Apart from the scattering of stars, the moon is undoubtedly the decoration of the night sky. Due to the combination of its size and distance from Earth, it is the second brightest celestial object and can completely obscure the solar disk during an eclipse. It is not surprising that the night star has been attracting the attention of mankind for more than one millennium.

If the Earth did not have the Moon, many things would have turned out differently:

• the day would be much shorter;
• the change of seasons and the climate would be characterized by instability;
• less pronounced ebb and flow would occur;
• the appearance on the planet of life in its present form would be questionable.

Moon diameter

The average value of the moon's diameter is not too large by cosmic standards - 3474.1 km. This is approximately half the distance from Moscow to Vladivostok.

However, the Moon is ranked fifth place in size among the natural satellites of the planets of the solar system:

1. Ganymede.
2. Titanium.
3. Callisto.
4. Moon.

But even when comparing the sizes of satellites in relation to their planets, the moon has no equal. With a diameter of a quarter of the earth, it ranks first. In addition, it is larger than Pluto.

What is the distance from the Earth to the Moon

The quantity is not constant. On average, the distance between the centers of the planet and its natural satellite is 384,400 kilometers. In this space, about 30 more Earths would fit, and light needs 1.28 seconds to overcome this distance.

What if the nearest celestial body could be reached by car at a speed of 95 km / h? Considering that the entire distance is about 10 circles of the Earth, the journey would take the same amount of time as 10 detours of the planet along the equator. That is, a little less than six months. So far, the fastest way to the Moon was covered by the New Horizons interplanetary station, which on its way to Pluto crossed the satellite's orbit eight and a half hours after launch.

The moon's orbit is not a perfect circle, and an oval (ellipse), inside which is the Earth. At different points, it is located closer to or further from the planet. Because of this, when rotating around a common center of mass with the Earth, the satellite either approaches or moves away. So, the least kilometers are separated by celestial bodies when the night star is in the place of the orbit called perigee. At the point designated as the apogee, the satellite is farthest from the planet. The minimum distance is 356 400 km, and the maximum is 406 700 km. So the distance fluctuates from 28 to 32 earth diameters.

The first close to correct estimates of the distance to the "neighbor" of the Earth were obtained in the II century. n. e. Ptolemy. Nowadays, thanks to modern reflective devices installed on the satellite, it was possible to measure the distance most accurately (with an error of several cm). To do this, a laser beam is directed at the moon. Then they note during what period it will return to the Earth, being reflected. Knowing the speed of light and the time it took for it to reach the sensors, it’s easy to calculate the distance.

How to visually estimate the size of the moon and its distance from the earth

Earth's diameter is about 4 times the Lunar diameter, and the volume - 64 times. The distance to the night star is approximately 30 times the planet's diameter. To visually assess the distance from the Earth to its satellite and compare their sizes, you need two balls: a basketball and a tennis one. Diameter ratio:

• Earth (12,742 km) and the Moon (3474.1 km) - 3.7: 1;
• standard basketball (24 cm) and tennis (6.7 cm) - 3.6: 1.

The values ​​are pretty close. Thus, if the Earth were the size of a basketball, then its satellite would be a tennis one.

You can ask people to imagine that the Earth is a basketball, and the Moon is a tennis ball, and to show how far the satellite is from the planet on this scale. Most are likely to assume a distance of 30 cm to a few steps.

In fact, to show the correct distance, you have to move a little more than seven meters. So, between the planet and its satellite, on average, 384 400 km, which is about 30 Earths or, respectively, 30 basketballs. Multiplying the diameter of the sports equipment by 30 gives the result of 7.2 m. This is approximately 9 male or 11 female steps.

The apparent size of the moon from Earth

360 angular degrees- the entire circumference of the celestial sphere. At the same time, the night star occupies about half of one degree on it (on average 31 minutes) - this is the angular (visible) diameter. For comparison: the width of the index finger nail at arm's length is about one degree, that is, two moons.

