There would also be a temperature change as each hemisphere would get less time to warm up from the Sun's rays. If it was slower than one full rotation would take more than 24 hrs. Thus making days & nights longer. Earth rotates once in about 24 hours with respect to the Sun, but once every 23 hours, 56 minutes and 4 seconds with respect to other distant stars. Earth's rotation is slowing slightly with time; thus, a day was shorter in the past. This is due to the tidal effects the Moon has on Earth's rotation.