The declination of the sun during a typical day is affected by the rotation of the Earth. The sun is actually a stationary object. As the Earth revolves around the sun it spins and tilts. The sun appears to rise over the horizon in the morning. Then, as the Earth tilts and spins, the sun appears higher in the sky. In the afternoon, the sun appears lower and lower in the sky and then disappears altogether. While we do not see the sun on our side of the Earth, people on the opposite side of the globe are seeing it.