By a unique coincidence, the apparent sizes of the Sun and the Moon for the inhabitants of the Earth are almost the same. This is possible due to the fact that the diameter of the nearest star 400 times the diameter of the satellite, but the daylight is also located the same number of times further. Due to this coincidence, among all the planets orbiting the Sun, only on Earth can its total eclipse be observed.

Is the size of the moon changing

Of course, the true diameter of the satellite remains the same, but the apparent size can vary. So, The moon appears to be noticeably larger during sunrise and sunset.... When a night star is low above the horizon, the distance to the observer does not decrease, but, on the contrary, slightly increases (by the radius of the Earth). The visual effect, it would seem, should be the opposite. There is no single answer to explain the reason for the illusion. We can only say with certainty that this beautiful phenomenon owes its existence only to the peculiarities of the work of the human brain, and not, for example, to the influence of the Earth's atmosphere.

The distance between the Moon and the Earth periodically changes from maximum (at apogee) to minimum (at perigee). Along with the distance, the apparent diameter of the satellite also varies: from 29.43 to 33.5 arc minutes. Thanks to this, not only total eclipses are possible, but also annular (when the apparent size of the moon at apogee is less than the solar disk). About once every 414 days, the full moon coincides with the passage of the perigee. At this time, you can observe the largest night star. The phenomenon has received the rather loud name of a supermoon, but the apparent diameter at this moment is only 14% larger than usual. The difference is very insignificant, and a simple observer will not notice the difference.

Thanks to precise measurements distance, scientists were able to detect a relatively slow, but constant increase in the distance between the Earth and its satellite. The speed at which the moon is receding - 3.8 cm per year - is too slow to notice a significant decrease in the apparent size of the star. Human nails grow at about the same rate. Nevertheless, after 600 million years, the Moon will be so far away and, accordingly, will decrease for terrestrial observers that total solar eclipses will remain in the past.

It is worth noting, what a satellite of the earth, formed according to modern theory from the collision of a planet with a large object 4.5 billion years ago, was originally 10-20 times closer. However, then there was no one to admire the sky, decorated with a luminary 10-20 times larger than it is now.

Video

You can understand how far the Moon is from the Earth by watching this video.

The ancient Greeks tried to measure the distance from the Earth to the Moon.

Only the composition has come down to us Aristarchus of Samos"On the magnitudes and distances of the Sun and the Moon" (III century BC), where he, for the first time in the history of science, tried to establish the distances to these celestial bodies and their sizes.

Aristarchus approached the solution of this issue very wittily. He proceeded from the assumption that the Moon has the shape of a ball and shines with light reflected from the Sun. In this case, at those moments when the Moon has the form of a half-disk, it forms a right-angled triangle with the Earth and the Sun:

If at this moment you can accurately determine the angle between the directions from the Earth to the Moon and the Sun (CAB), you can find from simple geometric relationships how many times the leg (the distance from the Earth to the Moon AB) is less than the hypotenuse (the distance from the Earth to the Sun AC). According to Aristarchus, CAB = 87 °; therefore, the ratio of these sides is 1:19.

Aristarchus was mistaken about 20 times: in reality, the distance to the Moon is less than to the Sun, almost 400 times. The catch is that it is impossible to accurately determine the moment when the moon is at the apex of a right angle, only on the basis of observations. The slightest inaccuracy entails a huge deviation from the true value.

The greatest astronomer of antiquity, Hipparchus of Nicea in the middle of the 2nd century BC. e. determined with great confidence the distance to the moon and its dimensions, taking the radius of the globe as a unit.

In his calculations, Hipparchus proceeded from the correct understanding of the cause of lunar eclipses: the moon falls into the earth's shadow, which has the shape of a cone with a top located somewhere in the direction of the moon.

Diagram explaining the definition of the moon's radius by the method of Aristarchus.
Byzantine copy of the 10th century.

Take a look at the picture. It shows the position of the Sun, Earth and Moon during a lunar eclipse. From the similarity of triangles it follows that the distance from the Earth to the Sun AB is as many times greater than the distance from the Earth to the Moon BC, how many times the difference between the radii of the Sun and the Earth (AE - BF) is greater than the difference between the radii of the Earth and its shadow at the distance of the Moon (BF - CG ).

