6.4 and 6.5 The Expanding Universe/The Big Bang Flashcards
What changes does the observer detect when the source of the waves moves away from them?
When the source moves away from the observer, the observed wavelength increases (bigger wavelength) and the frequency decreases (pitch decreases if sound waves)
What changes does the observer detect when the source of the waves moves towards them?
When the source moves towards the observer, the observed wavelength decreases (smaller wavelength) and the frequency increases (pitch increases if sound waves)
What type of waves can the Doppler effect be demonstrated with?
Sound waves
What are galaxies?
Large collections of stars
In which direction has the light observed from distant galaxies shifted? What does this mean? What is this known as?
Towards the red end of the spectrum (infrared etc)
This means it’s wavelength is increasing from a shorter visible light wavelength to a longer infrared radiation wavelength. This demonstrates that the galaxy is moving away from us because the Doppler effect states that when the source moves away from the observer, the observed wavelength (in this case, the colour) increases
This is known as red shift
What would a blue shift indicate to us?
That a galaxy is moving closer to us
How are we able to observe the effects of red shift?
By observing dark lines in the spectra from galaxies compared to the dark lines from a control source of white light
What are the dark lines when checking for red shift due to?
Absorption of light in the source
Which galaxies are moving the fastest away from us?
The ones furthest away are moving the fastest, in all directions
What is the relationship between the distance of the Galaxy from us and the size of the red shift? What does this suggest?
The further away the galaxy, the bigger the red shift
This suggests that distant galaxies are moving away from us and the most distant galaxies are moving the fastest
How do we know the whole universe is expanding?
All the distant galaxies are moving away from each other
How does red shift show that the universe is expanding?
We can use the Doppler effect to show that when the galaxies shift further to the red side of the spectrum then they are moving away from us
What is the Doppler effect?
The change is the observed wavelength and frequency of waves due to the motion of the source of the waves
What does red shift give us evidence of?
The universe is expanding outwards in all directions
What is the Big Bang theory?
The theory that the universe started with a massive explosion at a very small initial point