The moon does not have its own light, but its surface reflects the sun's rays, so it serves as our night luminary. During eclipses, our satellite turns red, which is why lunar eclipses are sometimes called “blood moons.”
Why do lunar eclipses occur?
These celestial phenomena occur when the Sun, Earth and Moon line up in a straight line. The Sun is behind the Earth, as a result the Earth casts a shadow on the Moon, and a lunar eclipse occurs.
They always occur on a full moon, but we cannot observe a lunar eclipse on every full moon. This is because the Moon's orbit is inclined at an angle of 5 degrees to the Earth's orbital plane, also known as the ecliptic (Earth's path around the Sun). The points where the two orbits intersect are called the lunar nodes, and eclipses can only occur when the full moon occurs near the lunar node. In other cases, the Earth cannot cast a shadow on the surface of the Moon.
Thus, for a lunar eclipse to occur, two conditions must be met:
Full Moon in the heavens;
The proximity of the Earth to one of the lunar nodes.
Types of lunar eclipses
There are 3 types: full, partial and penumbra.
A total lunar eclipse occurs when the central (dark) part of the Earth's shadow covers the entire visible side of the Moon. The Earth's shadow is about 1.4 million kilometers wide.
A partial lunar eclipse can be observed when only part of the visible surface of the Moon is covered by the Earth's shadow.
When the Sun, Earth and Moon are not in a perfectly level line, only the outer part of the Earth's shadow (penumbra) eclipses the Moon. Such an eclipse is called a penumbral eclipse.
Why does the moon turn red
Even if the Earth completely blocks sunlight from hitting the Moon's surface, our satellite is still visible in the skies. This occurs because the Earth's atmosphere refracts sunlight and indirectly illuminates the lunar surface. During a total lunar eclipse, the Moon darkens and turns red because the Earth's atmosphere is most permeable to rays of the red color spectrum. However, the Moon can also appear yellow, orange or brown because clouds and dust particles are present in the Earth's atmosphere, allowing waves of different lengths to reach the surface of our satellite.
Where can you see lunar eclipses?
This celestial phenomenon can be seen by everyone who is on the night side of the Earth. It can be observed with the naked eye. The chance of seeing a lunar eclipse is much higher than a solar eclipse (it is visible only in a narrow band in certain areas of the Earth), although both occur at similar intervals. In one calendar year there can be two lunar eclipses (about six months apart), sometimes three, but in some years none occur.
Myths and beliefs about eclipses
The ancient Incas believed that lunar eclipses were caused by a jaguar trying to devour the moon. The red or blood-red color that the earth's satellite turns during a total lunar eclipse was explained by the attack of a big cat. The Incas were afraid that after attacking the Moon, a huge jaguar would crash to Earth and start eating people. They tried to drive him away with noise and screams, and teased the dogs to bark loudly.
However, jaguars were not the only predators in mythology that wanted to eat the heavenly body. The people of ancient Mesopotamia also saw eclipses as attacks on the moon, but in their story the attackers were seven demons. Other peoples had similar beliefs, which included bloodthirsty dragons and other mythical creatures.
The Hupa American Indians of Northern California believed that Luna had 20 wives and many animals, most of them mountain lions and snakes. If they did not bring enough food, they attacked and inflicted wounds, then the blood turned the Moon red. The eclipse ended when the wives came to protect them, drove away the predators and healed the Moon.
The Indians of Southern California believed that the eclipse signaled that the moon was ill, so they sang chants and prayed for her to return to health.
Not all ancient cultures attributed negative meanings to lunar eclipses. According to a myth from Benin, the Sun and Moon fight each other, and people come to their aid to judge them. The ancient inhabitants of Benin believed that on the days of lunar eclipses it was necessary to get together, resolve old feuds and restore good relations.
Moon phases and eclipses
The Moon constantly changes its appearance from a narrow crescent to a full disk, brightly illuminated by the Sun.
The phases of the Moon are associated with a constant change in the relative positions of the Moon, Earth and Sun, which occurs as a result of the rotation of our satellite around the Earth.
