Sorry a typo. I meant FTL, not flt above. My take on time dilation is as follows, I welcome any corrections to my rudimentary calculations and thoughts. Every human being is moving at a very great and defined linear speed (m/s). We most likely have a rotational angular speed as well but that I will ignore. This is because we are on a planet orbiting a star with a linear speed. A star orbiting around a point in its galaxy, and a galaxy moving within a universe, relative to some fixed point within this universe (not sure what that point is), which means we have all of these combined velocities as well.
Therefore because a human on earth has a set and defined velocity, a person who leaves earth will have a "higher" net speed. This greater speed will result in a difference in time between the traveller and the earth resident, since time is dependent on speed. This suggests to me that our current human perception of time is due to our speed now (living on earth). The day we leave earth it will change, but it would seem that unless we travel at vastly greater speeds, says aporoaching FTL, we won't really notice the difference. The strange part about time dilation is it seems to point towards the possibility of time travel, which is something I have hard time believing in.
As part of my research for my fiction book, I have done various calculations of space travel near FTL, and came across a curious observation. It seemed that light speed (or rather the distance that light travels) is related to earth's gravity or g. I can't remember exactly the relation I saw, it was a few years ago, but I found that accelerating at g (9.81....m/s2) for very long periods of time, had a bearing on the distance over time, or light years. i think it was if you travel at g acceleration for one year, you will find a relationship with the number of light years you have travelled. Do 2 years and it appears again. That's weird because the speed of light and earth's gravity are unrelated? It seems obvious to me that space travel will be at g acceleration, the followed by g deceleration. Its what the human body needs. Weightlessness in space doesn't have to be an issue. Even Arthur C Clarke in the film Space Odyssey showed how rotating space stations can solve g forces for human habitability. Our only problem is finding an energy source capable of sustained acceleration, deceleration over years continuously.
By the way thanks for the explanation of the feather and the ball experiment. Yes I was thinking of experimental error too - not a good vacuum or something along those lines. I will look into that since I see there has been a more recent trial with impressive accuracy.