Hubble's parameter

Học thuật
Thân thiện
Definition
  1. Noun:
    • (Cosmology) Hubble's parameter: The ratio of the speed at which a galaxy is receding from an observer (due to the expansion of the universe) to its distance from that observer. It is a measure of the current expansion rate of the universe. Although historically called the "Hubble constant," it is not a true constant over cosmic time.
Usage Examples
  • Noun:
    • Astronomers use Hubble's parameter to estimate the age and expansion rate of the universe.
    • A precise measurement of Hubble's parameter is crucial for modern cosmology.
Advanced Usage
  • "The Hubble tension": Refers to the ongoing discrepancy between measurements of Hubble's parameter derived from the early universe (like the cosmic microwave background) and those from the local, late universe (using supernovae and other "distance ladder" methods).
    • Resolving the Hubble tension is a major goal in contemporary astrophysics.
Variants and Related Words
  • Hubble constant (H₀): The most common name for the present-day value of Hubble's parameter.
    • The latest measurements of the Hubble constant continue to be refined.
  • Hubble law: The observational correlation that the velocity of recession of galaxies is proportional to their distance, with Hubble's parameter being the constant of proportionality.
    • Edwin Hubble's discovery of the Hubble law provided evidence for an expanding universe.
Synonyms
  • Hubble constant
  • Expansion rate of the universe
Related Terms (Not Phrasal Verbs or Idioms)
  • Redshift: The increase in wavelength of light from a receding celestial object, used to measure recession velocity.
  • Cosmological scale factor: A function in cosmology that describes how the universe expands, related to the time evolution of Hubble's parameter.
Noun
  1. (cosmology) the ratio of the speed of recession of a galaxy (due to the expansion of the universe) to its distance from the observer; the Hubble constant is not actually a constant, but is regarded as measuring the expansion rate today

Từ đồng nghĩa