Lesson 3: Light as Evidence – Redshift and Electromagnetic Radiation

What is redshift and how does it relate to the motion of galaxies?

How do astronomers use light across the electromagnetic spectrum to gather information about celestial objects?

How does redshift provide evidence for the expansion of the universe?

What patterns in electromagnetic radiation help scientists understand stellar and galactic processes?

How can we use observational data from different wavelengths to construct models of the universe?

Redshift

Blueshift

Electromagnetic radiation

Spectrum

Galaxy

Recessional velocity

Doppler effect

Light spectra

Expansion of the universe

Astronomical observation

HS-ESS1-2 – Construct an explanation of the Big Bang theory and cosmic expansion based on astronomical evidence, including redshift measurements and light spectra.

NGSS Crosscutting Concepts:
Cause and Effect

Systems and System Models

Stability and Change

Patterns

Students will analyze galaxy spectra and redshift data to interpret velocity and motion patterns.

Students will develop skills in interpreting graphs, spectra, and data sets to support scientific explanations.

Students will construct evidence-based explanations linking observational data to models of universe expansion and cosmic structure.

Students will explore how light provides evidence about the universe, focusing on redshift as a key indicator of cosmic expansion. They will examine spectral data from galaxies, discuss the Doppler effect in light, and interpret patterns that support Hubble’s Law.

Activities may include:

Plotting galaxy redshift versus distance to visualize expansion

Using spectroscopic data to identify shifts in light

Simulating redshift and blueshift with classroom models or digital tools

Purpose: Reinforce the connection between observational data, electromagnetic radiation, and models of cosmic expansion.
DOK Level: 3 – Strategic Thinking / Reasoning (analyzing data to draw evidence-based conclusions)

Redshift observations are foundational to modern astronomy, telescope missions, and space exploration. Students can relate these measurements to news about galaxy discoveries, international observatories, and the technologies that allow us to understand the universe beyond Earth.

Students may think galaxies are moving through space rather than space itself expanding.

Students may confuse redshift and blueshift with visible color changes instead of wavelength shifts.

Students may struggle to connect redshift data with velocity and distance relationships.

Students may think redshift only applies to nearby galaxies instead of being a universal phenomenon.

Scaffolded instruction for plotting and interpreting redshift data.

Graphic organizers to visualize the relationship between galaxy velocity and distance.

Technology integration: simulations of redshift, blueshift, and electromagnetic spectra.

Peer collaboration for analyzing and interpreting spectral data.

Step-by-step guides for connecting light spectra to cosmic expansion.

Support for interpreting complex data patterns visually and numerically.

• Checkpoints during redshift plotting and spectral data interpretation activities.

• Quizzes on key vocabulary and concepts (redshift, Doppler effect, electromagnetic spectrum).

• Evaluation of student-created graphs showing galaxy velocity versus distance.

• Constructed-response assignments asking students to explain how redshift data supports the expanding universe model.

• Astronomy slides and worksheets on redshift and light spectra

• Galaxy redshift datasets (simplified for classroom use)

• Online simulations of spectral shifts and cosmic expansion

• Spectral images from distant galaxies (NASA/ESA databases)

• Articles or case studies explaining Hubble’s discovery and the significance of redshift