On the first day of spring (vernal equinox) and the first day of fall, the sun is directly above at noon on the equator (autumnal equinox). At noon on the first day of summer, the sun is directly above at a latitude of 23.5 degrees north of the equator (called the Tropic of Cancer). At midday on the first day of winter, it is below the horizon at a latitude of 23.5 degrees south of the equator (the Tropic of Capricorn).
The point where the sun is directly over your head is called "celestial north." The part of the sky that is north of celestial north is called "northern sky," and the part that is south of celestial north is called "southern sky."
The angle between the horizon and the sun is called the "altitude of the sun." At its highest point in the sky, the sun is at its greatest distance from the earth. It is also called "zenith" or "vertical position." At its lowest point in the sky, the sun is near the horizon. It is also called "nadir" or "horizontal position."
The time of year when the sun is directly over a particular location depends on the person's geographic location. If you are on the equator, there is only one time of year when the sun is directly over you at noon: at the equinoxes.
The Sun is directly overhead at "high-noon" on the Summer Solstice at the Tropic of Cancer latitude. At "high-noon" on the Winter Solstice, the Sun is directly above at the Tropic of Capricorn. At the two equinoxes, the Sun is directly above at "high-noon" on the equator twice a year.
On the Summer Solstice, the Sun is as high in the sky as it will get that day. On the Winter Solstice, the Sun is as low in the sky as it will get that day. On the equinoxes, the Sun is due north or south at "high-noon".
These are the only times when the Sun is directly over someone's head. During other parts of the year, it is always below the horizon from some point.
As far as seeing the Sun, it depends on where you are on Earth. If you're under a free-standing tree or large building with thick foliage, you won't see the Sun. Otherwise, you might be able to catch a glimpse of it between the branches.
You would need a telescope to see the Sun during other parts of the year. The telescope has to be equipped with a solar filter to prevent any light from reaching the eye-piece while looking at the Sun. Solar filters are available at astronomy stores and some science museums. They are usually gray or white pieces of glass framed in black or dark metal.
The vernal equinox On the first day of spring (vernal equinox) and the first day of fall, the sun is directly above at noon on the equator (autumnal equinox). As you move away from the equator, it takes longer for the sun to reach its highest point in the sky. At the poles, where it never gets dark, the vernal and autumnal equinoxes happen at the same time.
At the equator, the angle between the equatorial plane and the orbit of the Earth around the Sun is zero degrees, so the two are parallel. But as one moves away from the equator, this angle becomes more positive or negative.
Thus at the equator, the equinoctial line divides the earth into two equal parts, since the axis of the planet is always perpendicular to the orbital plane. But as one moves away from the equator, these two parts become increasingly unequal. The part of the earth's surface that receives direct sunlight from the equinoctial line is called the "summer hemisphere". The part that does not receive direct sunlight is called the "winter hemisphere".
At the moment, the equatorial line is passing through Israel, Egypt, and much of western Africa.
Only at the spring and fall equinoxes does the sun rise directly above the equator (90 degrees). During the northern hemisphere summer (June 21), the sun lies immediately above the Tropic of Cancer (latitude 23.5 degrees) and receives more sunlight than the equator, which now receives sunlight at a less direct angle. In the southern hemisphere winter (December 22), the sun again lies directly over the equator.
During the other 11 months of the year, the sun is never directly over the equator. It rises in the north and sets in the south, always crossing the equator at some point during its arc across the sky. The time it takes for the sun to make this traverse across the celestial sphere is called an hourglass figure. Because the earth travels around the sun, the location where the sun is in relation to the equator changes throughout the year. At mid-summer, when the sun is near the horizon at midday in the middle of the country, it reaches its highest position in the sky at midnight in the northern hemisphere and noon in the southern hemisphere. At midwinter, when the sun is high in the sky at midday in the middle of the country, it reaches its lowest position in the sky at sunrise in the northern hemisphere and sunset in the southern hemisphere.
The sun is directly over the equator only during these two periods.