Sunshine during Nighttime Darkness

Even the lighting conditions are considerably altered in space. As is generally known, the concept of day is associated with the notion of a blue sky or sunlit clouds and scattering of light in all directions, without direct sunlight being necessary. All of these phenomena are, however, due only to the presence of the Earth's atmosphere, because in it a part of the incident radiation of the sun is refracted, reflected and scattered in all directions many times; one of the results of this process is the impression of a blue color in the sky. The atmosphere produces a widespread and pleasant, gradual transition between the harshness of sunlight and darkness.

This is all impossible in empty space because air is absent there. As a result, even the concept of day is no longer valid, strictly speaking. Without letup, the sky appears as the darkest black, from which the infinite number of stars shine with extreme brightness and with a constant untwinkling light, and from which the sun radiates, overwhelming everything with an unimaginably blinding force.

And yet as soon as we turn our gaze from it, we have the impression of night, even though our back is being flooded by sunlight because, while the side of the object (e.g., an umbrella) turned towards the sun is brightly illuminated by its rays, nighttime darkness exists on the back side. Not really complete darkness! After all, the stars shine from all sides and even the Earth or Moon, as a result of their reflectivity, light up the side of the object in the sun's shadow. But even in this case, we observe only the harshest, brightest light, never a mild, diffuse light.

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