Formation of the Universe and the Solar System

Vocabulary flashcards covering major theories, evidence and terms related to the formation of the universe and the solar system.

Universe

All existing matter, energy, galaxies, stars, gas, dust and everything that will exist in the future.

Cosmology

The scientific study of the origin, structure and evolution of the universe.

Theory of Creation (Genesis)

Religious narrative describing God creating light, sky, land, sea, heavenly bodies and life in six days.

Oscillating Universe Theory

Model proposing cyclic expansion (Big Bang) and contraction (Big Crunch) of a positively curved universe.

Steady State Theory

Hypothesis that the universe expands but maintains constant density by continuous creation of matter.

Big Bang Theory

Widely accepted model stating the universe began ~14 billion years ago from an infinitely dense singularity and has been expanding since.

Singularity

Infinitely small, dense point from which the universe is thought to have originated according to the Big Bang model.

Georges Lemaître

Belgian priest-physicist who first proposed the Big Bang model in 1927.

Edwin Hubble

Astronomer whose observations of galactic redshift provided key evidence for an expanding universe.

Redshift

Stretching of light to longer wavelengths toward the red end of the spectrum as objects move away from an observer.

Cosmic Microwave Background (CMB)

Faint, oldest detectable radiation left over from the early universe, a major evidence for the Big Bang.

Visible Light Spectrum

Portion of the electromagnetic spectrum (≈380–740 nm) that can be perceived by the human eye.

Electromagnetic Radiation

Energy propagated as waves (radio to gamma rays) including visible light.

Encounter Hypothesis

Early solar-system model where a passing rogue star pulled hot gases from the Sun that later condensed into planets.

Nebular Hypothesis

Theory that the solar system formed from a rotating gas cloud that contracted into a disk with a dense central Sun.

Protoplanet Hypothesis

Modern model in which dust and gas in a collapsing interstellar cloud clumped into planetesimals that merged into planets.

Planetesimal

Kilometer-sized solid body formed from dust and gas that served as a building block of planets.

Angular Momentum Conservation

Physical principle causing a contracting gas cloud to spin faster and flatten into a disk.

Big Crunch

Hypothetical future reversal of cosmic expansion leading to the universe’s collapse in oscillating models.

Positive Curvature

Geometry of a closed, finite universe used in oscillating models to allow eventual contraction.

Constant Density

Key assumption of the Steady State Theory achieved by continuous matter creation during expansion.

Electromagnetic Spectrum

Complete range of electromagnetic radiation wavelengths, from radio waves to gamma rays.

Rogue Star

Passing star proposed in the Encounter Hypothesis to have gravitationally disturbed the early Sun.

Proto-Sun

Dense central mass in a collapsing nebula that eventually ignites nuclear fusion to become the Sun.

Interstellar Cloud

Large region of gas and dust in the galaxy from which stars and planetary systems can form.