Why can't we see the full moon. Why does the moon come in different shapes? Why does the moon glow

As you know, the moon does not emit light, but only reflects it. And therefore in the sky only that side of it, which is illuminated by the Sun, is always visible. This side is called the day side. Moving across the sky from west to east, the Moon overtakes and overtakes the Sun during the month. There is a change in the relative position of the Moon, Earth and Sun. In this case, the sun's rays change the angle of incidence on the lunar surface and therefore the part of the Moon visible from the Earth changes. The movement of the moon across the sky is usually divided into phases directly related to its modification: new moon, young moon, first quarter, full moon and last quarter.

Moon observations

The moon is a spherical celestial body. That is why, when it is partially illuminated by sunlight from the side, the appearance of a “sickle” appears. By the way, by the illuminated side of the Moon, you can always determine which side the Sun is on, even if it is hidden behind the horizon.

The duration of the complete change of all lunar phases is usually called the synodic month and it ranges from 29.25 to 29.83 Earth solar days. The duration of the synodic month varies due to the elliptical shape of the lunar orbit.

On the new moon, the disk of the Moon is absolutely invisible in the night sky, since at that time it is located as close as possible to the Sun and at the same time faces the Earth at night.

Next comes the new moon phase. During this period of time, for the first time in a synodic month, the Moon becomes visible in the night sky in the form of a narrow crescent and can be observed at dusk a few minutes before it sets.

Next comes the first quarter. This is the phase in which exactly half of its visible part is illuminated, as in the last quarter. The only difference is that in the first quarter, the proportion of the illuminated part at this moment increases.

The full moon is the phase in which the lunar disk is visible clearly and completely. During the full moon for several hours, you can observe the so-called opposition effect, in which the brightness of the lunar disk noticeably increases, while its size remains the same. This phenomenon is explained quite simply: for an earthly observer, at this moment all shadows on the surface of the Moon disappear.

There are also phases of the growing, waning and old moon. All of them are characterized by a very narrow crescent of the Moon, a greyish-ashy color typical of these phases.

From all of the above, we can conclude that, in fact, nothing obscures the Moon. It just changes the angle of its illumination by the sun's rays.

Moon phases

On a clear cold autumn night, you go outside. The moon has just risen, a huge round orange moon. A few days later, you notice that the moon is no longer so round. A few more days pass - the moon has turned into a horned month. After two weeks, the moon disappears altogether.

Why does the moon change shape?

What happened? Why is the Sun always facing us with its round, sparkling face, while the Moon has phases? The moon passes them regularly every month, either increasing or decreasing, like a balloon that is either inflated or released from it.

In reality, of course, the Moon always remains a ball, invariably hard and rocky. What actually changes is the amount of part of the illuminated surface of the Moon that we can see.

The Moon makes one revolution around its axis in almost the same time that it makes one revolution around the Earth (in 27/3 days), so the Moon almost always faces the Sun with only one side. But it is wrong to think that eternal night reigns on one side of the moon. Although slowly, but the change of day and night is still happening.

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Why do the moon and sun change color? Description, photo and video

Why does the moon glow?

What we call moonlight is actually sunlight reflected off the gray rocky surface of the moon. The Moon moves with the Earth around the Sun and is illuminated by the Sun. As the Moon moves, we see either a larger or a smaller part of the illuminated surface of the Moon, that is, the position of the Moon in relation to the Earth changes all the time.

What we call the "phases" of the moon are the angles from which we see the illuminated part of the moon. When we see it in full, this position is called the full moon. When, after a few days, the Moon becomes "flawed", we already see part of its illuminated half (the first quarter after the full moon).

To understand how the moon rotates, take a doll (it will be the Earth) and a car (it will be the Moon).
1) Put the doll on the table, take the car and drive it around the doll in a circle. If you were in the place of the doll, you would see only one side of the car all the time.
2) Now remove the doll and drive the car around again, but watch it so that your eyes are at the level of the table. The machine has made a complete revolution around its axis, and you have seen all its sides.

The moon shines because it reflects the sun's rays. The Moon, together with the Earth, revolves around the Sun and around the Earth itself - therefore, the visible part of its illuminated surface changes - from a full disk to a thin sickle, and this depends on all factors at once - and on the position of the Sun, and on the position of the Earth, and of course itself Moon, as well as from their relative position. On the new moon, we do not see the moon at all, because it is turned to us with its dark side. Then a thin sickle appears in the sky, it grows and turns into a crescent. Being behind the Earth (not falling into its shadow), a full disk is visible - a full moon is coming. Then everything goes in reverse order. When the moon is between the full moon and the new moon, it is called defective.

