Cosmology Flashcards
Describe that if a wave source is moving relative to an observer, there will be a change in the observed frequency and wavelength
Doppler Effect
When a source of waves is moving relative to the observer, the waves will undergo an change in frequency and wavelength when they are observed compared to when they were emitted. This is called the Doppler Effect. This happens with all types of waves including light.
Describe the red shift in light received from galaxies at different distances from the Earth
Explain why the red shift of galaxies provide evidence for the expansion of the Universe
If the light source is moving away from you, the light it emits will be shifted towards the red end of the spectrum with the lower frequency. This is called red shift. Measurements of red shift suggest that all the distant galaxies are moving away from us quickly. More distant galaxies have greater red shift than nearer galaxies. They show a bigger observed increase in wavelength. This means that more distant galaxies are moving faster away than nearer ones. This shows that the universe is expanding and because of this the galaxies are moving out.
Describe evidence that supports the Big Bang Theory (red shift and CMBR)
There is also another observation that scientists made. Scientists can detect low frequency microwave radiation coming from all directions and all parts of the universe. It’s known as the Cosmic Microwave Background Radiation (CMBR). As the universe expands and cools, this background radiation cools and drops in frequency. The galaxies that are moving away from each other at great speed suggests something must have got them going from a single starting point. That something is probably a very big explosion - the Big Bang. All matter in the universe occupied a single point. This tiny space was very dense and very hot. This single point that exploded, space started expanding and the expansion is still going on.
The Doppler Equation
Use the equation relating changing in wavelength, wavelength, velocity of a galaxy and the speed of light
Change in wavelength/ reference wavelength = velocity of a galaxy/ speed of light
