What is the distance between the Earth and the Moon? How is it measured?

We know that the Moon orbits the Earth and is a natural satellite of the Earth. The orbit of the Moon is elliptical, the perigee is 363,300 km, the apogee is 405493 km, and the average distance is 384,400 km. Generally speaking, the Earth-Moon distance refers to the average distance.

Let's convert kilometers to light years.

And the light year refers to its literal meaning, the distance traveled in a light year. The internationally recognized value of the speed of light is c = meter seconds, and the distance of one light year is the speed of light multiplied by the number of seconds in a year, which is about 9,460.5 billion kilometers. How many light years is 384400 km?

Mean distance between the Moon and the Earth = 384,400 (km) = 384,400 9,460.5 billion (light years) 4 * 10 -9 (light years).

Therefore, the distance between the earth and the moon is not light years at all, the average of the earth and the moon is 380,000 kilometers, and the speed of light is about 300,000 kilometers per second.

Light-years are commonly used in astronomy to measure large distances, such as the distance between the Sun and another star. In general, the distance of celestial bodies in the universe is very large, and it can be seen from the above calculation process that if it is calculated in the commonly used kilometers, the order of magnitude is very large, so light years are commonly used to calculate the distance of celestial bodies.

In general, the distance from the Earth to the Moon is not expressed in "light years (ly)". Although the light-year is a more commonly used unit of length in astronomy, this unit is simply too large, and the distance between the Earth and the Moon is too short to be expressed in light-years.

1 light-year refers to the distance traveled by light in a vacuum for one year. The speed of light in a vacuum is 299792458 meter seconds, a year is a day (the Julian year is used in astronomy as the length of a year), a day is 24 hours, and an hour is 3600 seconds. So 1 light year = 299792458 meters = 9460730472580800 meters, or about 9460 trillion meters.

As you can see, a light-year is a fairly large unit of length.

According to measurements, the average distance between the Moon and the Earth is 384,400,000 meters. If the Earth-Moon distance is expressed in light-years, its magnitude is: 384400000 9460730472580800 light-years Light-years.

Therefore, it is a bit "overkill" to express the distance between the Earth and the Moon in a unit of length as large as a light year.

Since the speed of light is about 300,000 kilometers per second, and the distance between the Earth and the Moon is about 380,000 kilometers, we can use "light seconds" to more vividly represent the distance between the Earth and the Moon. Similar to the definition of a light year, 1 light second is the distance traveled by light in a vacuum, i.e. 1 light second = 299792458 1 meter = = 299792458 meters. Therefore, if the Earth-Moon distance is expressed in light seconds, its magnitude is:

384400000 299792458 light seconds light seconds. This means that it only takes a second for light to travel from the Earth to the Moon.

Since the scales in astronomy vary greatly, different units of length are used at different scales to facilitate expression. In addition to light years, there are other units of length to represent astronomical distances, including astronomical units and parsecs. The astronomical unit (AU) is the average distance between the Earth and the Sun, 1 AU = 149597870700 meters, 1 light-year AU, and the distance between the Earth and the Moon is equivalent to AU.

When measuring the distances of celestial bodies within the solar system, AU is generally used. The parsecs (PC) is derived from the trigonometric parallax method used to measure the distance of a star, 1 PC light years, and the distance between the Earth and the Moon is equivalent to a PC. In addition, units larger than the parsec include the thousand-second and million-second differences, which are a thousand-fold and a million-fold difference, respectively.

1: The unit of light year is not suitable for use here, because the distance is too short for light to be described in light years, because the average distance from the Earth to the Moon is 380,000 kilometers, and light only needs a little more than a second to be enough.

2: However, we can extend a little bit, if a person walks to the moon, first of all, a person walks to the moon, first of all, you have to know the distance between the two, the average distance from the earth to the moon is about 380,000 kilometers, and each kilometer is equal to 1,000 meters (380,000 times 1,000) is equal to 380 million meters.

3: If you calculate according to the time of a person walking 1,000 meters, walk in five minutes of 100 meters, subtract ten minutes from the fast and slow speed, and comprehensively set it to 40 minutes per kilometer, a day and night is 24 hours, and a year is 262,800 hours, that is to say, it takes more than 8,500 kilometers in a year, and according to 380 million meters, it will take at least 40 years for people to travel to the moon, so if you start walking from the age of 20, you don't eat, drink or sleep on the road, You won't be able to reach the moon until you're 60, so think about it.

