key term - Hubble constant

Definition

The Hubble constant is the rate of expansion of the universe, typically measured in kilometers per second per megaparsec (km/s/Mpc). It quantifies how fast galaxies are moving away from each other due to the expansion of the universe.

5 Must Know Facts For Your Next Test

1. The Hubble constant is denoted by $H_0$.
2. Current estimates of the Hubble constant range between approximately 67 and 74 km/s/Mpc.
3. The value of the Hubble constant helps determine the age and size of the universe.
4. It was first measured by Edwin Hubble in 1929 using observations of distant galaxies.
5. Discrepancies in its measurement are known as the 'Hubble tension,' a significant issue in cosmology.

Review Questions

Related terms

Redshift:

A phenomenon where light from an object is shifted to longer wavelengths due to its motion away from us, often used to measure cosmic distances.

$\Lambda$CDM Model: 'Lambda Cold Dark Matter' model is the standard model of Big Bang cosmology that includes dark energy ($\Lambda$) and cold dark matter (CDM) components.

Cosmic Microwave Background (CMB): Radiation left over from an early stage in the development of the universe, providing evidence for its origin and evolution.