Essay by PaperNerd ContributorHigh School, 12th grade September 2001

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10 Is time travel to the past logically possible? Is it logically possible for you to travel back and have a conversation with your former self? Could you kill your former self? Could you do anything to anyone, or could they do anything to you, which you had not already done or had done to you? Would you, or anyone else, in such circumstances, be a free agent? Introduction Long a favourite topic of science fiction, the notion of time travel is one that raises an enormous number of philosophical problems and quandaries regarding causation, identity and the nature of time itself. While it is fascinating to study these merely as hypotheticals, research in the context of relativity has suggested some circumstances under which time travel, to the past as well as the future, might be possible.

Views of time Linear The traditional view of time has been of something flowing inexorably forwards, and in three distinct stages: past, present and future.

The past is fixed and unchangeable, the future is unwritten and does not exist yet, and the present is what we are experiencing now. This picture is still the most intuitive and natural way of viewing time. Since the theory of relativity has become more widely accepted, time is no longer seen as being so unique and separate, but as part of a four-dimensional framework. It is still different to the three space dimensions in many important aspects, but it can still be altered by factors such as speed and gravity. It is relativity that gives a little credibility to the possibility of time travel.1 Many-worlds Another view of time that I will mention is the "many-worlds" or parallel universe view, in which a time traveller may not actually be visiting their own past, but is actually travelling...