Redshift

Hubble’s Law

Redshift - absorption spectra

Plot of intensity

From doppler effect

From triangulation of movement of Earth

Increase in distance over time

AB

C

3 Galaxies A,B & C

AB

C

After time t

A

B

C

A

B

C

AB

C

Distance travelled

= H0d where Ho = 2·4 × 10−18 s−1

1Parsec = 3.262 light years

Edwin Hubble

Three astrophysicists are discussing the results of observations that show that all stars have their light

frequencies decreased by a small amount – ‘red shift’

• Professor Bubble “The red shift shows the stars are all moving away from our stationary Solar System”

• Doctor Toil “The red shift shows that we are moving away from the rest of the universe at high speed”

• Professor Trouble “The red shift shows the stars are moving away from each other”

• Which viewpoint do you agree with and why?• Why do you disagree with the other two or do

you think no one is correct?• What additional data from observations of

starlight would allow confirmation?

• Professor Bubble “The red shift shows the stars are all moving away from our stationary Solar System”

• Doctor Toil “The red shift shows that we are moving away from the rest of the universe at high speed”

• Professor Trouble “The red shift shows the stars are moving away from each other”