Slides
Lesson slides
Slides for the lesson
Open resourceLesson 04
The Universe
Describe the large-scale structure of the Universe and use redshift evidence to explain expansion and estimate cosmic age.
Objectives
Lesson outcomes
- State that the Milky Way is one of many billions of galaxies in the Universe and know that its diameter is about 100 000 light-years.
- Describe redshift and explain how it provides evidence that the Universe is expanding and supports the Big Bang theory.
- Explain why cosmic microwave background radiation is evidence from the early Universe.
- Use Hubble-law ideas to relate galaxy speed, distance, and an estimate for the age of the Universe.
Syllabus
CIE 0625 syllabus points
11 linked
- 6.2.3.1 Know that the Milky Way is one of many billions of galaxies making up the Universe and that the diameter of the Milky Way is approximately 100 000 light-years
- 6.2.3.2 Describe redshift as an increase in the observed wavelength of electromagnetic radiation emitted from receding stars and galaxies
- 6.2.3.3 Know that the light emitted from distant galaxies appears redshifted in comparison with light emitted on the Earth
- 6.2.3.4 Know that redshift in the light from distant galaxies is evidence that the Universe is expanding and supports the Big Bang Theory
- 6.2.3.5 Know that microwave radiation of a specific frequency is observed at all points in space around us and is known as cosmic microwave background radiation (CMBR)
- 6.2.3.6 Explain that the CMBR was produced shortly after the Universe was formed and that this radiation has been expanded into the microwave region of the electromagnetic spectrum as the Universe expanded
- 6.2.3.7 Know that the speed v at which a galaxy is moving away from the Earth can be found from the change in wavelength of the galaxy’s starlight due to redshift
- 6.2.3.8 Know that the distance d of a far galaxy can be determined using the brightness of a supernova in that galaxy
- 6.2.3.9 Define the Hubble constant H0 as the ratio of the speed at which the galaxy is moving away from the Earth to its distance from the Earth; recall and use the equation v H0 = d
- 6.2.3.10 Know that the current estimate for H0 is 2.2 × 10 –18 per second
- 6.2.3.11 Know that the equation d 1 = v H0 represents an estimate for the age of the Universe and that this is evidence for the idea that all the matter in the Universe was present at a single point
Definitions
Required definitions
Galaxy
a system made up of many billions of stars.
Light-year
the distance travelled by light in a vacuum in one year, about
9.5 x 10^15 m.Redshift
an increase in the observed wavelength of electromagnetic radiation from receding stars and galaxies.
CMBR
radiation produced shortly after the Universe formed, now observed in the microwave region because the Universe has expanded.
Hubble constant
the ratio of a galaxy's recession speed to its distance from Earth; a current estimate is
2.2 x 10^-18 per second.
Lesson Notes
Student guidance and lesson notes
Overview
This lesson should help you connect evidence to the biggest claims in the course. Keep the structure clear: galaxies, redshift, background radiation, and Hubble-law reasoning all point toward an expanding Universe with a finite age.
What You Need to Know
- Start from the Milky Way and widen out to the idea that the Universe contains many billions of galaxies.
- Connect redshift to the spectra of distant galaxies.
- Explain why widespread redshift supports the idea that the Universe is expanding and why this supports the Big Bang theory.
- Use cosmic microwave background radiation as evidence from the early Universe that has been stretched into the microwave region as space expanded.
- Use the Hubble constant, galaxy speed, and distance data to show how astronomers estimate the age of the Universe.
How to Work Through It
- Start with a retrieval task on stars, galaxies, and light-years so you have the scale language ready.
- Work through the Milky Way’s place in the wider Universe, then introduce redshift with simple spectral comparisons.
- Connect redshift, CMBR, and supernova-distance evidence to the case for an expanding Universe and the Big Bang.
- Finish with one Hubble-style calculation or interpretation task that links galaxy speed, distance, and age-of-the-Universe reasoning.
Check Your Understanding
- Check whether you can identify whether a spectral shift should move towards longer or shorter wavelengths for a galaxy moving away from Earth.
- Use a hinge question where you choose which observation supports the claim that the Universe is expanding.
- Try one short data question involving galaxy speed and distance and ask what it suggests about the age of the Universe.
Common Mistakes
- Mixing up the Solar System, galaxy, and Universe as if they were the same scale. Keep a nested-structure diagram visible.
- Some say redshift happens because light gets older or weaker. Keep the explanation tied to the source moving away and the wavelength increasing.
- CMBR can feel like an isolated fact. Always link it back to radiation from the early Universe that has been stretched by expansion.
- Hubble-law calculations can become mechanical. Keep asking what the answer means physically for the age and history of the Universe.
Next Steps
- Set mixed retrieval questions on scale, evidence, and the age of the Universe to secure the whole topic.
- Use this lesson as the final revision frame for the Year 11 space sequence.
Lesson Resources
Materials for this lesson
Use these videos, slide decks, documents, or links to work through the lesson.