What is meant by the apparent daily movement of the sun is the movement of the sun in the sky throughout one day when viewed from the surface of the Earth. This movement is called “apparent” because it does not reflect the actual movement of the Sun around the Earth.
Because this apparent movement actually occurs as a result of the Earth’s rotation around its axis from west to east. It is not the sun that revolves around the Earth as we see in this apparent daily movement.
The apparent daily motion of the Sun is also affected by the geographic location of the observer on the Earth’s surface, for example, differences in latitude and differences in time zones. The apparent daily movement of the sun plays an important role in determining time and in creating the difference between day and night.
The characteristics of the apparent daily movement of the sun are:
To facilitate understanding, here are some characteristics of the daily apparent movement of the sun:
- Sunrise: This phenomenon occurs in the morning, when the sun appears to rise from the east. Or more precisely, from the northeast direction for the northern part of the Earth and the southeast direction for the southern part.
- The sun is at its highest point: often called midday. The Sun currently appears to be at its zenith or zenith point.
- Sunset: This phenomenon occurs in the afternoon when the sun appears to be setting in the west (northwest in the Northern Hemisphere and southwest in the Southern Hemisphere).
The effect of daily apparent movement
The apparent daily motion of the Sun has many important effects on life on Earth. This movement affects many aspects of life on Earth and plays an important role in maintaining the balance of the ecosystem and the life of creatures on this planet. Here are some effects:
1. The difference between day and night
This apparent movement causes a cycle of change day and night every day. When the Sun’s position appears above the horizon, that part of the Earth is exposed to bright daylight. At the same time, when the sun appears below the horizon, the day becomes dark and is called night.
2. Timing
This apparent movement also helps people determine the basis for dividing time in a day. It is divided into hours, minutes and seconds. When there were no clocks, the ancients used the position of the sun and the shadows of objects to indicate time.
This object is called a sundial, which contains a single piece or needle that does not move. The position of the needle’s shadow is used to indicate the time. That’s why this sundial is placed in a garden or open space so you can take advantage of the sunlight and shadows.
This is also why there are time differences between regions. For example, eastern Indonesia will be earlier in the morning compared to western Indonesia. The time difference is about 2 hours. Many other regions in the world are also experiencing similar things in different regions.
3. Navigation
Since ancient times, humans have used this apparent movement for navigation. The movement of the sun in the sky helps determine direction and determine geographical location. It is commonly used by sailors and fishermen when going to sea.
4. Climate and seasonal changes
Differences in the duration of day and night, as well as the angle of incidence of sunlight, can lead to differences in temperature and climate at different latitudes.
5. The life of all living things
This apparent movement also plays an important role in the rhythm of the life of living organisms, including humans and animals. The biological activity of many organisms is regulated by changes in light and temperature during the day-night cycle.
Apart from that, it also affects the amount of light and temperature that plants receive. The duration and intensity of sunlight during the day plays an important role in photosynthesis and plant growth.
The process of the daily apparent movement of the sun
As mentioned above, the apparent movement appears as if the sun rises in the east and sets in the west. It is as if the sun is moving around the Earth, so that day and night change, which can determine the time of day.
In fact, the Earth moves around its axis from west to east, and this is called the Earth’s rotation. So it looks like the sun is moving. When the Earth rotates, the time it takes is about 23 hours, 56 minutes and 41 seconds.
But what appears as if the Earth is facing the Sun does not exceed 12 hours, even though the Earth’s rotation takes approximately 24 hours. Thus the rest of the time the Earth is far from the Sun until nocturnal conditions occur.
Time zone section
As a result of the Earth’s rotation, the apparent daily movement of the Sun occurs, leading to the division of time zones throughout the world. So it divides not only hours, minutes and seconds, but also time zones. For example, Indonesia is divided into eastern, central and western regions.
The whole world is divided into 24 time zones, the center of which is located in Greenwich, England. This is where the 00 longitude point is located. The hourly time difference occurs when there is a longitude difference of 150.
The portion of land east of Greenwich Point will have a faster time, or experience an earlier morning. Meanwhile, those in the West will have a slower time.
For example, East Indonesia (WIB) is at Greenwich Mean Time (GMT) +7 hours with a position of 105 degrees east longitude. Meanwhile, the central part (WITA) is GMT +8 hours at 120°E. Finally, the eastern part (WIT) is located at GMT +9 hours 135 degrees east.