From observations with the help of the simplest goniometric instruments, it followed that the radius of the Moon is 15 ", and the radius of the shadow is approximately 40", that is, the radius of the shadow is almost 2.7 times the radius of the Moon. Taking the distance from the Earth to the Sun as a unit, it was possible to establish that the radius of the Moon is almost 3.5 times less than the radius of the Earth.

It was already known that an object is observed at an angle of 1 ", the distance to which exceeds its size by 3,483 times. Consequently, Hipparchus reasoned, at an angle of 15" the observed object will be 15 times closer. This means that the Moon is at a distance of 230 times (3 483: 15) greater than its radius. And if the radius of the Earth is approximately 3.5 times the radius of the Moon, then the distance to the Moon is 230: 3.5 ~ 60 times the radius of the Earth, or about 30 Earth's diameters (this is about 382 thousand kilometers).

In our time, the measurement of the distance from the earth to the moon was carried out using the method of laser ranging. The essence of this method is as follows. A corner reflector is installed on the surface of the moon. From the Earth, a laser beam is directed to the reflector mirror with the help of a laser. At the same time, the time when the signal was emitted is precisely recorded. The light reflected from the device on the Moon returns to the telescope within about one second. Having determined the exact time during which the light beam travels the distance from the Earth to the Moon and back, you can set the distance from the radiation source to the reflector.

Using this method, the distance from the earth to the moon was determined with an accuracy of several kilometers (the maximum measurement accuracy is currently 2-3 centimeters!): On average, it is 384 403 km... "On average" not because this distance is taken from different or approximate measurements, but because the Moon's orbit is not a circle, but an ellipse. At the apogee (the point of the orbit farthest from the Earth), the distance from the center of the Earth to the Moon is 406 670 km, at perigee (the closest point of the orbit) - 356 400 km.

In ancient times, after the collision, the debris of Thea was thrown into Earth's orbit. Then, under the influence of gravity, they formed a celestial body - the Moon. The orbit of the Moon at that time was much closer than today and was at a distance of 15-20 thousand km. In the sky, its apparent size was then 20 times larger. Since the time of the collision, the distance of the Moon from the Earth has increased and today it averages 380 thousand kilometers.

Even in antiquity, people tried to calculate the distance to visible celestial bodies. So the ancient Greek scientist and philosopher Aristarchus of Samos, determined the distance to the Moon 18 times closer than the Sun. In reality, this distance is 400 times less.

More accurate were the results of calculations by Hipparchus, according to which the distance to the moon was equal to 30 earthly diameters. His calculations were based on calculations of the circumference of the Earth of Eratosthenes. By today's standards, this was 40,000 km, which is the diameter of the Earth at 12,800 km. This is in line with the actual modern parameters.

Modern data on the orbit of the moon

Today science has fairly accurate methods for determining the distance to space objects. During the stay of the astronauts on the moon, they installed a laser reflector on its surface, by which scientists now determine the size of the orbit and the distance to the Earth with high accuracy.

The shape of the moon's orbit is slightly elongated into an oval. The closest point to the Earth (perigee) is located at a distance of 363 thousand km, the farthest (apogee) - 405 thousand km. The orbit also has a significant eccentricity of 0.055. Because of this, its apparent dimensions in the sky are quite different. Also, the plane of the Moon's orbit is tilted by 5 ° to the plane of the Earth's orbit.

In orbit, the Moon moves at a speed of 1 km / s and bends around the Earth in 29 days. Its location in the sky shifts to the right every night, looking from the northern hemisphere, and for observers of the southern hemisphere - to the left. For them, the visible disk of the moon looks upside down.

The Moon is 400 times closer than the Sun and is just as much smaller in diameter, therefore solar eclipses are observed on Earth exactly the same as the sizes of the disks of the star and the satellite. And because of the elliptical orbit, the moon at the far point is smaller in diameter and due to this, annular eclipses are visible. The moon gradually continues to move away from the Earth by 4 cm per century, therefore, in the distant future, people will no longer have to observe such eclipses as now.

