Why Do We Have Day And Night? Fascinating Earth Facts For Kids

Oluniyi Akande
Feb 29, 2024 By Oluniyi Akande
Originally Published on Oct 12, 2021
3d illustration of Earth, Sun and Cosmos.
Age: 3-18
Read time: 9.3 Min

Day and night on Earth are governed by the intricacies of day and night science.

The shape of the Earth is spherical, like a ball, and it completes its orbit around the sun in 365 days. From one sunrise to the next sunrise, the duration taken by Earth to complete one rotation on its axis is 24 hours.

We experience day and night because the Earth spins on its axis. Earth's rotation and spherical shape are responsible for nighttime in the part of the Earth which is facing away from the sun and daytime in the part of the Earth which is facing the sun. Twenty-four hours is the length of time it takes for the Earth to complete the rotation around the axis. Have you ever wondered why phenomena like day and night exist in our world? What happens to the stars and sun in the sky during the day? Why don't we fall off the globe when we know that Earth is rotating around the sun? All these curiosities will be satisfied in this article as there is an answer to every question. Afterward, you should also find out why do we only see one side of the moon and winter facts.

How do day and night occur?

Did you know during the winter solstice, there are 24 hours of darkness around the North Pole? We observe the events of day and night every day. The Mesopotamians were the first to develop the notion of day and night. Roughly, if a particular region sees the sun, it is said to be a day there. If there isn’t a bright sky, we call it darkness as the night falls.

We understand the day and night phenomenon because our planet is spherical like a globe. Due to the Earth turning constantly, only one side of the Earth’s atmosphere faces light and heat from the sun while the other does not. It happens because of the rotation of the Earth. The Earth is also tilted and spins on its axis called a rotation. When both daytime and nighttime are completed, it is considered to be the Earth’s one full rotation on its axis. This is termed as one day. The motion of the Earth around the sun is called a revolution.

During dawn and dusk, when the sun crosses the horizon, we experience sunrise and sunset. It takes a little less than 24 hours for the Earth to complete one rotation however the day and night's length differs from season to season. This 24-hour cycle is deeply integral to all life on Earth.

What causes day and night on Earth?

The day and night cycle of our world is essentially caused by the rotation of the Earth. The Earth is not stationary, but it rotates around a tilted imaginary line called its axis of rotation, similar to a top spinning on its axis. The Earth rotates from west to east which makes the sun appear from east to west. When facing the sun from one side of the Earth, it is daytime there and the other side which is not facing the sun has nighttime. That side of the world experiences darkness. The day and night are related to the location and the distance from the equator. This entire day and night cycle together form one day.

At the North and South Poles, the incline in the Earth’s rotation has the maximum effect. The North Pole and the South Pole during their summers face the sun and get constant sunlight for 24 hours during the day, which is also called the midnight sun. This sort of summer is experienced in the Arctic and the Antarctic Circles.

The places near the polar circles experience longer twilights during winter due to the sun just lowering at the horizon to not be visible but the light in the atmosphere scatters the sunlight making it appear pink or red. In polar regions, during the winter season, the sun appears below the horizon. When the sun does not appear for more than 24 hours the phenomenon is called the polar night, where nighttime lasts for 24 hours. A part of Finland receives constant sun in the summer as it lies in the Arctic region and no sunlight during the winter for around six months from March to late September.

No, day and night do not occur in space as day and night are a planetary phenomena. While all the planets orbiting the sun experience day and night, in space, there is no concept of day and night. There are no side faces away from the sun, so there is constant sunlight in space.

But if there is constant sunlight, why does space appear dark?

It seems the solution to this question is pretty simple. It is because in space there is the sun but it's dark there because there are no objects in space that we can see. When we say we see something, it means that light from an object is hitting our eyes, and the brain processes it as information such as color. Objects which can produce their light like the sun have it easy, as the light from the sun directly hits our eyes which makes it glow very bright. Although one should never glance at the sun with one's naked eyes as it can damage our eyes with harmful ultraviolet rays. Objects which cannot produce their light simply reflect the light from other objects into our eyes which makes them visible. That is why it is hard to see without any source of light in a dark room. So, even though there is plenty of sunlight in space, there are no objects to reflect it that is why space appears dark.

Science Of Day And Night On Earth

View of Earth in deep space.

