Cold dark matter

Definition

Cold dark matter (CDM) is a form of matter that does not emit or interact with electromagnetic radiation, making it invisible and detectable only through its gravitational effects. It plays a crucial role in the formation of cosmic structures, influencing the distribution of galaxies and clusters in the universe. The characteristics of cold dark matter help explain phenomena such as the rotation curves of galaxies and the large-scale structure of the universe, linking it to models of cosmic evolution and the behavior of dark energy.

5 Must Know Facts For Your Next Test

1. Cold dark matter is thought to make up about 27% of the total mass-energy content of the universe, dominating over baryonic matter.
2. CDM is characterized by slow-moving particles, meaning they are 'cold' compared to other potential dark matter candidates like hot dark matter.
3. The structure formation in the universe occurs through the gravitational clumping of cold dark matter, which helps in the formation of galaxies and larger cosmic structures.
4. Observations of galaxy rotation curves show discrepancies between visible mass and gravitational influence, indicating the presence of cold dark matter.
5. Models that include cold dark matter have been successful in explaining the cosmic microwave background radiation and large-scale structure observed in the universe.

Review Questions

• How does cold dark matter influence the formation and distribution of galaxies in the universe?
  • Cold dark matter acts as a gravitational scaffold for the formation of galaxies. Its slow-moving nature allows it to clump together under gravity, leading to denser regions where galaxies can form. The gravitational pull from cold dark matter affects how galaxies move within clusters and how they interact with one another, shaping their distribution across the universe.
• Discuss the implications of cold dark matter on our understanding of cosmic evolution and structure formation models.
  • The inclusion of cold dark matter in cosmological models provides a framework for understanding how large-scale structures develop over time. CDM helps explain observed phenomena such as the uniformity in the cosmic microwave background radiation and the intricate web-like structures seen in galaxy distributions. These insights are critical for refining our models of cosmic evolution, indicating that both CDM and baryonic matter play essential roles in shaping the universe.
• Evaluate how observations supporting cold dark matter have impacted theories regarding dark energy and the cosmological constant.
  • Observations supporting cold dark matter have led to a deeper investigation into the nature of dark energy and its relationship with the expansion of the universe. The presence of cold dark matter affects gravitational interactions on large scales, which must be reconciled with observations showing an accelerated expansion attributed to dark energy. This interplay has prompted discussions on adjusting existing models or considering new physics beyond current understandings, ultimately impacting how cosmologists approach the cosmological constant in contemporary theories.

Related terms

Baryonic Matter: The ordinary matter composed of protons, neutrons, and electrons, which makes up stars, planets, and living organisms.

WIMPs:

Weakly Interacting Massive Particles, a leading candidate for dark matter that interacts via weak nuclear force and gravity.

Gravitational Lensing:

The bending of light from distant objects due to the gravitational influence of massive objects like galaxy clusters, providing evidence for the existence of dark matter.