In scientific terms, the thickness of the earth should be the diameter of the earth. As for the height of the sky, scientists observed the distance of 65.438+0 billion light-years by scientific methods, but did not see the edge of the universe. In other words, the current concept should be that the sky is infinitely high (at least it should be greater than 65.438+0 billion light years).
How high is the sky? Humans have been tirelessly looking for and exploring this problem:
1783, French montague brothers successfully released the first human hot air balloon, carrying two brave men into the sky. This hot air balloon rose more than 900 meters.
1804, the French scientist Grusack rose to a height of about 7 kilometers by balloon.
1892, scientists designed unmanned balloons with instruments so that they could rise higher.
In 1930s, scientists designed a sealed cabin that can keep the pressure and temperature on the earth's surface, so that humans can enter a higher atmosphere.
1938, the balloon named "Explorer 2" rose to the height of 2 1 km.
1960, manned balloons can rise to 34.5 kilometers, and unmanned balloons can reach an altitude of 40-50 meters.
Later, the invention of airplanes, rockets and artificial earth satellites made people have a more scientific understanding of the atmosphere.
The atmosphere varies with the height of the earth's surface, and its composition, physical and chemical characteristics are also different. In order to reveal the secrets of the atmosphere, scientists divide the whole atmosphere into several levels according to the temperature change, composition and electromagnetic characteristics of the atmosphere with height distribution.
Temperature Change Scientists divide the atmosphere into five layers:
Troposphere: from the ground to about 10 ~ 16 km (about 8 ~ 9 km in the polar region and about 15 ~ 18 km in the equator), it is the lowest layer of the atmosphere. This layer concentrates about three-quarters of the mass of the whole atmosphere and almost all the water vapor. The atmospheric convection in this layer is very developed, and the temperature drops evenly with the height increase, with an average drop of 0.6℃ per rise 100 m and -55℃ near1km. In this layer, the activity of the atmosphere is extremely intense, rising, falling or even rolling. It is precisely because of these ever-changing atmospheric movements that various complex weather changes have been formed. Wind, clouds, rain, snow, fog, dew, thunder and hail also occur in this layer, so some people call this layer the meteorological layer.
The top of this layer is called the tropopause, where the temperature no longer decreases with the increase of height, but is basically unchanged. This is a very stable layer, and the weather in the troposphere is not affected here. Wan Li has clear skies, high visibility and smooth air, which is very suitable for jet polite flight.
Stratosphere: from the tropopause up to a height of 55 kilometers. . This layer is the place where ozone is concentrated in the earth's atmosphere, especially in its lower part, that is, the ozone concentration is the highest at the height of 15 ~ 25 km, so this layer is also called ozone layer. Because the ozone layer can absorb a lot of solar radiation heat and make the air temperature rise greatly, the biggest feature of this layer is that the temperature rises with the height and the top temperature rises to the maximum.
Although there are few water vapor and weather phenomena in the stratosphere, with the launch of meteorological rockets and satellites, it is found that the change of airflow in this layer is closely related to the weather change in the troposphere and affects each other.
Mesosphere: From the top of the stratosphere upward, that is, from 55 km to 80 km, this range is named mesosphere, which is called mesosphere for short. Here, the temperature decreases with height, reaching the lowest point at about 80 kilometers, which is about -90℃.
Thermosphere: the range from the middle atmosphere to about 500 kilometers. It is called thermosphere because the air molecules and ions in this layer directly absorb the energy of solar ultraviolet radiation, so they move very fast, just like high-temperature gas. The air here is extremely thin. Although the temperature at the top of the thermosphere can reach 1000℃ (when the sun is calm) to 2000℃ (when the sun is active), in fact, there is no heat at all.
Escape layer: More than 500 kilometers is the outer atmosphere, and the top of this layer is also the top of the earth's atmosphere. The gravity of the earth here is very small. In addition, the air is extremely thin, and the probability of gas molecules colliding with each other is very small. So air molecules fly around at high speed like miniature missiles. Once they fly up, they will enter an area with a very small probability of collision. Finally, they will bid farewell to the earth and enter interstellar space, so the outer atmosphere is called the escape layer. The temperature of this layer is extremely high, but almost isothermal. The air here is also highly ionized.
In addition to temperature stratification, the atmosphere can be divided into neutral layer, ionosphere and magnetosphere according to its electromagnetic characteristics. Neutral layer refers to the height from the ground to 60 kilometers, where most of the atmospheric components are neutral, that is, non-ionized; The atmosphere between 60 km and 500 km is called ionosphere. More than 500 kilometers is called magnetosphere.
Ionosphere: Here, due to the influence of solar radiation, atmospheric substances begin to ionize. According to the concentration of electrons in the ionosphere and their different effects on electromagnetic wave inversion, it can be divided into D layer (about 60-90km height), E layer (about 1 10km height), F 1 layer (about 160km height) and F2 layer (about 300km height). According to the observation of meteorological rockets and satellites, it plays an important role in long-distance radio communication about 300 meters from the ground. Radio waves propagate through multiple reflections between the ground and the ionosphere to realize long-distance radio communication. People describe the ionosphere as a mirror that reflects radio waves. "
The ionosphere only reflects the frequency band used by ordinary radio broadcasting, and cannot reflect short-wavelength radio waves. The TV uses shorter wavelength radio waves, which is why the TV can't watch the programs of distant TV stations. In order to watch TV programs on the other side of the ocean, scientists use the geostationary satellite with a height of 36 thousand kilometers above the equator to spread TV signals, so that vivid TV pictures can be transmitted to the TVs of thousands of families on the other side of the ocean or on the mainland.
We still have the feeling that some radio stations in distant places can't receive their broadcasts during the day, but they can receive them at night. This is because the D layer is often formed during the day and dissipated at night, which plays a role in attenuating the propagation of radio waves during the day.
Magnetosphere: In atmospheric science, the atmosphere over 500 kilometers is sometimes called magnetosphere. Because here, the earth's magnetic field plays a decisive role in the movement of the atmosphere. The magnetosphere has undergone a series of changes under the action of the solar wind: the side facing away from the sun has been compressed, and the side facing away from the sun has formed a long-tailed jujube magnetic tail similar to a comet. The end facing the sun is about a dozen radius of the earth from the center of the earth, that is, 70,000 to 80,000 kilometers, and its tail length (the end facing the sun) is about 100 radius of the earth, that is, more than 6 million kilometers.
The solar wind is a steady stream of particles thrown by the sun. Its boundary with the magnetosphere is the top of the magnetosphere, and beyond the top is interstellar space. So some people think that the top of the magnetosphere is the top of the atmosphere.