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Hawking, Stephen - A Brief History of Time - On time



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A Brief History of Time – Stephen Hawking

The probability that the particle, say, passes through some particular point is found by adding up the waves associated with every possible history that passes through that point.  When one actually tries to perform these sums, however, one runs into severe technical problems.  The only way around these is the following peculiar prescription.  One must add up the waves for particle histories that are not in the real time that you and I experience but take place in what is called imaginary time.  Imaginary time may sound like science fiction but it is in fact a well defined mathematical concept


This might suggest that the so-called imaginary time is really the real time, and that what we call real time is just a figment of our imaginations.  In real time, the universe has a beginning and an end at singularities that form a boundary to space-time and at which the boundaries of space time break down.  But in imaginary time, there are no singularities or boundaries.  So maybe what we call imaginary time is really more basic, and what we call real is just an idea we invent to help us describe what we think the universe is like.

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Hawking, Stephen

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