Origin of The Universe and The Solar System

Vocabulary flashcards summarizing key terms, people, and concepts from the lecture on the origin of the universe and the solar system.

Religious cosmology

Explanations of the universe’s origin, history, and evolution based on creation stories or mythology of specific faith traditions.

Old Testament creation

Biblical view stating that God created the heavens and the Earth "in the beginning."

Scientific cosmology

Study of the universe’s origin and structure using natural laws, observations, and the scientific method.

General Theory of Relativity

Einstein’s 1915 theory describing gravity as the curvature of spacetime; cornerstone of modern cosmology.

Edwin Hubble

Astronomer who, in the 1920s, discovered that galaxies are moving away, revealing an expanding universe.

Expanding Universe

Observation that galaxies recede from one another, implying the cosmos is growing in size over time.

Steady State Theory

1948 model (Hoyle, Gold, Bondi) proposing a universe that is uniform, eternal, and continuously creating matter.

Cosmological Principle

Assumption that the universe is homogeneous and isotropic—looks the same in every direction and place.

Cosmic Microwave Background (CMB)

Faint remnant radiation from 380,000 years after the Big Bang; key evidence against the Steady State model.

Big Bang Theory

Leading explanation that the universe began ~13.8 billion years ago in a rapid expansion from a hot, dense state.

Red Shift

Lengthening of light wavelengths from receding galaxies, indicating universal expansion.

Light-element abundance

Presence of primordial hydrogen, helium, lithium, and beryllium matching Big Bang nucleosynthesis predictions.

Inflation (cosmology)

Brief period (~10⁻³⁵ s) of exponential expansion just after the Big Bang.

Nucleosynthesis

First 3 minutes when protons and neutrons fused to form light nuclei.

Recombination

Epoch (~380,000 years post-Bang) when electrons joined nuclei to form neutral atoms, freeing photons (CMB).

Nebular Hypothesis

Kant–Laplace idea that the Sun and planets formed from a rotating cloud of gas and dust ~4.6 billion years ago.

Bode’s Law

Empirical relation describing approximate distances of planets from the Sun.

Angular momentum (planetary)

Product of a planet’s mass, orbital distance, and velocity; conserved, so distant planets move more slowly.

Encounter Hypothesis

Group of early 20th-century ideas (Collision & Tidal) positing planets formed from material pulled from the Sun by a near pass of another body.

Collision Theory (Buffon)

18th-century proposal that a Sun-comet collision produced the planets.

Tidal Theory

Jeans & Jeffreys’ suggestion that a star’s tidal forces drew matter from the Sun to create planets.

Planetesimal Theory

Chamberlin & Moulton’s model where small solid bodies (planetesimals) gradually merged to build planets.

Accretion

Process of growth by collision and sticking together of dust, rock, or ice particles in a protoplanetary disk.

Protoplanet Hypothesis

Safronov’s refinement describing how planetesimals merged into larger protoplanets, eventually becoming full planets.

Vortex Theory

Descartes’ 17th-century idea of whirlpool-like motions organizing presolar material into circular orbits; later disproved by Newtonian gravity.

Oort Cloud

Hypothetical spherical shell of icy bodies 750 billion km to ~100,000 AU from the Sun, source of long-period comets.

Kuiper Belt

Doughnut-shaped region beyond Neptune (~30–50 AU) containing icy rocks and dwarf planets.

Maha Yuga

Hindu cosmological “great cycle” lasting 4.32 billion years, featuring creation and destruction sequences.

Cosmic Microwave Background discovery

1965 observation by Penzias & Wilson that detected relic radiation, supporting the Big Bang and refuting Steady State.

Galaxy

Massive system of stars, gas, dust, and dark matter; the Milky Way is one of an estimated 170 billion in the observable universe.