Orbit of the Earth

By analyzing the anisotropy of microwave background radiation, scientists have been able to determine the speed at which the Sun is moving from the constellation Aquarius to the constellation Leo. This speed is estimated to be around 400 kilometers per second.

This represents the Sun’s absolute motion speed within the vast expanse of the Universe, or in space.

If we consider a relatively short period of time, such as 10 to 20 thousand years, we can assume that the Sun’s trajectory is a straight line.

As the Sun moves along this trajectory, the Earth and the other planets in the solar system accompany it, following a wave-like path. This wave is essentially flat, as the Earth and the planets orbit the zodiacal constellations on the zodiacal plane.

Another point to consider is that when we examine the movement of the Sun and Earth in relation to a moving object, we often observe a spiral pattern, such as when we consider their motion in relation to the center of the galaxy or the galaxy’s center of mass. It’s important to note that the galaxy as a whole is also in motion, including its centers.

Therefore, both the Sun’s and Earth’s movements in the vast expanse of the Universe are progressive motions.

Contrary to popular belief, the Earth’s movement in relation to the Sun is not rotational, but rather progressive. This is a commonly misunderstood concept.

In reality, the Earth’s motion relative to the Sun is the combined result of the progressive and absolute movements of both celestial bodies within the Universe.

Incidentally, it is imperative to clarify this movement rather than the notion that the Earth revolves around the Sun, which is commonly believed worldwide, as it does not align with the truth.

Furthermore, it is worth mentioning that the idea that the Earth’s motion in relation to the Sun is rotation is derived from the viewpoints of our esteemed predecessors. However, in reality, individuals such as Copernicus, Kepler, Galileo, Newton, Lomonosov, and Maxwell never existed; they are purely fictional characters, mere “literary heroes”.

Additionally, it should be noted that the Earth’s motion in relation to the Sun is in a forward direction.

(And taking into account the Earth’s rotation on its axis, it is a superimposition.)

It wouldn’t be a challenge for me to answer this query as astronomy is my field of expertise. 🙂 However, I’d like to tackle the question from a different angle: why does everything in the Universe experience rotation? I’ll attempt to elucidate this concept below, and I’ll also share an intriguing tidbit.

Earth’s Movement in Space

Similar to all celestial entities, our planet is constantly in motion, following a complex trajectory. To comprehend this process, it is necessary to put everything in its rightful place. There are three forms of motion:

• Orbiting the star – 365 days;
• Precession – a complete cycle lasting approximately 25,000 years;
• Rotation around the axis – 24 hours.

What is the concept of precession?

Precession, as defined by science, is a phenomenon characterized by a slight shift in the axis of rotation of an object. In simpler terms, the axis appears to trace out a cone-like shape, resembling a “wolf” losing its pace. Consequently, it is predicted that the North Star will cease to indicate the northern direction in the near future. Some scientists believe that this phenomenon is also linked to the most recent global warming and climate change.

What causes the rotation of planets

It is believed that the rotation of planets starts within a cloud of interstellar dust, which acts against gravity and prevents the cloud from collapsing into a small point. This cloud then transforms into a disk shape, with a star being formed at its center where gravity is particularly strong. However, the exact circumstances that give rise to these vortices of matter are still unknown. It is presumed that the initial motion of planets is derived from these vortices, but this motion is further enhanced through a series of tangential collisions, causing them to spin.

The stars and nearby planets have a significant impact on the axial rotation of the Earth. This rotation is influenced by various factors, leading to unpredictable consequences. Notably, Uranus and Venus rotate in the opposite direction compared to the rest of our solar system, rotating from east to west.

The Earth’s Core Rotation

Recent studies have uncovered an intriguing fact about our planet’s core: it consists of two distinct parts – a liquid outer core and a solid inner core. The inner core, much like the Earth itself, rotates in the same direction but at a slightly faster pace, leading the outer core by 2/3 of a second. However, what makes this discovery even more captivating is the revelation that the outer core rotates in the opposite direction. This peculiar phenomenon can be attributed to several factors:

• The solid core experiences acceleration due to the magnetic field.
• The outer core counteracts this acceleration.
• The resulting recoil force causes the outer core to rotate in the opposite direction.

Throughout my life, I have always made an effort to stay abreast of the latest developments in the field of science. I find it incredibly fascinating to learn about how our planet, solar system, and the broader cosmos are structured. Out of all the planets that we know of, Earth stands out as the only one where a wide array of living organisms have been discovered and cataloged. However, Earth is merely a tiny speck in the vastness of the Universe, and even the observable portion of it is mind-bogglingly difficult to comprehend due to its sheer scale. The various celestial objects in space are all intimately connected through the force of gravity, which originated from the Big Bang. As a result, over billions of years, clusters, galaxies, systems, and other formations of celestial bodies have come together and become intertwined through the powerful force of gravity.

How the Earth’s Movement in Space

The primary essential motion of the Earth is its rotation on its own axis. In other words, the planet is not stationary, but it revolves in circles. For instance, if you rotate the globe, you can visualize how it appears. appears. Everything on the planet revolves along with the planet. However, humans are unable to perceive it. The only noticeable effect on the Earth’s inhabitants is the alternating pattern of day and night, which constitutes a day. During this period, the planet completes one full rotation on its axis.

Furthermore, the Earth follows a trajectory around the Sun known as its orbit. It completes this orbit in a period of 365 days, except for every four years when it takes 366 days. This phenomenon occurs because, within the solar system, the star holds the highest level of influence, causing all lesser celestial bodies to be affected by its gravitational force.

The general arrangement of celestial objects

Contrary to popular belief, the Sun is not stationary in outer space. It actually orbits around the center of the Milky Way at a speed of 200 kilometers per second. Scientists speculate that a major component of any galaxy is a massive black hole. At the very least, this is true for the galaxies nearest to us:

Even these galaxies are not stationary. In fact, in a few billion years, the Milky Way and Andromeda will merge. What will happen after that remains uncertain.

The Earth is in constant motion, constantly rotating on its axis and revolving around the Sun. This movement causes a change of seasons on the planet. It is important to remember that while the Earth is circling the Sun, it also rotates around its own axis, resulting in the change of day and night. This rotational movement is known as diurnal.

To gain a better understanding of the Earth’s rotation around the Sun and its axis, we turned to Alexander Perkhnyak, an astrophysicist and employee of the Moscow Planetarium, who provided valuable insights.

The Earth’s Rotation around its Axis

What is the speed of the Earth’s rotation around its axis?

The Earth rotates around its axis at a velocity of 465 meters per second, which is equivalent to 1,674 kilometers per hour. The speed of the Earth’s rotation decreases as you move further away from the equator.

“It is not widely known that the speed of the Earth’s rotation decreases as you move away from the equator. To illustrate this, consider the city of Quito, which is located near the equator. The residents of Quito rotate with the Earth at a speed of 465 meters per second. However, for residents of Moscow, who are much further north of the equator, the rotation speed would be almost half of that, at 260 meters per second,” explained Perkhnyak.