What is an eclipse?

Sometimes, moving around the Sun, the planets cast shadows on each other. The moon, being between ours and the Earth, partially or completely covers the Sun. The shadow from it falls on the Earth, and then a solar eclipse occurs. During a total eclipse, the sky darkens, and only one corona remains from the Sun, which can be seen through special filters. A lunar eclipse occurs when the Moon enters the Earth's shadow. However, the Moon does not disappear, but acquires a reddish hue, because the sun's rays scattered in the Earth's atmosphere fall on it.

moon crescent

If the crescent of the Moon is turned with a hump to the right and it can be turned into the letter "P" by attaching a vertical stick to the tips of the "horns", then the Moon "R" is astet. If the sickle is in the shape of the letter "C", then the Moon "C" is fading.

Why do we only see one side of the moon?

The moon revolves around the earth in a counterclockwise direction, making a complete revolution in 27.3 days. It takes the same amount of time to turn around on its own axis. That is why the Moon always faces us with one side, and it seems to us that it does not rotate at all. But try to observe the moon as if from the side.

Moon month

The period between two new moons is called a lunar month. It lasts about 29.5 days.

The side of the Moon facing the Earth is colored yellow. Having made a complete revolution around the Earth, the Moon also made a complete revolution around its own axis.

Some people answer this question without hesitation: the moon is covered by the shadow of the Earth. This is the wrong answer, because the shadow of the Earth is always directed in the direction opposite to the Sun, and Moon, moving in its orbit, circumnavigates the earth on all sides.

“Astronomers carefully study the motion of the moon and describe it formula, containing a total of about 700 component, and the calculations are carried out with an accuracy up to 15 decimal places”(I.A. Klimishin “Astronomy of Our Days”, M. “Nauka”, third edition, p. 95).

Such accuracy is necessary for astronautics.

In this article, without going into details, we will consider only the simplest question: why does the appearance of the Moon change, or, in other words, why does the lunar phases and conditions of their visibility change.

The figure shows that wherever the Moon is in orbit, half of it is illuminated by the Sun, here it is day on the Moon, and the second half is dark, night. An observer from Earth can only see the side of the Moon that faces the Earth. Only the part that is illuminated by the Sun is visible from it. The outer circle of the figure shows what the Moon looks like from the point of view of an observer standing on the Earth. In position (1), a large part of the night side of the Moon and a small fraction of the day side are facing the earthly observer, it is she who looks like a narrow crescent. With each passing day, the Moon advances in its orbit, as shown by the arrow, and the appropriate earthly observer is able to see an increasing fraction of the day side of the Moon. In positions (2) and (3) it is seen that the Moon is gradually "growing".

In position (4), the Moon is opposite the Sun, the entire day side of the Moon is facing the Earth. This phase is called the full moon. Why didn't the Moon fall into the shadow of the Earth, directed in the direction opposite to the Sun? Because the plane of the lunar orbit is inclined to the plane of the earth's orbit at an angle of 5 degrees 9 minutes, and the Earth's shadow usually passes by the Moon. The moon falls into the earth's shadow only during lunar eclipses, the conditions for the onset of which must be considered specially.

After the full moon, the daytime fraction of the Moon, visible from the Earth, gradually decreases - phases (5), (6), (7). The latter is again a narrow sickle, but from the point of view of an observer standing on the Earth in position (7), its horns are directed in the direction opposite to the growing sickle and resemble the letter "C".

Then comes the new moon phase (8). The moon is above the day side of the Earth, the night side is turned to the Earth and is lost in the bright daytime sky. At this time, the nights are dark, moonless.

To make it easier to figure out when which phases are visible, the drawing is made in such a way that we look at the Earth and the Moon's orbit "from above", from the north pole of the Earth, which is placed in the center of the drawing. The sun's rays illuminate the day half of the Earth. The arrow shows the direction of the daily rotation of the Earth and, accordingly, the change of day to evening, night and morning. Approximately 28 Earth days (a lunar month) will elapse in the time it takes for the Moon to make a complete revolution around the Earth. Phase change occurs gradually and continuously. 3-4 days pass between the described phases.

The duration of the lunar month differs from the duration of the solar month, so the same lunar phases fall on different dates of our solar calendar.

Due to the movement of the Moon in its orbit, its rise, culmination and setting occur almost 50 minutes later than on the previous day, so the visibility of the Moon shifts to an increasingly later time.

In position (1), the young sickle rose before dark and before it sets beyond the western horizon, it can be seen in the early evening after sunset. In position (2), the moon rises at sunset and is visible all evening. In position (3), the visibility time is shifted to the first half of the night. In a full moon (4), the moon shines all night. After the full moon, the visibility of the moon first passes to the second half of the night (5), then to the morning (6) and to twilight before sunrise (7). During the new moon, the moon is not visible at all.