The Moon is invisible (this is a new moon) when it is between the Sun and the Earth on a straight line connecting these two luminaries; in this position, the unlit part of the lunar surface faces us. If the Moon is located on the side opposite to the Sun, its reflected light falls on the Earth. It's a full moon. If the angle between three celestial bodies is 90°, only half of the illuminated disk can be seen from Earth (First Quarter and Last Quarter). In the intermediate stages of the arrangement of the luminaries, a crescent (more or less narrow) can be observed. The lunar cycle begins with the new moon. After it, the Moon begins to grow and after about two weeks the full moon occurs, followed by a decrease in the Moon. “Age of the 1st Moon” is determined from the new moon.
The Moon revolves around the Earth, which moves counterclockwise (i.e. from west to east). If you watch the Moon at the same time on different days, its deviation to the east will be noticeable against the background of the stars. It will appear and fade 50 minutes later than on the previous day.
Sidereal and synodic months
The moon makes a full revolution in its orbit in a certain time. There are two ways to de-terminate this time. It should be taken into account that during the Moon’s revolution around the Earth, the latter is by no means a stationary body - in turn, our planet rotates around the Sun. The period of rotation of the Moon around our planet, calculated in relation to the stars (we define their position as fixed) lasts 27 days 7 hours 43 minutes and 11 seconds. This is the “sidereal month”. But the time required for Lupa to completely change phases is somewhat different, because the movement of the Earth should also be taken into account.
The full period of changing phases of the Moon is called a “synodic month” and is 29 days 12 hours and 44 minutes.
Eclipses yes, eclipses no
When the Sun, Moon and Earth line up in space in a straight line, eclipses occur. They come in two types: solar and lunar. During solar eclipses, the Moon is between the Sun and the Earth and completely or partially obscures the luminary from us.
When the Earth is between the Sun and the Moon, a lunar eclipse occurs: the satellite falls into the shadow of the Earth.
If the plane of the lunar and earth's orbits coincided, eclipses would occur approximately once every two weeks, that is, once per synodic month. But the planes are inclined to each other at an angle of 5° and intersect along a line called the “line of nodes.” “Nodes” are the two points of intersection of the lunar orbit with the ecliptic.
Simply finding the Earth's satellite in the “correct phase” is not enough for a lunar eclipse. It is necessary that the Moon be close to one of the nodes. Only during the full moon can you see a lunar eclipse, and a solar eclipse - during the new moon.
Eclipses repeat in the same sequence. This period of repetition of eclipses is called “saros”. Even in ancient times, it was calculated that it lasts 6585.3 days, which is 18 years, 11 days and 8 hours (if there were 4 leap years during this period).
An eclipse is considered total when the Moon completely covers the solar disk. There are not many places from which a total solar eclipse can be observed: the shadow from the Moon “sweeps” the earth’s surface, leaving a stripe whose maximum width is about 200 km. This is the area from which the eclipse appears as total. Around this area there is another, vast one, from there the eclipse looks partial. The maximum duration of a total eclipse is approximately 8 minutes.
Annual eclipses occur when the shadow of the Moon does not completely cover the Sun; the outer part of the solar disk is visible in the shape of a ring. This spectacle depends on the distance between the Moon and the Earth, and it is not a constant value, because The lunar orbit has a pronounced elliptical shape. When a satellite is closer to our planet, it appears larger; when it moves away, it appears smaller. When an eclipse occurs at a greater distance from the Earth, the diameter of the lunar disk is too small to cover the entire Sun.
Lunar eclipses
Lunar eclipses are easier to observe; they are visible from almost half of the earth's surface, from the entire hemisphere not illuminated by the Sun. They last for several hours, between the phase of darkness and twilight, since the Moon takes a long time to cross the cone of the Earth's shadow.
It is through this time period that eclipses are repeated with similar characteristic features.
Different types of solar eclipses
Solar eclipses can be total, partial or annual.
Gianluca Ranzini
Once, after during one of the expeditions of Christopher Columbus, all food supplies and water on the ship came to an end, and attempts to negotiate with the Indians did not bring success, knowledge of the approaching lunar eclipse provided the navigator with a colossal service.
