English: Free picture about the dark, blue night sky that is covered in cold lights and clouds of the stars and the frozen frost of the winter. This beautiful tree and sky of the winter season was created for you by the self-less epSos.de and it can be used for free, if you link epSos.de as the original author of the image.

The share is called in general night one day between sundown and sunrise, so the period in which the sun stands for the location of an observer under the horizon.

In the strictly astronomical sense the night is the time of complete darkness, so between the end of the astronomical dusk in the evening and their beginning in the morning. The crossing between day and night side of the earth or from planets is called Terminator.

He widens to a dusk zone if the heavenly body owns a noticeable atmosphere. Night sky is a name for the sight of the sky at night. In the night sky the stars which are illuminated during the day by the sun appear at least at clear nights.

For most people the night is the time of the sleep, however, for nocturnal animals like owls, bats, many insects etc. the time of the activity. Most countries have a row of noise regulations and other protective regulations for the nighttime and for necessary night services, mostly also for early services and shift services.

This is called sky in general of the earth or even more in general from the surface of a planet by the atmosphere with look in the direction of the space seen panorama.

The dark sky is called night sky in the deep dusk or at night. In the astronomy one understands above all the starry sky by it, i.e. the night sky with few or no cloudiness.

Timewise the concept is limited by the period between the astronomical dusk and daybreak, i.e. if the sun stands more than 12 ° under the mathematical horizon of the concerning place. With this depth corner and pure air the scenery horizon is hardly to be recognised more, however, a bigger number of stars. However, entire darkness rules when the sun stands more than 18 ° under the horizon.

With light-strong photo objectives and highly sensitive films or digital cameras one can expose on locations in the Hochgebirge up to some hours, before the clarifications become effective as "a grey veil" and the weaker stars are illuminated by the picture background. On the edge of a city this maximum exposure time on few minutes decreases.

With surface-like sky properties this restriction still becomes substantially more clearly perceptible, which is why one can see, for example, the luminous tape of the Milky Way only in towns more once in a blue moon.

The Bremen doctor and amateur astronomer Wilhelm Olbers employed about 1800 important considerations to the brightness of the night sky and to the structure of the whole universe. His question, why the night sky generally dark seems to us, has become known under the name „Olberssches of paradox“.

Thank you for sharing this night sky picture with your friends !