Origin of the Universe – Key Vocabulary

Vocabulary flashcards covering essential terms, concepts and scientists discussed in the lecture on competing hypotheses for the universe’s origin.

Universe

All of space-time and everything it contains, including matter, energy, planets, stars, galaxies and the vacuum itself.

Cosmology

The branch of science that studies the origin, structure, evolution and eventual fate of the universe.

Baryonic Matter

‘Ordinary’ matter made of protons, neutrons and electrons; about 4.6 % of the universe.

Cold Dark Matter

Invisible matter that exerts gravity but emits no light; comprises roughly 24 % of the universe.

Dark Energy

A mysterious form of energy causing the accelerated expansion of the universe; about 71.4 % of the cosmos.

Big Bang Theory

Cosmological model proposing the universe began ~13.8 billion years ago from an extremely hot, dense state and has been expanding ever since.

Singularity

A point of infinite density and temperature predicted to have existed at the very start of the Big Bang.

Raisin-Bread Model

Analogy for cosmic expansion where the loaf is space and raisins are galaxies; as the bread rises, raisins move apart without expanding themselves.

Nucleosynthesis

Process that formed the first light elements (mainly H and He) soon after the Big Bang, enabling later star and galaxy formation.

Georges Lemaître

Belgian priest-physicist who first proposed an expanding universe (1927), laying groundwork for the Big Bang model.

George Gamow

Physicist who refined and popularized the Big Bang theory, emphasizing element formation in the early universe.

Edwin Hubble

Astronomer who discovered galactic redshift in 1929, providing evidence that the universe is expanding.

Redshift

Shift of spectral lines toward longer (red) wavelengths, indicating an object is moving away from the observer.

Hubble’s Law

Relationship stating that a galaxy’s recessional velocity is directly proportional to its distance from Earth.

Cosmic Microwave Background (CMB)

Uniform, faint microwave radiation (≈2.7 K) permeating space, regarded as remnant heat from the early universe.

Arno Penzias & Robert Wilson

Radio astronomers who accidentally discovered the CMB in 1964, earning the 1978 Nobel Prize in Physics.

Steady State Theory

Model claiming the universe is eternally expanding yet maintains constant average density through continuous creation of matter.

Fred Hoyle

British astronomer who, with Bondi and Gold, formulated the Steady State theory and coined the term “Big Bang” (ironically).

Hermann Bondi

Austrian-British physicist who co-developed the Steady State theory in the 1940s.

Thomas Gold

Austrian-British astrophysicist and co-author of the Steady State cosmological model.

Law of Conservation of Energy and Mass

Scientific principle stating that matter-energy cannot be created or destroyed; poses a major inconsistency for the Steady State theory’s matter-creation idea.

Non-Scientific Thought (Creation Myths)

Explanations of cosmic origins rooted in religion or folklore—e.g., Mbombo’s vomiting of stars or Purusha’s sacrifice—that cannot be tested by the scientific method.