He told the local residents that if they did not send him food by the evening, he would take away the night star from them. They only laughed in response, but when the moon began to darken at night and acquired a crimson hue, they were simply horrified. Water and food supplies were immediately delivered to the ship, and the Indians on their knees asked Columbus to return the luminary to the sky. The navigator could not refuse their request - and a few minutes later the Moon shone in the sky again.
A lunar eclipse can be seen on a full moon, when its shadow falls on the Earth’s satellite (for this, the planet must be between the Sun and the Moon). Since the night star is separated from the Earth by at least 363 thousand km, and the diameter of the shadow cast by the planet is two and a half times the diameter of the satellite, when the Moon is covered by the Earth's shadow, it turns out to be completely darkened.
This does not always happen: sometimes the shadow partially covers the satellite, and sometimes it does not reach the shadow and ends up near its cone, in the penumbra, when only a slight darkening of one of the edges of the satellite is noticeable. Therefore, in lunar calendars, the degree of darkness is measured in values from 0 and F:
- The beginning and end of the partial (partial) period of the eclipse – 0;
- The beginning and end of the private phase – from 0.25 to 0.75;
- Beginning and end of the total period of the eclipse – 1;
- The period of the highest phase is 1.005.
Lunar nodes
One of the indispensable conditions necessary for the occurrence of a total lunar eclipse is the proximity of the Moon to the node (at this point the lunar orbit intersects the ecliptic).
Since the plane of the orbit of the night star is inclined to the plane of the earth's orbit at an angle of five degrees, the satellite, crossing the ecliptic, moves towards the North Pole, upon reaching which it turns in the opposite direction and moves down to the South. The points where the satellite's orbit intersects the points of the ecliptic are called lunar nodes.
When the Moon is near a node, a total lunar eclipse can be seen (usually every six months). It is interesting that it is not typical for the lunar nodes to constantly remain at one point on the ecliptic, since they constantly move along the line of the Zodiac constellations against the course of the Sun and Moon, making one revolution every 18 years and 6 months. Therefore, it is best to determine when the next total lunar eclipse will be using the calendar. For example, if they occurred in November and May, then next year they will occur in October and April, then in September and March.
When a miraculous phenomenon occurs
If the Moon's orbit always coincided with the ecliptic line, eclipses would occur every month and would be an absolutely common occurrence. Since the satellite is mainly located above or below the Earth's orbit, the shadow of our planet covers it two, maximum three times a year.
At this time, the new or full Moon is just near one of its nodes (within twelve degrees on either side), and the Sun, Earth and Moon are located on the same line. In this case, you can first see a solar eclipse, and two weeks later, during the full phase of the moon, a lunar eclipse (these two types of eclipses always come in pairs).
It happens that a lunar eclipse does not occur at all: this happens when the Sun, Earth and Moon are not on the same line at the right moment, and the earth's shadow either passes by the satellite or affects it with penumbra. True, the event is practically indistinguishable from Earth, since the brightness of the satellite at this time decreases only slightly and can only be seen through telescopes (if the Moon, being in a penumbral eclipse, passes very close to the shadow cone, you can see a slight darkening on one side) . If the satellite is only partially in the shadow, a partial lunar eclipse occurs: part of the celestial body darkens, the other remains in partial shade and is illuminated by the rays of the Sun.
How does an eclipse occur?
Since the Earth’s shadow is much larger than its satellite, it sometimes takes a lot of time for the night star to pass it, so a total lunar eclipse can last either a very short period of time, about four to five minutes, or more than an hour (for example, the maximum recorded duration of the phase on the night of the lunar eclipse was 108 minutes).
The duration of this phenomenon will largely depend on the location of the three heavenly bodies to each other.
If you observe the Moon from the northern hemisphere, you can see that the Earth's penumbra covers the Moon on the left side. After half an hour, the satellite of our planet is completely in the shadow - and on the night of a lunar eclipse, the star acquires a dark red or brown tint. The sun's rays illuminate the satellite even during a total eclipse and, passing along a tangent line relative to the earth's surface, are scattered in the atmosphere, reaching the night star.
