High school · for use with the Next Generation Science Standards*

HS-ESS1-2: The evidence for the big bang

What students must show for performance expectation HS-ESS1-2, with a lesson sequence built on live data, the misconceptions to expect, and assessment questions with answers.

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At a glance
5lesson steps
3live tools
5assessment questions
14 to 18age range

Last updated . Curriculum links last reviewed November 2026.

What students must show

Our summary
  • Students construct an explanation of the big bang theory from astronomical evidence: light spectra, the motion of distant galaxies and the makeup of matter in the universe.
In scope

The redshift of distant galaxies (the universe is expanding), the cosmic microwave background as leftover radiation, and the observed mix of ordinary matter: about three-quarters hydrogen and one-quarter helium.

Not assessed

The official page sets no assessment boundary for this standard.

Our summary, in our own words. Read the official wording.

The three dimensions

High school
Practice

Constructing explanations

Build an explanation from several independent pieces of evidence.

Core idea

ESS1.A and PS4.B

Spectra reveal what stars are made of and how they move; each element absorbs and gives off its own wavelengths of light.

Crosscutting

Energy and matter

Energy cannot be created or destroyed, only moved between places, objects and fields.

Live tools for this standard

3 tools
Space telescopesthe observatories that measure redshift and the faint light of the first galaxiesJWST trackerthe infrared telescope built to see the earliest galaxiesHubble trackerthe telescope behind the deep fields and the expansion rate

Lesson sequence

Engage to evaluate
  1. Engage10 min

    Show a deep-field image from the telescope page. Ask: has the universe always looked like this, or is it changing?

  2. Explore25 min

    Give a table of galaxy distances and the speeds at which they move away. Students graph speed against distance: a straight line. What does it mean if nearly everything is moving away, and the farther galaxies faster?

  3. Explain20 min

    Three lines of evidence: the redshift and expansion; the cosmic microwave background, a faint glow from about 380,000 years after the big bang; and the hydrogen-helium mix, which matches what the first minutes would have made.

  4. Elaborate15 min

    JWST tracker: why does a telescope hunting the first galaxies work in infrared? (Their light has been stretched by the expansion.)

  5. Evaluate15 min

    Students write one explanation paragraph that uses all three pieces of evidence.

Common misconceptions

3 to watch for
Students often think

The big bang was an explosion at one point in space.

In fact

It was the expansion of space itself, happening everywhere at once. There is no center.

Try this

Dots drawn on a balloon all move apart as it inflates, and no dot is the middle.

Students often think

Galaxies redshift because they fly through space like cars.

In fact

For distant galaxies, most of the redshift comes from space stretching while the light travels.

Try this

Draw a wave on a rubber band and stretch it.

Students often think

The big bang theory explains what came before the universe.

In fact

It describes how the universe expanded and cooled from a hot, dense early state, not a "before".

Try this

Ask what evidence could tell us about a time before any evidence existed.

Assessment questions

Answers folded away

HS-ESS1-2: The evidence for the big bang · orbitalradar.com/schools/us/standards/hs-ess1-2

  1. What does it mean that distant galaxies' light is redshifted?
    1. They are moving away from us
    2. They are red stars
    3. They are getting hotter
  2. What is the cosmic microwave background?
    1. Radio noise from Earth
    2. Leftover radiation from the early universe
    3. Light from the Sun
  3. Why is the ratio of hydrogen to helium evidence for the big bang?
  4. Why does a telescope searching for the first galaxies observe in infrared?
  5. Claim, evidence, reasoning: is the universe expanding?
Answer key
  1. They are moving away from us.
  2. Leftover radiation from the early universe.
  3. The hot early universe would have made about three-quarters hydrogen and one-quarter helium by mass, and that is what we see in the oldest stars and gas.
  4. The expansion has stretched their visible and ultraviolet light into infrared.
  5. Yes: redshift grows with distance, so the farther a galaxy is, the faster it moves away.

Worksheet

US Letter

No live-data worksheet for this standard yet: print the assessment questions above. All sheets: the worksheet library.

The same idea in state standards

Texas, Florida, Georgia

No close Texas match in the TEKS we cover.

Related, not equivalent: each state words and groups its standards differently.

More standards pages

High school

Grade 1: 1-ESS1-1 1-ESS1-2

Grade 5: 5-PS2-1 5-ESS1-1 5-ESS1-2

Middle school: MS-ESS1-1 MS-ESS1-2 MS-ESS1-3 MS-PS2-4

High school: HS-ESS1-1 HS-ESS1-2 HS-ESS1-3 HS-ESS1-4 HS-ESS1-6 HS-PS2-4

High school activities All 15 standards

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Codes are performance expectations of the Next Generation Science Standards*, for example 5-ESS1-2. Each summary is our own wording; follow the link on a standard page for the official text.

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Orbital Radar. (2026, November 6). HS-ESS1-2: The evidence for the big bang. Retrieved November 6, 2026, from https://orbitalradar.com/schools/us/standards/hs-ess1-2

“HS-ESS1-2: The evidence for the big bang.” Orbital Radar, 6 Nov. 2026, orbitalradar.com/schools/us/standards/hs-ess1-2. Accessed 6 Nov. 2026.

Orbital Radar (2026) HS-ESS1-2: The evidence for the big bang. Available at: https://orbitalradar.com/schools/us/standards/hs-ess1-2 (Accessed: 6 November 2026).

Orbital Radar. “HS-ESS1-2: The evidence for the big bang.” Last modified November 6, 2026. https://orbitalradar.com/schools/us/standards/hs-ess1-2.

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