Hollywood movies are full of monsters, bad guys, aliens and mythological creatures, which make the good guys look better after saving the world, or at least some damsel in distress. While some depictions are scientifically documented, some of them are just plain impossible and could only exist in people's imagination.
Science laws debunk many of these myths and prove that they simply can't exist in the physical world, as we know it. So let's look at one example of "beings that can not be".
The ghost is thought to be the apparition of a deceased person, frequently similar in appearance to that person, and encountered in places he or she frequented, or in association with the person's former belongings. It also often refers to the souls, of spirits of those who can't find eternal rest and wonder the world in search of resolution.
walking through walls
Nobody has been able to prove ghosts don't exist, but science has proven that they can't act the way they do. For instance, their ability to walk through walls is a common talent of Hollywood ghosts. There's one problem here. Newton's laws of physics say that if a ghost can walk, it shouldn't be able to pass through walls, since a body at rest will remain so until it's subjected to an external force and for every action there is an equal but opposite reaction.
This is exactly the case with walking ghosts. If it walks, it must by applying a force to the ground it steps on and the ground must apply to the ghost an equal and opposite force, that pushes the body forward. This means that a ghost must be made of matter, and not energy.
Supposing it's made of energy could explain the fact that ghosts may pass through walls, but most certainly, they couldn't walk. And if a ghost could walk through walls, this means it could also pass through the floor. If a ghost were able to stay on the floor without passing through it, then it would have to apply a force to the floor, whose equal reaction should keep her on the floor. Pure energy couldn't do that, so either way, a ghost can do both things, stand or walk and pass through walls.
Another ghost myth says that sharp drops in temperature are also associated with the arrival of a spiritual presence.
It has become almost a Hollywood cliché that the entrance of a ghostly presence is foreshadowed by a sudden and overwhelming chill. Again physics says it's not possible, or at least that ghosts can't be responsible for such a phenomenon.
In fact, when a warm object is placed next to a cold object, energy flows from the warm body to the cooler body, cooling the warm body. So if a ghost causes the air in a room to cool down, that means the original heat of the air must transfer onto a cooler body, which rapidly warms up.
It seems that when a ghost causes the temperature in a room to drop, the ghost itself warms up, so all ghosts should be hot. But if ghosts are made of pure energy, where did the warmth go? Energy doesn't just heat up, like matter.
Again, if ghosts were made of matter, they could absorb the thermal energy of the surrounding air, becoming hot themselves, but they won't be able to pass through walls, so they must enter and leave through a door or window.
A more likely explanation for the chilling effect would be a sudden draft, occurring in a room with a high window or a door with a gap, where the cool air from outside displaces warm air inside, creating a system of heat cycles and eddies. This creates a combination of air currents that may cause temperatures to drop up to 2°C, and the effect would be increased by the fact that humans are more sensitive to rapid changes in temperature even if the absolute change is small.
Another phenomenon associated with ghosts is the sound. Most ghosts in alleged sightings are not talking, but some of them are, even though this is not possible. Speech can be described as an act of producing voice through the use of the vocal folds and vocal apparatus to create a linguistic act designed to convey information.
Speech involves air, and air can't be manipulated into forming recognizable sounds by a ghost who's made of energy. So ghosts can't talk. Some of you would say that maybe the ghost is able to communicate through telepathy. That hasn't been proven so far, but supposing they posses this form of communication, why don't all them talk?
A possible explanation for the ghosts is in fact related to sounds. Frequencies lower than 20 hertz are called infrasound and are normally inaudible, but British scientists Richard Lord and Richard Wiseman have concluded that infrasound can cause humans to feel a "presence" in the room, or unexplained feelings of anxiety or dread.
The traditional perception of ghosts wearing clothing is considered illogical, given the supposed spiritual nature of ghosts, suggesting that the basis of what a ghost is said to look like and consist of is quite dependent on preconceptions made by society.
The last, and probably the most important with ghosts is that we shouldn't be able to see them. Why? Because the sight is the ability to interpret visible light information reaching the eyes, after it bounces off a surface.
How can light bounce off an inexistent surface, when ghosts are made of energy?
Although the physical arguments present above do not deny the existence of ghosts, I hope that they made you at least ask yourself some questions, before believing everything Hollywood is shoving down our throat.