Since red has the longest wavelength, it, unlike other colors, does not disappear and reaches the lunar surface, illuminating it with a red color, the hue of which largely depends on the state of the earth's atmosphere at a given moment. The brightness of the satellite on the night of a lunar eclipse is determined by a special Danjon scale:
- 0 – total lunar eclipse, the satellite will be almost invisible;
- 1 – The moon is dark gray;
- 2 – Earth satellite of gray-brown color;
- 3 – the Moon is characterized by a reddish-brown tint;
- 4 is a copper-red satellite, visible very clearly and all the details of the lunar surface are clearly visible.
If you compare photos that were taken on the night of a lunar eclipse at different times, you will notice that the color of the Moon is different. For example, the Earth's satellite during the summer eclipse of 1982 was red, while in the winter of 2000 the Moon was brown.
History of the lunar calendar
People have long understood how important the role the Moon plays in the life of the planet, and therefore they planned all their activities based on its phases (new moon, full moon, waning, eclipses), since they were the most observed celestial phenomena.
It is not surprising that the lunar calendar is considered the most ancient calendar in the world: it was by it that people in the early stages of their development determined when to start and finish sowing work, observed the influence of the Moon on the growth of vegetation, the ebb and flow of tides, and even how night the luminary affects the human body, which, as is known, contains a large amount of liquids.
It is impossible to determine which people were the first to create the lunar calendar. The first objects that were used as lunar calendars were found in France and Germany and were created thirty thousand years ago. These were crescent-shaped marks or sinuous lines on cave walls, stones or animal bones.
Also found were lunar calendars created eighteen thousand years ago in Russia near the city of Achinsk in the Krasnoyarsk Territory. A calendar was also found in Scotland, which is at least ten thousand years old.
The Chinese gave a modern look to the lunar calendar, who already in the 2nd millennium BC. formed the main provisions and used it until the 20th century. Also, an important role in the development of the lunar calendar belongs to the Hindus, who were the first to give basic descriptions of the phases, lunar days and positions of the Moon relative to the Earth and the Sun.
The lunar calendar was replaced by a solar one, since during the formation of a sedentary lifestyle it became obvious that agricultural work was still more tied to the seasons, that is, to the Sun. The lunar calendar turned out to be inconvenient due to the fact that the lunar month does not have a stable time and is constantly shifted by 12 hours. There is one extra lunar year for every 34 solar years.
Nevertheless, the Moon exerted sufficient influence. For example, the modern Gregorian calendar, adopted about five hundred years ago, contains such statements, drawn from lunar calendars, as the number of days in the week and even the term “month”.
– is this a bad omen?
Lunar eclipses instilled real panic in ancient people. Entire generations of people considered lunar eclipses a bad omen until man mastered science and some laws of cosmic and universal scales. It was believed that the burgundy color of the Moon signifies the approach of war, blood, and death. Fortunately, science was able to remove the veil of mystery from this phenomenon, and all supernatural ideas about lunar eclipses have sunk into oblivion.
When do lunar eclipses occur?
They appear at certain times, but only when there is a full moon. At this time, the night star begins to pass away from the Earth, opposite the Sun. Here the Moon can fall into the shadow cast by the Earth at this time. That's when people can watch.
How do lunar eclipses occur?
They occur differently from solar ones. The fact is that the Moon does not disappear completely, as the Sun does during a solar eclipse. The moon is only faintly visible. This happens for the following reason: part of the sun's rays, passing through the earth's atmosphere, are refracted in it and enter inside the earth's shadow, falling directly on the Moon. It is known that the air transmits red rays of light, which is why the night star turns brown or copper-red.
It is known that the diameter of the Earth is exactly 4 times greater than the diameter of the Moon. Accordingly, the shadow of the Earth is 2.5 times larger than the Moon. All this leads to the fact that the night luminary can sometimes completely enter the earth's shadow, which causes a total lunar eclipse. Scientists have calculated and come to the conclusion that total lunar eclipses are longer than total solar eclipses and can last up to 1 hour 40 minutes!
According to astronomers' observations, up to three lunar moons can occur in one year. It is worth noting that they repeat exactly after the same period of time as solar eclipses, which is equal to 18 years 11 days and 8 hours. Scientists even gave this period a name: saros (repetition). It is curious that saros was calculated in ancient times, so calculating and predicting the exact day is not difficult. But predicting the exact time of its occurrence, as well as the conditions for its visibility, is a more difficult task: different generations of astronomers have been studying the movement of the Moon and the Earth for centuries to solve this problem. Currently, possible errors in calculating the moments of lunar eclipses do not exceed 4 seconds!
