Dark matter

Definition

Dark matter is a type of matter that does not emit, absorb, or reflect any electromagnetic radiation, making it invisible and detectable only through its gravitational effects on visible matter. This mysterious substance constitutes about 27% of the universe's total mass-energy content and plays a crucial role in the formation and structure of galaxies and cosmic structures.

5 Must Know Facts For Your Next Test

1. Dark matter does not interact with electromagnetic forces, which means it cannot be seen directly with telescopes that observe light.
2. Its existence was first proposed in the 1930s to explain discrepancies in the rotational speeds of galaxies that couldn't be accounted for by visible mass alone.
3. Experiments searching for dark matter particles include direct detection methods like underground detectors and indirect detection through astronomical observations.
4. Dark matter is thought to be responsible for the observed structure of the universe, influencing how galaxies form and cluster together over time.
5. Despite extensive studies, dark matter's exact composition remains unknown, leading to various theoretical candidates such as weakly interacting massive particles (WIMPs) and axions.

Review Questions

• How does dark matter influence the formation and behavior of galaxies in the universe?
  • Dark matter plays a significant role in shaping galaxies due to its gravitational influence. It helps determine how galaxies cluster together and affects their rotational speeds. Without dark matter, the gravitational pull from visible matter alone would be insufficient to account for the observed motion of stars within galaxies, leading to inconsistencies in our understanding of cosmic structure.
• Discuss how gravitational lensing provides evidence for the presence of dark matter in the universe.
  • Gravitational lensing occurs when light from distant objects is bent around massive objects, such as clusters of galaxies, due to their gravitational field. This bending reveals more mass than what is visible through traditional observations. By analyzing lensing effects, astronomers can map out dark matter's distribution, showing that it exists in large quantities around galaxy clusters and further supporting the concept of dark matter.
• Evaluate the significance of ongoing research into dark matter and its potential implications for our understanding of fundamental physics.
  • Ongoing research into dark matter is crucial as it challenges our current understanding of fundamental physics. The search for its nature could lead to groundbreaking discoveries about the composition of the universe and fundamental forces. If dark matter is found to consist of new types of particles or interactions, it may revolutionize particle physics and cosmology, influencing theories about everything from galaxy formation to the fate of the universe itself.

Related terms

baryonic matter: Baryonic matter refers to the ordinary matter composed of protons, neutrons, and electrons that make up stars, planets, and living organisms.

cosmic microwave background (CMB): The cosmic microwave background is the afterglow radiation from the Big Bang, providing evidence for the early universe's conditions and influencing our understanding of dark matter.

gravitational lensing: Gravitational lensing is the bending of light from distant objects due to the gravitational field of massive objects, used as a method to infer the presence and distribution of dark matter.