384 467 kilometers - this is the distance that separates us from the nearest large cosmic body, from our only natural satellite - the Moon. This begs the question: how did scientists find out about this? After all, you cannot, in fact, walk from the Earth to the Moon with a meter in your hands!

Nevertheless, attempts to measure the distance to the Moon were made in antiquity. The ancient Greek scientist Aristarchus of Samos tried to do this, the one who was the first to express the idea of ​​a heliocentric system! He also knew that the Moon, like the Earth, has the shape of a ball and does not emit its own light, but shines with the reflected sun. He suggested that at the time when the Moon looks like a half-disk for an observer from Earth. Between it, the Earth and the Sun, a right-angled triangle is formed, in which the distance between the Moon and the Sun and between the Moon and the Earth are legs, and the distance between the Sun and the Earth is the hypotenuse.

Therefore, you need to find the angle between the directions to the Moon and the Sun, and then, using the appropriate geometric calculations, you can calculate how many times the Earth-Moon leg is shorter than the Earth-Sun hypotenuse. Alas, the technologies of that time did not allow us to accurately determine the time when the Moon occupies a position at the apex of the said right-angled triangle, and in such calculations, a small error in measurements leads to large errors in the calculations. Aristarchus was mistaken almost 20 times: it turned out that the distance to the Moon is 18 times less than the distance to the Sun, in reality it is 394 times less.

A more accurate result was obtained by another ancient Greek scientist - Hipparchus. True, he adhered to the geocentric system, but he understood the cause of lunar eclipses correctly: the Moon falls into the shadow of the Earth, and this shadow has the shape of a cone, the top of which is located away from the Moon. The contour of this shadow can be observed during an eclipse on the disk of the Moon, and by the bend of the edge it is possible to determine the ratio between its cross section and the size of the Moon itself. Given that the Sun is much farther away than the Moon, it was possible to calculate how far away the Moon had to be for the shadow to shrink to that size. Such calculations led Hipparchus to the conclusion that the distance from the Earth to the Moon is 60 Earth radii, or 30 diameters. The diameter of the Earth was calculated by Eratosthenes - in translation into modern measures of length 12,800 kilometers - thus, according to Hipparchus, the distance from the Earth to the Moon is 384,000 kilometers. As you can see, it is very close to the truth, especially when you consider that he had nothing but simple goniometric devices!

In the XX century, the distance from the Earth to the Moon was measured with an accuracy of three meters. For this, several reflectors were delivered to the surface of our space "neighbor" about 30 years ago. A focused laser beam is sent to these reflectors from the Earth, the speed of light is known, and the distance to the Moon is calculated from the time it takes the laser beam to travel back and forth. This method is called laser ranging.

Speaking about the distance from the Earth to the Moon, it should be remembered that we are talking about the average distance, because the Moon's orbit is not circular, but elliptical. At the point farthest from the Earth (apogee), the distance between the Earth and the Moon is 406 670 km, and at the closest (perigee) - 356 400 km.

The moon has always attracted the attention of a person. Probably, each of us dreamed in childhood to be an astronaut and visit it. Since space tourism is actively gaining momentum in the world today, many are interested in the question of the time spent on the road from the Earth to the Moon.

The minimum distance from the Earth to the Moon is 354,988 kilometers... To overcome this path, a person will need:

• 9 years continuous walking at a speed of 5-6 kilometers per hour;
• 160-163 days if you drive a car at a speed of 100-105 km / h;
• 20-21 days continuous flight by plane, covering 800-850 kilometers per hour;
• To fly from the Earth to the Moon in the Apollo spacecraft, you will need 72-74 hours;
• If you move to the moon at the speed of light, which is 300,000 km / sec, then the entire road will take 1.25 light seconds.

