Universe and the Solar System: Theories of Origin

A set of vocabulary flashcards covering the composition of the universe, various historical and modern theories of origin, and key scientific evidence such as Hubble's Law and Redshift.

Universe

The totality of everything that exists, including all physical matter and energy, from the smallest atom to the biggest galaxy.

Baryonic Matter

The type of matter that makes up $4.6\%$ of the universe as we currently know it.

Cold Dark Matter

Matter that makes up $24\%$ of the universe; it possesses gravity but does not emit light.

Dark Energy

A source of anti-gravity that accounts for $71.4\%$ of the composition of the universe.

Genesis

A book from the Hebrew Bible and Christian Old Testament describing how God created the heavens and the earth.

Creationist Theory

The theory stating that God, a Supreme Being, created the whole universe out of nothing.

Big Bang Theory

The currently accepted model of the formation of the universe, suggesting it originated from an infinitely tiny and dense point around $14$ billion years ago.

Singularity

The infinitely tiny, infinitely dense single point from which the universe originated.

Monsignor Georges Lemaitre

The Belgian Roman Catholic priest and astronomer who first attributed the Big Bang Theory in $1927$.

George Gamow

The Russian-born cosmologist who helped explain the Big Bang Theory and proposed the Oscillating Universe Theory.

Hubble's Law

A law credited to Edwin Hubble stating that galaxies move away from Earth at a speed proportional to their distance.

Redshift

The phenomenon where the frequency of light from a source moving away from the observer is shifted toward the red end of the spectrum; evidence for the Big Bang.

Cosmic Microwave Background Radiation

Radiation discovered in $1964$ by Arno Penzias and Robert Wilson that is considered leftover light from the Big Bang.

Oscillating Universe Theory

The theory that the expansion of the universe will eventually halt and collapse back to its original form, leading to another Big Bang.

Steady-State Theory

Proposed by Hermann Bondi, Thomas Gold, and Fred Hoyle, it claims the universe has always been the same and will remain in its present state for eternity.

Cosmic Inflation Theory

The hypothesis that immediately after the Big Bang, the universe expanded much faster than the speed of light before slowing to a lower expansion rate.

Big Crunch Theory

A theory suggesting the universe will stop expanding and instead shrink until all materials collide; it posits no possibility of another Big Bang afterward.

Atomist Universe

A model by Leucippus and Democritus stating the physical world is composed of invisible, indivisible particles called atoms in an infinite void.

Brahmanda (Cosmic Egg)

A Hindu cosmological concept representing the universe as a sphere or egg formed by Brahma the creator.

Aristotelian Universe

A geocentric model where a fixed, spherical Earth rests at the center of a finite cosmos divided into sublunary and celestial realms.

Heliocentric Universe

A model re-proposed and developed by Nicolaus Copernicus that places the Sun at the center of existence while Earth and other planets revolve around it.

The Ptolemaic System

A $2^{\text{nd}}$-century geocentric model by Claudius Ptolemy that used complex paths called epicycles and deferents to explain planetary motion.