The science of day and night evolves from the discovery that the Earth is a sphere as proposed by Greek mathematician Eratosthenes. Hundreds of years of research were put up to comprehend that the Earth has a constant rotating motion around the sun and along the way we have come across and solved many myths, such as the sun rode on a chariot across the sky, the sun rotates around the Earth, or the Earth is flat (this one is funny). However, an intelligent thinker named Copernicus discovered that the Earth rotates on its axis and revolves around the sun. Based on the concept that it rotates on its axis, early Babylonians developed a system of dividing days into 24 hours each of 60 minutes which we still use today. It was also used to create sundials that could indicate the time during the day. The Jantar Mantar in Jaipur, India can measure time up to two seconds of accuracy which is a World Heritage Site as designated by UNESCO.

An angle of about 23.5 degrees is made from the rotation of the Earth's axis, which causes some very interesting phenomena. Due to this one side of the Earth is tilted towards the sun and it faces sunlight for a longer time, which causes temperatures to rise which causes summer. While the other end is tilted away from the sun which experiences less sunlight, shorter days and longer nights, and temperature drops which is winter. This is why while Australia in the Southern Hemisphere experiences summer, Canada, in the Northern Hemisphere, experiences winter. The UAE is considered to be the hottest country in the summer, and Antarctica is the coldest place on Earth in winter. As the Earth turns around the sun, each pole tilts towards or away from the sun during a certain time of the year. The incline does not have major effects near the equator, but as we move further towards the Southern Hemisphere and Northern Hemisphere, the distance between the geographical and the rotational axis increases, and its effects are more pronounced.

Summer and winter are also believed to be caused due to the elliptical shape of the Earth’s orbit near the sun which results in the Earth getting closer to the sun for a certain period of the year.

Some people might believe that stars, just like the sun, tend to rise in the east and set in the west. But the truth is, the stars are still there in the sky, even during the daytime. We just cannot see them as the sky is too bright because of the local star, the sun. So as night falls, when the sun is shining on the other side of the Earth, we can see the stars, because the sun's rays are further away.

Unlike how we face away from the sun during the night, we don’t face away from the stars during the day. The night sky is simply not visible because the sun, being too close to the Earth, provides way more light than the stars. Hence as the sun outshines them during the day, stars are only visible during the night in the sun’s absence.

What is the day and night cycle?

The day and night cycle is another phenomenon where after each day we experience another night and after every night we experience another day every 24 hours. This is caused due to the rotation of the Earth. The cycle repeats every 24 hours because it takes 24 hours to complete one rotation around the Earth's axis.

Imagine if the Earth wasn’t spinning or if it were to rotate very slowly, one side would be constantly exposed to the direct sun for months like it is during the summer. It would heat up immensely, burning everything on the surface and evaporating our oceans, while the other side would be in complete darkness and freeze to subzero temperatures turning the water on this side into vast ice lakes. Almost all life on Earth would vanish if such an event were to occur, except some small aquatic deep sea creatures who might survive such harsh conditions or some locations near the North Pole and the South Pole where humanity has a slim chance of surviving. Thankfully the Earth doesn’t spin that slowly.

The ball shape of the Earth is not completely spherical, but it bulges near the equator, which is an imaginary line. This wideness in the Earth’s radius near the equator is explained by the Earth’s spinning.

Any rotating object experiences a centrifugal force that pulls it outwards. If you tie a pebble to a string and spin it, you’ll feel that the rock is being pulled outward. The centrifugal force depends on the radius of the object, meaning the length of the string will determine how much of a force the pebble will be pulled outward with. As the radius of the Earth is largest at the equator, the centrifugal force near this region will be greatest as compared to other places away from the equator. This greater centrifugal force makes the Earth experience a larger outward force near the equator making it bulge.

Here at Kidadl, we have carefully created lots of interesting family-friendly facts for everyone to enjoy! If you liked our suggestions for why do we have day and night then why not take a look at zodiac facts or why do seasons change?

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Written by Oluniyi Akande

Doctorate specializing in Veterinary Medicine

Oluniyi Akande picture

Oluniyi AkandeDoctorate specializing in Veterinary Medicine

With an accomplished background as a Veterinarian, SEO content writer, and public speaker, Oluniyi brings a wealth of skills and experience to his work. Holding a Doctor of Veterinary Medicine degree from the University of Ibadan, he provides exceptional consulting services to pet owners, animal farms, and agricultural establishments. Oluniyi's impressive writing career spans over five years, during which he has produced over 5000 high-quality short- and long-form pieces of content. His versatility shines through as he tackles a diverse array of topics, including pets, real estate, sports, games, technology, landscaping, healthcare, cosmetics, personal loans, debt management, construction, and agriculture.

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