If you take only special flying vehicles, then on the road to the Moon you will spend:

• 1 year 1.5 months if flying a device like a probe ESA SMART-1... Its feature is the ion engine, which is considered the most economical of its kind. Despite the fact that this flight was the slowest, it was technologically the most advanced. The ESA SMART-1 lunar probe was launched on September 27th, 2003 and used a revolutionary ion drive to fly to the moon. Although ESA SMART-1 reached the Moon after 410 days, it consumed only 82 kg of fuel during its voyage. At the moment, this is the most economical way of driving.
• 5 days on a Chinese satellite Chang'e-1... The flight of the device is carried out thanks to rocket engines. But he had to hang in low-earth orbit until October 31, waiting for the correct departure point. He arrived on the moon on November 5, using conventional rocket engines in flight.
• 36-37 hours if you fly on a device such as a Soviet satellite Moon-1... The satellite passed at a distance of only 500 km from the Moon, after which it entered a heliocentric orbit. It took the satellite only 36 hours to reach the moon.
• Almost 9 hours if using development NASA "New Horizons" mission Pluto.

To date, the fastest flight to the moon is NASA's New Horizons Pluto mission. From the very beginning, the satellite was faithfully accelerated - the speed was about 58,000 km / h. This was done so that the satellite could overcome the pull of the Sun in the solar system. However, despite such an impressive speed, it still took the satellite eight hours and thirty-five minutes to cover the 380,000-kilometer distance.

Thus, space tourism companies have several options for sightseeing tours around the moon. They can offer long cruises - using ion thrusters, or short ones - using fast and powerful rockets in order to take visitors to the moon for the weekend.

Why have flights to the moon and work on its development been stopped?

Has anyone been on a satellite of the Earth? And if so, why did countries stop flying to the moon? As the Americans said, the first expedition was sent in 1969, or more precisely, on July 20. Neil Armstrong led the astronaut team. At the time, the Americans were simply jubilant. After all, they were the first to set foot on the surface of the moon. But many doubted this.

Numerous photographs and recordings of conversations between representatives of the expedition with the Earth became the reason for the disputes of the skeptics. However, at that time it was quite difficult to fake any pictures. Not to mention the equipment and laser reflectors that were left on the lunar surface for further study. Some suggest that the technician was delivered by an unmanned module. It is almost impossible to prove that someone has visited or not visited the surface of an Earth satellite. In addition, many documents remain classified to this day.

Political situation

This is the first reason why missions to the moon have been canceled. Do not forget that at that time there was a race between two large states for the possibility of being the first to launch a rocket into space. The decisive event in this battle was the use of nuclear reactions. The opportunities that were associated with such a discovery were not only exciting but also daunting. Moreover, there was no clear leader in this race. Both the USSR and America paid a lot of attention to space travel. The Soviet Union is the first state to send a man into space. If the USSR achieved such an opportunity, then why did the flights to the moon fail? Why did they stop before they even started?

America was challenged. In turn, NASA went to great lengths to make the return move. The sensational flights to the moon are not just an achievement. This is an attempt to show their superiority over the whole world. Maybe this was the reason for the closure of the program. After all, other states did not have enough funds to go beyond America in their developments. So is it worth the state to spend its energy and resources further?

Economies of countries

Of course, there is another reason why flights to the moon have been stopped - the economies of the countries. A lot of financial resources have been allocated by states for the development of spacecraft, as well as for their launch. If the surface of a satellite of the Earth could be divided, then its territories would become a tidbit for many wealthy people.

However, after some time, an agreement was created according to which absolutely all celestial bodies are the property of mankind. Any space exploration was to be carried out only for the benefit of all countries. It follows that the allocation of large financial resources for space exploration programs simply will not be beneficial. And the state that allocated the money will simply not be able to develop. As a result, there is simply no sense in high costs. After all, you can take advantage of the achievements of other countries.

Production area

Not so long ago, it was more expedient to re-equip any enterprise for the needs of the state. Now it is simply impossible to produce missiles with certain parameters just because there is nowhere to do it. In any case, re-profiling an enterprise is a rather complicated process.

The problem in this case is not only the financial side of the issue. The reason lies in the lack of the required number of trained specialists. The generation that worked on the lunar program has long since retired. As for the new hires, they are not yet that experienced. They do not have all the knowledge in this area. And flights to the moon do not forgive mistakes. Their price is usually the lives of the astronauts. It is for this reason that it is best not to fly to the moon. And why they stopped is easy to guess.