When a change occurs in an atom by convention we say that the transition is the movement of matter as Time.
An atom that travel in the form of light has its physical transformations temporarily suspended until they return to the original speed.
Traveling at the speed of light does not change the links atomic and therefore the object aging in the same proportion of the state of rest.
Now travel in a state of the light atoms are converted into energy not occurring changes in atomic structures that are connected in a body structure.
If any matter travels in a state of light will return when their state of preservation identical to the time of departure and the other in the three-dimensional plan will have aged.
For those who are traveling at the speed of light when the same old will return both an object in three-dimensional plan.