Aly,

You must be following the Shetland Pony Circuit.

The standard that has long been used in racing is that 1/5 of a second equals 1 length. We now know that is not quite right, as horses run at different speeds during the race, but what follows is a good approximation:

A good horse can run 6f in 1:10. That is 38.7 mph. At 38.7 mph, the horse travels about 57 feet per second (38.7*5280/3600). At 57 feet per second, 1/5 of a second = 11.4 feet.

Earlier in the race, fractions are faster and later in the race they are slower. Some horses run faster than 38.7 mph and some run significantly slower.

Obviously the speed at which horses run does not affect its length (thus the roughness of the assumption), but unless a horse is a small little mule, 8-9 feet is going to lead to some Suffolk Downs in the winter-like (or Perfect Drift in the Belmont-like)assumptions about the speed of racehorses.

And for a reality check -- when was the last time you stood next to a thoroughbred? The distance from the nose on an outstretched neck to the tail has got to be more than 11-12 feet for a fully grown horse.

Anybody care to weigh in on this?