The Sun travels through the sky in the same direction; but, the Sun's position along the route at any one moment varies from day to day; it rises or descends to a higher or lower point in the sky at different times of the day. The location of the sun in its daily passage across the sky is affected by a variety of variables. For example, the shape of the Earth itself affects where the sun appears each day; the orientation of the Earth with respect to other stars and galaxies outside our own galaxy influences where the sun will appear every night during a solar eclipse.
The path the sun takes across the sky from morning until evening is called its ecliptic. The word "eclipse" comes from a Greek word for "to cut out," because of an ancient legend that the sun was once replaced by a shadow as big as the moon. Actually, though, eclipses occur when the Moon, or some other object, gets in the way of the sunlight reaching the Earth. During a total lunar eclipse, the Earth's atmosphere causes all direct sunlight coming from the moon to be blocked out. Only light from the sun before it reaches the moon can reach it. This means that only the far side of the moon is illuminated during a total lunar eclipse. All over the country, people are able to see a reddish color on either the morning or evening side of the moon during a total lunar eclipse.
The apparent motion across the sky is caused by the Earth's rotation. This is because its path takes it over the surface of the Earth at different distances from the center.
During a single day, the position of the Sun changes more than 10 degrees (from zenith to nadir). Over the course of an entire year, the change is even greater: about 57 degrees.
This is because the axis around which the Earth spins is not exactly perpendicular to its orbit around the Sun. It is tilted by about 23.5 degrees toward the plane of the Earth's orbit.
This means that at any given time, part of the Sun's disk is above the horizon and part is below it. The amount that it rises and falls each day depends on where it is in its annual cycle. If the Sun is near the top of its cycle, it will rise more slowly and set later in the evening; if it is near the bottom, it will rise more quickly and set earlier.
For example, if the Sun was first light tomorrow morning, it would be close to the North Star and so would appear to rise as far north as it can go in the night before turning south again.
The amount of movement of the sun along your horizon at sunrise and sunset varies with the time of year as well as your latitude. Furthermore, the daily shift in position of the sun along the horizon is higher the farther north or south you are from the Earth's equator. All these factors combine to produce differences in both the height and angle of the sun at its highest point in the sky and its lowest point on the horizon at each hour throughout the day.
The altitude of the sun relative to the horizon changes during the day for any given location because the center of the earth is not flat but round, like a ball. The axis about which it spins is called its "pole." The North Pole is the direction in which the axis is pointing right now, which is changing over time. The South Pole is the opposite direction. At the North and South Poles, the axis points directly up or down out of the plane of the page. For locations near the Equator, the difference between the high and low points of the sun at midday is greatest when the sun is due west or east, depending on whether you are viewing the northern or southern hemisphere. Locations far from the Equator have more extreme differences in elevation between the sun at its highest point and its lowest point on the horizon.
At the North Pole, the sun reaches its highest point in the sky at noon, when it is directly overhead.
The location of the Earth's axis relative to the Sun varies as it revolves our Sun. As a result, the observed height of our sun over the horizon changes. The Sun is seen to trace a higher route above the horizon in the summer and a lower path in the winter at any given place on Earth. This is called its altitude.
The apparent altitude of the Sun is greater when viewed from a northern latitude and less when viewed from a southern latitude. At the equator, where there are no days or nights, the Sun is always at an equal distance from the earth regardless of what phase of the moon is happening to be up there at any given moment.
At the poles, the Sun is at its highest point in the sky during the summer and its lowest point in the sky in the winter. But due to the fact that the radius of the planet is not constant, but increases with distance from the center, at any given spot on the surface of the planet the Sun is at a constant angle above that spot. This is called its zenith.
At the zenith, the top of the Sun's atmosphere reaches 13,000 miles away from the center of the planet. Anything farther away than this is outside the sphere of influence of the solar wind which is what keeps our galaxy free of any significant amount of interstellar matter.
So, where exactly does the sun rise and set? Though it rises from the east, it also moves somewhat north or south in the sky from day to day. That means we view sunrises and sunsets in slightly different locations around the horizon every day. But on average, sunrises happen about an hour after sunrise and sunsets occur about an hour before sunset.
The exact location of both sunrise and sunset can vary significantly from day to day as well as from year to year. Because of this uncertainty, scientists don't know exactly where in the sky the sun will rise or set any given morning or evening. They estimate how far east or west (northing or easting) that spot will be using astronomical observations from many sites around the world. Then, they calculate what time it will rise or set at those sites using clocks that are perfectly accurate to within a few minutes per year.
Because the earth is not flat, but round, the sun appears to move across the sky each day. The part of the sun's orbit that lies in the northern hemisphere travels south each day, while the part that lies in the southern hemisphere travels north each day. So, the days get shorter as you go further from the equator. At the poles, the days are longest of all-they only see night and day once per rotation!