Question

Recall the raisin cake model of the universe. Our universe is expanding between the galaxies. You measure the recession velocity of Galaxy A to be 2,000 km/sec and the recession velocity of Galaxy B to be 6,000 km/sec. What can you say about the distances to these galaxies?

Answer 1

Step-by-step explanation:

Recession velocity of a galaxy is related to the distance at which the galaxy is located. This relationship is given by the hubble constant, as follows:

`v_r=HD`

Hubble constant is aproximate
`70(km/s)/(Mpc)` and 1 megaparsec (Mpc) is 3.26*10^6 light years. Rewriting for D:

`D=(v_r)/(H)`

For galaxy A:

`D=(2000(km)/(s))/(70(km/s)/(Mpc))\\\\D=28.57Mpc\\\\D=28.57Mpc*(3.26*10^6ly)/(1Mpc)=9.31*10^7ly`

For galaxy B:

`D=(6000(km)/(s))/(70(km/s)/(Mpc))\\\\D=85.71Mpc\\\\D=85.71Mpc*(3.26*10^6ly)/(1Mpc)=2.79*10^8ly`