Topic 4.3 - Cosmology Flashcards
What are spectral black lines on a diagram?
Absorbtion lines Created when light from star is absorbed by elements in the outer layers
What is redshift?
The displacement of spectral lines towards longer wavelengths (the red end of the spectrum) in radiation from distant galaxies and celestial objects. The further a star is away from us, the more it’s red-shifted
What can we deduce from redshift?
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.
Talk about light waves.
Light waves are affected in the same way if the source of the light is moving relative to the observer. Instead of pitch as with sound, it is the colour of the light that is affected. So sources of light moving away from the observer will undergo redshift and sources of light moving towards the observer will undergo blueshift
What is hubbles law?
Hubble saw that fainter galaxies showed greater redshift. The recession velocity is proportional to the distance from us.
Who coined the phrase “The Big Bang”?
Fred Hoyle 1949
How old is the universe?
14 billion years
What is cosmic microwave backround radiation?
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
Who discovered cosmic microwave background radiation and how?
Arno Penzias and Robert Wilson 1965. By accident they 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
What is dark matter?
Matter which does not emit or reflect radiation but has detectable gravitational effects. Makes up 95% of our universe
What could dark matter be made of?
We don’t know, possibly: Black holes Neutrino’s WIMPs Weakly Interacting Massive Particles
Who first proposed the existence of dark matter and when?
Fritz Zwicky 1933
Give evidence for the existence of dark matter.
Gravitational lensing Light bent and distorted through huge amount of matter 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
What is dark energy?
Mysterious repulsive force causing accelerating expansion of universe
What is the significance of dark energy?
Expansion of universe not slowing down as previously thought
