Origins of the Universe & Solar System

Vocabulary flashcards covering cosmological theories, fundamental forces, particle formation, star and planet origins, and profiles of the Sun and major planets.

Hypothesis

A testable explanation to a scientific question, not yet widely supported by evidence.

Theory

An explanation of how nature works, strongly supported by a large body of scientific evidence.

Scientific Law

A description of what nature does under certain conditions, often expressed mathematically.

Divine Creation Theory

The idea that a supernatural being (God) created the universe, based on the Book of Genesis.

Big Bang Theory

Model stating the universe began ~13.8 billion years ago from a singularity and has been expanding ever since.

George Lemaître

Belgian physicist–priest who first proposed the Big Bang Theory in the 1920s.

Singularity

Infinitesimally small, infinitely dense point from which the universe originated in the Big Bang model.

Cosmic Inflation

Extremely rapid expansion of the universe fractions of a second after the Big Bang.

Eternal Inflation

Extension of inflation suggesting universe keeps spawning new universes, creating a multiverse.

Multiverse

Hypothetical collection of multiple, separate universes produced by eternal inflation.

Oscillating Universe

Model in which the universe alternates between expansion and contraction phases.

Big Crunch Theory

Scenario where universal expansion reverses, leading all matter back into a singularity.

Fundamental Forces

The four basic interactions: gravity, electromagnetic, strong nuclear, and weak nuclear forces.

Gravity

Attractive force between masses; governs large-scale structure of the universe.

Electromagnetic Force

Force that binds atoms into molecules and governs electricity, magnetism, and light.

Strong Nuclear Force

Force that binds protons and neutrons together inside atomic nuclei.

Weak Nuclear Force

Force responsible for radioactive decay and nuclear transmutation.

Quark

Elementary particle that combines to form protons and neutrons; types include up, down, strange.

Proton

Positively charged particle in an atomic nucleus, made of two up quarks and one down quark.

Neutron

Neutral particle in an atomic nucleus, made of one up quark and two down quarks.

Electron

Negatively charged subatomic particle orbiting an atomic nucleus.

Hydrogen

Lightest, most abundant element formed after the Big Bang; nucleus has one proton.

Helium

Second-lightest element formed when protons and neutrons fused after the Big Bang.

Galaxy

Massive system of stars, gas, and dust bound by gravity; formed from giant hydrogen-helium clouds.

Star

Luminous sphere of plasma powered by nuclear fusion in its core.

Nuclear Fusion

Process where light nuclei combine to form heavier nuclei, releasing vast energy in stars.

Supernova

Explosive death of a massive star that disperses heavy elements into space.

Solar Nebula Hypothesis

Theory that the Sun and planets formed from a rotating disk of gas and dust ~4.6 billion years ago.

Sun

Yellow-dwarf star at the center of our solar system; orbits Milky Way every 250 million years.

Planet

Celestial body orbiting a star, massive enough for self-gravity to make it round and clear its orbit.

Mercury

Smallest and closest planet to the Sun; no moons; year lasts 88 Earth days.

Venus

Second planet; hottest surface (≈462 °C); rotates clockwise and has a day longer than its year.

Earth

Third planet; only known world with life; one moon; strongest planetary magnetic field among terrestrials.

Aphelion

Point in a planet’s orbit farthest from the Sun.

Perihelion

Point in a planet’s orbit closest to the Sun.

Mars

Fourth planet; known as the Red Planet; hosts Olympus Mons, the tallest mountain in the solar system.

Jupiter

Largest planet; gas giant with 67+ moons and the persistent Great Red Spot storm.

Great Red Spot

Gigantic, long-lived storm in Jupiter’s atmosphere, larger than Earth.

Saturn

Ringed gas giant; least dense planet; has over 60 moons including Titan.

Uranus

Ice giant discovered in 1781; rotates on its side and completes an orbit in 84 Earth years.

Ice Giant

Planet composed mainly of volatile ices like water, ammonia, and methane (e.g., Uranus, Neptune).

Neptune

Most distant known planet; smallest gas giant; orbits Sun every 165 Earth years; has faint rings.

Gas Giant

Large planet composed predominantly of hydrogen and helium, lacking a solid surface (e.g., Jupiter).