Earth Science - Universe and Solar System Flashcards (1st Term, AY 2024–2025)

A set of Q&A flashcards covering key concepts from the Universe and Solar System sections of the Earth Science notes, including the Big Bang, galaxies, the Milky Way, interstellar matter, the Solar System, planetary types, moons, and basic cosmological models.

What is Hubble's Law?

Galaxies recede at speeds proportional to their distances from the observer.

What is cosmological red shift?

Shifts toward the red end of the spectrum observed in most galaxies, indicating they are moving away due to the expanding universe.

Who proposed that the universe began as a single point and expanded?

Georges Lemaître.

Approximately how old is the universe according to the module?

About 13.7 billion years.

What is the Cosmic Microwave Background (CMB)?

Thermal leftover radiation from the early universe; discovered by Robert Wilson and Arno Penzias; Nobel Prize in Physics 1978.

What evidence supports the Big Bang related to light elements?

Abundances of hydrogen and helium in the oldest stars and gas clouds match Big Bang nucleosynthesis predictions.

What is a galaxy?

A large group of stars, gas, and dust bound together by gravity.

What are the three main components of the Milky Way (a barred spiral galaxy)?

Bulge, disk, and halo.

Approximately how many stars are in the Milky Way?

About 100 billion stars.

What is the approximate diameter of the Milky Way's disk?

About 100,000 light years.

What is interstellar matter and its composition?

Matter between stars within galaxies; roughly 90% hydrogen, 9% helium, with the remainder being heavier-element dust.

What are nebulae?

Interstellar clouds of gas and dust; nurseries of stars; bright nebulae are illuminated, dark nebulae are not.

What constitutes the Solar System?

The Sun and the planets and other bodies bound by gravity; includes terrestrial and Jovian planets.

How far is the Solar System from the Milky Way's center?

About 25,000 light years away.

When did the Solar System form and how?

About 4.5 billion years ago from the collapse of a giant interstellar cloud of gas and dust.

What are terrestrial planets?

Mercury, Venus, Earth, and Mars; rocky and solid.

What are Jovian planets?

Jupiter, Saturn, Uranus, and Neptune; gas giants with thick atmospheres and rings.

What is the Kuiper Belt?

A region beyond Neptune filled with icy bodies; Pluto is a member and classified as a dwarf planet.

What is Pluto's current classification?

Dwarf planet (one of the Kuiper Belt objects).

What is a moon?

A natural satellite that orbits a planet; Earth’s Moon is an example.

Which planet has no true atmosphere and only an exosphere?

Mercury.

What is Earth's atmosphere primarily composed of?

Nitrogen and oxygen.

What are the atmospheric compositions of Venus and Mars?

Mostly carbon dioxide.

Which planets have atmospheres primarily of hydrogen and helium?

Jupiter, Saturn, Uranus, and Neptune (the Jovian planets).

Which planet is known as the 'living planet'?

Earth, due to its life and protective atmosphere and magnetic field.

What is the difference between bright and dark nebulae?

Bright nebulae are illuminated by nearby hot stars; dark nebulae are too distant to be illuminated and appear dark.

What is the geocentric model?

An Earth-centered model in which Earth is at the center and others orbit Earth.

What is the heliocentric model?

A Sun-centered model in which the Sun is at the center and the planets orbit it.

Who proposed the heliocentric model in antiquity?

Aristarchus of Samos.

In Copernican theory, what is the center of the cosmos?

The Sun.

In Copernican theory, what is the order of the planets from the Sun?

Mercury, Venus, Earth, Mars, Jupiter, Saturn.

What explains retrograde motion in the Copernican view?

The relative motion of Earth and other planets (Earth’s motion creates apparent backward motion).

How does the module describe the distance from Earth to the Sun compared to the distance to the stars?

The Earth–Sun distance is small compared to the vast distance to the stars.

What is the living planet’s significance in this module?

Earth is the living planet due to presence of life, atmosphere, and magnetic field.