The Moon is only 10,000 kilometers away from the Earth when it is closest to the Earth, and the Moon can reach 10,000 kilometers when it is farthest from the Earth. What we are familiar with is the average distance, about 385,000 kilometers. The distance between the Earth and the Moon can be said to be quite large compared to the size of the Earth and the Moon itself.

Therefore, measuring the distance between the Earth and the Moon is actually a very difficult thing to do. Aside from theoretical calculations, how do we know the distance between the Earth and the Moon? If a measurement method is used, what are the specific methods?

Today, let's talk about that.

The astronomical community is a very common problem in the astronomical community, and there are various methods of ranging and ranging.

For example: triangulation, spectroscopy, laser ranging. You must know that measuring the distance between the earth and the moon is not something that only us modern people can do, but the ancients can do. So I'll first introduce the measurement methods of the ancients.

There was an ancient Greek astronomer named Eva Valley, who invented many sophisticated observation instruments. To measure the Earth-Moon distance, he assumed that sunlight was parallel light. Then observations were made in Turkey and Alexandria by total solar eclipse observation in two different places, Turkey and Alexandria.

What was seen in Turkey was a total solar eclipse, and when you arrived in Alexandria, a solar eclipse was observed, in which the moon obscured four-fifths of the sun's area. This makes it possible to calculate the time difference of the moon. Time difference refers to two different observation points far away from the target, observing the difference in the direction of this target, and the two observation points and the target form an angle, the difference angle.

If there is a time difference, a similar triangle can be made, and the distance between the Earth and the Moon can be calculated to be 370,000 kilometers using plane geometry, which can be said to be relatively close to the value we have measured now.

If we measure distances in our daily lives, there will generally be rulers. But can we find such a long ruler in **? Even with such a long ruler, we can't measure it with this ruler.

Is there nothing that can replace a ruler and a rangefinder tool that we hold in our hands? The answer is with lasers. Obviously, a laser can be used to go back and forth, and then the distance between the Earth and the Moon can be obtained by time * speed of light = distance.

But this also requires a mirror or receiving device on the moon. In fact, scientists do. Here's how it works.

At that time, when the United States and the Soviet Union were vying for supremacy, an arms race was held, in which space technology was competed. Both sides are competing to see who will land on the moon first. Later, Armstrong's "Apollo 11" landed on the moon, which was the first manned lunar landing technology for mankind.

It can be judged by the time it takes for light to arrive, multiplied by the speed of light.

The distance between the Earth and the Moon is measured by satellites launched into the universe by humans, and it is only at the end that the difference between the two is determined.

The distance between the Earth and the Moon is measured with a laser, and this is also a new technology developed in the sixties of this century.

1. Laser ranging is now used. After the Apollo moon landing, a total reflecting prism was installed on the moon, and ground-based observatories used lasers to measure the round-trip time (equivalent) and calculate the distance between the two.

2. The method of ultrasonic waves can also be used to send ultrasonic waves from the earth to the moon, and the ultrasonic waves will rebound and return to the earth after reaching the moon.

Let the distance between the moon and the earth be s, the speed of the ultrasonic wave is v, and the round-trip time is t, because the ultrasonic wave has traveled a round trip, so the distance traveled by the ultrasonic wave is 2s, so 2s=vt, so we get s=vt 2

Measuring the distance between the Earth and the Moon with a laser is a new technology developed in the sixties of this century. Its principle is: through the telescope, a pulse laser beam is emitted to the moon from the ground observation station (station), and then the laser echo reflected back from the surface of the moon is received, and the timer on the ground records the time of the laser round trip, from which astronomers can calculate the distance between the earth and the moon.

For more than two decades, the technology has been evolving. In order to improve the accuracy of ranging, the astronauts first placed five backward reflector devices on the moon, and the observation equipment on the ground was constantly improved. At present, the ranging accuracy has reached the level where the error does not exceed eight centimeters.

