In what way can you see the ecliptic on earth? Why?

There is no ecliptic in the world, and many people say it. So I can't see the ecliptic anywhere! No matter on the earth or on the celestial sphere, it only comes to mind, just like making auxiliary lines of geometric figures.

The ecliptic is an astronomical name invented by scientists for the convenience of research. It has no entity, just like the axis of rotation, celestial sphere and coordinate system. ...

First of all, what is the "ecliptic of the earth"? Simply put, the ecliptic is the orbital plane of the earth around the sun, and the equator of the earth is tilted by 23.5? The intersection of the equator and it is the vernal equinox and autumnal equinox. But the theory based on geocentric theory is the trajectory of the sun rotating around the earth, assuming that the earth is stationary.

The word ecliptic has existed since ancient times, and the earliest record is Historical Records in the Warring States Period. In the early years of the Eastern Han Dynasty, Liu Xiang also recorded that "the sun and the moon follow the ecliptic" in Wang Ji Lun. It seems that the ancients have long known that the ecliptic is the orbit of the sun above the earth.

How can we see the ecliptic? As mentioned earlier, the ecliptic is the imaginary plane of the sun's orbit, which is invisible to the naked eye. Since it is imaginary, you can only imagine it with your clever brain. If you have good hands-on ability, you can use paper and strokes.

Since the ecliptic is the trajectory of the sun, draw a sun first (many people don't draw the sun), which is easier to understand, then draw an earth next to it, and then draw an ellipse as the orbit of the earth's revolution. This orbit and the sun form a disk-shaped plane, which is the ecliptic plane.

Is it simple? Liao Liao drew it in a few strokes. Of course, you must have simple astronomical knowledge first.

If the ecliptic is an existing entity, it can be seen day and night as long as the sun shines on the earth.

The ecliptic plane comes from the movement of the sun, so there will be ecliptic in the whole solar system, and all the celestial bodies in the system will revolve around the sun in the orbit near this plane.

In the early solar system, the sun just formed, dragging a huge disk nebula to rotate. As time goes by, these nebulae gradually condense into planets under the action of universal gravitation, and at the same time they also revolve within the gravitational range of the sun. At the same time, due to the centrifugal force, angular momentum and other forces, the scattered nebulae and celestial bodies move further and slowly the equatorial plane of the sun moves closer. Under the influence of the solar wind, the lighter gaseous planets are blown far away, while the heavier terrestrial planets stay near the sun, forming a galaxy.

Then the earth, one of the eight planets, also orbits the sun, and its orbit around the sun is called the ecliptic plane. On earth, it is the orbit of the sun on the celestial sphere.

What is the ecliptic? In ancient times, we often said that "the zodiac is auspicious" refers to the zodiac! The so-called "auspicious day" is the day or time node when the influence of the sun on the earth is beneficial to human survival. Also known as "light track".

The orbit of the sun's annual movement imagined by the ancients. That is, the great circle where the earth's orbital plane around the sun intersects with the celestial sphere. Around 80 BC, China had a clear concept of the ecliptic, and measured the position of celestial bodies with the ecliptic as the basic circle.

The Book of the Later Han Dynasty quoted the star sutra in the Book of the Stone God of the Han Dynasty: "The zodiac rules lead the ox to fight straight for 20 degrees at the beginning and 25 degrees at the top (it should be 115 degrees)."

"Han Shi Tian Wen Zhi": "There is a middle way in the day and nine lines in the month. Middle way, ecliptic, bright way. Guangdao north to Tokyo, near the North Pole; South to Petunia, as far as the North Pole; East to the corner, west to the building, to the extreme. As for Tokyo from summer solstice, the north is close to the pole, so it is short; The table is eight feet, while the landscape (shadow) is five inches and eight minutes long. As for the morning glory in winter solstice, it is far away, so it is long; The table is eight feet, while the landscape is three feet, one inch and four minutes long. In the spring and autumn, it is divided into Lou and Jiao, and it is extremely neutral; The table is eight feet, and the landscape is seven feet, three inches and six points. This day is far away, and the length of the scene is also certain. It's hard to say how far you go, but you still have to look at the scenery. Those who watch the scenery know the north and south of the sky. "

Textual research on the four fields in the history of the New Five Dynasties: "The ecliptic is also the track of the sun. Half in the equator and half outside the equator, 24 degrees apart. "

When measuring the shadow of the sun on the ground, we can get the Taiji diagram of the 24 solar terms of the solar polar shadow.

