How big is the universe, and what is the evidence that it began with the Big Bang?
Describe galaxies and the scale of the universe, explain the Big Bang theory and its evidence (redshift and the cosmic microwave background), and outline how the electromagnetic spectrum and telescopes are used to study space (Virginia 2018 Earth Science SOL ES.12).
A SOL-level answer on the universe for the Virginia Earth Science EOC: galaxies and their types, the vast scale measured in light-years, the Big Bang theory and its evidence (the redshift of distant galaxies and the cosmic microwave background), and how the electromagnetic spectrum and telescopes let us study space, with worked exam questions.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this topic is asking
Virginia Earth Science SOL standard ES.12 asks you to describe galaxies and the scale of the universe, to explain the Big Bang theory and its evidence, and to outline how the electromagnetic spectrum and telescopes let us study space. The EOC tests this with redshift items (the headline evidence), Big Bang items, and nature-of-science items about why the Big Bang is a strongly supported theory. It is the largest-scale topic in the course and a natural place to revisit how evidence builds scientific knowledge.
Galaxies and the scale of the universe
The Big Bang theory
The evidence
This is a strong nature-of-science example: a theory in science is an explanation backed by many lines of evidence.
Studying space with the electromagnetic spectrum
Astronomers cannot travel to the stars, so they study the light and other radiation that reaches us. The electromagnetic spectrum runs from radio waves (longest wavelength) through microwave, infrared, visible light, ultraviolet, X-rays to gamma rays (shortest). Different objects and processes emit different wavelengths, so using telescopes (optical, radio, space telescopes) and space probes across the spectrum reveals things invisible to the eye, for example radio telescopes map cold gas, and X-ray telescopes detect very hot, energetic objects. Advancing technology (better telescopes and detectors) keeps revealing more of the universe, another nature-of-science theme.
Try this
Q1. State what the redshift of distant galaxies tells scientists about the universe. [2]
- Cue. The galaxies are moving away from us (their light is stretched to longer wavelengths), and farther ones move faster, showing the universe is expanding.
Q2. Name the faint radiation detected from all directions that supports the Big Bang. [1]
- Cue. The cosmic microwave background (CMB) radiation, the leftover heat from the early universe.
Exam-style practice questions
Practice questions written in the style of VDOE exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
VA Earth Science SOL 2023 (style)1 marksThe light from distant galaxies is shifted toward the red (longer wavelength) end of the spectrum. What does this redshift indicate? (A) the galaxies are moving toward us. (B) the galaxies are moving away from us, so the universe is expanding. (C) the galaxies are not moving. (D) the galaxies are getting hotter.Show worked answer →
A 1-point multiple-choice item on the evidence for the Big Bang.
The correct answer is B. Redshift means the light waves are stretched to longer wavelengths, which happens when a source moves away from us. Because distant galaxies show redshift (and more distant ones are receding faster), the universe is expanding, key evidence for the Big Bang. Light from an approaching source would be blueshifted (A is wrong).
The test rewards interpreting redshift as galaxies moving away, showing an expanding universe.
VA Earth Science SOL 2024 (style)2 marksThe Big Bang theory is the leading explanation for the origin of the universe. (a) State one piece of evidence that supports the Big Bang. (b) Explain why scientists call it a theory rather than just a guess.Show worked answer →
A 2-point item on the Big Bang and the nature of science.
(a) 1 point for either: the redshift of distant galaxies showing the universe is expanding (galaxies moving apart), or the cosmic microwave background radiation, the faint leftover heat detected from all directions.
(b) 1 point: a scientific theory is a broad, well-tested explanation supported by many independent lines of evidence (redshift, the cosmic microwave background, the abundance of light elements), not an untested guess; it has withstood repeated testing.
Markers reward one valid line of evidence in (a) and the idea that a theory is a strongly evidenced explanation in (b).
Related dot points
- Explain that stars produce energy by nuclear fusion, describe the Hertzsprung-Russell diagram and the relationship between a star's color, temperature and luminosity, and outline the life cycle of a star (Virginia 2018 Earth Science SOL ES.12).
A SOL-level answer on stars for the Virginia Earth Science EOC: how stars produce energy by nuclear fusion, what the Hertzsprung-Russell diagram shows about color, temperature and luminosity, the main sequence, and how a star's life cycle depends on its mass, with worked exam questions.
- Describe the structure of the solar system (the Sun, terrestrial and gas-giant planets, and small bodies), explain that orbits are elliptical (Kepler), and explain how gravity and inertia keep planets in orbit (Virginia 2018 Earth Science SOL ES.2 and ES.11).
A SOL-level answer on the solar system for the Virginia Earth Science EOC: the Sun and the inner terrestrial versus outer gas-giant planets, asteroids, comets and other small bodies, the nebular hypothesis, Kepler's elliptical orbits, and how gravity and inertia combine to keep planets orbiting, with worked exam questions.
- Explain how Earth's rotation causes day and night, how the Moon's orbit causes its phases, and how the alignment of the Sun, Earth and Moon causes solar and lunar eclipses (Virginia 2018 Earth Science SOL ES.11).
A SOL-level answer on the Earth-Moon-Sun system for the Virginia Earth Science EOC: how rotation causes day and night, the cause and sequence of Moon phases, why eclipses happen only at certain alignments, the difference between a solar and a lunar eclipse, and why eclipses are not monthly, with worked exam questions.
- Construct, use and evaluate models, distinguish a fact, hypothesis, theory and law, and explain how scientific knowledge is built from evidence and changes over time (Virginia 2018 Earth Science SOL ES.1).
A SOL-level answer on the nature of science for the Virginia Earth Science EOC: what a scientific model is and its limitations, the difference between a fact, hypothesis, theory and law, how evidence and peer review build reliable knowledge, why scientific ideas change, and the difference between observation and inference, with worked exam questions.
- Explain radioactive decay and half-life, and calculate the age of a sample or the fraction of parent remaining using the number of half-lives that have passed (Virginia 2018 Earth Science SOL ES.9).
A SOL-level answer on absolute dating for the Virginia Earth Science EOC: what radioactive decay and half-life mean, the parent-to-daughter ratio, how to count half-lives to find an age or the fraction remaining, why carbon-14 dates young organic material and uranium dates ancient rock, and how Earth's age (about 4.6 billion years) is known, with worked calculations.
Sources & how we know this
- 2018 Science Standards of Learning (Earth Science) — Virginia Department of Education (2018)
- SOL Practice Items (All Subjects) — Virginia Department of Education (2024)