Relationship Between Earth’s Rotation Speed and Latitude

It is important to note that the Earth’s rotation speed varies depending on the latitude due to the changing circumference of the planet. As we move closer to the poles, the Earth narrows and therefore spins at different speeds at different latitudes. The speed of rotation decreases as the radius decreases, which means that at the North Pole and South Pole, the rotation speed is essentially zero.

If you are curious about the rotation speed that can be achieved at other latitudes, you can simply multiply the cosine of that latitude (which can be calculated using a calculator or referenced in a cosine table) by the rotation speed of the planet at the equator (1674 km/h). For example, the cosine of 45 degrees is equal to 0.7071, so the speed at this latitude would be 1674 x 0.7071 = 1183.7 km/h.

Is the speed of the Earth’s rotation constant?

No, the speed of the Earth’s rotation is not constant. It slows down by an average of 4 milliseconds per year.

“Astrophysicists explain this phenomenon by the gravitational pull of the Moon, which is known to influence the tides on our planet. So, when these tides occur, the Moon seems to be trying to attract the water towards itself, causing it to move in the opposite direction of the Earth’s orbit. As a result of this unique counteraction, a small friction force is generated at the bottom of water bodies, which, in accordance with the laws of physics, decelerates the Earth’s rotation. This deceleration is minimal, only around 4 milliseconds per year,” Perkhnyak specified.

The orbit of the Earth around the Sun

The Earth is a spinning orb that rotates around an imaginary axis, much like a spinning top. If you were to place the base of a top on a flat surface in an unwound state, it would stay balanced. However, if the top’s rotation slows down, it will eventually fall over.

Unlike a top, the Earth doesn’t have a fixed base to keep it stable. It is influenced by the gravitational forces of the Sun, Moon, and other celestial bodies in our solar system and the universe. Despite this, the Earth manages to maintain its position in space. The speed at which it rotates, which was established when the Earth’s core formed, is enough to sustain a state of relative equilibrium.

The Earth’s axis is not perpendicular to the planet’s sphere. It is tilted at an angle of 66°33′. The rotation of the Earth around its axis and the Sun allows for the changing of seasons. Without this specific orientation, the planet would “tumble” in space, making it impossible to maintain consistent environmental conditions and life processes on its surface.

Why doesn’t the Earth plummet into the Sun?

“As the Earth orbits the Sun, it generates a centrifugal force that constantly attempts to propel our planet away. However, this force is counteracted by the Earth’s consistent speed and its optimal distance from the Sun, which is precisely balanced with the centrifugal force that could potentially disturb its orbit. Consequently, the Earth remains steadfast in its trajectory and does not succumb to the gravitational pull of the Sun, thereby averting any potential collision or deviation into outer space,” stated Alexander Perkhnyak.

According to the Director of the Institute of Astronomy of the Russian Academy of Sciences, the Earth is currently lacking protection. Read More

The Earth rotates on its axis, which is an imaginary straight line that extends from the North Pole to the South Pole and passes through the center of the Earth.

Earth’s orbit refers to the path that the Earth takes around the Sun.

The equator is an imaginary line that divides the Earth into the Northern and Southern hemispheres.

Scientists estimate that the Earth, as a member of the Solar System, was formed over 4.5 billion years ago. Throughout this extensive period, the planet has maintained a relatively constant distance from the Sun. This stability is due to a delicate equilibrium between the Earth’s velocity and the gravitational force exerted by the Sun. Although the Earth’s orbit is not perfectly circular, it remains secure. If the Sun’s gravitational pull were stronger or if the Earth’s velocity were significantly reduced, the planet would be pulled towards the Sun. Conversely, if the Earth’s velocity were too high, it would eventually escape the Sun’s gravitational pull and drift off into space, no longer being a part of the Solar System.

The Earth’s distance from the Sun allows for the maintenance of an ideal surface temperature. The atmosphere also plays a vital role in this process. As the Earth orbits around the Sun, the seasons undergo a transformation. Nature has evolved to adapt to these recurring patterns. However, if our planet were positioned further away, the temperature would plummet to negative degrees. Conversely, if it were closer, the intense heat would cause all bodies of water to rapidly evaporate, surpassing the boiling point recorded on a thermometer.

The Zodiac

As the Sun moves among the stars in its yearly journey, it traces a complete circle on the celestial sphere known as the ecliptic. Along this path, the Sun passes through 13 constellations, collectively known as the zodiac. These constellations form a belt and are referred to as zodiacal. The term “zodiac” shares the same root as the word “zoo,” and in Russian, it translates to “circle of animals.” Many of the zodiacal constellations indeed have animal names, while others have been given symbolic names by popular imagination.

There are various constellations representing the signs of the zodiac.

1. During the month of March, the Sun can be found in the constellation of Pisces. The stars in this constellation are relatively dim, with no star brighter than 3rd magnitude. The constellation of Pisces is also home to the vernal equinox, which marks the transition of the Sun from the Southern Hemisphere to the Northern Hemisphere.
2. In the month of April, the Sun moves into the constellation of Aries. Aries is associated with the masculine gender of the word “sheep.” However, around 2 thousand years ago, the vernal equinox was located in this constellation. Due to precession, the vernal equinox has now shifted to the constellation of Pisces.
3. During the month of May, the Sun can be found in the constellation of Taurus. This constellation is home to approximately one hundred stars that are visible to the naked eye. Among these stars, the brightest is Aldebaran, which is a red giant. It is worth noting that in the year 1054, a supernova eruption took place in Taurus, and as a result, the Crab Nebula was formed.
4. When June arrives, the Sun moves into the constellation Gemini. Notably, the brightest stars in this constellation are Pollux and Castor. Additionally, it is worth mentioning that the point of the summer solstice can be found within this constellation.
5. July brings the Sun to the constellation of Cancer. Unfortunately, there are no particularly bright stars within this constellation.
6. On the twentieth of August, the Sun transitions into the constellation Leo. This constellation is home to several dozen stars, with the brightest ones being Regulus and Denebola.
7. During the month of September, the position of the Sun aligns with the constellation Virgo, known for its prominent star Spica. Interestingly, Virgo is also the location where one of the first quasars was discovered. Additionally, this constellation houses the point of the autumnal equinox.
8. As we transition into October, the Sun traverses the constellation Libra. Despite its small size, Libra boasts three stars that are visible to the naked eye.
9. November brings the Sun’s presence in the constellation Scorpius. Notably, the brightest star in Scorpius is the reddish Antoros. Another intriguing star in this constellation is Zeta Scorpio, which shines with a luminosity that exceeds that of the Sun by 400,000 times.
10. Continuing into November, the Sun moves through the constellation Sagittarius. It is worth noting that the center of our galaxy lies in the direction of this constellation.
11. During the months of November and December, the Sun travels through the region of the Serpentine constellation (although it is not considered in astrology, the visible path of the Sun passes through it).
12. In January, the Sun can be found in the Capricorn constellation, which does not contain any prominent stars.
13. In February, the Sun is located in the Aquarius constellation.

In ancient times, all zodiac constellations were assigned symbolic representations, which are still in use today. However, the Serpentine constellation lacks a symbol.

