This photograph is one of my all time favourites, too. One of those photographs which can be distilled into one word: Speed!
I think what JHL said (reportedly when he was 7 or 8 years old) also sums up something essential: “It's marvellous, marvellous! Nothing will ever be as much fun. I'm going to photograph everything, everything!”
I still get a kick out of that photograph and those words. The wonder of the world still lies in front of us.