Study Notes
Cosmology explores the universe's expansion and the phenomena that support it, such as the Doppler Effect and Hubble's Law.
- Doppler Effect — change in frequency or wavelength of a wave in relation to an observer moving relative to the wave source. Example: The sound of a passing siren changing pitch.
- Redshift — increase in wavelength (or decrease in frequency) of electromagnetic radiation from an object moving away from the observer. Example: Light from distant galaxies appears redder.
- Hubble's Law — the observation that the recessional velocity of galaxies is proportional to their distance from Earth. Example: Galaxies farther away move faster.
- Big Bang Theory — the theory that the universe originated from an extremely hot and dense state and expanded over time. Example: The universe expanding from a singular point.
Exam Tips
Key Definitions to Remember
- Doppler Effect
- Redshift
- Hubble's Law
- Big Bang Theory
Common Confusions
- Confusing redshift with blueshift
- Misinterpreting Hubble's Law as galaxies moving through space rather than space itself expanding
Typical Exam Questions
- What is the Doppler Effect? It is the change in frequency or wavelength of a wave in relation to an observer moving relative to the wave source.
- How does redshift provide evidence for the expanding universe? Redshift indicates that galaxies are moving away, suggesting space is expanding.
- What does Hubble's Law state? It states that the recessional velocity of galaxies is proportional to their distance from Earth.
What Examiners Usually Test
- Understanding of how redshift supports the Big Bang Theory
- Ability to apply Hubble's Law to calculate the universe's expansion rate