The Expanding Universe

A collection of vocabulary flashcards related to the topic of the expanding universe, covering key concepts, definitions, and important figures.

Edwin Hubble

An astronomer who measured distances and redshifts of galaxies using a 100-inch telescope at Mt. Wilson in 1927.

Redshift

The increase in the wavelength of light from an object moving away from an observer, indicating that the object is receding.

Hubble's Law

States that the farther away a galaxy is, the faster it is receding from us, with the relationship described by the Hubble constant.

Radial Velocity (vr)

The velocity at which an object is moving away from or towards an observer, calculated using the change in wavelength.

Standard Candle

A type of astronomical object with a known luminosity used to measure distances in space, such as Cepheid variables or Type Ia supernovae.

Parallax

The apparent displacement of an object because of a change in the observer's point of view, used to measure distances to nearby objects.

Hubble Time

The approximate age of the Universe calculated using Hubble's Law, relating distance and velocity.

Lookback Time

The time it takes for light to reach us from a distant galaxy, indicating how far back in time we are observing.

Cepheid Variables

A type of star used as a standard candle in measuring astronomical distances, known for their regular brightness variation.

Type Ia Supernovae

A category of supernova that serves as a bright standard candle for measuring distances; it occurs when a white dwarf star explodes.

Galaxy Clusters

Groups of galaxies held together by gravity, where members preserve their positions despite the expansion of the universe.

Expanding Universe

The observation that galaxies are moving away from us, indicating that the space itself between them is expanding.

Gravitational Binding

The force that holds stars within galaxies and galaxies within clusters, preventing them from expanding with the universe.

Light-year

A unit of distance that light travels in one year, commonly used to express astronomical distances.

Hubble Constant (H0)

The unit of measurement that determines the rate of expansion of the Universe as a function of distance.