Oscillations of the axis during rotation

The direction of the Earth’s rotation axis periodically changes due to the gravitational force of the Moon and, to a lesser extent, the Sun, as well as the uneven distribution of matter within the planet. This phenomenon can be visualized as a cone-shaped trajectory.

One of the most noticeable effects of this phenomenon is the precession of the equinoxes. Each year, the vernal equinox arrives approximately 20.5 minutes earlier. This precession follows a cyclic pattern with a period of 25,776 years.

Another phenomenon related to the Earth’s axis is called nutation, which refers to the variation in the inclination of the ecliptic to the equator. This nutation occurs with a period of 18.61 years.

Since the beginning of the 21st century, it has been observed that the rate at which the Earth’s axis drifts towards the east has increased to approximately 17 cm per year.

In the past, people used to think that the Earth was not moving and that the stars were fixed in the sky and rotated around it. For a long time, no one paid attention to the speed at which the Earth orbits or rotates around an axis because these concepts did not fit into the scientific understanding of that time. In 1851, Jean Foucault provided experimental evidence of the Earth’s constant motion around its axis, which finally convinced those who still had doubts in the previous century.

In the Paris Pantheon, an experiment took place where a pendulum and a circle with markings were positioned. With each swing, the pendulum would shift by a certain number of divisions. This phenomenon can only occur if the Earth is rotating.

Irregularity in the Rotation

Throughout history, humanity has grown accustomed to the constant rhythm of day and night. It has served as a time standard and a representation of the consistent nature of life’s processes. The Earth’s rotation period is influenced by factors such as the ellipticity of its orbit and the presence of other planets in the solar system.

There is another peculiarity that occurs in the length of the day. The Earth’s axial rotation is not constant. There are several main factors that contribute to this phenomenon. One important factor is the seasonal fluctuations caused by the dynamics of the atmosphere and the distribution of precipitation. Additionally, the tidal wave, which moves in the opposite direction of the Earth’s motion, constantly slows it down. Although this effect is minimal (only 1 second every 40 thousand years), it has had a significant impact over a billion years, increasing the length of the day by 7 hours (from 17 to 24).

The Sun and the galaxy are in constant motion

The Sun, situated within the vast expanse of the Milky Way, possesses its own unique orbit. Positioned approximately 25,000 light years away from the galactic center, the Milky Way spans an impressive distance of at least 100,000 light years. Remarkably, the Sun and the solar system maintain a velocity of 200 kilometers per second, equating to an average speed of 720,000 km/h. Even at this remarkable pace, it would require the solar system a staggering 230 million years to traverse the entirety of the Milky Way.

Notably, the Milky Way itself is not stationary, but instead propels forward through space in relation to other galaxies. In approximately 4 billion years, the Milky Way will encounter its closest neighboring galaxy, Andromeda. These two cosmic entities are hurtling towards one another at a velocity of 112 kilometers per second.

Consequently, the intricate dance of cosmic bodies within the universe is a perpetual spectacle of ceaseless movement and eternal change.

Characteristics of Earth’s orbit

As mentioned earlier, the speed of Earth’s orbit is influenced by its unique characteristics. Unlike a perfect circle, Earth’s orbit is slightly elongated, resulting in the planet moving closer to and farther away from the Sun. When Earth is at its closest distance to the Sun, this position is called perihelion. On the other hand, when Earth is at its farthest distance from the Sun, this position is called aphelion. Perihelion occurs on January 3rd, while aphelion occurs on July 5th. The speed at which Earth orbits the Sun differs at these two points. At aphelion, Earth orbits at a speed of 29.27 km/s, whereas at perihelion, Earth orbits at a speed of 30.27 km/s.

Vernal and Autumnal Equinoxes

The Vernal and Autumnal Equinoxes are two significant events that mark the changing of seasons. The Vernal Equinox occurs in the spring, around March 20th, and marks the beginning of the spring season in the Northern Hemisphere. On this day, the length of daylight and darkness is nearly equal all over the world.

The Autumnal Equinox occurs in the fall, around September 22nd, and marks the beginning of the autumn season in the Northern Hemisphere. On this day, the length of daylight and darkness is also nearly equal all over the world.

These equinoxes are caused by the tilt of the Earth’s axis and its orbit around the Sun. During the equinoxes, the Sun is directly above the equator, resulting in equal lengths of day and night. After the Vernal Equinox, the days start to become longer and the nights shorter, leading to warmer temperatures and the arrival of spring. After the Autumnal Equinox, the days start to become shorter and the nights longer, leading to cooler temperatures and the arrival of autumn.

The Vernal and Autumnal Equinoxes are important astronomical events that have been observed and celebrated by various cultures throughout history. They mark the changing of seasons and have significance in various religious and cultural traditions. Understanding the equinoxes can give us a greater appreciation for the natural cycles of the Earth and the changing of the seasons.

• March 20. – Vernal equinox
• September 22 – autumnal equinox
• June 21 summer solstice
• December 22 – winter solstice

The points where the plane of the celestial equator intersects the plane of the ecliptic are indicated by the vernal equinox (March 20) and autumnal equinox (September 22). On these days, the length of day and night is equal, and the Sun’s rays fall on the equator line at a 90-degree angle, evenly illuminating and warming the areas of the hemispheres facing the Sun. The vernal and autumnal equinoxes mark the astronomical beginning of spring and fall in their respective hemispheres.

To differentiate between the summer (June 21) and winter (December 22) solstices, the Sun’s rays become perpendicular not to the equator line, but to the Southern and Northern Tropics (23.5° south and north latitude). On the summer solstice, June 21, the day is longer than the night in the Northern Hemisphere up to the 66.5° parallel, while in the Southern Hemisphere, the night is longer than the day. This date marks the astronomical start of summer in the northern latitudes and winter in the southern latitudes.

On December 22 (the day of the winter solstice), in the Southern Hemisphere up to the 66.5° parallel, the duration of the day is longer, while in the Northern Hemisphere north of the same parallel, it is shorter. The winter solstice date signifies the astronomical beginning of winter in the Northern Hemisphere and the start of summer in the Southern Hemisphere.

The cycle of the seasons

So, as the Earth orbits around the Sun, how long does this process take? The answer is already known. The total number of days is 365. At the same time, our planet, as previously mentioned, is moving in an eastward direction. During this journey, the Earth maintains the same tilt angle. As a result, within a specific orbital area, it always faces a particular side. This period of time is experienced by humans as summer. On the side that is “facing away” from our star, on the other hand, winter will prevail. This repetitive motion is what causes the transition of seasons.

Therefore, in the course of a year, the Earth completes a full orbit around the Sun, experiencing the changing seasons of winter, spring, summer, and fall. At two points during this cycle, both the northern and southern hemispheres are in the same seasonal state. This occurs because the Earth tilts on its axis in such a way that sunlight is evenly distributed across its entire surface. These points in time are known as the equinoxes, which happen in the fall and spring.

