Edwin hubble calculated the expansion rate of the universe. on what evidence did he base his calculation?
\l "\l " a. levels of background radiation
\l "\l " b. differences in redshift for galaxies
\l "\l " c. the existence of planets outside of our solar system
\l "\l " d. levels of helium in the universe

Edwin Hubble calculated the expansion rate of the universe. The evidence that he base his calculation is the differences in redshift for galaxies. The answer is letter B. the red shift of galaxies was directly proportional to the distance of the galaxy from earth.  It means that bodies farther away from Earth were moving away faster. The Hubble’s constant is the ratio of distance to redshift equal to 170 kilometers per second per light year of distance.

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.