Would there be day and night if Earth didn't rotate on its axis & what would happen to Earth if Sun were suddenly replaced with a one solar mass black hole?
If earth doesn't rotate on its axis there won't be any life on Earth because there won't be day and night. The world facing the sun will become extremely hot. The world facing far away from the sun will become cold. If our Sun was suddenly replaced with a black hole of the same mass, Earth's orbit around the Sun would be unchanged. Of course, Earth's temperature would change, and there would be no solar wind or solar magnetic storms affecting us.