The mean distance between the Earth and the Sun

To summarize, it can be stated that we inhabit a perfect planet. Our year is neatly divided into four seasons, and nearly anywhere on Earth (excluding the poles) can support life throughout each season. While some regions may be more challenging than others, they are still within the realm of human capability. The same can be said for the day: Earth’s flora and fauna have adapted to the 24-hour cycle and thrive within it. Therefore, it is our responsibility to care for the planet we have inherited, as there may never be another quite like it!

We inhabit the most exceptional planet in the entire Universe.

The alternation of day and night

At a particular moment, a spherical object with a solitary source of illumination is only partially illuminated. In the case of our planet, a portion of it experiences daylight at that moment, while the unilluminated part remains concealed from the Sun, resulting in night. This alternation is made possible by the planet’s axial rotation.

In addition to the changes in the light patterns, the planet’s surface is subject to alterations in the way it is heated by the Sun’s energy. This cyclical process is of great significance. The transition between light and heat conditions occurs relatively rapidly. Within a span of 24 hours, the surface does not have enough time to become excessively heated or to cool down below the optimal temperature.

The consistent speed at which the Earth rotates around the Sun and on its axis plays a crucial role in supporting animal life. It is this constancy in the orbit that keeps the planet within the ideal temperature range for sustenance. Additionally, the rotation of the Earth on its axis ensures the occurrence of day and night, which are vital for the development and continuation of life.

Categories of orbits

There are two main categories of orbits: relative orbits and absolute orbits.

A relative orbit refers to the path of a celestial body within a specific reference frame. It is defined in relation to other objects or points of reference. For example, the orbit of a satellite around the Earth is a relative orbit.

An absolute orbit, on the other hand, is the trajectory of a body within an established universal reference frame. It is not dependent on other objects or points of reference. An example of an absolute orbit is the motion of celestial bodies within the Universe as a whole.

A relative orbit refers to the curved path followed by a body in a reference frame, where its velocity varies. For instance, when describing the path of an artificial satellite, we indicate its movement in relation to a planet. In the simplest terms, it can be considered an elliptical path with the Earth at its focus, while the plane of motion is considered stationary relative to the stars. In this measurement scenario, it becomes evident that the trajectory of the satellite is a relative orbit, as it is defined in relation to our Blue Planet, which itself orbits the Sun. However, if we observe the satellite’s path relative to the stars, a helical trajectory becomes apparent – this is an absolute orbit of the artificial satellite.

During the 17th century, the scientists had full confidence in the laws formulated by I. Kepler, which explained the movements of celestial bodies. However, as the accuracy of measurements improved, deviations from the Keplerian theory started to emerge. Kepler’s model was based on two simplifications:

• It was assumed that the weight of any planet was negligible compared to the weight of the Sun;
• Only the gravitational influence between the Sun and the planet was taken into account, disregarding the influence of neighboring celestial bodies.

A visual representation illustrating the historical variations of the solar system’s barycenter. Attributed to Wikimedia Commons.

In contemporary scientific calculations of orbital characteristics, an additional crucial factor is acknowledged. This factor considers the combined movement of both the planet and the “celestial body-star” unit as they orbit around the barycenter, a hypothetical point in space that represents the system’s center of mass. Given the significance of solar dimensions, the barycenter of our system is situated within the Sun and experiences slight shifts in location over time.

Nowadays, the gap between the Earth and our star is expanding by 15 cm per year, and after 67 thousand years, the difference in the semi-major axis value will reach one kilometer – a negligible amount in the grand scheme of space and time. However, we won’t always be drifting away: every 100 thousand years, the period of drifting will be followed by a period of approaching and vice versa.

This cyclic pattern has been observed on our planet for millions of years and has led to various global cataclysms, such as ice ages.

In addition to the distance from the Sun, the eccentricity of our orbit is constantly changing. Throughout different years, its value has varied from what we have today, ranging from 0.05 to 0.005.

The Path of the Earth in Space

The Earth’s orbit is not a perfect circle but rather an ellipse, with the Sun located at one of its focal points. Throughout the course of a year, the distance between the Earth and the Sun can vary, ranging from 147 million kilometers to 152 million kilometers. The total length of the Earth’s orbit is approximately 930 million kilometers. Our planet travels around the Sun in a counterclockwise direction at a speed of about 30 km/s. It takes the Earth 365 days, 6 hours, 9 minutes, and 9 seconds to complete one full orbit around the Sun. This period of time is known as a sidereal year.

Additionally, there is the notion of a tropical year, which represents the duration between specific successive occurrences of the Sun passing through the vernal equinox. This interval spans 365 days, 5 hours, 48 minutes, and 46 seconds.

Milankovitch cycles

Astronomer Milutin Milankovitch made a groundbreaking discovery in the early 20th century. He found that the Earth’s tilt, eccentricity, and precession are not constant values. Instead, they undergo cyclical changes over extended periods of time. For instance, every 41,000 years, the Earth goes through a cycle where its tilt shifts from 24.2 – 24.5 degrees to 22.1 – 22.6 degrees and then returns to its original position. At present, the Earth’s tilt is gradually decreasing, and we are currently halfway along this cycle, with the minimum tilt of 22.6 degrees expected to occur in approximately 12,000 years. Additionally, the Earth’s eccentricity follows a much less predictable pattern, fluctuating between 0.005 and 0.05 over a period of 100,000 years.

As previously stated, the current value is 1/60 or 0.0166, but it is currently decreasing. It will eventually reach its lowest point in 28,000 years. It has been proposed that these cycles are responsible for the occurrence of ice ages. When the tilt and eccentricity values are exceptionally high, and the precession causes the Earth to tilt away from or towards the Sun, it results in excessively cold winters in the western hemisphere and excessive ice melting during the spring or summer seasons.

Time Measurement

Humans rely on the Gregorian calendar to measure time, which is adjusted to account for the length of the tropical year but with a slight variation. Therefore, even in fifty thousand years, winter will still occur during the winter months and summer will still occur during the summer months.

Currently, the Earth’s axis is tilted at an angle of 66.5 degrees relative to its orbital plane. As the planet completes its orbit around the sun in 365 days, it maintains a parallel movement within cosmic space. This motion results in the changing of seasons and variations in the lengths of day and night.

Distance between the Sun and the Earth

The distance from our planet to the Sun is determined by its position in space. The distance can be described as:

• at its closest point to the Sun (perihelion) – 147.1 million km;
• at its farthest position from the Sun (aphelion or apogee) – 152.1 million km.

For approximate calculations, the average distance (orbital semi-major axis) is considered to be 149.6 million km. This value is commonly used as a standard unit of measurement in space, known as 1 astronomical unit (a.u.). It simplifies the determination of distances in outer space compared to calculating absolute values.

The mean distance between the Earth and the Sun measures about 0.000004848 parsecs, equivalent to approximately 150 million kilometers. Credit: telegramfor.me.

This measurement was established during the Middle Ages, but initially lacked a numerical value – all linear distances were expressed in terms of the conventional distance from the Earth to the Sun. It was not until 1672 that the European scientist J. Cassini first estimated the Earth’s orbital radius to be 140 million kilometers. This value was only refined by Soviet astronomers in 1961, who obtained a value of 149.5993 million km with an error margin of +/- 2000 km.