Fig. 24 Taiji diagram of solar polar shadow in solar terms

Figure The daily trajectory of the sky "8"+the shadow of the sun on the ground "Taiji map"

So we will eventually get such a picture: the "8" day track map in the sky and the "Tai Chi map" of the sun shadow on the ground. Of course, in fact, the annual movement cycle of the sun not only leads to these synchronous phenomena, but these two are the most obvious astronomical phenomena!

How can I see the ecliptic on the earth? Let's take "Twenty-four solar terms" and "Zodiac" as examples to see the observation range of the ecliptic and equator:

Zodiac and equator

Twelve stars, because the 24 solar terms are determined according to the different visual positions of the sun on the ecliptic. The ancients divided the balance around the ecliptic into twelve o'clock, such as astrology and mystery. When the sun moves to a certain moment, it is called a solar term (in fact, 24 solar terms represent 24 different positions of the earth in its orbit around the sun). Twelve times correspond to the zodiac. )

Celestial orbits and solar terms in the western zodiac.

The yellow line is the ecliptic and the red line is the equator.

As can be seen from the above picture, the western zodiac signs are distributed on the circular track of the "Yellow Line", and the China zodiac signs are located around the "Twenty-four Solar Terms". The red line in the figure is the celestial equator (that is, the projection of the earth equator), and the determination of the vernal equinox needs to be observed by the rising intersection of the ecliptic and the celestial equator.

Zodiac map, zodiac equator

As we can see from the above picture, since there is no celestial equator above the western "ecliptic coordinate system", there is no celestial equator constellation, so it is naturally impossible to measure the "vernal equinox", and the "ecliptic zero degree" starts from the vernal equinox.

Figure 12 Dynamic diagram of the motion of the ecliptic on the celestial sphere.

From this dynamic picture, we can see that the zodiac is rotating along the ecliptic. In the absence of celestial-equatorial coordinate system, how did the West draw the all-sky star map? !

How to measure the ancient "winter solstice, spring and autumn equinox, summer solstice"?

China knew the concept of the ecliptic in ancient times. Although China is in the equatorial coordinate system, it is inevitable to know the ecliptic because of observing vernal equinox. The determination of the winter solstice is very important for the beginning of the calendar. It is impossible not to know that China already had the vernal equinox and autumnal equinox in the Western Zhou Dynasty, and these four solar terms have made a preliminary division of the four seasons!

But strangely, the "ecliptic coordinate system" used in the west does not use the "twenty-four solar terms" in the calendar, especially the "dichotomy". How can we know the four seasons without knowing this concept? How to make a calendar? How can there be "ecliptic" or even "ecliptic coordinate system" I can't help asking, is the ecliptic coordinate system really invented by the west? !

Because the earth's rotation axis (earth axis) is inclined to its orbital plane by 66 34'. This relationship between the earth's rotation and revolution is usually expressed by its complementary angle (23 26') in astronomy and geography, that is, the intersection angle between the equatorial plane and the orbital plane.

But this intersection angle is difficult to measure in reality. What should we do?

So we need "celestial equatorial coordinate system", which has actually been mentioned before, and now I will say it again.

To put it simply, imagine the sky as an imaginary big ball. All the celestial bodies we see are projections on this big ball, which is called the celestial sphere. The projection of the earth's orbit on the celestial sphere is the ecliptic, and from the earth, it is the circle that the sun passes through in the sky; The celestial equator is the projection of the earth's equator on the celestial sphere; The white road is the projection of the moon's trajectory in the sky on the celestial sphere.

The celestial equator is the projection of the earth's equator on the celestial sphere.

Therefore, the equator of the earth is projected on the celestial sphere, and the relative relationship between the sun and the equator of the celestial sphere is calculated by observing the relative position of the sun and the equator of the celestial sphere. In this way, we can observe the winter solstice, the vernal equinox and the summer solstice.

The moon on the map, vernal equinox and autumnal equinox, summer and winter solstice and Huang Chibai Road.

Therefore, the inclination angle between the earth's axis and the orbital plane is expressed by the intersection angle between the ecliptic and the celestial equator on the geocentric celestial sphere, which is also called the intersection angle between the ecliptic and the Huang Chi distance. However, it is a pity that only the mid-latitude areas can observe the phenomenon of "inclination" of the earth!

