dark matter

Thân thiện

A scientist points to a diagram representing dark matter in a lecture.

Definition

1. Noun:
   • (Cosmology) A hypothetical form of matter: "Dark matter" refers to a type of matter that is theorized to exist in the universe. It is called "dark" because it does not interact with electromagnetic radiation, meaning it does not emit, absorb, or reflect light, making it invisible to telescopes.
   • A major component of the universe: It is believed to constitute a significant portion (approximately 85-90%) of the total matter in the universe. Its primary evidence comes from its gravitational effects on visible matter, such as the rotation of galaxies and the bending of light (gravitational lensing).

Usage Examples

• Noun:
  • Scientists are searching for direct evidence of dark matter.
  • The existence of dark matter helps explain the observed motion of stars within galaxies.
  • The gravitational pull of dark matter is thought to shape the large-scale structure of the cosmos.

Advanced Usage

• "Cold dark matter": A specific theoretical model where dark matter particles move slowly compared to the speed of light.
  • The standard cosmological model is based on the theory of cold dark matter.
• "Dark matter halo": A theoretical component of a galaxy, a roughly spherical halo of dark matter that surrounds and permeates it.
  • Our Milky Way galaxy is embedded within a vast dark matter halo.

Variants and Related Words

• Dark energy (n): A hypothetical form of energy that permeates all of space and accelerates the expansion of the universe. It is distinct from dark matter.
  • The universe's composition is thought to be mostly dark energy and dark matter.

Synonyms

• Non-baryonic matter: Matter not composed of ordinary protons and neutrons (baryons), a category that includes most theoretical candidates for dark matter.
• Invisible mass: A descriptive term emphasizing its undetectable nature via light.

Related Phrases and Collocations

• Dark matter particle: A hypothetical elementary particle, such as a WIMP (Weakly Interacting Massive Particle), that could constitute dark matter.
  • Experiments deep underground aim to detect a dark matter particle.
• Dark matter distribution: Refers to how dark matter is spread throughout the universe.
  • Astronomers map the dark matter distribution using gravitational lensing.

Học thuật

Noun

1. (cosmology) a hypothetical form of matter that is believed to make up 90 percent of the universe; it is invisible (does not absorb or emit light) and does not collide with atomic particles but exerts gravitational force