The distance to the luminary does not affect the change of seasons, which solely depends on the axial tilt of the celestial body.

The Earth’s perihelion occurs between January 2 and January 5 annually. Despite the increased solar heat during this time, the northern hemisphere experiences winter. Conversely, aphelion takes place between July 3 and July 7, during which the reduced light and heat from the sun does not impede the continuation of summer in all regions north of the equator.

The path of the planet’s movement around the Sun is depicted in the image above. Image credit goes to wikiwand.com.

After considering the duration of daylight and nighttime, as well as the positions of the Sun at various points, scientists have reached the conclusion that our planet does not follow a circular path in its orbit, but rather an elliptical one. This discovery was initially documented by Kepler, who also determined that both Mars and Earth experience periods of acceleration and deceleration. Through careful observations and calculations, Kepler deduced that the movement of the planets does not conform to a circular orbit, but instead follows an elliptical trajectory.

The factor responsible for the occurrence of seasons

The occurrence of seasons on the planets in our solar system is determined by the angle at which their axis of rotation is tilted in relation to their orbit. When the angle is smaller, the weather on the celestial body remains more stable, and there is no noticeable change in seasons. On the other hand, celestial bodies with an inclination angle of more than 90° also do not experience seasonal changes.

Seasonal changes are typically seen on objects with an axis inclination angle between 20-30 degrees:

Despite its minimal axis tilt, Mercury still experiences “summer” and “winter” seasons due to the high eccentricity of its orbit. The temperature difference between the perihelion and aphelion points on Mercury is a staggering 620 degrees Celsius.

Therefore, the dimensions and form of the trajectory that describes the entity’s orbit around the Sun greatly influence the establishment of temperature conditions upon it. The Earth’s mild eccentricity and relatively close distance during its movement, combined with the ideal axis tilt angle, have resulted in a temperature that is highly conducive to the survival of living organisms.

The movement of objects in space

By understanding that orbits exist and the various possibilities they present, scientists have been able to describe the paths of movement for a wide range of celestial objects. Comets, satellites, planets, and stars all have elongated trajectories in their motion. For instance, there are comets that have highly elongated orbits and can even intersect with a planet’s orbit. If at a certain point the planet and the comet align in their paths, a collision may occur or the gravitational force could alter the comet’s orbit, effectively trapping it. Scientists believe that this is how comet rings form around certain planets, as well as satellites.

Rotation Period of Celestial Bodies

The complete rotation of a celestial body along its path is known as its sidereal period of rotation. In the case of planets, this is commonly referred to as the “planetary year”. The duration of a planetary year is determined by the average distance from the planet to its orbit and the speed at which it orbits.

For ease of measurement, planetary years are often expressed in terms of terrestrial days and years. For instance, on Mercury, a year is equivalent to 0.24 Earth years or 89 Earth days. This makes it the shortest planetary year in our solar system. On the other hand, the planet Neptune has the longest year, which is approximately 164 Earth years.

Several years after the introduction of the initial ISV from the USSR, the United States of America successfully deployed a communication satellite. The impressive aspect of this satellite lies in its composition, as it is constructed from sturdy metal but takes the form of a massive “balloon.” In fact, this satellite measures an astonishing 32 meters in diameter, making it equivalent in size to an 11-story building.

Normally, satellites have a lifespan of several years, although there are some outliers. One such example is the LAGEOS SATELLITE, which was launched with an expected duration of 7 million years. Its surface is adorned with a unique plaque that carries a message intended for future generations of inhabitants of our planet.

The spacecraft ESTCube is affectionately referred to as the “Estonian Sailing Ship”. It is pioneering the use of the groundbreaking “electric sail” technology, which is currently undergoing practical tests. If successful, this technology will revolutionize spacecraft acceleration, enabling them to achieve unprecedented speeds. With the implementation of this “sail”, a spacecraft could reach the outer reaches of the solar system in a mere 8 years.

Installed on the renowned International Space Station (ISS), anyone can experience the sensation of being an astronaut and witness the breathtaking view of our planet from orbit, all from the convenience of their own home. Personally, I find it fascinating to occasionally observe Earth from the vastness of space.

Fluctuations in the Seasons

The path that the Earth follows around the Sun is called its orbit. One important factor to consider is the tilt of the Earth’s axis. It is this tilt that causes the four seasons to occur, with the axis tilted at an angle of 23.4 degrees. This tilt gives rise to astronomical events known as equinoxes and solstices.

The tilt of the axis remains fixed and does not change. As a result, the distribution of solar radiation varies. When the northern hemisphere is tilted away from the Sun, it experiences winter, while the southern hemisphere experiences summer. This system is reversed after six months. The winter solstice occurs on December 21, while the summer solstice occurs in June. The spring and autumn equinoxes occur on March 20 and September 23, respectively.

Decrease in Rotational Speed

The Earth’s rotational speed is gradually decreasing due to the friction caused by tides and stray particles in space. Scientists estimate that with each passing century, it takes an additional five hundredths of a second for the Earth to complete one full rotation. In the early stages of Earth’s formation, a day lasted only 14 hours compared to the current 24-hour day. This slowing of the Earth’s rotation is the main reason why, every few years, we must add a fraction of a second to the length of a day.

Nevertheless, the distant future holds the possibility of our 24-hour system becoming obsolete, and this raises the question of what we will do with the surplus time. Few have pondered this issue, but there are a few theories. One suggestion is to incorporate an additional segment into each day, resulting in a 25-hour day. Alternatively, we could alter the duration of an hour by dividing the day into 24 equal intervals.

Short answer

The reason why the planets’ orbits are almost in the same plane can be explained by the nebular theory of solar system formation. This theory suggests that the Sun was created when a gas-dust cloud suddenly compressed. In the center of this cloud, a star formed, and around it, a protoplanetary disk developed. Over time, the planets were born from this disk – in simple terms, they formed from the same material. Instead of drifting off into space, the planets orbit the Sun in elongated paths due to the force of gravity (since the Sun makes up 99% of the entire system’s mass).

Seasonality

The start of each season is represented by the solstice and equinox, rather than the middle. This is because it takes time for the Earth to heat up or cool down. As a result, seasonality is determined by the amount of daylight. This phenomenon is known as seasonal delay and varies based on where the observer is located. The closer one is to the poles, the greater the delay.

In numerous cities throughout North America, there is typically a delay of approximately one month, resulting in the coldest temperatures occurring on January 21st and the warmest temperatures on July 21st. However, individuals residing at these latitudes also have the opportunity to experience warm summer days in late August, allowing them to wear lighter clothing and even visit the beach. Conversely, on the “opposite side” of the summer solstice, the same date would correspond to around April 10th. This leaves many people eagerly anticipating the arrival of summer.

The Moon’s Distance from Earth is Increasing

Every year, the Moon’s distance from Earth expands by 4 centimeters. This phenomenon is caused by the gravitational pull it exerts on Earth, resulting in tidal forces.

The gravitational force of the Moon on the Earth causes a slight deformation of the Earth’s crust, resulting in a displacement of a few centimeters. Due to the Moon’s faster rotation compared to its orbit, these bulges exert a pulling force on the Moon, causing it to deviate from its original orbit.

