A good one for the urban warriors, this. You really never know how handy it might be. It’s about a year since I posted this, but the academic controversy rages on. Propellorheads can be astonishingly passionate about their work….
First choice of course is to pull the emergency handle. Or break into the driver’s cab on the train and remove the heart attack victim’s body from the dead man’s handle. Train stops, problem solved. Or call the control centre, tell them to kill the power to that section of line. That would work.
All a bit mundane though, so I’ve got a much better idea. Get bitten by a radioactive spider. I realise this may not be as easy as it sounds. Radioactive spiders aren’t that common. Even if you find one, it’s not likely to bite you. In the UK, the likelihood of getting bitten by a spider is about 1:2,000,000 head of population per year. What you might call vanishingly small, except it’s not; I’ve been bitten twice. And not by anything 6” across staggering out of a bunch of bananas. Native hedge spiders. They must like me.
For the purposes of argument, you’ve got yourself bitten. You’ll develop amazing powers that will help you avert train-based disasters. There are drawbacks to this approach. Expect to suffer terrible social isolation, have to tackle lots of mad scientists with eight mechanical limbs, and have a serious talk with your ex-BFF about his nocturnal habits as a supervillain. I’m afraid it goes with the territory.
You may be wondering where this idea came from. A group of physics postgrads at Southampton University recently published a paper showing that a spider’s web could stop a subway train, just as Spiderman does in the film. It wasn’t a serious piece of research, they just did it as a lark in their spare time, but it’s fun. Never let it be said that scientists are a humourless lot. I’m one for starters.
The guys in Southampton did some calculations based on the experimental breaking strain of spider gossamer and the force needed to stop a notional train. It’s all a bit heavy on the numbers, and involves terms such as ‘gigapascals,’ but based on some assumptions, including the apparent size of the web that Spidey uses in Spiderman II, it would work. It’ll put a strain on your shoulders, mind you, but if your arms don’t pop out of their sockets you’re on a winner here.
You may have read that spider gossamer is stronger than the same diameter wire made of high-tensile steel. It’s true, but it’s nowhere near as simple as that if my memory serves me correctly. There’s another measure, toughness, and in this spider silk not only thrashes steel but also shows a clean pair of heels to Kevlar.
Spider gossamer is a very very complex structure indeed, and it’s largely composed of polypeptides or small protein chains. The threads consist of filaments, like wire, but also have blobs on them at intervals, like a string of beads. Inside the blobs there are more coils of filament folded into sheets. When an insect or other prey blunders into the web, there’s a lot of energy to be absorbed if the insect is not to simply bounce of like a ball off the head of a tightly strung tennis racket. It has to act more like the safety net when a trapeze artist falls into it. The folded fibres simply unravel to allow the filaments to extend and absorb energy. This makes the filaments much more elastic, or stretchy, than steel. You can extend their length for a whole bunch before they snap, and they do that gradually. It’s a bit like pulling a string of gum or toffee, which sags and stretches but doesn’t snap until the very last minute, unlike steel which gives up in one big hurry when it lets go. You’ll know about that if you’ve ever snapped a top string on a guitar. It doesn’t go saggy, it goes ‘Twang!’
So next time you see a subway train in trouble, just hope Peter Parker is on the case and not suffering one of his teenage-angst ‘Nobody loves me!’ moods and hasn’t had a falling out with his Aunt May. If he has, it’s up to you, kids. Go and get bitten and do it now.
Other interesting snippets on spider webs.
Spider silk’s density is such that a thread long enough to go round the world would weigh about 18g, or just over ½ an oz.
In days of yore, spider webs were used as a wound dressing dressing for cuts and slashes. The matrix of the web gave a foundation for blood platelets to hang onto during the clotting process, and help to stop haemorrhaging. Unlike Band Aids, spider web is biocompatible too. Not a lot of people know that.
In China, bags woven from spider silk were used to carry objects such as arrowheads, which were heavy and dangerous.
Queen Victoria was presented with a cloak woven from spider silk.
Spider silk has been used to make artists’ canvas.
Spiders on acid spin webs webs that do sort ofconform to their species pattern. Caffeine really messes them up.
They have genetically modified goats to express spider silk proteins in their milk.
Nobody is quite sure why spiders do not stick to their own webs.