Dark Matter
Dark Matter is a form of matter thought to account for approximately 27% of the mass and energy in the observable universe. It does not emit, absorb, or reflect light, making it extremely difficult to detect directly with telescopes that observe electromagnetic radiation. Here are some key points about dark matter:
- Historical Context: The concept of dark matter was first proposed in the 1930s by Fritz Zwicky, who observed that the mass calculated from the movement of galaxies in the Coma Cluster was much greater than what was visible. Zwicky suggested that there might be "missing mass," later termed dark matter.
- Evidence for Dark Matter:
- Gravitational Effects: Observations of the rotational speeds of galaxies suggest they contain far more mass than can be accounted for by visible matter alone. This was notably observed by Vera Rubin and Kent Ford in the 1970s.
- Gravitational Lensing: Dark matter's gravitational influence can bend light from distant galaxies, an effect known as gravitational lensing. This has been observed in numerous galaxy clusters like the Bullet Cluster.
- Cosmic Microwave Background (CMB): The distribution of dark matter influences the cosmic microwave background radiation, which has been measured with high precision by experiments like the WMAP and Planck Satellite.
- Composition: The exact nature of dark matter is still unknown. Theories include:
- Detection Efforts:
- Direct Detection: Experiments like LUX-ZEPLIN attempt to detect dark matter particles through their interactions with ordinary matter.
- Indirect Detection: Observations of cosmic rays, gamma rays, or neutrinos from dark matter annihilation or decay are pursued by projects like Fermi Gamma-ray Space Telescope.
- Collider Searches: Particle accelerators like the Large Hadron Collider (LHC) look for signs of dark matter in high-energy particle collisions.
- Implications: Understanding dark matter is crucial for cosmology because it affects the formation, evolution, and structure of the universe. It also has implications for theories of particle physics, potentially requiring new physics beyond the Standard Model.
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