# How frequently does the Earth rotate when it is orbiting the sun?

The Earth revolves once every 24 hours in relation to the Sun, but once every 23 hours, 56 minutes, and 4 seconds in relation to other, distant stars (see below). Because the Earth's rotation slows gradually with time, a day used to be shorter. But since the invention of artificial light at about 3100 BC, days have been getting longer as well.

Why does the length of a day vary? The amount of daylight varies from season to season and location to location on the Earth because the Moon affects how much sunlight reaches each region. As the Moon orbits the Earth, it passes over different parts at different times of the day or night, causing the appearance of different parts of its orbit to be illuminated by daylight or darkness. For example, when the Moon is near the horizon, only the part of its orbit above the horizon is exposed to direct sunlight. When the Moon is high in the sky, it blocks out all but the lowest parts of the Earth's shadow.

During a lunar eclipse, the Earth's atmosphere refracts light from the Sun that would otherwise reach the moon and transforms it into a reddish hue. The color varies depending on which part of the path of the eclipse one is watching from; those located far away from the center of the event see a red-colored Moon because they are looking through more air than water.

## What do you notice as the earth rotates?

Every 24 hours, the Earth rotates on its axis. The sun appears to move across the sky as the Earth spins, but it is actually the Earth that is rotating. One rotation takes 24 hours to complete, which is why there are 24 hours in a day. As the Earth turns, so too will all living things on it. With respect to the fixed stars, everything on Earth except for the north pole is in constant motion.

With respect to the south pole, it is as if someone threw a rock into water: It creates a circle of waves around the rock's location. This is because every part of the world receives sunlight at some time during the year. At the north pole, however, there are no clouds to block out the sun; instead, it goes straight through and hits the ground with full force. Because plants need light in order to grow, without any vegetation at the north pole, we would never see the end of summer. At the south pole, however, there are no days; instead, it is always dark due to the fact that the sun is constantly rising over the horizon and setting below it.

At the equator, the Earth's surface experiences no direct sunlight nor darkness.

## How long does it take for people to notice the rotation of the Sun?

When most people look at the sun in the morning, they have no notion that it is revolving as the Earth and other planets orbit around it. People observe the shift between night and day when the Earth revolves. That means the Earth takes 24 hours to spin on its own axis. But because the Sun takes about 25,780 years to complete one revolution around the Earth, there is a small but significant shift between noon and midnight every day.

This is called "the solar day." The solar year is almost exactly equal to 365 days, but due to some irregularities in the motion of the Earth's axis, the month of August returns to the same position in the sky each year (this is called "seasonal variation"). So each day is actually shorter than 31 minutes 52 seconds.

The length of time from one sunset to the next is called "the solar hour." Because the Earth orbits the Sun at about 30 miles per second, we travel about 150 million miles from sunset to sunset. This means that the distance between the Sun and the Earth changes by nearly a quarter of a million miles every day!

At first glance this might not seem like much, but remember that the entire width of the Pacific Ocean lies between California and Hawaii! The closest approach that the Sun makes to us is when it reaches its maximum distance from Earth, which happens when it is directly over the Equator.

##### Regina Rivera

Regina Rivera is an astrologer, spiritual coach and mindfulness teacher. She believes that each of us has the power to change our lives for the better by tapping into our inner wisdom. She loves teaching people how to connect with their intuition through meditation, journaling and other practices in order to create a more fulfilling life.