Elijah, an astrophysicist, was observing the celestial bodies in the night sky. He made three observations and noted down the time of the observations. His observations were made at 7:00pm, 9:30pm and 11:20pm. He needs to know by what angle the Earth had rotated by the time he made his 2nd and 3rd observations relative to his 1st observation. Can you help him out?