On the equinoxes, the Sun is directly above at solar noon at the Equator, at the Tropic of Cancer (23deg26'11.4" N) on the June solstice, and at the Tropic of Capricorn (23deg26'11.4" S) on the December solstice. At other times of the year, the sun is higher or lower than 90 degrees, causing a diurnal variation in altitude.
At mid-latitudes such as in North America, solar noon occurs around 1 p.m., but near the poles it can be as early as 11 a.m. or as late as 3 p.m.
The angle between the horizon and sun varies throughout the day, reaching its minimum at sunrise and maximum at sunset. During twilight, the sun is never completely hidden from view; it simply rises or sets beyond the horizon.
At any time of year, if you look up at the sky during daylight hours you will see that the sun is never exactly overhead. It ranges from close to the horizon at morning and evening to high in the sky during midday heat waves or cold fronts.
This means that no matter where you are on Earth, you will experience some form of daily sunlight exposure. Whether it's just your hands or entire body, make sure you protect yourself from overexposure by using an umbrella or sunshade when outdoors during peak sunlight periods.
The sun would be directly overhead (90 degrees from all horizon directions; the zenith) at noon in the southern hemisphere (the winter solstice, December 21) as seen from a latitude of 23.5 degrees south at midday (the winter solstice). In the northern hemisphere (the summer solstice), the sun is directly overhead at noon at the same location on the planet.
In addition, because the earth is not a perfect sphere, there are two more regions where the sun is at its zenith: one in the middle of the Atlantic Ocean and another in the Indian Ocean.
These regions are known as the tropics. The tropical mid-Atlantic and mid-Indian oceans contain land areas so large that they do not affect the position of these two points on Earth's surface. However, people who live in these regions experience only one half of the year when the sun is at its zenith due to their locations within the continents/islands.
People who live near the equator can look up and see the sky is completely clear on a daily basis. This is because the earth's atmosphere blocks out most of the darkness during the day thanks to all the water vapor in it.
At the poles, however, the atmosphere is very cold and dense so little light gets through it to reach the ground.
Seasonal Variations As you can see in the link, the Tropic of Cancer is the latitude at which the Sun is directly overhead on the summer solstice. At this time, the Sun is at a declination of 23 degrees N of the celestial equator, and the corresponding latitude on Earth is 23 degrees N of the equator. The region directly north of the tropic of cancer is called the Arctic Circle, and south of the tropic of cancer is called the Antarctic Circle.
The angle that the Sun makes with the horizon at midday varies throughout the year. It is highest in June when it makes 90 degrees east of north, and lowest in December when it is nearly half way between the sky and earth. This is because the axis of rotation of our planet is not fixed, but instead wobbles like a spinning top. As a result, the distance between the Sun and the Earth changes throughout the year, causing differences in climate across the globe.
The point on Earth's surface where the sun is vertically over head at midday during the summer solstice is known as the Summer Solstice Point. The location depends on which hemisphere you are in, but since the Northern Hemisphere is less than 10 degrees away from the sun, we can assume that it is within 100 miles (160 km).
Is it possible for the sun to shine directly overhead here? It doesn't work that way. In other words, the sun does not reach its peak. You've undoubtedly heard of the "Tropic of Cancer" and the "Tropic of Capricorn" lines on a globe map. These are the points on the planet where you would be able to stand under the sun and have your head blow up like a balloon. The Tropics are really big areas on Earth where there is a lot of sunlight for most of the year.
The sun never reaches the top of the sky at any time or place on Earth. But when you look up at the sky during the daytime, you will see that the sun is always near the horizon. This is because we live on a sphere and the North Pole is always pointing down at the earth. So even though the sun is never directly overhead, it's close enough to cause no problems for us living on ground level.
During a total solar eclipse, the moon comes between the sun and the earth preventing direct light from reaching our planet. Because we live on an elliptical orbit, there are times when the moon is far away from the earth when the sun is completely covered by the moon. At these times, there is complete darkness everywhere within the path of totality.