1. What are the black lines in the spectrum above?
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- Absorbtion lines
- Created when light from star is absorbed by elements in the outer layers.
2. What is Redshift?
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- Black lines are shifted towards the red end of the spectrum when we look at the most distant galaxies. Their wavelength is longer than it should be.
Click here for an interactive demonstration of the Doppler Effect
3. What can we deduce from Redshift?
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- That distant galaxies are moving away from us and that the universe is expanding.
- The universe began as an extremely small initial point in the Big Bang.
4. Give an example of blueshift and explain what this means.
5. What is Hubble’s law?
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- Hubble saw that fainter galaxies showed greater redshift.
- The recession velocity is proportional to the distance from us.
- v=Hd
6. What are the units for the Hubble Constant?
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- Km/s/mpc (mpc = mega parsecs)
- If we convert the km into mpc then we can express the units of the Hubble Constant as /s
7. What is the significance of this?
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- 1/H gives the age of the universe in seconds
8. Who coined the phrase “The Big Bang”?
9. How old is the universe?
10. What is Cosmic Microwave Background Radiation?
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- Microwave radiation that can be detected coming from the sky in every direction.
- Perfectly matches the radiation emitted by a black body with a temperature of 2.7 k
11. Who discovered it and how?
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- Arno Penzias and Robert Wilson
- 1965
- By accident
- Were trying to detect faint reflections from balloon satellites
- Discovered “noise” all around sky from all parts of the sky at all times of day and night
- Given Nobel prize in1968
- Provides strong evidence for Big Bang theory
12. Name 2 probes built to study CMB.
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- COBE
- NASA 1989
- Confirmed CMB, Detected ripples in radiation
- WMAP
- NASA 2001
- Wilkinson Anisotropy Probe
- Allows us to learn more about the structure of the early universe
- Estimate dark matter
- Confirm dark energy
13. What is Dark Matter?
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- Matter which does not emit or reflect radiation but has detectable gravitational effects.
- Makes up 95% of our universe
14. What could Dark Matter be made of?
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- We don’t know, possibly:
- Black holes
- Neutrino’s
- WIMPs
- Weakly Interacting Massive Particles
15. Who first proposed the existence of dark matter and when?
16. Give evidence for the existence of Dark Matter.
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- Gravitational lensing
- Light bent and distorted through huge amount of matter (click here for an interactive demonstration)
- Rotational curve for a spiral galaxy
- Stars far away from nucleus traveling much faster than expected.
- Only explicable if a great deal of invisible mass was present.
17. What is Dark Energy?
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- Mysterious repulsive force causing accelerating expansion of universe
18. What is the significance of Dark Energy?
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- Expansion of universe not slowing down as previously thought