True that my friend (the planes). New studies of the data though also put the planes that were at whatever altitude, as being at the exact altitude that would cause the clocks to slow down, by as much as they did. So, was SR or GR the cause? We don't know. But the Hafele-Keaton experiment was done in a gravitation well. Funny, I do believe that time slows down relative to a gravity field. Like I said, I think GR is great. But SR was thought experiments, which lead to the math. OK, Xei, I will meet you halfway. I don't believe that SR (relating to time dilation, length contract, etc.) is factual because no test has been done to prove it outside of a gravity field. And I will keep an open mind as to it's validity. The speed of light is assumed to "C" in any and all references. We don't know that. I did the math one time taking the speed of the Earths' rotation and revolution, and the speed of the galaxy spin, so forth. The variable of how we could possible measure viewed light, is something like (I don't remember exactly) .0001% of the speed of light. (This referring to the Michelson-Morley experiment). Basically meaning... of course the speed of light is measured as "C" in our reference frame. An analogy - if I am going 100 miles per hour in a vehicle, and I slow down .0001% of that, you will still measure me going 100 miles per hour! And yes, I know CERN can't keep anything to go faster than "C". All the above is my problems with SR, it's equations, and it's assumptions, all based on the assumed fact that light is "C" is ALL reference frames. I enjoy this conversation with you. SELL ME DUDE!