Spider-Man is no longer science fiction -- well, some of his amazing powers aren't, anyway. Being bitten by a radioactive spider probably isn't going to let you scramble up the sides of tall buildings, but yes, it's true -- you really could stop a speeding train with webbing if you were the Spidey one.
For the betterment of humanity, three physicists from the University of Leicester crunched the numbers and worked out how much force the webbing would have to suck up to slow and stop a speeding, runaway New York tube train like Spider-man managed in Spider-Man 2. That would be a colossal 300,000 Newtons, or some insane 500 million joules per cubic metre, by the way. If you're not suitably impressed by that figure, you should be, because it's a monstrous sum.
Anyway, armed with said train-stopping figure, the trio set out to find the strongest spider web around, which of course his Spideyness would spew. They found the Darwin's bark spider, which spits-forth a web that can absorb up to 520MJ per cubic metre -- enough to stop the train if anchored properly.
So, next time you're watching Spider-man romp around New York, leaving a trail of sticky web about the town like a nosey arse that just won't go away, you'll be rest assured that at least some of his antics are based in reality. Now, how about we work on the ability to fly without wings, Superman-style? [Physics Special Topics via Dvice]