For centuries, humans have pondered the transformation of night into day, the transition from winter to spring, and the change from summer to fall. Subsequently, as initial inquiries were resolved, researchers embarked on a more comprehensive examination of Earth as a celestial body within the solar system, striving to determine the velocity at which our planet revolves both around the Sun and on its own axis.

The Earth’s Movement

All celestial objects are in constant motion, and the Earth is no exception. It undergoes both axial rotation and orbital motion around the Sun.

To better understand the Earth’s movement, imagine a spinning top rotating on its axis while simultaneously zooming across the floor. This dual motion is crucial for the Earth’s habitability. Without it, our planet would become uninhabitable. Without axial rotation, one side of the Earth would constantly face the Sun, resulting in scorching temperatures exceeding +100 degrees Celsius and causing water to evaporate into steam. The other side would be in a permanent state of freezing cold, with the entire surface covered in ice.

Rotational trajectory

The Earth’s movement around the Sun is determined by its orbit, which is shaped by the gravitational pull of the Sun and the planet’s velocity. If the gravitational pull were stronger or the planet’s velocity lower, the Earth would be pulled towards the Sun. On the other hand, if the gravitational pull disappeared or significantly decreased, the planet would be propelled tangentially into space due to its centrifugal force. It would be similar to spinning an object tied to a rope above your head and suddenly letting it go.

The Earth orbits the Sun in a west to east direction, commonly referred to as “counterclockwise”.

Rate of Revolution around the Sun

The Earth completes one revolution around the center of the solar system in 365 days, 5 hours, 48 minutes, and 46 seconds, which is equivalent to one astronomical year. However, for the sake of convenience, a calendar year is considered to be 365 days, with the remaining time being “accumulated” and adding one day to each leap year.

The Earth’s orbital distance is 942 million kilometers. According to calculations, the Earth’s speed is 30 kilometers per second or 107,000 kilometers per hour. Although this speed may go unnoticed by people, as all individuals and objects move in the same way within the coordinate system, it is actually quite significant. For instance, the highest speed of a racing car is 300 kilometers per hour, which is 365 times slower than the Earth’s speed as it travels in its orbit.

However, the velocity of 30 km/s is not consistent as the orbit is an ellipse. Our planet’s speed fluctuates slightly throughout its journey. The largest variation occurs when passing the perihelion and aphelion points, reaching a difference of 1 km/s. Therefore, the assumed velocity of 30 km/s is an average.

Axial rotation

The Earth’s axis is a line that can be drawn from the north pole to the south pole. It is inclined at an angle of 66°33′ relative to the plane of our planet. One complete rotation takes 23 hours, 56 minutes, and 4 seconds, and is known as a sidereal day.

The primary consequence of axial rotation is the alternation of day and night on Earth. Additionally, this motion results in:

• The Earth having a slightly flattened shape at the poles;
• Displacement of objects (such as river currents and wind) in a horizontal plane (to the left in the Southern Hemisphere and to the right in the Northern Hemisphere).

The velocity of axial movement varies significantly in different regions. The highest velocity, known as linear velocity, is 465 m/s or 1674 km/h at the equator. This speed can be observed, for instance, in the capital of Ecuador. As one moves towards the north or south of the equator, the rotational speed decreases. In Moscow, for example, the speed is nearly half of the equator’s velocity. These speeds are referred to as angular velocities, and their magnitude decreases as one approaches the poles. At the poles themselves, the velocity is zero, meaning that they are the only parts of the planet that remain stationary relative to the axis.

The change of seasons is determined by the location of the axis at a certain angle. Different areas of the planet receive varying amounts of heat at different times due to this position. If our planet were positioned vertically relative to the Sun, there would be no seasons because both the northern and southern latitudes would receive the same amount of heat and light during the daytime.

There are several factors that affect axial rotation:

• seasonal changes, including precipitation and atmospheric movement;
• tidal waves that go against the direction of axial motion.

These factors cause the planet to slow down, resulting in a decrease in velocity. Although the rate of decrease is very small, only 1 second in 40,000 years, over the course of 1 billion years, the length of a day has increased from 17 to 24 hours.

Ongoing research is being conducted on the movement of the Earth. This data is instrumental in creating more precise star charts and understanding the correlation between this motion and natural phenomena on our planet.

Throughout history, scholars have sought to comprehend the nature of the Earth and the universe we inhabit. The orbit and rotational axis of the Earth remained elusive to philosophers and scientists in ancient times, but through gradual advancements, we have come closer to unraveling these mysteries. Today, our ability to harness advanced technologies is a testament to the efforts of those curious individuals who first gazed upon the heavens.

Understanding the Earth’s Orbit and Axis

The universe is in constant motion, with each element moving at incredible speeds. One such element is the Earth, which travels through space at a velocity of approximately 30 km/s. As you read these words, your position in the universe has already shifted by 150-200 kilometers. However, the Earth’s movement is not limited to a linear path – it also rotates around its axis.

The rotation of the Earth is not immediately apparent to the casual observer. This is because the motion is relative. While the position remains constant in relation to objects on the planet, it is constantly changing in relation to celestial bodies. As the Earth spins on its axis, it carries humanity along for the ride, rotating around the Sun, the center of the galaxy, and beyond.

The axis refers to an imaginary line that runs through the planet’s north and south poles.

Rotation around this line, known as revolution, occurs. If we were to visualize this movement on a plane, the axis would be at an angle to it rather than perpendicular. When observed from the north pole of the Sun, the Earth moves counterclockwise, while from the south pole, it moves clockwise.

The orbit of the Earth represents the path it takes as it moves around the Sun.

Instead of being a circle, in this instance, it is a somewhat elongated oval, known as an elliptical orbit. Furthermore, the inclination of the path in relation to the Sun is in a constant state of flux. If we were to envision the Sun as stationary, the Earth would revolve around it in a non-uniform plane. To put it figuratively, our planet appears as if it were weaving thread on the surface of the Sun, with each stitch being equidistant from the others.

Organization of the solar system

The solar system is composed of the central star known as the Sun, the planets, their moons, and asteroid belts, along with various comets, meteoroids, and other celestial objects, including space debris. These objects all follow different orbits, revolving either around the Sun or around the planets.

Within our system, there are a total of eight complete planets (listed in order of their distance from the Sun):

1. Mercury (0)
2. Venus (0)
3. Earth (1)
4. Mars (2)
5. Jupiter (79)
6. Saturn (62)
7. Uranus (27)
8. Neptune (17)

The number of moons is indicated in parentheses. Additionally, the last four planets possess ring systems comprised of smaller objects, meteorites, and quasi-satellites.

The initial four are referred to as the Earth-group planets, distinguished by their unique composition predominantly comprised of silicates and metals. The subsequent two are classified as gas giants, primarily composed of helium and hydrogen. The final two, in addition to their gas giant status, are further characterized as ice giants within the planetary group.

