4.8.2 Red Shift (physics only)

Question 1

What is red shift?

Answer 1

• observed increase in wavelength of light from more distant galaxies compared to light from closer galaxies
• the further away the galaxies the faster they are moving and the bigger the observed increase in wavelength
• so more distant galaxies appear more red as red is longest wavelength in light
• this effect is called Red Shift

Question 2

What does red shift tell us?

Answer 2

• tells us that galaxies are moving away from each other
• as the galaxies are moving away their light waves are stretched aka their observed wavelength is increased
• so these galaxies are moving faster than galaxies that are closer

Question 3

Difference between nearby and distant galaxies?

Answer 3

• nearby galaxies have a small redshift showing us that they are moving away
• more distant galaxies have a larger shift showing us that they are moving away faster

Question 4

What can the observed red shift provide evidence for?

Answer 4

the observed red shift (the fact that distant galaxies are moving faster than nearby galaxies) provides evidence that space itself (the universe) is expanding and supports the Big bang theory

Question 5

What does the Big Bang theory suggest?

Answer 5

• Big bang theory suggests that the universe began from a very small region that was extremely hot and dense
• this region then expanded into the Universe we see today

Question 6

What happened around 1988?

Answer 6

• sine 1988 onwards observations of supernovae suggest that distant galaxies are receding faster than ever
• scientists had assumed that gravity would cause the expansion of the universe to gradually slow down
• so rather than gradually growing down the universe is expanding faster - scientists cannot easily explain this

Question 7

What are some theories scientists have suggested?

Answer 7

• scientists have suggested that the universe contains matter and energy that we cannot detect - dark matter and dark energy
• possible that these could explain why the expansion of the universe is speeding up
• still much about the universe that is not understood e.g. dark mass and dark energy

Question 8

How might new evidence support a theory?

Answer 8

• supports prediction
• provides evidence that theory/equation is true

Question 9

What do new observations suggest is happening to the universe?

Answer 9

Expanding at ever greater rate

Question 10

Why is peer review important?

Answer 10

• can detect false claims
• detects inaccurate data
• detects bias
• verifies new data
• provides a consensus of opinions

Question 11

What shows that the universe began from a very small region?

Answer 11

• galaxies furthest away moving the fastest
• suggests that the Universe is expanding from a very small region

Question 12

How can predicted data be considered accurate?

Answer 12

If it is very close to actual data