Experimental Confirmation:

The relativistic time dilation and mass rise have both been measured under controlled situations, and the outcomes concur with the Einstein's formulas stated former. Thus, such effects are more than just tricks of the imagination.

To determine time dilation, a super accurate atomic clock was positioned on board an aircraft, and the aircraft was sent up in journey to cruise about for a moment at some hundred kilometers per hour. The other atomic clock was reserved at the position where the aircraft took off and landed. Though the aircraft's speed was only a minute fraction of the speed of light and the resultant time dilation hence was very small, it was large sufficient to measure. Whenever the aircraft arrived back at the terminal, the clocks that had been synchronized (if placed right next to each other, obviously!) before the trip start were compared. The clock which had been on the aircraft registered a time somewhat earlier than the clock which had been resting comfortably on the Earth.

To compute mass rise, particle accelerators are used. It is possible to establish the mass of a moving particle based on its recognized rest mass and the kinetic energy it holds as it moves. Whenever the mathematics is completed, Einstein's formula is forever shown to be right.