# What affects the length of the daytime?

The rotation of the Earth on its axis causes the variation between day and night. The durations of days and nights vary depending on where you are on Earth and the season. In addition, the tilt of the Earth's axis and its route around the sun influence daylight hours. These effects combined make for some interesting seasonal changes in our daily lives.

Daytime length is determined by the angle of the Earth's axis relative to its orbit around the Sun. When this angle is 90 degrees, the Earth is at its most distant point from the Sun and daytime length is long. If the angle is 0 degrees, the Earth is at its closest point to the Sun and daytime length is short. Between these two extremes, there is a period when the Earth is at its farthest distance from the Sun and then moves back toward it, causing daytime length to fluctuate over the course of the year.

The amount of time it takes the Earth to rotate once on its axis is called its spin period. This value is about 24 hours for places on the surface of the Earth's crust but it varies slightly from place to place due to differences in mass. The spin period is important because it determines how many times per day the Earth's axis points directly towards the Sun, which in turn determines whether it is day or night on Earth.

## How will the length of a day change?

Why does the length of the Earth's day fluctuate over the year? Every region on Earth receives an average of 12 hours of light every day, however the amount of hours of daylight on any given day of the year varies. Because the Earth revolves on its axis, we have day and night. But due to the orbit of the Earth around the Sun, we also have seasons: cold months in the north polar region, hot months in the south. The angle between the equator and the plane of the Earth's orbit around the Sun is called the Earth's obliquity. It is different at different times during the year because of factors such as earthquakes and volcanic activity that alter the Earth's orientation with respect to the sun.

The length of a day depends on when you are on Earth. If you're standing on the North Pole, then the length of a day would be 24 hours. If you were standing on the South Pole, then the length of a day would be 24 hours too. But if you travel west across the Arctic Ocean or east across the Antarctic Sea, then the length of a day starts to get shorter because you are getting farther from the source of light (the Sun). By the time you reach the westernmost point of Greenland or the easternmost point of Australia, the length of a day has become less than 12 hours. When you arrive back at the South Pole or North Pole, the length of a day has become more than 12 hours again.

## What affects the hours of daylight?

Our amount of daylight hours is determined by our latitude and the Earth's orbit around the sun. The Earth's rotation axis is inclined from its orbital plane and always points in the same directionâ€”-towards the North Star. This tilting causes variations in solar energy that vary with latitude. At the equator, days are long and warm; at the poles, they are short and cold.

The length of a day is about 24 hours at the equator, but it varies depending on where you are on Earth. Days are shorter near the poles and longer near the equator. A day at the South Pole is about 22 hours long, while a day at the North Pole is nearly 26 hours long.

At any given time, parts of the Earth are illuminated by sunlight, while others are in darkness. These areas of daytime and nighttime occur in cycles, called seasons. The seasons influence many aspects of life, including climate, agriculture, and human health. They are caused by differences in distance between the Earth and the Sun during its annual journey around the center of the Milky Way Galaxy. In late fall and early spring, the Earth is caught between these two bodies: the Sun is bright yet distant, and only a small part of it is visible above the horizon; conversely, in late summer and early winter, the Earth is out of sight behind the Sun, which is bright and hot like the rest of the galaxy.

## Why is there a difference between the durations of the days?

At the equator, day and night last about the same amount of time. However, as we travel further from the equator and toward the poles, the changes in the length of day and night become more pronounced. At the poles, day is longer than year-round temperatures would lead us to expect (because of the planet's rotation), while at the equator, night is longer than day.

As we orbit the globe around the Sun, the Earth's axis becomes tilted with respect to its orbital plane. This is called "obliquity". The angle between the Earth's rotational axis and its orbital axis varies over time because of gravitational forces acting on the planet's core. But over long periods of time (10,000 years or more), these angles remain nearly constant at approximately 23.5 degrees for north-south orientation and 45 degrees for east-west orientation.

During a total solar eclipse, only those areas within a few miles of the path where the eclipse is visible will experience completely dark skies with no moonlight. Otherwise, at any given place on Earth, some fraction of the sky will be illuminated by sunlight during an eclipse.

In partial eclipses, where less than all of the sun is obscured, the duration of daylight and darkness are almost exactly equal.

##### Cathy Strebe

Cathy Strebe is a spiritual healer who specializes in yoga techniques. Her goal as a healer is to help people feel better and live their best life possible. Cathy knows all about the struggles of being human, and how hard it can be to want things but not have them. She has overcome many obstacles in her own life, and she wants to share that with others so they too can find peace within themselves.