You might naturally and understandably reply, 'one you fool', but think about it for a minute. A little vespa scooter produces about 10 horsepower. If this is actually 10 times the power of a horse then a vespa weighed down to 400kg (my guess at the weight of a horse) should not only be able to move itself at considerable speed, but should also be able to beat up to 9 horses in a tug-of-war. Obviously it can't. Can it? The first thing that comes to mind is traction. We could eliminate this factor by running the vespa engine in a 400kg rail carriage on toothed rails, giving it massive traction - would this allow it to pull the horses backward? Instinctively it still seems ridiculous. So what's wrong? Does a horse have more than one horsepower? Is it really all down to traction? Or am I confusing horsepower with torque? Or something equally dumb?