Prior to 2006, our Solar System had nine planets, including Pluto. However, Pluto was later reclassified as a dwarf planet due to the formal definition of planets that it does not meet. Meanwhile, there is still an unconfirmed hypothesis about the existence of another planet in our Solar System, which is currently referred to as the “ninth planet”.

In addition to the main planets, there are dwarf planets in our Solar System, including Pluto.

The officially recognized list is as follows:

(The number of satellites is also indicated in parentheses.) Scientists speculate that there may be over forty dwarf planets in our Solar System that have not yet been discovered.

The Earth’s axial tilt

The Earth’s axis of rotation is inclined in relation to the ecliptic plane. If we visualize the plane on which the Earth orbits around the Sun, this is it. Technically, the Earth never returns to the exact same point, so it can only be considered a plane conditionally, but for the sake of simplicity, this terminology is used.

The rotation around the axis happens at an inclination, as the axis of our planet is tilted at an angle of 23.4° (the precise value being 23.439281°) to this plane.

Consequently, our Earth “exposes” its northern hemisphere to the Sun at one point and then its southern hemisphere at another point.

Research Background

Ancient civilizations have been extensively researched through the use of two main disciplines: archaeology and history. Archaeology focuses on the analysis of artifacts, physical objects created and used by past societies. History, on the other hand, relies more heavily on the examination of written documents and sources.

Approximately 3000 years ago, the ancient Sumerians were able to identify and distinguish various planets. However, their understanding of the universe was primarily rooted in astrology, which served more as a means of prophecy and fortune-telling rather than an explanation of planetary parameters, the solar system, and the universe as a whole. It is possible that some Sumerian scholars hypothesized that the Earth was spherical and rotated, given the consistent semicircular shape of the shadow on the Moon. Unfortunately, no written records exist to support this theory, so it remains unverified in historical context.

The prevailing belief in ancient times was that the Earth was immobile and at the center of the cosmos, with the sun and stars orbiting around it.

There were various theories regarding the Earth’s shape, with one popular view suggesting that it was flat like a disk.

However, in 300 BC, Aristotle presented evidence that our planet is actually spherical, with one piece of proof being the shape of the shadow cast on the moon.

Aristotle built upon the work of Eudoxus, the pioneer of Greek theoretical astronomy, and also utilized mathematical calculations in his arguments. Aristotle’s geocentric model, which posited that the Earth is the center of the universe, remained dominant in the scientific community until the time of Copernicus and Galileo.

Prior to that, during the 5th century B.C., a number of Greek scientists put forth the theory that our planet revolves on its axis every day. However, the majority of their peers disagreed and believed that the Earth’s surface was stationary. By the time Aristotle provided his proof, there was already a hypothesis suggesting that the Sun was the central component, although this idea was not widely supported by most scientists.

Approximately two hundred years after Aristotle, specifically in 140 B.C., Claudius Ptolemy published a work known as the Almagest. This book contained the latest knowledge in astronomy and mathematics from Greek and Arab scientists of that era. Additionally, it provided descriptions of various instruments used for measurements, showcasing its advanced nature.

While the Almagest was comprehensive and included meticulous calculations, it was also based on inaccurate assertions regarding the Earth’s immobility and the celestial sphere’s rotation around it.

Efforts to support the concept that the Earth revolves around its own axis persisted throughout the Middle Ages. In the 5th-6th centuries A.D., this idea was mentioned by Indian astronomer Aryabhata, and in the 13th-14th centuries A.D., it was frequently discussed by Muslim and Latin astronomers who presented arguments against the theory of immobility.

Eventually, in 1543, the renowned Nicolaus Copernicus published his work titled On the Rotation of the Heavenly Spheres.

The author dedicated over forty years of work to this book, which was published posthumously, and Nicholas never had the opportunity to see a printed copy. His work is rightfully regarded as the “primary catalyst” of the initial technological revolution.

The teachings of Galileo encountered significant resistance from the European church because, according to the Holy Scriptures, which were influenced by Sumerian and Babylonian concepts, the Earth was believed to be stationary while the Sun revolved around it.

At first, Galileo received some support from the church for his defense of Copernicanism. He was accepted by Pope Paul V, became a member of the scientific “Accademia dei Lincei,” and even created a telescope with the approval of the clergy. However, things changed when he attempted to interpret Scripture and dismissed its scientific relevance. These actions led to a strong reaction.

In 1616, Copernicanism and the heliocentric system were declared heretical. It took two centuries for this decree to be overturned. Galileo narrowly avoided execution by the stake.

The church’s attempts may have hindered but did not halt scientific advancement. Prior to the decree in 1600, Giordano Bruno, who built upon Copernicus’ theories and extrapolated philosophical implications regarding the existence of unexplored celestial entities within our solar system, the plurality of worlds, and the stars functioning as distant suns akin to our own, was executed by being burned at the stake. It is worth mentioning that even on the 400th commemoration of this incident, the Pope did not acknowledge the culpability of the Church.

Johannes Kepler significantly improved the works of Copernicus and completely updated them. He formulated three laws of planetary motion, which explained the irregularities in their movement. Kepler replaced the use of epicycles, which were complicated curves used to describe planetary motion, with the concept of an ellipse. He also introduced the idea of an orbit and derived the “Kepler equation” to determine the position of planets. Newton later used Kepler’s work and is credited as the founder of the science of dynamics, which applies to the motion of celestial bodies. Newton’s law of gravitation scientifically and mathematically proved the relationship between gravity and the paths of planets.

Even prior to the time of Copernicus, numerous scientists and philosophers advocated for the Earth’s rotation, positing that it is easier to conceive of a small planet rotating than a vast universe.

Starting from the latter half of the 16th century, regular astronomical observations were conducted. These discoveries led to an increasing number of proofs for certain astronomical phenomena. It was determined that comets were not a result of atmospheric conditions, as Galileo had believed, which clearly demonstrated their movement in the vacuum of space rather than on celestial spheres. This confirmed that it is not the spheres that revolve around us, and at incredibly high speeds, but rather it is we who are revolving.

One more piece of evidence supporting the theory of Earth’s rotation was Galileo Galilei’s principle of relativity. Critics argued that if the Earth were rotating, an object dropped from a height would fall in the opposite direction of the rotation. However, the principle of relativity explained why the Earth’s rotation does not cause such a deflection when in uniform motion. Interestingly, even today, a stone dropped from a tower does not fall exactly perpendicular, with corresponding experiments only being conducted in the early 19th century.

For centuries, numerous anonymous scientists and astronomers have worked tirelessly to comprehend the mechanics of our universe. Their combined efforts have led to a new cosmology that posits the infinite nature of the universe.

The Sun is the center of our system, and the Earth and other planets orbit around it while also rotating on their own axes. This groundbreaking discovery was made possible by the collective contributions of Copernicus, Galileo, Newton, and numerous other scientists and philosophers.

Motion Speed

The Earth undergoes a rotation in an eastward direction.

Sidereal motion refers to the planet’s rotation around its axis relative to distant stars, while solar motion refers to rotation relative to the center of the Sun. The difference in rotation periods between the two is 3 minutes and 56 seconds. Solar rotation takes exactly 24 hours, while stellar rotation takes slightly less time (23 hours 56 minutes 4.09971 seconds).

