Why is dark at night: a scientific explanation
At any point of the earth, there is a time when it's light, andtime when it's dark. This is primarily due to our main luminosity, the Sun. It moves across the sky, changing the level of illumination. Simply put, at night it is dark, because the sun goes beyond the horizon.
An interesting point of view of ancient people
In ancient times, people assumed that thisThe sun is spinning around our planet and hiding behind the horizon. No one for a long time could even imagine that it was our planet that rotates in the vast cosmic space around the luminary. The same goes for the Moon. The sun and moon were given divine origin: they were worshiped, brought gifts, praised in songs and rituals. But the era of science has come, which proved that everything is just the opposite. The planet Earth is not the center of the universe, but only its tiny component, and why it is dark at night is not associated with any divine manifestations.
What is the rotation of the Earth and what does it affect?
There are two simultaneous movements and movementsplanets in space: the orbital motion around the Sun, and also around its own axis, like a children's top. That is, at the same time, when the planet flies in outer space, it revolves around itself, and the combination of these factors is the reason why it is dark at night and light in the daytime. The orbital movement in space, coupled with the fact that the Earth's axis is tilted to this very orbit at an angle of about 66 degrees, is the reason for the change of seasons and their "dissimilarity."In different parts of the Earth, depending on the degreeheating rays of the luminary, in its time, change the fall, winter, spring and summer. Thus, the middle latitudes most often visit all four seasons, to varying degrees of their intensity (for example, in Italy summer, like winter, is much warmer than in Moscow). On the Equator, which is mostly under direct sunlight, close during the midday to a corner of 90 degrees, the day lasts somewhat longer than 12 hours.
Pole: why is it cold, although the day there is six months?
At the poles, the picture is quite specialway - the sun's rays fall so that they glide and almost completely reflect off the surface, without lingering or leaving heat in it, although day and night here last almost six months each. Why the north and south pole are the coldest regions of our planet.
Different duration of the day and night
Rotation of the planet around the Sun, the main starfor us, sets the change of the seasons, as well as the change of day and night. The spherical shape of the planet, the heterogeneity of the surface and the property of the light rays to be reflected complement and make the climate more diverse in similar regions. But there are days when in all latitudes up to the polar belt comes the day, having the same distribution of time between the clear part of the day and the dark - the days of the spring and autumnal equinox. At this time on the equator, any object will give the smallest shadow, because the sun lets its rays at an angle of 90 degrees to its surface.
Basically, with a question, why at night happensdark, everything is clear. But it's interesting that it's dark for a long time, and sometimes it's a bit. For our Northern Hemisphere is characterized by a decrease in the duration of the night from March 21 (spring equinox) to September 23 (autumn equinox), and vice versa - long nights are observed in winter. In the southern hemisphere, the situation is reversed.
But how can this be explained to the children?
Explain to children the phenomenon of what happens at nightit's dark because the sun does not shine, not quite right. After all, in fact, the sun always shines. It does not turn on and does not turn off by someone's decision, like a desk lamp. But it is not necessary to talk about the position of the Earth in space, about the angles of incidence of rays and about other abstruses that can be understood already by school-age children. For this, parents are best able to show wit and demonstrate clearly how this happens. In order to explain why it is dark at night, you need to introduce the child to two concepts: what is the sun and what is the planet Earth. To do this it is quite simple: to draw two balls, one - yellow and with rays (actually the Sun), and the other - blue with the likeness of the outlines of the continent. Further, without going into complicated terminology, to tell about the form, and to demonstrate clearly with the help of the model of the solar system. It will be enough to have a yellow ball and a small globe, and if there is an opportunity, it is better to buy a full-fledged model or to do it yourself, and even together with the child.Show that the sun is standing still, and wewe turn, why its rays to different parts of the globe do not always fall. Then the child will understand that at night it is dark, because at this time we turn away from him, we substitute the back to the sun, so to speak. For full visibility, you can demonstrate this phenomenon in the dark at the same time with the help of the same globe and a flashlight acting in the role of the Sun.