# When does the Earth go through a full rotation?

When the Earth's rotation rotates us such that we face away from the Sun, we experience nighttime darkness. The Earth goes through one cycle of day and night each 23 hours, 56 millimeters, or 4 seconds. This figure is often rounded up to 24 hours. Each 24-hour cycle represents one complete revolution.

The Earth's rotation is not perfectly uniform. There are places on Earth where it takes 24 hours for the sun to rise completely over the horizon. These locations are called equidistant territories because people living there can expect the sun to rise and set at almost exactly the same place every day. The only variation in sunrise and sunset is due to weather conditions such as clouds or wind. Other places rotate more slowly, taking 26 hours for the sun to rise fully over the horizon. These locations are called tropical countries because the climate is mostly hot and humid all year round.

In addition to these geographical differences, the Earth goes through different phases of rotation at various times during its year. As a planet, our own sphere of influence, the rotation of the Earth is governed by two large gyroscopes: the core and the atmosphere. The core tends to be solid across most of its surface, but it contains many small regions where it is liquid. The core's gravity causes it to spin faster when it is full of solid material and slower when it is filled with liquid.

## What cycle is a direct result of the Earth’s rotation?

Explain how the rotation of the Earth creates day and night. Because the Earth spins or revolves on its axis, there are periods when specific portions of the Earth do not face the sun. As a result, there is darkness, or night. A full revolution takes around 23 hours and 56 minutes. During this time, all points on the Earth's surface experience night and then day again as the Earth continues spinning.

Day and night occur because the angle between the Earth's axis and its orbit around the Sun varies with respect to the position of the Earth in its orbit. The line from the center of the Earth to any point on its surface passes through the center of gravity of the planet. This line is called the equator. It is also the place where the amount of land and water intersects itself out evenly across the globe. At the poles, there is no land or water at all.

When the Earth orbits the Sun, each point on its surface sees the sun rise and set twice per year. In the northern hemisphere, the seasons are caused by changes in the length of the day—not the length of night. As the length of day increases, so does the temperature; thus, spring follows winter. As the length of day decreases, so does the temperature; thus, fall follows summer. But north of the Arctic Circle, the days are long enough for the temperature to drop below zero in the middle of the night.

## How does the Earth’s rotation determine whether it is day or night?

Each planet spins or revolves on its axis. Day and darkness are caused by the Earth's rotation on its axis. Because the Earth revolves, only one-half of the Earth is always facing the sun. The half that faces the sun is bright (day), whereas the half that faces away from the sun is dark (night). The period of time when the Earth is completely illuminated is called a day. The period when it is completely dark is called a night. The length of a day depends on where you are on Earth. If you live near the equator, then the Earth spins very quickly, so almost all of it is in daylight for a few hours each day. If you live farther from the equator, then less of the Earth is in daylight at any given time.

At the North Pole, the Earth spins very slowly, so there is always midnight during the winter months. During the summer months at the South Pole, the Earth spins very quickly, so there is always noon.

Days and nights change because the angle between the Earth's axis of rotation and the plane of its orbit changes throughout the year. This is known as "obliquity". It is different for every place on Earth, but on average it amounts to 5 degrees north or south of perpendicular orientation with respect to the sun.

## How does Earth’s rotation cause daytime?

We have day and night because the Earth spins (or rotates) on an imaginary line known as its axis, and various areas of the world face the Sun or away from it. It takes 24 hours for the Earth to complete one full rotation, which we call a day. But there are times when those things don't happen simultaneously across the planet. For example, at some points in time, parts of Africa are in darkness while others are not, due to the fact that the African continent is tilted upon itself, causing certain regions to experience night twice per day! This is called a diurnal cycle and it's why we need days and nights together with a monthly cycle to keep life on Earth stable and able to sustain itself.

The direction the Earth spins is called its "axis of rotation". The term refers to the fact that people used to think that gods had to be thanked before meals or during battles because they were acting out their will through human actions. Thus, we must give credit where credit is due - by linking this concept with rotation, scientists now know that planets must rotate on their axes for us to have days and nights.

You may wonder how the Earth's axis of rotation causes daytime.

## What changes do we see as a result of the Earth’s rotation?

The changes in day and nighttime are caused by the Earth's rotation as it rotates on its axis. When that axis is slanted towards the sun, the northern hemisphere receives more radiation than the southern hemisphere, and vice versa when it is tilted away from the sun. As a result, the ice caps grow or shrink, depending on which direction the axis is pointing.

Changes to the length of the day and night occur because the planet's axis of rotation is not exactly perpendicular to its surface but leans toward the center of the planet at an angle called "obliquity". The amount of tilt varies over time, with some recent studies suggesting that obliquity may have increased by as much as 5 degrees since the Middle Ages due to heat from greenhouse gases changing the shape of the Earth's crust and mantle.

As the Earth spins, so does its orbit around the Sun. The distance between the Earth and the Sun varies throughout the year, from its minimum value in January (when the Earth is at its farthest point from the Sun) to its maximum in July (when the Earth is at its closest). This results in different amounts of sunlight reaching various parts of the planet, which in turn affects life processes at both global and local scales. For example, during winter most of North America and Europe is frozen under a layer of ice; but in summer all of these lands are exposed to the sun's rays.

## How is the rotation of the Earth captured in the night sky?

In other words, the Earth revolves on its axis while concurrently circling the Sun, causing the Sun's location in the sky to catch up by 4 minutes each day. Long-exposure photography captures 6 hours of spinning in the night sky. Photographer: Chris Schurr.

The effect is called "earthshine" and it's seen by everyone living on a lit continent. It's how people around the world can look up at night and see the moon and stars even though they're hidden from view during the day. The color comes from reflections of sunlight off of water molecules in the atmosphere. Blue colors are caused by oxygen molecules; red colors result from molecules of carbon dioxide.

Earthshine is strongest when the moon is full. At these times it can be as bright as the stars do during the day. In fact, ancient peoples used earthshine to navigate at night!

Look toward the south after sunset for best viewing quality. Be sure to avoid clouds if you want to see all the way to the moon.

The color will change if you go outside during the day to view it directly with your eyes. That's because colors in nature result from the interaction of light with molecules in the atmosphere that absorb certain wavelengths and reflect others. As long as there are molecules around to do this, the color will change throughout the day.

##### Shirley Peacock

Shirley Peacock is a spiritual development specialist and yoga instructor. She has been doing healing work for the last 8 years with an open heart and pure intentions. Shirley believes that everyone deserves love and acceptance from those around them as well as from themselves. One of her main goals in life is to help people live their best lives possible by teaching them how to heal their minds, bodies and souls.