It sounds like a joke but I just want to know if shadows have mass, since shadows are formed when there is blocking of light. It forms a black pattern with no energy therefore it has no mass.
[Physics] Do shadows have mass
massshadow
Related Solutions
Lightning is not 'just light', it is according to this NOAA National Severe Storms Laboratory FAQ,
Lightning, as best we understand, is a channel of electrical charge, called a stepped leader that zigzags downward
So, technically speaking, the mass of a lightning bolt could be the sum of all the electrons and the plasma within the electrical charge channel. (thank you to tpg2114)
Each electron has a mass of about $9.11 × 10^{-31}$ kilograms, but it would not really be feasible to exactly count how many electrons there are in a single lightning bolt, hence, not feasible to get an exact mass.
Given the image in your question, I think the answer has nothing to do with diffraction and is related to the light source not being point-like.
The discussion in this answer will be entirely based on geometric optics where all optical phenomena are described by light as a ray.
I will base my discussion on the image below (from Wikipedia). The image is in the context of the Earth's shadow, but the description applies to any scenario with a light source and a shadow casting object.
For an extended light source (non-point-like), such as the sun, the light does not originate from a single direction and results in three shadow regions:
- Umbra - In this region of the shadow the complete light source is blocked by the shadowing object. The shadow is maximally dark and uniform over the region.
- Penumbra - Within the penumbra region only a portion of the light source is block so the shadow here is not as dark. The depth of the shadow is in proportion to the area of the light source blocked by the shadowing object. This region results in a gradual transition from the dark umbra to the shadowed region. As you move farther away from the light source the relative angular size of the shadowing object decreases faster than that of the light source so the penumbra region becomes larger while the umbra shrinks.
- Antumbra - The final region, the antumbra occurs when you move far enough away from the obscuring object that it no longer completely cover the light source. Here the shawdows are not a deep as in the umbra and gradually transition from the full umbra so unshadowed, once again making the edges of the shadow less deep.
When you are closer to the shadowing object, relative to the light source, the umbra region is greater and the penumbra is thin. As you move farther away, the umbra region shrinks and the penumbra grows. This causes the effect asked about in the question.
The above discussion applies when the size of the obscuring object is smaller than the light source. For example a lamp post and the sun. When the shadowing object is bigger the situation is somewhat different and there is no antumbra.
For a point-like source, or an extended source that is far enough away to be considered point like the only region that remains is the umbra as seen from the shadow, the light route is either visible or completely blocked, leading to sharp shadow boundaries.
Best Answer
A shadow is a lack of light. Therefore, a shadow has no mass, for a shadow is not an object or energy. Shadows can go faster than light in certain cases because they are not objects. In the same way, a vacuum has no mass.