Sun and earth in the sky of the moon

The disk of the Earth is 15 times larger than the lunar one visible from the Earth, in addition, the Earth shines much brighter than our Moon, as it reflects 40% of sunlight (oceans, ice, clouds), and the Moon only 12% (basalts, dusty areas ). As the Moon moves in orbit, an observer on the Moon sees the changing phases of the Earth, but the boundary between the light and dark regions of the Earth is not clear, but blurred due to clouds and light scattered in the atmosphere. From the Moon you can see how clouds float above the Earth, notice the daily rotation of the Earth, because during the lunar day it makes thirty revolutions around its axis.

Let's see what happens in the sky of the Moon during its day.

Here in the east the sky began to brighten, but this is not dawn, the corona of the Sun is slowly rising from behind the horizon. When the Sun rises in a black sky with a crown, the Earth looks like a half: part of the day and part of the night. The sun rises very slowly, because the day lasts 15 of our days. While the Sun reaches its highest position, the light part of the Earth decreases, turning into a thin sickle, supplemented to a circle by a light blurred border.

At lunar noon, the Earth faces the Moon at night, its dark disk surrounded by an orange-red halo. The fact is that sunlight passes through the Earth's atmosphere, and the size of the particles of the Earth's atmosphere is such that they scatter the short-wave, blue, light of the solar spectrum, and the long-wave, red-orange, passes through the atmosphere freely. This phase can be called a new earth by analogy with the new moon. In the afternoon, the Sun slowly sinks to the west, and the crescent of the Earth gradually grows and turns into a half by sunset.

The night time is coming. At lunar midnight, the Earth faces the Moon with its day side, the full disk of the Earth illuminates the lunar landscape with a bluish-greenish light. This is how the blue earth's atmosphere and the green regions of the earth change the reflected sunlight.

By the next sunrise, the Earth will again take the form of a half-disk.

RMR_astra writes:

In the black starry sky of the Moon, the Sun rises and sets, and the Earth, swaying slightly, stands in one place.

I'm not kidding. The earth can rise. It all depends on where the observer is on the surface of the moon. And these sunrises and sunsets are connected with ....

Right. With the libration (wiggle) of the Moon in latitude and longitude.

And the day lasts longer than a day

The lunar day lasts 14 Earth days, the night lasts the same, the lunar day is equal to the lunar month. Why such long days? Why does the moon rotate so slowly on its axis?

Once it rotated faster, but the Earth slowed it down. The Earth causes a tidal wave in the body of the Moon. The moon rotated around its axis, and the tidal wave, which is always directed towards the Earth, rolled over the surface of the moon in the direction opposite to its rotation.

Now the Moon rotates so that the tidal hump does not roll, but always "looks" at the Earth. Therefore, the shape of the Moon slightly resembles an egg, and therefore the Moon always faces the Earth with its more convex side.

Only about half of the moon is visible from Earth, and earthlings first saw what the opposite side looks like when the Soviet Luna-3 station transmitted its image to Earth.

How little we even know about the moon. I adhere to the lunar calendar when working in the country, visiting a hairdresser. Resolve the issue, dear RMR_astra.

If the Moon is always turned to us in the same way, why then in the lunar calendar in different months there are 28, 29 or 30 lunar days?

It is convenient to divide your question into two questions: is the side of the moon facing us equal to half of its surface, and how correctly does the lunar calendar describe its movement.

We have already noted that the motion of the Moon is very complex, therefore, as before, we will take into account only the main factors. The orbit of the moon is not a circle, but an ellipse, so it becomes possible to look either behind the left side of the lunar disk, or behind the right, so not 0.5, but 0.6 shares of the lunar surface are accessible from the Earth.

The period of the daily rotation of the Moon coincides with its complete revolution around the Earth relative to the stars (27.3 Earth days), and the phases of the Moon are determined by the full revolution of the Moon around the Earth relative to the Sun. This period is slightly longer, since in one revolution the Moon, together with the Earth, has time to move along the Earth's orbit (29.5 Earth days). Since these inaccuracies are not visible to the naked eye, as a first approximation, it is considered that half of the Moon is visible from the Earth.

The lunar calendar is based on a period of phase change, contains 12 lunar months, and the length of the year is 355 days, that is, 10 days less than the solar calendar, corresponding to the seasons of agricultural work. Over time, the lunar and solar calendars diverged so much that, in order to bring them together, in some countries they added the 13th month to the lunar calendar (not every year), while in others they preferred to add days to some months. These calendar changes practically do not affect the correctness of the determination of the lunar phases and the validity of the statement that the Moon faces the Earth on one side.

