Earth and Life Science – The Universe and the Solar System

Fifty question-and-answer flashcards summarizing key concepts on the origin of the Universe and Solar System, Big Bang evidence and issues, inflation theory, and planetary classification.

What is the widely accepted age of the Universe according to the Big Bang theory?

About 13.8 billion years

Roughly how old is our Solar System?

Approximately 4.6 billion years

Which two scientists of the 1920s are credited with formulating the Big Bang theory?

Alexander Friedmann and Georges Lemaître

What name is given to the point of infinite density and heat from which the Universe began?

A singularity

During which extremely brief period did the Universe inflate from sub-atomic size to about 10^35 m across?

The inflationary epoch (≈10^-35 s after the Big Bang)

Name the four fundamental forces that became distinct shortly after the Big Bang.

Gravity, strong nuclear force, weak nuclear force, and electromagnetic force

What is the term for the early-Universe process in which hydrogen nuclei fused to form helium nuclei?

Big Bang nucleosynthesis

Which early phase was dominated by radiation such as light, X-rays, and radio waves?

The radiation era

At about what time after the Big Bang did matter begin to dominate over radiation?

Roughly 300,000 years after the Big Bang

What formed when slight density irregularities in gas clouds collapsed under gravity, eventually producing light?

Stars and, collectively, galaxies

What key observation did Edwin Hubble make in 1924 about distant galaxies?

Almost all galaxies are moving away from us, indicating an expanding Universe

What remnant radiation discovered by Penzias and Wilson in 1965 supports the Big Bang theory?

Cosmic microwave background (CMB) radiation

Which three light elements are most abundant and match Big Bang nucleosynthesis predictions?

Hydrogen, helium, and trace amounts of lithium/beryllium

Which Big Bang problem refers to the nearly flat observed geometry of the Universe?

The flatness problem

What problem concerns the predicted but unobserved heavy magnetic particles?

The monopole problem

Which theory claims the Universe is uniform and unchanging in time?

The steady-state theory

Name one of the three scientists who proposed the steady-state theory in 1948.

Herman Bondi, Thomas Gold, or Fred Hoyle (any one)

Which theory by Guth, Linde, Steinhardt, and Albrecht adds a brief exponential expansion before the Big Bang expansion?

Inflation theory

According to inflation theory, what key event solved the horizon problem?

An early exponential expansion that put distant regions in causal contact before stretching them apart

Who first suggested a whirlpool-like motion (vortex) model for Solar System formation?

René Descartes

What did Buffon’s collision theory propose produced the planets?

Debris from a collision between the Sun and a giant comet

What does the Kant-Laplace nebular theory state formed the Sun and planets?

Collapse and spinning of a large gas–dust cloud (nebula) under gravity

According to Jeans and Jeffreys’ tidal theory, how were planets created?

Material was torn from the Sun by a passing massive star and later condensed

What central concept does the Solar Nebular Theory (SNT) emphasize?

Condensation and accretion of an interstellar gas–dust cloud into the Sun, planetesimals, and planets

In what direction do all planets revolve around the Sun?

Counter-clockwise (as viewed from above the Sun’s north pole)

Which empirical rule relates planetary distances from the Sun?

Bode’s law

Between which two planets is the main asteroid belt located?

Mars and Jupiter

Because of their rocky composition, what are asteroids sometimes called?

Minor planets

Of what two main components are comets primarily made?

Ice (frozen gases/water) and non-volatile dust

Which outer-Solar-System region is the source of short-period comets?

The Kuiper belt

From which distant spherical shell do long-period comets likely originate?

The Oort cloud

What collective name is given to Earth-like, rocky planets?

Terrestrial planets

Name the four terrestrial planets.

Mercury, Venus, Earth, and Mars

What is another term for the gas giants Jupiter, Saturn, Uranus, and Neptune?

Jovian planets

Which planets are classified as inner planets by position relative to the Sun?

Mercury, Venus, Earth, and Mars

Which two planets are considered inferior planets from Earth’s viewpoint?

Mercury and Venus

What maximum orbital period defines a short-period comet?

Less than 200 years

In cosmology, what does the term “nucleosynthesis” mean?

The formation of new atomic nuclei (e.g., fusion of protons into helium) in the early Universe

Which fundamental force holds protons and neutrons together in the nucleus?

The strong nuclear force

Which fundamental force governs radioactive decay processes?

The weak nuclear force

Which long-range attractive force binds together the Solar System?

Gravity (gravitational force)

What unobserved phenomenon predicted by the Big Bang involves isolated magnetic charges?

Magnetic monopoles

Define the cosmic microwave background in one sentence.

It is the faint, uniform microwave radiation that is the cooled remnant heat from the early Universe.

What causes a comet’s tail to form when it nears the Sun?

Solar heat sublimates frozen gases, producing jets that stream dust and gas away from the comet

How does inflation theory explain the present undetectability of magnetic monopoles?

Rapid early expansion diluted their density to extremely low, unobservable levels

Roughly how long after the Big Bang did the first stars and galaxies begin forming?

About 300 million years

What shared plane of planetary orbits indicates that the Solar System is flat?

All major planets orbit nearly in the same ecliptic plane

At what extremely high-energy scale were all four forces thought to be unified?

The Planck scale

In the Solar Nebular Theory, what are planetesimals?

Kilometre-sized solid bodies formed by accretion that later merged into protoplanets