It's a little emotional that ancient astronomy in China was described by astrology, numerology and medicine. It is often said that Chinese medicine is metaphysics and its theory is unpredictable, which is ignorance of China tradition.

However, few people know the knowledge of ancient astronomy today. At the end of the Ming Dynasty, Gu said, "Everyone knows astronomy for more than three generations. "Fire in July" is the words of farmers; Samsung is in the sky', the language of women is also; The end of the month', the merit of guarding the pawn; The story of "The Long Tail Theory and Chen Fu" is also a rumor aimed at children. Later scholars learned the soil, and the questioner was at a loss. " ("Rizhilu" Volume 30). Because of this, many people in China can't understand the culture of China!

If you know the basic knowledge of ancient astronomy in China, you can learn a lot about China culture. Only by observing the celestial phenomena for a long time can we know that the ancients were not stupid and understand their concept of time and space, and then we can make such a sound of "harmony between man and nature"!

The starry sky, the sun and the moon are the only means for the ancients to understand the universe. At this point, there are many similarities between the East and the West. For example, there are zodiac signs in foreign countries, zodiac signs in China, sundials in China and sundials abroad. These similarities are too numerous to mention, all of which stem from the observation of the same objective phenomenon. However, it must be mentioned that when the West can combine the precise timing system obtained by machinery with the telescope obtained by glass (both machinery and glass come from the demand of the church to build the main church, bell tower and colored windows), it will leave the East behind in the understanding of celestial bodies.

References: 1. The dance between heaven and earth, the "harmony between man and nature" in ancient China and the trajectory of Xuan Ji (the zodiac); Observation range of ecliptic and equator

The ecliptic is invisible, just an imaginary plane that exists in theory. Now let's use our imagination. First of all, we should know that the earth we live in is spherical and the universe is vast and huge. Although the universe is limited, because the earth is too small in the universe, we can imagine the universe as boundless.

In this boundless universe, there are 10 trillion galaxies and trillions of stars. Our sun is just an ordinary star among these trillions of stars, and the earth is just a satellite planet of the sun, with a mass about one third of that of the sun.

We can also imagine that with the earth as the center, the whole universe surrounds our earth, so we call the sphere around the earth a celestial sphere.

The earth is wrapped in this celestial sphere and rotates around the sun once a day and once a year. Thus, from the earth's point of view, it seems that both the celestial sphere and the sun revolve around us. Every day, the celestial sphere rotates once and the sun rises in the east and sets in the west.

This is also the origin of ancient geocentric theory.

In a year, the sun moves on the big screen with the celestial sphere as the background, once a year, from the position of a star to the position of a star. In this way, the sun revolves around the celestial sphere, forming a surface, cutting the celestial sphere in half, and this surface is called the ecliptic surface.

In fact, stars are constantly moving, just because they are too far away from us and the nearest ones are several light years away, so their movement is very small compared with the distance to us. From this point of view, they seem to have changed very little, and have hardly changed for thousands of years. Ancient people thought they were eternal, so they called them stars.

In this way, humans can draw the ecliptic with the stars as the reference coordinates on the celestial sphere.

To put it simply, we can draw a circle on paper with the sun in the middle and a small ball on the circle. This small ball is the earth. This circle is the earth's orbit around the sun. Draw this circle with yellow pigment, and this yellow face is the ecliptic.

So you can see the ecliptic. We can also imagine the earth spinning like a football. This rotation has an imaginary axis of rotation, which runs through the north and south poles of the earth, and the earth rotates around this axis.

Every rotating ball has a surface point, which produces the longest circumferential line with the rotation of the ball. The plane of the longest circumference of a right circular ball makes an angle of 90 degrees with the axis. The earth's rotation also has such a circle, which is called the equator. Because the earth's rotation axis is not perpendicular to the ecliptic plane, it forms an angle of 66 34' with the ecliptic plane, so the equator of the earth is not in the same plane, but forms an angle of 23 26'.

Don't underestimate this included angle. It is this angle that makes the position where the earth receives direct sunlight constantly change on the earth, forming the Tropic of Cancer, which leads to the alternation of cold and hot temperatures throughout the year and creates the necessary conditions for the birth and evolution of life.

The reason why the earth turns its neck askew is because it collided with a planet the size of Mars when it was born.

This is a long story, which is not discussed in this article. Let's stop here.

Welcome to the discussion and thank you for reading.