Why do perihelion and aphelion occur

The earth's atmosphere changes continuously into space, so that it is not sharply delimited at the top. Their mass is about 5.13 × 1018 kg and thus makes up almost a millionth of the earth's mass. In the atmosphere at sea level, the mean air pressure under standard conditions is 1013.25 hPa. The atmosphere on the ground consists primarily of 78% by volume of nitrogen, 21% by volume of oxygen and 1% by volume of noble gases, predominantly argon. In addition, there is 0.4% by volume of water vapor in the entire earth's atmosphere. And the proportion of carbon dioxide, which is important for the greenhouse effect, increases as a result of human influence and is around 0.04% by volume.

The temperature extremes measured meteorologically on earth are −89.2 ° C (measured on July 21, 1983 at an altitude of 3420 meters in the Vostok station in Antarctica) and 56.7 ° C (measured on July 10, 1913 in Death Valley at 54m below sea level). The mean temperature near the ground is 15 ° C. At this temperature, the speed of sound in the air at sea level is 340 m / s.

The earth's atmosphere scatters the short-wave, blue spectral component of sunlight about five times more than the long-wave, red, and thus colors the sky blue when the sun is high. The surface of the seas and oceans also appears blue from space, which is why the earth has also been called the “blue planet” since the beginning of space travel. However, this effect is due to the stronger absorption of red light in the water itself. The reflection of the blue sky on the surface of the water is only of secondary importance.

The magnetic field surrounding the earth is generated by a geodynamo. The field resembles a magnetic dipole near the earth's surface. The magnetic field lines exit in the southern hemisphere and re-enter the earth through the northern hemisphere. The magnetic field is deformed in the earth's mantle. The magnetic field is compressed by the solar wind outside of the earth's atmosphere. The Earth's magnetic poles do not exactly coincide with the geographic poles.

The earth has a satellite, the moon. The moon orbits the earth as a natural satellite. The ratio of the diameter of the moon to its planet of 0.273 (mean moon diameter 3,476 km to mean earth diameter 12,742 km) is significantly larger than that of the natural satellites of the other planets.

As far as we know today, the moon was formed after the proto-earth collided laterally with the Mars-sized Theia, an asteroid.