Can a spider’s web stop a subway train, say in NYC? What will it take for a spider’s web to do so? Or was the scene where Spiderman stops the train by his web just a useless fantasy?
A group of students went into this question and surprisingly found out that some spiders can surely stop a train .. and have some tensile strength to spare!
First, the team calculated how much four R160 New York City subway cars — packed with a total of 984 people — would weigh (about 200,000 kilograms, or roughly 10 Atlas V rockets). Then, they calculated how fast the train was going (24 meters per second, or about 53 miles per hour) and how much resistance the track would have offered as it charged forward (negligible). From there, they could work out how much force the webbing would have needed to exert upon the train to stop it: about 300,000 Newtons, or about 12 times the amount of force exerted by a large American alligator as its jaws snap shut.
After considering the relative geometry of the train, webs, and buildings used to anchor the silk, the team calculated the amount of stiffness, or tensile strength, required to hold the train in place without snapping. That value is known as Young’s modulus, a measure of the stiffness in elastic materials, and works out to be 3.12 gigapascals (one Pascal = 1 Newton applied over a square meter).Turns out, orb-weaving spiders produce silk that ranges in strength from 1.5 to 12 gigapascals — meaning that yes, Spider-Man could have stopped a moving train by flinging sticky silk at it. Coincidentally, the properties of the silk produced by Darwin’s Bark Spider (Caerostris darwini), an arachnid that lives in Madagascar and spins the largest webs observed (sometimes hanging from 25-meter long anchor threads), match those of the webbing Spider-Man deployed in this scene.
Here is the scene for you.