Every day, the Earth makes a complete revolution around its axis. With the onset of morning, the Sun rises again, becomes brighter and warmer. Why is this happening, and why is the night longer or shorter? Does night change everywhere with the seasons?
These are interesting questions that need to be answered. Modern science can analyze them in detail, give answers to all the points of interest to a person.
Earth's rotation around its axis and around the Sun
The Earth never stands still, it constantly rotates - both around the Sun and around its axis. A complete revolution around its axis takes the planet about 23 hours, 56 minutes and 3 seconds. But this is not an absolutely accurate value, since the length of the day can vary within a few seconds - in this regard, the Earth can both “slow down” a little and “accelerate”. These are barely noticeable variations, but for convenience it is generally accepted that a day is 24 hours exactly.
When the planet rotates, its zone, which is illuminated by the star closest to us, gradually moves from one point to another. So, the sun's rays first fall in the region of Japan, then move to Vladivostok, and then the illuminated point moves westward until it returns to its original position. At that moment, when it shifts from its position, for example, leaves the territory of Japan further west, in this place evening begins, twilight, and then night falls.The dark time of the day will continue until the sunlight falls again on the territory, having passed a full circle on a rotating planet.
Interesting fact: the sun's rays move across the planet from east to west. From here came the word east - the place where the Sun rises. The West is the territory where it falls over the horizon, disappears. Japan is called the "Land of the Rising Sun", as the locals are the first to observe the appearance of the sun each new day.
Polar day and polar night
But why is the day longer in summer and short in winter? This phenomenon is observed almost throughout Russia, as the country has a northern location. It should be noted that in addition to the rotation of the planet, another factor plays the role - the inclination of the earth's axis. The closer the latitude to the poles, the stronger the presence of this factor is felt.
The inclination of the earth's axis is approximately 66 degrees, because of this, the effect of the sun rising low in winter, shortened daylight hours, is created. Also, thanks to this, in the summer, nights are short on the territory of Russia, and it is possible to observe such a phenomenon as “white nights” when complete darkness does not actually occur.
In the polar territories, this phenomenon is even more pronounced - during the 3 summer months the sun does not set at all. It makes a certain path across the horizon, barely touching the horizon, and then rising again. But in the winter months the sun does not rise, and the polar territories plunge into complete darkness.
Day at the equator
At the equator, the opposite phenomenon is noted.Here, the inclination of the earth's axis does not actually play any role, at any time of the year night and day are equal, amounting to 12 hours. These areas are illuminated by sunlight at an angle of 90 degrees, because the lighting is more intense, and daylight is more stable.
If the inclination of the earth's axis did not exist, the inclination of the illumination would not change. In this case, in any of the territories, the Sun would always rise to the same height, ensuring equal duration of day and night. However, the nature of our planet is more diverse in this regard. It should be noted that the tilt of the axis of each of the planets is individual. So, Uranus does lie on its side.
Scientists also emphasize that the inclination of the earth's axis throughout the evolution of the planet could repeatedly change. Perhaps the change in slope proceeded abruptly, creating completely new climatic conditions, which entailed the mass extinction of prehistoric living creatures. However, this statement to this day remains only one of the hypotheses, although the evidence for it is very strong.
Thus, darkness at night is caused by the fact that the Sun temporarily remains on the other side of the planet due to its rotation, not being able to illuminate the entire globe at the same time. However, it still continues to shine, as evidenced by the light of the moon at night. The only satellite of the Earth shines only with reflected light; by itself, it cannot produce glows. It can be partially covered by the earth’s shadow, which causes a change in the lunar phases, but in most cases the moon is noticeable at night - just because of the sunlight that it reflects.
