“Why is it always dark in space”: How is it that all space photographs always show absolute darkness
A fairly common question that both children ask physics teachers and fans of popular science publications is why it is always dark in space? After all, the sun is even closer there than on the planet, and nothing prevents the spread of light. How does it happen that in all space photographs there is always absolute darkness, informs Ukr.Media.
To answer this question, you need to understand the physical nature of light. Despite the fact that light is a wave and that it is more correct to compare light with a flow of energy, remembering somewhere inside about dualism, it will be easier to imagine light as a flow of physical particles. A kind of flying cloud of balls. Let's say right away that this is an incorrect analogy, but it is useful here.
We see objects on Earth only because light rays are reflected from them. Look at a completely black body that absorbs all the rays that fall on it, and it will no longer seem to really exist. All because there are no reflected particles.
The usual scheme is that a stream of balls flew in, hit an object, bounced off it and flew towards our eyes. The balls interacted with the eye and an image was obtained. The scheme, when the object is invisible, is different – the stream of balls flew in and did not bounce back from the object. Nothing interacted with our eyes. It is logical that then we would not see anything with our eyes.
This leads to a simple fact – there is nothing in space. There is no matter there from which the balls could bounce. Light has nothing to reflect off, so everything seems to be absolute darkness. And although there is a certain amount of one or another matter in space in a vacuum, this is not enough for a full reflection of light. At the same time, all objects such as planets and spaceships are quite visible. The “balls” bounce off them perfectly.
Everything seems clear here, but where does the “backlight” in the Earth's atmosphere come from? After all, although there is a certain amount of matter in the air, it is most likely not enough.
A group of factors are at work here. Near the planet we are also dealing with volumetric reflection of light from the planet's surface. It is not the air that is illuminated, but the rays reflected from the surface that are illuminated. The air itself, although not so dense as to be a full-fledged source of reflected rays, still contains a certain number of reflective objects: dust, particles, water vapor, etc.
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