When most people look at the sun in the morning, they have no notion that it is revolving as the Earth and other planets orbit around it. People observe the shift between night and day when the Earth revolves. That means the Earth takes 24 hours to spin on its own axis. But because the Sun takes 86400 seconds (or a little more than 24 hours) to complete one rotation, there is no change visible from Earth's surface if you measure the angle between the Sun and the horizon. The effect of the rotation of the Sun on people was first noted by Aristotle who observed that certain plants will not grow toward the light if exposed all day long. He thought this must be due to a difference in their circadian rhythms vs. those of humans who live by sunlight. Modern scientists now know that even during darkness each part of the planet receives direct exposure to the sun for a small fraction of each rotation. It is just that where we are on Earth at any given moment has already passed for the south. Aristotle also noted that at certain times of the year trees near the equator grow taller during the summer than others further north or south. He concluded that the earth must be hollow inside and this is what allowed hot air to rise within it so that trees farther from the equator could grow taller.