The "twin paradox" can be explained in terms of Einstein's theory of relativity (more specifically his "special theory of relativity). The reason for the time dilation activity that is exhibited as objects increase in velocity can be understood as a consequence of the theory of relativity that suggests that since energy is mass and mass is energy (e=mc2), that, since, as Einstein seems to think, mass is "frozen energy", that the energy equivalent of any mass can be measured by multiplying itself times the velocity of light (squared), that objects in accelerative motion acquire a degree of mass that would become infinite if the speed of light were ever able to be reached, and that this infinity is also an impossibility which places the speed of light as that ultimate upper potential velocity for any object. Now, if you consider that the speed of light is as fast as anything can move than what is going on when a beam of light is produced by a source generated by an object attached to the roof of a moving train, a train moving say at one half the speed of light. Imagine that we have our so called paradoxical twins. One twin is on the train in motion observing the light beam and one twin is observing from a stationary point on the side of the track. The twin on the train will observe that in the course of one second, the light moves from the top of the train to the bottom of the train, seemingly covering the distance that light can traverse in one second. The stationary twin observing from the side of the tracks would, in a reality impossible to exist according to the theory of relativity, see that, in one second, this beam of light covers the distance it is traveling vertically, plus the distance the train, moving at one half the speed of light, covers horizontally. Since it is considered that in one second, the beam of light cannot move further than the speed of light limit would allow for, an adjustment (in the "special" theory of relativity) is found to explain the activity in a way which will allow for the stationary twin to observe what is happening in a way which does not mean that a beam of light generated by a source attached to an object moving at one half the speed of light will cover more ground than an object moving at a speed of light plus the velocity of the train. This adjustment, which Einstein proposed in one his "thought experiments", was that the stationary twin observing the train in motion with the light generation, would not observe that there was something going past the speed of light but rather, to slow everything down and prevent the impossibility of faster than light motion, time itself would dilate for the twin on the train, for the train, and for everything moving as fast as the train, time itself for the twin in motion would move at a speed relatively slower to the stationary twin. Since this relativistic slow down in time would mean that the train would not be moving as fast and the light beam would be slowed down, the laws of light speed limit are no longer being violated; However since the speed of TIME is thought here as no longer absolute but RELATIVE, the laws of the universe allow for the speed of time to be slowed down for the twin on the train in relative relation to the stationary sibling. The so called "twin paradox" is not a paradox at all but a result of the adjustment in universal law that Einstein made for objects as they moved closer to the speed of light to prevent them from violating the speed limit of light. Astronauts in vehicles that have accelerated to a speed far beyond the velocities we normally experience, have discovered that atomic clocks onboard their ship did indeed move at a rate which indicated that, for them, time was slowing down in relation to the measurement activities of atomic clocks that were situated on Earth. Astronauts have discovered that upon their return to Earth, they were now younger than their twin siblings that were born at the same time as themselves.
