Cosmology
Visão Geral
About 14 billion years ago, everything in the universe was compressed into a single, incredibly hot, dense point. Then it exploded outward in an event we call the Big Bang, and it has been expanding ever since. The evidence for this remarkable claim comes from two independent observations: the red-shift of distant galaxies and the faint microwave glow that fills every corner of the sky.
In this lesson you will learn how the Doppler effect stretches light from receding galaxies, how this red-shift reveals that the universe is expanding, and how the cosmic microwave background radiation provides a snapshot of the early universe. You will also use the red-shift equation and explore how astronomers estimate the age of the universe. These ideas are tested on Edexcel Papers 1 and 2, often as explain-the-evidence questions.
Objetivos
- Describe the past evolution of the universe and the main arguments in favour of the Big Bang theory
- Describe evidence that supports the Big Bang theory (red-shift and cosmic microwave background radiation)
- Describe that if a wave source is moving relative to an observer, there will be a change in the observed frequency and wavelength
- Use the equation relating to change in wavelength, reference wavelength, velocity of a galaxy and the speed of light: (lambda - lambda0) / lambda0 = v / c
- Describe the red-shift in light received from galaxies at different distances away from the Earth
- Explain why the red-shift of galaxies provides evidence for the expansion of the universe
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- What does it mean when light from a distant galaxy is red-shifted? A) The galaxy is getting hotter B) The galaxy is moving towards Earth C) The galaxy is moving away from Earth D) The galaxy is slowing down Answer: C
- The cosmic microwave background radiation has a temperature of approximately: A) 0 K B) 2.7 K C) 273 K D) 6000 K Answer: B
- What happens to the red-shift of a galaxy as its distance from Earth increases? A) It decreases B) It stays the same C) It increases D) It changes to blue-shift Answer: C
- Which of the following is NOT evidence for the Big Bang theory? A) Red-shift of galaxies B) Cosmic microwave background radiation C) Stars emitting light D) More distant galaxies receding faster Answer: C
- A spectral line has a reference wavelength of 500 nm. It is observed at 520 nm from a galaxy. The red-shift value (z) is: A) 0.02 B) 0.04 C) 20 D) 0.96 Answer: B
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