The mass of the earth mis-5.972*10 kg and the radius r is-4000 miles a. calculate the mean density pe of earth in g/cc. the composition earth is approximately 50% iron (p-8 gec) and s0% rock (p-3 eec. does your answer in a. make sense? probably not. how would you explain that. b. 4. the distance between our nearest star (other than the sun) proxima centauri and the planct earth is about 4.22 light years. oar most speedy space craft moves about 25,000 miles/h. how long will you take to reach that star if you are in that space ship? the earth moves around the sun roughly in a circle in 365.25 days and the average distance between the sun and earth is 150,000,000 km (150 million km- 1.5x10 m). calculate the average speed of spaceship earth in space around the sun (we really do not know the real speed because the sun also moves at a tremendous speed? 5. 6. use the information from 5. and calculate the time in minutes light will take to come to earth from the sun if the speed of light isc 300,000 km/s?