Although the Sun remains in a relatively fixed position with respect to the solar system, Earth rotates daily and revolves around the Sun once a year. The rotations are around an imaginary pole that cuts through the center of the planet in the north-south direction. If you could look down on Earth from above the North Pole, you would see the planet spinning counterclockwise.

Every 24 hours, Earth completes one rotation. With each rotation, most locations on Earth alternately experience day and night. Because Earth is spherical, about half the planet is illuminated by the Sun at any given time. The portion of Earth facing toward the Sun experiences daytime, while the portion facing away from the Sun experiences nighttime. As a location rotates into sunlight, observers from that location see the Sun appear to rise in the east. Similarly, as a location rotates into darkness, observers see the Sun appear to set in the west.

The length of daylight during each rotation is not constant throughout the year. Because Earth's axis is tilted at an angle of about 23.5 degrees, the relative position of the axis in regard to the Sun changes as Earth orbits, resulting in day and night and the seasons. For example, when the North Pole is pointed towards the Sun, the northern hemisphere experiences summer, and locations in the northern hemisphere have longer days than locations in the southern hemisphere. Most people in the northern hemisphere see the Sun appear to rise early, reach high above the horizon during midday, and set late in the evening. In a phenomenon called the "midnight sun," locations very close to the North Pole can remain in sunlight continuously because the Sun never sets. Alternatively, people in the southern hemisphere experience winter during the northern hemisphere summer. To observers in the southern hemisphere, the Sun appears to rise later, remain low near the horizon, and set earlier.

Sunrises and sunsets are an everyday reminder of Earth's motion. Their beautiful colors are due to a physical phenomenon called scattering, in which sunlight is scattered by the particles in Earth's atmosphere. Because Earth is spherical, sunlight must travel through more of the atmosphere when the Sun is near the horizon, such as at sunrise or sunset. The more air the light travels through, the more scattering will occur. Therefore, shorter wavelengths of light are more easily scattered when the Sun is near the horizon. By the time the light reaches your eyes, the atmosphere has scattered most of the colors except for the long wavelengths such as red and orange.

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