I'll try and recall it as best I can as told to me by a professor who was in the Air Force. Basically, a Uranium clock is the most accurate clock known to man, accurate to something like one second per million years. A uranium clock was put on each of two AF jets, with the clocks both precisely at the same readings. One flew at top speed with the rotation of the Earth, and one flew at top speed opposite the Earth's rotation. Upon landing, it was discovered that the uranium clocks were no longer in synch, but rather one was now behind the other by 2 seconds. This would probably tie into what you said about "time slowing down". Either way, fascinating stuff.