Stellar Shift

Lesson 05 Teacher Guide

The Big Picture

The goal of this final lesson is to show students that physics principles are universal. The same Doppler effect that explains an ambulance siren explains the history of the entire universe.

Teacher Tip: Barcode Analogy

Compare absorption spectra to barcodes. When a galaxy is moving, the whole "barcode" (set of lines) shifts over, but the pattern of the lines stays exactly the same. That's how we know it's Hydrogen, just shifted.

Critical Discussion: Andromeda

Students often get confused by the fact that the Andromeda Galaxy is blueshifted.

Key takeaway: Local gravity (between Andromeda and Milky Way) can overcome the general expansion of space at small scales. This proves that galaxies are not just "moving through space," but that space itself is expanding (on larger scales).

Worksheet 05 Key

Q1: Redshift \( z \)

z = 0.0088

Q2: Velocity

v = 2,640 km/s

(Away from Earth)

Q3: Andromeda

Moving Toward us; collision predicted in ~4-5 billion years.

Sequence Conclusion

By the end of this sequence, students have traveled from the micro-scale of ripple tanks to the macro-scale of the cosmos. Use this final moment to emphasize the predictive power of mathematics in science.

Stellar Shift Teacher Guide

Stellar Shift Teacher Guide