structure Formation**: Dark matter is believed to play a critical role in the formation of large-scale structures in the universe by providing the necessary gravitational pull to allow normal matter to clump together.
3. **Non-Baryonic**: The leading candidates for dark matter are non-baryonic particles, meaning they are not made of protons or neutrons. WIMPs (Weakly Interacting Massive Particles) and axions are two of the leading theoretical candidates, though none have been definitively detected.
4. **Cosmic Microwave Background**: Measurements of the cosmic microwave background radiation provide evidence for dark matter, revealing patterns of temperature fluctuations that suggest the presence of additional mass not accounted for by visible matter.
5. **Ongoing Research**: Despite extensive research and many experiments aimed at detecting dark matter directly, its nature remains one of the biggest mysteries in modern astrophysics. Various experiments are ongoing to search for dark matter particles and to better understand their properties.
In summary, dark matter is a fundamental component of the universe, influencing its structure and evolution, even though it is not directly observable.
Key characteristics of dark matter include:
1. **Gravitational Effects**: Dark matter's presence is inferred from its gravitational influence on the motion of galaxies and galaxy clusters. Observations show that galaxies rotate at such speeds that they should fly apart if only visible matter were present. The additional mass provided by dark matter helps account for the observed gravitational binding.
2. **Cosmic Structure Formation**: Dark matter is believed to play a critical role in the formation of large-scale structures in the universe by providing the necessary gravitational pull to allow normal matter to clump together.
3. **Non-Baryonic**: The leading candidates for dark matter are non-baryonic particles, meaning they are not made of protons or neutrons. WIMPs (Weakly Interacting Massive Particles) and axions are two of the leading theoretical candidates, though none have been definitively detected.
4. **Cosmic Microwave Background**: Measurements of the cosmic microwave background radiation provide evidence for dark matter, revealing patterns of temperature fluctuations that suggest the presence of additional mass not accounted for by visible matter.
5. **Ongoing Research**: Despite extensive research and many experiments aimed at detecting dark matter directly, its nature remains one of the biggest mysteries in modern astrophysics. Various experiments are ongoing to search for dark matter particles and to better understand their properties.
In summary, dark matter is a fundamental component of the universe, influencing its structure and evolution, even though it is not directly observable.