Time travel fascinates us all.  For the scientist there are discussions of its feasibility.  How would it work?  For those of that enjoy literature there are novels that take us back in time and forward into the future.  Novels that go back in time give the time traveller a chance to observe history in the making.  Books that head for the future give us a glimpse into utopian and dystopian worlds.  Literature seems to give less attention to the implications of time travel itself.

Consider the case of a boy who hates his grandfather.  He hates his grandfather so much that he would like to kill him.  The clever boy builds a time machine and steps back in time.  He enters an era in which his grandfather was a young man.  This is an era before his father was born.  The clever boy purchases a shotgun and fires….

Can the clever boy kill his own grandfather?

 If grandad dies the chain of events that leads to the boy’s birth is broken…….

We enter a world of philosophical puzzles for which I believe there are  three possibilities

• Nature could apply a cosmic censorship.  Does a natural law prohibit the time traveller from committing an inconsistent act?  The boy might not be allowed to fire the gun.  For me, this thought raises more problems than it solves.  How could nature possibly keep tabs on all the events and decide whether they were consistent?  I believe that the boy’s behaviour would become very constrained if he was excluded from any undertaking that might influence the future that developed from grandad’s era.
• Time travel could take the traveller into a parallel universe.  We could imagine that the time machine was like a giant tape recorder.  It can spool forwards and backwards. When the time traveler leaves the time machine he picks up the music that has been played to date and is free to play a new tune. When the boy makes a decision to kill grandad he opens up an entirely new universe.  Two universes can exist simultaneously.  In one the boy is born. In the other grandad dies as a young man.  When we extend the arguement this leads us to think of about an infinite number of universes.  A new universe is needed every time a decision of any kind was taken. I am not going to contemplate whether on not the time machine would be better described as an ipod!
• Life, memory and consciousness could be distorted by time travel.  When scientists discuss time travel their thinking is dominated by the theory of general relativity.  These equations do not distinguish between forward and backward travel.  They also permit exotic solutions that could jump through time. However, nature is a good deal more complicated than one set of equations.  When a baseball player strikes a run we could use equations to trace the ball back to the bat but we could not explain the social interaction between the players. Their behavior would look very strange if played in reverse.  In all our speculation I do not think that we know anything about whether the social organisation that we call life could survive time travel.  My personal take is that memory would not survive time travel.  The boy could not kill his grandad because he would not have the intent.

Scientists and philosphers do not know the answer to these puzzles.  You as a reader could have the valuable insight.  What do you think?