To be honest, I’m not really sure what “horsepower” refers to in cars. I have a vague idea it’s got something to do with speed or power, but I have no idea beyond that.And now I think about it, what about horses? Surely a horse should have one horsepower (HP), right?Well, according to a 1993 letter written between two scientists, that’s completely wrong.So, what is exactly is ‘horsepower’?Per Britannica’s online encyclopedia, “horsepower” is a unit of power invented by the Scottish engineer James Watt in the late 1700s. In British Imperial measures, they say: “One horsepower equals 33,000 foot-pounds of work per minute — that is, the power necessary to lift a total mass of 33,000 pounds one foot in one minute.” The term is actually related to horses, too. James Watt conducted a series of experiments on strong horses to see how much power they exerted over a normal day’s work.Horsepower can also be expressed as watts (746 watts) and heat (92,545 BTU, or British Thermal Units, per hour). For engines in cars, planes and other vehicles, “indic