It should also be noted that the illumination of the earth's surface by the Sun is almost 1,000,000 times greater than by the full Moon.

I am not interested in predictions of either the lunar or astrological calendar, but in connection with your question, I read it on the Internet.

Scientific prediction differs from pseudoscientific one in that in the first case it answers the questions “Why?”, “How?”, “What is the mechanism of influence?” etc. For example, by studying the movements of the Moon and the Earth, one can predict when a solar eclipse will occur, in what areas it will be observed, how long it will last, what fraction of the Sun will be covered by the Moon.

In the second case, the listed questions do not even arise either for the authors or for the users of their predictions. Because of misunderstanding, they say: “Probably, there is something in this.”

But you are a thinking person, try to understand what is the connection between the Moon and your hair. If you explain to me, I will be grateful to you.

Good afternoon, dear RMR_astra.

Thanks to you, I understood why a variety of information from the Internet is not assimilated. She is impersonal. And when the ray of knowledge is directed personally at you, it hits the target. Now the difference between the words "about half" and "exactly half" is clear.

The lunar calendar before your question was not in doubt at all. I know summer residents well who always adhere to the lunar calendar, and their fruits ripen faster than their neighbors. But this, of course, can be explained by better care and constant care. They even talk to plants and treat them as if they were alive.

Relationship between the Moon and hair. If there really is no scientific explanation, then this is the concept of FAITH. Some patients recover after taking a placebo pacifier, why not believe in the power of the growing moon?

Consistent change of the visible moon in the sky

The moon goes through the following phases of illumination:

• new moon- a state when the moon is not visible. New Moon is the phase of the Moon when its ecliptic longitude is the same as that of the Sun. Thus, at this time, the Moon is between the Earth and the Sun approximately on the same straight line with them. If they are exactly on the same straight line, a solar eclipse occurs. The moon at the new moon is not visible in the night sky, since at that time it is very close to the Sun in the celestial sphere (no further than 5 °) and at the same time turned to us by the night side. But sometimes it can be seen against the background of the solar disk (solar eclipse). In addition, after some time (usually about two days) after or before the new moon, with a very clear atmosphere, you can still see the disk of the Moon, illuminated by weak light reflected from the Earth (ash light of the Moon). The interval between new moons averages 29.530589 days (synodic month). On the new moon, the Jewish New Year and the Chinese (Japanese, Korean, Vietnamese) New Year of the 60-year cycle begin.
• young moon- the first appearance of the moon in the sky after the new moon in the form of a narrow sickle.
• first quarter- a state when half of the moon is illuminated.
• waxing moon
• full moon- a state when the entire moon is illuminated as a whole. The full moon is the phase of the moon when the difference between the ecliptic longitudes of the sun and the moon is 180°. This means that the plane through the Sun, Earth and Moon is perpendicular to the plane of the ecliptic. If all three objects are on the same line, a lunar eclipse occurs. The moon in the full moon looks like a regular luminous disk. In astronomy, the moment of a full moon is calculated to within a few minutes; in everyday life, the full moon is usually called the period of several days, during which the moon visually almost does not differ from the full one. During a full moon, the so-called opposition effect can occur for several hours, in which the brightness of the disk noticeably increases, despite its unchanged size. The effect is explained by the complete disappearance (for a terrestrial observer) of the shadows on the surface of the Moon at the moment of opposition. The maximum brightness of the Moon during a full moon is -12.7m.
• waning moon
• last quarter- a state when half of the moon is again illuminated.
• old moon

To distinguish the first quarter from the last, an observer located in the northern hemisphere can use the following mnemonic rules. If the lunar crescent in the sky looks like the letter "C (d)", then this is the moon "Aging" or "Descending", that is, this is the last quarter (in French dernier). If it is turned in the opposite direction, then, mentally putting a wand to it, you can get the letter “P (p)” - the moon is “Growing”, that is, this is the first quarter (in French premier).

The growing month is usually observed in the evening, and the aging month is usually observed in the morning.

It should be noted that near the equator the moon is always seen "lying on its side", and this method is not suitable for determining the phase. In the Southern Hemisphere, the orientation of the crescent in the corresponding phases is opposite: the growing month (from new moon to full moon) looks like the letter "C" (Crescendo,<), а убывающий (от полнолуния до новолуния) похож на букву «Р» без палочки (Diminuendo, >). Interesting Facts Usually, there is one full moon for each calendar month, but since the phases of the moon change a little faster than 12 times a year, sometimes the second full moon in a month occurs, called the blue moon.