Grow older than dad. How this is possible?
Okay lets see, There are places far away from earth, in space. There are many galaxies around. while we travel to such places with a very high speed approximately equal to the speed of light we can experience TIME DILATION.
What is time dilation?
Time dilation is a difference in the elapsed time measured by two clocks, either due to them having a velocity relative to each other, or by there being a gravitational potential difference between their locations. After compensating for varying signal delays due to the changing distance between an observer and a moving clock (i.e. Doppler effect), the observer will measure the moving clock as ticking slower than a clock that is at rest in the observer’s own reference frame. A clock that is close to a massive body (and which therefore is at lower gravitational potential) will record less elapsed time than a clock situated further from the said massive body (and which is at a higher gravitational potential).
These predictions of the theory of relativity have been repeatedly confirmed by experiment, and they are of practical concern, for instance in the operation of satellite navigation systems such as GPS. Time dilation has also been the subject of science fiction works, as it technically provides the means for forward time travel.
So when someone travels long distances, like light years far at a speed approximately equal to speed of light then, the time for him tends to be slower for the person travelling then the person on earth. If your dad is the traveler and if he stays in space for for few mins in his frame of reference than in earth it will be a difference of few years. May be when you dad is of 40years you may be of 80years.