Physics Laws That “Don’t Apply” in Movies Part I
Physics Laws Generally, filmmakers have no choice but to comply with the laws of Physics in the films that they make. However, there are times that they have to “cheat” to create very good special effects.
Let us identify a few movie effects that could make us believe things that are far from the realities of life.
You are watching a heart-pounding action film, with a very good and exciting car chase. Suddenly, one of the cars crash, gasoline leak and within a few seconds… BANG! A terrific but disturbing explosion which is completely violent. In reality, gasoline doesn’t easily explode! Calvin Feist identified several factors that could cause a car to burst into flames and rare occasions that it would explode. It was only recently that this kind of car explosions was discovered on film. You wouldn’t see those in black-and-white movies. It’s pretty good to see effects like these but sometimes, audiences take it for granted. So it’s not really necessary to go rushing out of your crashed car or risk injuries to those inside one by hurriedly pulling them out because of the fear of explosion – there’s a probability that it won’t happen.
Sound at light speed
Okay. There’s a volcano that erupted at a distance and the eruption is heard instantly. Wrong! There’s also thunder and lightning heard simultaneously. Wrong again! How about this? You hear the crack of a baseball bat as the ball comes in contact with it. Still wrong!
In real life, you will see the action first, especially if the action produces light, before actually hearing it. This is because light travels a lot faster than sound. You might have noticed that thunder is heard a few seconds after lightning strikes, not as you see it. This is the reality in the speeds of light and sound.
Glow in the dark
There were movies that made us believe that radioactivity could make you glow in the dark and is contagious. I could not really say which film started this all but the truth about this is that radioactive materials only glow in the dark when the radioactive element is combined/mixed with materials such as fluor, which creates the “glow” effect.
Another thing is, radioactivity is not contagious. A person exposed to radioactive neutrons can become slightly radioactive (but he won’t glow). And even though there have been studies that show the interactions between the cells radiation-exposed fishes to those who were not exposed to radiation (bystander effect), there are still no studied effects on humans. Brant Ulsh CHP, PhD, answered a posted question “Can his exposure be transferred to me and affect my cells?” with “I don’t think you should worry about being involved with a radiation worker.”
Kicks and gun shots that make people fly
Here’s another one. We often see people fly backwards as they receive a very good Kung Fu kick or a “surprise” gun shot from someone. And sometimes, for a very dramatic special effect, goes through a glass window or something similar (see next item for this). This is good to see in a movie but in real life, the law of conservation of momentum says this isn’t possible. A small bullet, or even a shotgun blast, doesn’t have enough momentum to make people/victims violently fly backwards.
Similarly, a Kung Fu kick would send both the kicker and the victim flying in opposite directions. That is, if the kick is hard enough to send them both flying.
Even as a grownup, I really get a good laugh every time the coyote or any other cartoon character runs off a cliff, gets suspended momentarily and falls off only when he gets aware of the situation. We don’t see this in movies but a somewhat similar event is when cars and buses “jump” across gaps after gaining enough acceleration, which is never true. In fact, the vehicle would fall off even if it moves at a very high speed. In a real life situation in 1989, during the San Francisco earthquake one car drove off the edge of the gap, crashing onto the lower deck and killing the driver.