A lunar eclipse is observed when the Earth's satellite enters the shadow that our planet casts from the Sun, that is, the Earth in this case is between the luminary and the Moon. In this case, the Moon can only partially fall into the shadow, or it can be completely covered by it, so a distinction is made between partial and total eclipses. Every year you can observe two or more lunar eclipses with different phases.
Instructions
When the Sun shines on the Earth, a cone of dense shadow is formed on the other side of the planet, surrounded by penumbra. If the Moon at this moment partially or completely enters this cone, a lunar eclipse will be observed from the surface of the planet on the side where our satellite is visible. It does not look as impressive as the sun, but it is easier to observe. The brightly lit Moon slowly begins to veil, but remains visible thanks to scattered rays of sunlight in the Earth's atmosphere, which illuminate its surface with a reddish light. An eclipse can last for more than 30 minutes; the Moon gradually emerges from the shadow and is illuminated by the Sun again. If the eclipse is partial, then only part of the satellite becomes dark. In some cases, the Moon does not enter total shadow, but remains in partial shadow - the eclipse is called penumbral.
On average, 2-3 lunar eclipses occur every year, but in some years this phenomenon is not observed at all, and in other years you can see 4 or even 5 lunar eclipses. The number of eclipses varies from year to year with a certain frequency, which repeats every 18 years and 11 days. This period is called the saros or draconic period. During this period, 29 lunar eclipses occur - 12 less than solar eclipses. Two thirds of all eclipses are partial, one third are total.
Nowadays, even a junior schoolchild is unlikely to be frightened by stories about a terrible wolf who lives in the night and at times devours the Moon in the black sky, foreshadowing misfortune.
However, until relatively recently, by astronomical standards, a lunar eclipse caused horror among humanity. Many cave paintings depict this astronomical phenomenon, which was mainly interpreted as a sign of the wrath of the gods and a harbinger of misfortune. And the blood-red appearance of the Moon clearly hinted at imminent bloodshed. In ancient China, for example, such an eclipse was considered “abnormal” or even “terrible.” In ancient Chinese texts you can find hieroglyphs that mean “the unnatural connection of the Moon and the Sun,” “devour,” “misfortune.” Court astronomers believed that the Moon was being “devoured by a dragon.” In order to help the dragon spit out the luminary as quickly as possible, residents took mirrors out into the street, since the latter were associated with celestial bodies due to their ability to reflect light. It is noteworthy that mathematicians of Ancient China already during the Han Dynasty (206 BC - 220 AD) could predict both lunar and solar eclipses for many decades in advance, but this knowledge was kept secret . The Indian Mahabharata says that a lunar eclipse occurs when the gods of the Indian pantheon gather to brew soma, the elixir of immortality. The Vikings firmly believed that two voracious wolves took turns devouring the stars to satisfy their unbridled hunger. Unlike other peoples, the Australian aborigines, on the contrary, associated a lunar eclipse with love.
Early astronomers and eclipse predictions
How did people’s attitudes towards such an interesting astronomical event change? As mentioned above, in Ancient China, despite the deep mystical attitude towards eclipses, astrologers inquisitively studied this natural phenomenon. Thanks to the high development of mathematics and algebra in the Middle Kingdom, ancient scientists managed to unravel the astronomical mystery. It turned out that using seemingly simple mathematical calculations, it is possible to predict the onset of a lunar eclipse with a high degree of probability. There is evidence that even earlier, during the reign of the great Pharaohs of Ancient Egypt, people were already able to predict many astronomical phenomena. But what is most striking is that almost before the construction of the Egyptian pyramids, there was an entire observatory capable of predicting not only lunar eclipses, but also charting most of the most important astronomical events related to our planet, its satellite and the Sun. The famous Stonehenge made it possible to make a large number of predictions and observations of astronomical phenomena, and it deservedly bears the title of the oldest observatory of mankind.