So, if WIB is at 8.00 AM, that means WITA is at 9.00 and WIT is at 10.00. Each zone has a one hour difference. Eastern Indonesia Time (WIT) will be first in the morning and end in the evening.
Other effects of the Earth’s rotation
Aside from the apparent daily motion of the Sun, which results from the Earth’s rotation, this rotation has been shown to have other effects as well. Here is the explanation:
1. Ocean currents
This is called the Coriolis effect, i.e. the change in the direction of ocean currents. In the southern part of the world, ocean currents change their direction clockwise. At the same time, the northern part of the Earth is shifting its current direction counterclockwise.
2. Thickness of the atmosphere
The Earth’s atmosphere consists of several layers, namely the stratosphere, troposphere, mesosphere, ionosphere, thermosphere, and exosphere. As a result of the difference in climatic conditions between the equatorial region (near the equator) and the polar region, the thickness of the atmosphere also varies.
3. Effect of jet lag
Jet lag is often experienced by those who travel long distances by plane. This occurs due to changes in circadian rhythm as the Earth rotates. The effect of the time difference between departure and destination can cause this effect.
For example, departing from Indonesia to the United States, where the time zone is clearly different. After a long-time flight in the air and then a difference in time zone, the psychological state of the person making this flight will feel uncomfortable.
What is felt is disturbed sleep, an inability to sleep soundly, and the body feels as if it is floating a little, and some even lose their appetite. The influence of a person’s body clock on their time zone can influence their jet lag condition.
The difference between daily and annual apparent movement
In the above discussion, it has been explained that the apparent daily motion of the Sun occurs because the Earth rotates on its axis. The effect of the Earth’s rotation is the occurrence of day and night, as well as the difference in time throughout the day.
What is the difference with the apparent annual movement of the sun? The answer is that the Earth is revolutionizing. If the daily apparent motion is the result of the Earth’s rotation around its axis, then the annual apparent motion is the result of the Earth’s rotation around the sun.
Some of the effects of annual apparent movement are no less important than the effects of daily apparent movement. If daily movement has an effect on day, night and time of day, semi-annual movement has an effect throughout the year.
It is known that the Earth rotates around itself for approximately 24 hours, and therefore the Earth’s revolution takes 365 days or one year. This apparent annual movement appears to show the rising movement of the sun towards the north and then moving towards the south in its downward movement throughout the year.
Effect of annual apparent movement
Like daily movement, this annual movement also has an effect throughout the year that can then be seen and utilized by living organisms, i.e. differences in the seasons. Some have two seasons and others have four seasons.
Impact in Indonesia and the world
In Indonesia, which is close to the equator, there are only two seasons: the rainy season and the dry season. The rainy season usually runs from the middle to the end of the year, while the dry season extends from the beginning to the middle of the year.
Meanwhile, in other countries or regions in the world, they face four seasons. Known as spring, summer, fall and winter (snow). All of this is linked to the Earth’s revolutionary movement, so that the sun appears to rise from the north and descend from the south.
The scale used is the equator, where the sun appears to rise in the north, then descend to the equator again, and continue to descend to the south, before finally returning to the equator again. This event continues to repeat as long as the Earth makes a revolution around the Sun. The estimate is as follows:
- Using the equator as a measure, on March 21 and September 23, the sun appears directly above the equator. So that areas of the world close to the equator feel hot weather.
- On June 21, the sun will be at 23.5 degrees north latitude, or the so-called northern equinox. Its location is above the equator, so summer comes in a region that experiences four seasons
- On December 22, the sun will be at 23.5 degrees south latitude, or the so-called southern solstice. Its location is below the equator, so some areas experience winter.
Between March 21 and June 21, four-season regions will generally experience spring. Then comes summer when the sun approaches the equator again until September 23.
After that, the sun will move south, causing fall until around December 22nd. Then, the sun seemed to move up again toward the equator, which then became winter. Until about March 21, which repeats the seasonal cycle.
Close
After listening to the above explanation, we can understand that the apparent daily movement of the Sun occurs due to the Earth’s rotation around its axis. As the center of the solar system, the Sun is actually stationary. Other planets move around it, including Earth.
But the Earth is special, because in addition to rotating on its axis, the Earth also revolves around the Sun. The effect is the daily apparent movement and the annual apparent movement. They are interconnected and have a significant impact on human life and other living organisms.
