Physics in Spider-Man

Wanda L. Berrios Cerpa

Whenever watching a movie one does pay attention to the action sequences, the dialogue the characters have, the scenery used, and the score which in some cases determines the whole mood of the movie itself. But it never crosses our minds to think about the physics involved when making movie magic. This article approaches the scene in Spider-Man 2 in which our hero stops a train from running off of the tracks using his web (1). This is a time in a movie when you probably say to yourself “nah, that’s impossible” and it only leaves to answer: is this really possible?

A group of physicists at the United Kingdom's University of Leicester have done some research and say it is possible. Spiders produce silk to make their webs or other structures, which function as nets to catch other animals or as nests or cocoons for protection for their offspring and also use it to suspend themselves (2). The silk that spiders produce is five to six times stronger than high-grade steel by weight, and is stronger than any known natural or synthetic fiber on Earth (3).  Silks’ strength is comparable to that of high-grade alloy steel which is around 450 - 1970 MPa, and about half as strong as aramid filaments, such as Twaron or Kevlar, which are around 3000 MPa (2). Since spider silk can be  stronger than steel, these physicists were interested in knowing whether that scene in the movie could actually be possible due to the nature in films to exaggerate things like that. 

To determine if it was possible, they calculated that the force needed to stop four New York City subway cars packed with nearly 1,000 people total would be 300,000 N, after taking into account the momentum of the train at full speed, the time it takes the train to come to rest after the webs are attached, and the driving force of the subway car.  They estimated that Spider-Man’s silk would need to be almost 500 megajoules per cubic meter and while comparing and testing the strength of different types of silk, they found one that matched: silk from Darwin’s bark spider(4). Darwin's bark spider has the toughest silk ever seen, more than twice as tough as any previously described silk, and more than 10 times stronger than Kevlar (5). 

Another parameter used was the stiffness of the silk, which Spider-Man’s web was of 3.12 gigapascals and this is reasonable because real spider silk stiffness ranges from 1.5 gigapascals to 12 gigapascals. The conclusion of the research was that Spider-Man’s webbing is a proportional equivalent of a real life spider, specifically a weaker orb-weaver spider, but its toughness is more alike that of a stronger spider silk (4). The "typical" orb-weaver spiders are the most common group of builders of spiral wheel-shaped webs often found in gardens, fields and forests. Their common name is taken from the round shape of this typical web (6). 

So after researching more about spiders, their silk, and what is it capable of doing, we are now ready to answer our question: is it possible for Spider-Man’s silk to stop a train? And the answer is yes, it is possible.

References

1- Spider-Man 2 scene in which he stops a train: http://www.youtube.com/watch?v=GYOYewO_Veg

2- Spider silk: http://en.wikipedia.org/wiki/Spider_silk

3- How do spiders make silk?: http://www.lifeslittlemysteries.com/523-how-do-spiders-make-silk.html

4- Spiderman’s silk really could stop a train: http://www.livescience.com/27430-spiderman-silk-could-stop-a-train.html

5- Itsy Bitsy Spider’s Web 10 Times Stronger Than Kevlar: http://www.livescience.com/8686-itsy-bitsy-spider-web-10-times-stronger-kevlar.html

6- Orb-weaver spider: http://en.wikipedia.org/wiki/Orb-weaver_spider