Speed of Darkness - sciencenerds

Light travels at the fastest possible speed for a physical object. The darkness is erased when the light appears and returns when the light goes out. The speed of darkness is the speed of light, but there are other types of darkness that can move faster than the speed of light. For example, a shadow.

 Over a distance, a shadow can be made much larger than the object that creates it, but still mimics its origin, moving in the same way during the same time. Then, when a shadow is larger than the object that casts it, it moves a greater distance when the object moves but in the same period of time.

Make a shadow large enough and you can travel across the surface faster than light. If you, here on Earth, cast a shadow on the Moon, it is not an easy thing to do, which pointed from, say, point A on the surface of the moon, and then moved your finger so that the shadow moved to point B, your finger would only move a few centimetres in a fraction of a second. But the shadow cast on the moon would move thousands of kilometres in the same amount of time.

Do it right and you will easily produce a shadow that breaks the light barrier. But nothing happens here. The rule is that information cannot travel faster than light. You cannot make something happen in another place faster than light could travel from you to that other place. And our superluminal shadow is not transferring information from point A to point B. Of course, point B is being thrown into the dark before a light-speed message from A can warn it to approach, but darkness does not travel from point A to point B You are travelling from you to point A and point B at the speed of light.

What call shadow is really just a cross-section of a three-dimensional region. The darkness it is causing only changes to shape when the newly unlocked light fills the previous space. That's all shade is a gap. So, in a way, a shadow does not travel at all. That is an illusion caused by us to think that a shadow is something physical when in reality a shadow is just the lack of physical things: photons

They advance in the speed limit of the universe. But that does not mean that two shadows cannot kiss. Or, at least, it seems they are. Watch as a boy brings two shadows close to each other. Just before they really make contact, the shadows seem to magically bulge each other, in a kind of dark kiss.

What is happening is the shadow blister effect and has to do with the anatomy of a shadow. Umbra is the region where an object completely blocks a light source. It is the darkest part of the shadow in the most prototype part of the shadow. Where only part of the light source is blocked, we find the weakest penumbra. But as two or more penumbras approach and overlap, the combined amount of light they block may be sufficient to produce a noticeable difference, the shadow blister.

 The Earth has a large umbra, it is 1.4 million kilometres long. This is how far it should be from Earth so that it no longer has an apparent diameter large enough to block all suns. Here, on the surface of the Earth, we are not so far away, so the night is so threshold. The night is only the shadow of the Earth that falls on you. To You eclipse (I mean your eclipse ... that's funny!).

The sunsets are great, they are beautiful to look at, but look the other way and you can see the shadow of our planet. Our atmosphere disperses the shorter wavelengths of light more than the longer wavelengths, which makes the sky look blue. But in the shadow of the Earth, there is less light to disperse and the sky seems darker. During twilight, you can see the demarcation.

This is the night shadow that approaches Earth. The beautiful pink band on her? That is the belt of Venus. It is caused by the sky that reflects the colours of the sunset behind us. You have probably noticed that just after the sun sets, it disappears from view, there is still light in the sky, scattered by the sun that is no longer visible. 

If the sun is less than six degrees below the horizon, it is technically a civil twilight. You can still do many things outdoors without the need for artificial lights.

At 12 degrees below the horizon, we have a nautical twilight: artificial lights are more or less necessary, but the sky still scatters enough light to be bright enough for ships in the sea to navigate when seeing a contrast of the horizon between the dark and dimly lit sea sky.

Up to 18 degrees, astronomical twilight occurs. It seems at night but the sky can still darken. Until astronomical twilight is over, astronomical observations cannot be made overnight.

Less than 18 degrees is technically, honestly, at night. If you live at more than 48.5 degrees north or south latitude, during the summer the sun never goes more than 18 degrees below the horizon. Technically it is never night.

But that is slow darkness. Let's get to the point because we are looking for fast darkness. When the scissor blades cut, the point of intersection between both blades moves faster than the blades themselves.

Think of it this way: if I had a pair of scissors with blades that would last a light year and take a second to close, the intersection point would have travelled a full light year, not a year, but ... one second.

Laws are not being violated here because such a cut would be physically impossible. As I mentioned before, rigid objects do not move instantaneously when a thrust force is applied. Instead, that force moves through electromagnetic forces, from one atom to the next, and so on in the line. A compression wave that travels through the material at the speed of sound.

But what if we ignore that problem by allowing the blades to simply be separated in motion? Well, your point at an intersection can still travel faster than light, because it is not something physical. It is only a geometric point and does not carry more information than it could already gather when witnessing the approaching blades. But don't count that geometric point of the intersection yet.

It is the key to another type of darkness that can move faster than light. When waves collide, their ridges can merge into larger ridges, their channels into larger channels. This is constructive interference. But the ridges that collide with the channels are cancelled. If the waves are light, the result of destructive interference is darkness. And, in certain circumstances, the darkness created in this way can travel as the intersection between two lines, faster than light. Imagine concentric circles as light waves. The lines are wavy ridges and the intermediate spaces are channels. When they meet the points where they cross, they flee up and down faster than the waves travel, especially in the middle, which, in the case of light waves, makes them faster than light. The superluminal speeds of these dark patches can be seen very clearly if we make the crests of a source's waves black and the background. The overlapping regions in which red looks out represents destructive interference: darkness.

~sciencefreak