Monday, October 15, 2007
The History and Future of Time
I found this article, by Adam Hill and Dr. Peter Storey, called The History and Future of Time. Thought you might enjoy a few excerpts; I have edited a bit for simplicity. "In recent years physicists have arrived at new possible concepts of time. One theory proposed by Cumrun Vafa is that of ‘Hypertime’ which proposes that there is more than one time dimension in the universe. The second theory is proposed by Julian Barbour, in which time does not exist at all but is purely a construct of the psyche. Before explaining these recent theories, the concepts of Newtonian and Relativistic time are described to give a background.
Newton was the first scientist to ever properly define time. Aristotle believed time to be motion as this was how it was perceived; the motion of the sun and stars across the sky. Plato believed that time was not real, but a mental creation, that the world was really a timeless domain of pure and perfect Forms which occupy the realm of eternity. Galileo was the first scientist to record time as a quantity through his experiments with the pendulum. The laws that Newton laid down defined ‘absolute, true and mathematical time, of itself, and from its own nature, flows equably without relation to anything external.’ Newton believed time to be a separate entity from space which could be measured with unlimited accuracy.
The next major advance following Newton’s incorporation of time into the laws of physics was made by Einstein in his general theory of relativity. At the end of the nineteenth century scientists using Newton’s laws were finding that strange things were happening when they were applied to light signals and material bodies. Einstein solved these problems by disposing of the concept of ‘absolute time’. Einstein put forward a model of the universe in which space and time were a united entity and formed a four-dimensional existence in space-time; one time dimension and three space dimensions. Einstein had destroyed the ‘common sense’ perception of time and brought about a much stranger and alien concept in which everyone had their own ‘now,’ and clocks could run faster or slower depending on how they moved.
For many years physicists have been adding extra dimensions to the universe – in addition to the common three space and one time dimension – in attempts to simplify the laws of physics and unify them in a single theory. The general consensus today is that there are eleven dimensions; the additional seven are spatial dimensions curled up so small that they are invisible to us. More recently Cumrun Vafa of Harvard has increased the total to twelve by adding an additional dimension of time.
The use of higher dimensions was first instigated by the mathematicians Kaluza and Klein in the 1920’s. By adding a fifth dimension they achieved the combination of gravity and electromagnetism. Superstring theory, developed in the 1980’s, required nine dimensions of space and one of time. In 1995 Edward Witten of Princeton and Paul Townsend of Cambridge added one more spatial dimension to unite the multitudes of string theories into M-Theory. Most recently Vafa added his additional time dimension, bringing the total to twelve, to create F-Theory.
Another modern theory which has been fielded in recent years does away with time as a physical entity altogether. ‘Physicists struggling to unify quantum mechanics and Einstein’s general theory of relativity have found hints that the Universe is timeless,’ says Julian Barbour, a theoretical physicist from Oxford. Time is now completely remiss from the description of the universe as there are no paths to be traced just multiple possibilities, where each possibility is a point described by a probability. Hence there are many versions of ‘now’. The ‘now’ that is experienced as an instantaneous state of the universe is just the state which has the highest probability of occurring. The past becomes a set of consistent events for which the probability of occurring was high relative to the other potential states. (This) theory harks back to the ancient argument that time is purely an invention of the human consciousness, a form of ‘temporal dizziness’.
In each case there are interesting arguments and consequences. Modern physics still does not have a complete grasp of the concept of time and only through further research into this area will it be obtained."