The shadow is the smallest around 12 o'clock since the sun's rays are striking through our heads. If the sun is slanted, it will most likely throw a lengthy shadow.
The length of the shadow varies by solar elevation. When the sun is low on the horizon, its light reaches Earth directly from below. So the angle at which it hits the ground is steepest here, and we get a long shadow. As it rises above the horizon, it begins to reflect off of earth's atmosphere, which is why shadows are shorter when it is high in the sky. At zenith (directly overhead), there is no reflection and so the shadow is longest here.
The graph below shows the average length of summer day across the globe, along with the average height of solar elevation each day. You can see that days are getting longer as solar elevation increases, which means that people are going underground later into the day.
The exact moment that the sun's shadow falls on the ground depends on two things: how far away is it, and how fast it is moving. The more distant it is, the longer it takes for it to reach the ground. And the faster it is moving, the shorter the shadow gets.
Noon The length of a shadow produced by an item changes as the sun travels through the sky. The smallest shadow is cast when the sun is at its greatest position, which is at local noon. The size of the shadow increases as it moves toward sunset or sunrise.
The direction that the shadow falls in relation to the sun's position in the sky determines how long it will take to traverse its path across the ground. If the shadow is falling north of east (NE) then it will reach its maximum distance north (or south) from the sun while if the shadow is falling south-east (SE) then it will have traversed the greatest distance south (or north). Maximum shadows occur around noon because that is when the sun is at its highest position in the sky. At other times of the day the shadow will appear shorter.
Shadows become longer as the sun lowers in the sky and eventually disappear when the sun is below the horizon. At this point air currents block out portions of the sunlight reaching the ground; these are called "wind shadows". Wind shadows can be seen in all directions except down wind where there is no difference in temperature between the sunlit and shadowed areas. Down wind is the direction from which the wind comes.
The length of a shadow produced by an item changes as the sun travels through the sky. At this time, the sun is directly over the center of the earth, so all points on the globe are receiving direct sunlight. Any object in the path of this light will experience a shadow.
Because the earth is not flat but round, shadows can be seen anywhere on it. These shadows are called solar eclipses and they occur about every 18 months, during new or full moons. A total solar eclipse can only happen at certain times and places, but a lunar eclipse can take place at any time. During a total lunar eclipse, the Earth's moon passes through the shadow of the planet Venus.
Lunar eclipses are visible on half of Earth because it is between the moon and the sun that it is dark enough to see such an eclipse. However, people on the other half of Earth can watch via telescopes or cameras as the Moon disappears behind a ring of red-colored Earth!
Total lunar eclipses are visible on all of Earth, while solar eclipses are visible on half of it. But remember: Only observe through properly filtered lenses or cameras!
The sun is straight overhead at midday. As a result, the sun's rays strike the body vertically. As a result, the shadow is relatively brief. The sun's rays fall in an angled position in the morning and evening. So, the shadow is longer in the morning and evening.
Noon is half way between sunrise and sunset. At noon, the angle of the sun with respect to the horizontal plane is 90 degrees. On the horizon, it is either rising or setting depending on the direction you are looking.
If you were to draw a line from the center of the earth to the sun at noon, that line would be perpendicular to the surface of the earth. Because the radius of the earth is 6371, that means that the line would be 18,189,600 miles long.
The reason that the shadow is shorter in the morning than in the evening is because the angle of the sun is smaller in the morning than in the evening. At midnight when both the sun and the earth are facing directly north or south, the sun's rays are falling on the earth at a right angle. That means that the shadow is longest at midnight.
However, during the day when the sun is not exactly north or south, its rays are falling on the earth at an angle.