Down here in Devon, the only contact we had with Concorde was the spine-tingling "whomp-bomp" every evening as flights out of CDG lit up down the channel. Replaying that sound in my memory, I would say that the time between the two thumps was between 1/3 and 1/2 sec, and yet a bit of maths tells me that at 1300 MPH, Concorde travelled her own length in less than 1/10 sec. This always puzzled me at the time, and I still can't explain it. Any ideas, anyone?