How everything works
But what is the genius of ancient astronomers and mathematicians? What could be so complex hidden in such a seemingly simple phenomenon as the eclipse of the Moon by the Earth? Let's try to understand this issue. After the discovery of the heliocentric system of the world by Nicolaus Copernicus, it became clear that the Moon, revolving around the Earth in 29.5 days, crosses the ecliptic plane twice at the so-called lunar nodes. The node, crossing which the Moon goes up to the North Pole of the Earth, is called North or Ascending, the opposite is called Lower or Descending. But due to the discrepancy between the planes of the Lunar and Earth orbits, not every full moon is accompanied by an eclipse.
Total, partial and partial eclipses
Also, not every lunar eclipse is total. And if the full moon occurs when the Moon passes such a node, then we will be able to observe an eclipse. But only half of the globe can observe this phenomenon, since it will only be visible where the Moon is above the horizon. Due to the precession of the Moon's orbit, the nodes move along the ecliptic. The nodes complete a full cycle along the ecliptic in 18.61 years or in the so-called Draconian period. That is, Lunar eclipses occur exactly after this period of time. Knowing where and when the eclipse took place, you can predict the next similar event with very high accuracy. Essentially, an eclipse occurs when the Moon enters the cone of the shadow cast by the Earth. At the distance of our satellite's orbit, or 384,000 kilometers, the diameter of the shadow spot is approximately equal to 2.6 times the disk of the Moon. As a result, the Moon may well be completely darkened, and the maximum time of the total eclipse phase may be no more than 108 minutes. Such eclipses are called Central eclipses because the Moon passes through the center of the shadow cast by the Earth.
Why is the moon "blood"?
It is noteworthy that even when the Moon passes through the center of the shadow, it does not remain completely dark. The fact is that under the influence of the Earth's atmosphere, sunlight is refracted, which leads to partial illumination of the surface of the Moon even at the peak of the eclipse. And because our atmosphere is most permeable to the orange-red spectrum of sunlight, it is this light that reaches the surface of the Moon, turning it blood red. A similar effect can be seen in the sky after sunset or before dawn. However, if the Moon does not pass through the center of the Earth's shadow, then a so-called incomplete or penumbral Lunar eclipse may occur, as a result of which part of the satellite will remain illuminated.
The rarest and most unusual lunar eclipses
In addition to the above facts, there is another no less surprising one. Paradoxically, a lunar eclipse can actually be observed when both the Moon and the Sun are above the horizon and are clearly not exactly at opposite points. In other words, a lunar eclipse can be observed when the rising or setting Moon is on your left, and the Sun is on your right, also in one of two phases. This phenomenon may occur due to the fact that the Earth's atmosphere bends the movement of light. This is one of the strangest natural phenomena that can occur, and which at first glance seems impossible, considering that an eclipse occurs when three bodies line up (syzygy). This anomaly occurs due to atmospheric refraction. The sun has actually already set, and the moon has not yet risen, but the lensing of light by the Earth's atmosphere distorts the surrounding astronomical reality. As a result of the “double” displacement of celestial bodies, their apparent convergence occurs by more than 1 degree of the great circle.
This kind of incredible eclipse was observed by Pliny the Elder on February 22, 72 AD. But the exotic views of lunar eclipses do not end there. Sometimes the Moon passes through the shadow of the Earth, being in the so-called supermoon, that is, the point of closest approach to the Earth. Since the Moon’s orbit is eccentric, at certain periods of time our satellite either approaches the Earth or moves away. When all circumstances coincide, along with the coincidence of the full moon and the passage of the Moon through the orbital node, the maximum approach of the Moon to the Earth also occurs. The last total lunar eclipse with a supermoon occurred on the morning of September 28, 2015. In addition, a lunar eclipse may coincide with the summer or winter solstice. On December 21, 2010, for the first time in 372 years, a lunar eclipse coincided with the winter solstice. The next time something like this will happen will only be on December 21, 2094.
When is the next Lunar Eclipse?
Next year 2016 there will be two lunar eclipses: March 9 at 5:57 am and September 1 at 13:06 Moscow time. Not only will daytime illumination interfere with enjoying the eclipse in both cases, but the eclipses themselves will be only penumbral.
Lunar eclipse of October 8, 2014 compressed to 1 minute