The angular velocity can be calculated using the formula: 2 Pi ÷ stellar days = 7.29211115078-10-5-5 c-1.

The Earth orbits the Sun at a speed of 108,000 km/h (equivalent to 30 km/sec). Its orbital path spans approximately 940,000,000,000 kilometers. It completes one full revolution in approximately 365.242199 days.

Seasons

The Earth’s path around the Sun varies in distance, with the point of closest approach called perihelion and the point of farthest approach called aphelion. However, the seasons and temperature are not dependent on this variation. The difference between perihelion and aphelion is only about 1.5-2% of the average distance to the Sun, known as an astronomical unit, which is approximately 149,600,000 km. In other words, our orbit can be considered almost circular, and these small deviations have minimal impact on the changes in seasonal temperatures.

The Earth takes approximately 365.242199 average solar days to complete one orbit around the Sun, which is nearly equivalent to our calendar year.

The calendar year and the astronomical year differ slightly in length, resulting in the addition of an extra day every four years, known as a leap year. This extra day is added in February.

The Earth’s axis is oriented in such a way that at certain times, the south pole is closer to the Sun, while at other times, the north pole is closer. As a result, the southern hemisphere receives more sunlight during one period, while the northern hemisphere receives more sunlight during the other period. This phenomenon is responsible for the changing seasons. The angle between the Earth’s axis and the plane of its orbit, known as the ecliptic plane, remains constant at 23.4 degrees. From a front view, the north pole is positioned on the extreme left side facing the Sun, while the south pole is positioned on the extreme right side.

It is fascinating to note that the expression of seasonality at the equator differs significantly from that in the middle latitudes due to its minimal dependence on the axis of rotation. However, the angle at which the Sun is located relative to the Earth’s equator does change, and this angle determines the division of the seasons into four peak points. These points, known as the solstice and equinox points, mark the beginning of winter/summer and spring/autumn, respectively.

Equinox

The equinox is the moment when the Sun crosses the celestial equator. This means that the Sun is nearly perpendicular to the Earth’s equator, resulting in equal amounts of light and heat for both the northern and southern hemispheres.

The term “equinox” gets its name from the fact that on this date, day and night are almost equal in length. This balance between the Earth and the Sun occurs twice a year, marking the spring and autumn equinoxes, respectively.

Solstice

Solstices are the occurrences when the Sun is in its most extreme position in relation to the equator, meaning that the angle of deviation from the perpendicular to the Earth’s equator is the highest. These events, along with the equinox, happen twice a year. They are known as the winter solstice and the summer solstice, which take place on December 21-22 and June 20-21, respectively.

In the northern hemisphere, December 21 marks the day with the shortest daylight and the longest night. After this date, the daylight gradually increases (and the night decreases) until the reverse process starts on June 21. Daytime is defined as the period between sunrise and sunset. The principle of opposites also applies here: what is the shortest day in the northern hemisphere is the longest day in the southern hemisphere.

Changes in the position of the Sun above the horizon at noon can be observed at the local level in the middle latitudes. During the winter solstice, the Sun will be at its lowest point above the horizon, gradually rising higher with each passing day. Conversely, during the summer solstice, it will reach its highest point and then descend, resulting in shorter days as well.

Characteristics of the calendar

Due to the fact that the complete duration of the Earth’s orbit around the Sun is not divisible evenly by the number, the calendar year is approximated to 365 days for convenience. However, the actual duration is slightly longer, so approximately every four years an extra day is added. This year is known as a leap year, while the remaining years are non-leap years accordingly.

Nevertheless, even this does not result in a full correspondence, as the astronomical year between the equinoxes is (once again, approximately) around 365 days 5 hours and 49 minutes. Just another 11 minutes and it would be absolutely perfect, but this relatively insignificant gap also accumulates over larger spans of time.

After 128 years, an additional day has to be incorporated.

This peculiar observation was made in light of religious celebrations, which were meant to align with the equinox but, in reality, were nearly 10 days late by the 16th century (the equinox occurred earlier).

This error was rectified almost 16 centuries later following the implementation of the leap year (introduced in 45 BC, rectified in 1582 AD). Towards the conclusion of the 16th century, the calendar underwent a reform: it was no longer sufficient for a year to be divisible by 4 in order to qualify as a leap year. Years divisible by 100 were no longer recognized as leap years, with the exception of those that are also divisible by 400.

Causes of variations in seasons

Seasonal variations occur due to the Earth’s proximity to the Sun at different poles throughout the year, as the Earth’s axis is tilted relative to the plane of its orbit. As a result, the Sun, which provides the majority of the planet’s energy, warms the hemisphere that is closer to it more intensely. This cyclical motion around the Sun also leads to the cyclic change of seasons.

Additionally, geographical features such as the uneven distribution of mountains and plains, as well as the presence of water and land, can also impact weather patterns.

The temperature difference at the same latitude in different regions can be as high as 7 °C, and the duration of the warm period can vary significantly.

The Sun’s directed energy is delivered in a greater volume to the equatorial and nearby regions, resulting in a different perception of summer compared to the tropics or equatorial belt for residents of the middle zone of Russia. The same principle applies to other seasons.

The astronomical dates that mark the change of seasons are the days of equinox and solstice.

During an equinox, the Sun is at its maximum angle to the equator, signifying the change of autumn and spring seasons in different hemispheres. During a solstice, the Sun is perpendicular to the equator, marking the astronomical transitions between summer and winter seasons. The seasons are always opposite in different hemispheres.

Fascinating trivia

The phrase “leap year” originated from the Latin term bis sextus, which translates to “second sixth”. In the Roman calendar, one of the units of measurement was the “calendas” – the first day of the month. Therefore, a special designation was given to a date six days before the calendas, which in February was the 24th day. By adding one more day to February, Gaius Julius Caesar, who introduced the concept of leap year, effectively added a second sixth day to the date of the first day of March.

The Earth not only revolves around the Sun and spins on its axis, but the axis itself undergoes a revolution. In other words, if we envision a plane on which our planet orbits the star, the tilt of the axis is 23.4°, but the axis also undergoes a rotation around an imaginary line perpendicular to this plane. This occurrence is known as the precession of celestial bodies. However, the total revolution of our planet’s axis takes approximately 25,765 years, so this phenomenon has minimal impact on our day-to-day existence.

There are three different calendar systems: lunar, solar, and luni-solar. Each of these systems coordinates the months differently, with the lunar calendar following the phases of the Moon, the solar calendar based on the movement of the Sun, and the luni-solar calendar coordinating with both. A well-known example of a luni-solar calendar is the Hebrew calendar, which adds an entire month during leap years instead of just a day. Leap years occur every second or third year. Currently, we are in the year 5779 according to the Hebrew calendar. The Islamic calendar, on the other hand, indicates that it is now the year 1440. The Japanese calendar marks this as the 29th year of the Heisei era, which means “Peace Establishment.” Lastly, the Chinese calendar designates this year as 2019, the year of the Yellow Earth Pig.