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Aadya Patel

The Speed of Dark

Nyctophobia is the fear of the dark. There is another fear that is far more blood-curdling, the fear that darkness will go away- Optophobia.

We know that light travels at the fastest speed possible for a physical object. Darkness appears when light leaves and is erased when light appears. The speed of dark is the speed of light, but some types of darkness can travel faster, for example, a shadow. This can become a little hard to wrap your head around but it's true. Without breaking the law of Physics, we can conduct an experiment to demonstrate this phenomenon.


Let’s say you have a light source that is powerful enough to reach the planet Jupiter. Also, it casts a beam in a cone that’s wide enough to cover the entire diameter of the planet. Now you pass your finger over the lens (the light source) and the shadow will cross the entire diameter of the planet that is a distance of 86881 miles. The speed of light is 3 times 10 to the power 8 metres per second which will be 186000 miles per second. So, if it takes you less than half a second to move your hand that distance then that shadow will have broken the speed of light!



Shadows are nothing but the absence of photons, or particles of light. As there is nothing that is travelling the distance, the only thing that is in motion is an area where photons are not present. There's no information that's being transmitted faster than light, only a blockage of information. The rule is information cannot travel faster than light and the shadow is not transferring any information.


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