6.15 Red Shift Flashcards
What is red shift?
Red-shift is when light from distant galaxies show an absorption spectra pattern that has been shifted to the red side of the spectra
What is the evidence for red shift?
- When we look at light from the most distant galaxies, we find that the wavelengths are all longer than they should be - they’re shifted towards the red end of the spectrum. This is called red-shift.
- This suggests the source of the light is moving away from us. Measurements of the red-shift indicate that these distant galaxies are moving away from us (receding) very quickly - and it’s the same result whichever direction you look in.
What is the conclusion from the evidence of redshift?
The whole universe (space itself) is expanding
How does the Big Bang theory support our theory of universal expansion?
- Initially, all the matter in the universe occupied a very small space. This tiny space was very dense and so was very hot.
- Then it ‘exploded’ - space started expanding, and the expansion is still going on.
What is cosmic microwave background radiation?
- It is electromagnetic radiation that is observed in all directions.
- Initially radiation from the big bang was incredibly hot.
- As the universe has expanded and cooled, the background radiation has dropped in frequency
How many galaxies show a red-shift?
Nearly all
Why does red shift occur?
Because the light emitted by an object moving away from us will be stretched. The stretching causes the light’s wavelength to increase. The faster an object moves away from us, the larger the red shift.
What is the basic idea of the Big Bang theory?
The Universe expanded from a single tiny point of high density and pressure
Give one strength and weakness of the balloon model in representing the idea of an expanding Universe.
Strength - As the balloon expands the dots get further apart, which represents the galaxies moving
Weakness - The dots are only on the surface of the balloon, whereas galaxies are throughout the universe.
