When people think about Sci-Fi, most of them think about Star Wars. This Legendary Franchise re-defined books, television, movies, and so much more. The phrase "I am your father" has become a permanent fixture of pop culture.
Often times in Science fiction, writers use a futuristic setting as a way to explain phenomenon that aren't currently impossible. Whats interesting about Star Wars is that the things which the characters do are not only impossible now, but ever.
In many different Sci-Fi movies and television shows, grand battles occur in space between spaceships. During those fights, ships often shoot lasers at one another, creating an audible sound as they are discharged. Star Wars is particularly well known for this. However, such is not possible. In order for sound to exist, a wave traveling at whatever frequency must travel through some kind of solid, liquid or gas. And since space is a vacuum, this phenomenon does not make any sense. In order for the sound to carry, the portion of space that the battle is occurring in could not be a vacuum.
In Star Wars, some of the most enjoyable moments are those involving light sabers. Whe'ther it be the 'sword fights between the Jedi and the Sith or the reflection of incoming laser blasts, it is these events which truly made the Star Wars Franchise. Unfortunately, they are all impossible. Let's start with the lightsaber itself. One of the basic properties of a light wave is that it will continue to propagate unless there is a change in medium. What that means in context is that in order for a lightsaber to be a spec'ific length, the end of the beam has to be coming into contact with something else. And since that is not the case, lightsabers, at least how they are depicted in Star 'Wars, are already impossible. Only if some object was placed at the end of the blade to either relfect or refract the light would these kinds of swords be impossible. In that situation, however, things like stabs and slashing with certain ends would not be possible. The only way for lightsabers to be possible would for them to be composed of something other than light.
Next, there is the issue of swords clashing and reflecting laser blasts. In regards to the former, such a phenomenon could not happen. Lightsabers are, by definition, swords composed of light and light is made up of photon waves. Photons are a type of boson, a sub-atomic particle that can occupy the same space as another Boson. This, as a result, makes lightsaber battles impossible. For because of this property, the two beams of light would not collide, but simply pass through one another. Once again, the only way for light sabers to be possible is for them to be made of some substance other than light waves.
Besides the duels, there is the issue of deflecting laser blasts. Lasers lights w'ould move at the speed of light, or 3 x 10^8 meters per second. That is almost 100000 times faster than the fastest fighter
' jet in the world a'nd nearly a million times faster than the average bullet. This is relevant because it 'means that, even if a someone shot a laser from a gun at a distance of a mile away , a Jedi holding a lightsaber would have to react within 5 millionths of a second in order to react in time and deflect the shot. And since the delay between between the human eye observing information and the brain processing it is a thousandth of a second, it is impossible for such an event to occur.