- A new U.S. optical probe at the White Sands spaceport can measure the distance of the Moon from Earth more than 10 times more accurately than previous measurement equipment. The test will launch a laser from Earth onto a specular reflector mounted on the surface of the Moon, and the distance between the Moon and the Earth can be calculated by recording the time of the emitted and reflected lasers. It is understood that in this experiment, scientists can make the calculation of time accurate to one trillionth of a second.

In addition to this, scientists carefully consider the effects of the atmosphere and the Earth's motion on the reflection distance of the laser. It is said that the error of this measurement will be in the range of two millimeters.

The basic idea of calculating the distance of a celestial body according to the law of gravitation is: according to the motion of the planet (or satellite), the centripetal force of the planet (or satellite) is calculated, and the f direction = f gravitational force. According to this series of equations.

For example, if the mass of the Earth is known, the period of the Moon's orbit around the Earth is 30 days, find the distance from the Moon to the Earth's center of the sphere.

The centripetal force of the Moon orbiting the Earth, i.e., the gravitational force between the Moon and the Earth, is:

f direction = f lead = gm m month r 2 = m month (2 t) 2*r

r3=mgt 2 4 2=

r=4×10^8m,2,

<>1. The average distance from the Earth to the Moon is 384,400 km. The perigee of the Moon from the Earth is 10,000 kilometers. The distance from the farthest apogee to the earth is 10,000 kilometers away from the manuscript.

2. The distance between the Moon and the Moon refers to the distance between the Earth and the Moon, including the average distance, the distance between the Moon and the Earth's perigee, and the farthest apogee distance from the Earth. Current studies have found that the Moon will move farther and farther away from Earth. Stay away from it about centimeters or so every year.

1. The distance between the Earth and the Moon is about 363,300 kilometers, the farthest is about 405,500 kilometers, and the average is about 384,400 kilometers.

2. The Moon, commonly known as the Moon and Taiyin in ancient times, is a satellite orbiting the Earth. It is a solid-state satellite of the Earth and the closest celestial body to the Earth.

3. There are dark parts and bright areas on the surface of the moon, the bright areas are highlands, and the dark areas are low-lying areas such as plains or basins, which are called lunar land and lunar sea respectively. When early astronomers looked at the Moon, they thought that the dark areas were covered with seawater, so they called them "seas". The famous ones are the sea of clouds, the wet sea, the still sea, etc.

The bright part is the mountains, which are dotted with craters, known as moon craters, which are low-lying shapes that are raised in circles.

4. There are more than 33,000 craters with a diameter of more than 1,000 meters on the moon. Located near Antarctica, the Bailey crater is 295 kilometers in diameter and can fit the entire island of Hainan. The deepest mountain is Newton's crater, which is 8,788 meters deep.

In addition to craters, there are also ordinary mountains on the lunar surface.

1. The average distance between the Moon and the Earth is about 10,000 kilometers.

2. At present, the accurate measurement of the distance between the Earth and the Moon is based on the angular mirror arrays (3 in the United States and 2 in the Soviet Union) on the surface of the moon by the United States and the Soviet Union in the last century, of which the Soviet Union is placed by machine control, and the United States is placed by manned landing on the moon, with a total of five sides.

3. The special structure of the angle mirror array can be prepared to let the frontal light return along the original path, and the scientists on the ground, as long as they aim at the corresponding position of the moon to emit a strong laser beam, they can receive the peak reflected back from the mirror spike rolling surface, and can accurately measure the distance between the Earth and the Moon according to the time of the laser going back and forth.

1. The average distance between the Moon and the Earth is about 10,000 kilometers.

2. At present, the accurate measurement of the distance between the Earth and the Moon is to use the United States and the Soviet Union in the last century, leaving an array of angle mirrors on the surface of the moon (3 in the United States and 2 in the Soviet Union), of which the Soviet Union is a guessing stove placed by machine control, and the United States is placed by manned landing on the moon, a total of five sides.

3. The special structure of the angle mirror array can make the frontal light return along the original path, and scientists on the ground, as long as they aim at the corresponding position of the moon to launch a strong laser beam, they can receive the peak reflected back from the mirror, and according to the time of the laser back and forth, they can accurately measure the distance between the earth and the moon.