8.2.3 Dark Energy & Dark Matter

• Why is understanding dark energy and dark matter important in modern cosmology?

  It is crucial for grasping the structure of the universe.
• What are the main components of the universe according to modern cosmology?

  • Various forms of energy and matter
  • Most of it is invisible or not directly observable
  • Dark energy and dark matter make up about 95% of the universe's total energy and matter
• What percentage of the universe's mass and energy is believed to be dark matter?

  About 27%
• How is dark matter detected if it does not emit, absorb, or reflect light?

  It is detectable only through its gravitational effects.
• What are the three main pieces of evidence for dark matter?

  Galactic rotation curves, galaxy clusters, and gravitational lensing.
• How do galactic rotation curves provide evidence for dark matter?

  They show that stars in galaxies orbit much faster than expected without dark matter.
• What role does dark matter play in galaxy clusters?

  It contributes to the total mass, influencing the cluster dynamics.
• What is gravitational lensing and how does it relate to dark matter?

  Gravitational lensing is the bending of light from distant objects, revealing the presence of dark matter.
• What type of matter is dark matter classified as?

  Non-baryonic matter.
• Why is dark matter considered weakly interacting?

  It does not interact with electromagnetic forces, making it invisible.
• What are some candidates for dark matter?

  Weakly Interacting Massive Particles (WIMPs), axions, and sterile neutrinos.
• What is dark energy?

  A mysterious form of energy driving the accelerated expansion of the universe.
• What percentage of the universe's total energy content is thought to be dark energy?

  About 68%
• What evidence supports the existence of dark energy?

  Observations of an accelerating universe and measurements of the cosmic microwave background (CMB).
• How does dark energy affect the expansion of the universe?

  It counteracts the force of gravity, leading to accelerated expansion.
• What is the cosmological constant (Λ)?

  A fixed amount of energy filling space homogeneously, proposed by Albert Einstein.
• What is quintessence in relation to dark energy?

  A dynamic form of dark energy that changes over time and space.
• What are the implications of dark matter and dark energy for our understanding of the universe?

  • Critical to understanding the overall structure and fate of the universe
  • Dark matter played a key role in the formation of galaxies and large-scale structures
• What future research directions are being pursued regarding dark matter and dark energy?

  • Developing new experiments to detect dark matter directly or indirectly
  • Ongoing and future observations of cosmic phenomena to refine understanding of dark energy
• What is the summary of dark matter and dark energy?

  • Dark Matter: Invisible, makes up about 27% of the universe, detectable through gravitational effects.
  • Dark Energy: Mysterious, drives accelerated expansion, makes up about 68% of the universe’s energy content.