2010-08-18

Time paradox. Nobel Prize winner Tony Leggett speaks about time’s “forward motion”.

A new video features Sir Anthony Leggett discussing the paradox of the time flow.
We can remember the past and affect the future, and not vise versa. So the future and the past have very distinct properties from the human prospective. Yet, the basic laws of physics appear to be completely invariant under time reversal. In other wards they make no distinction between the forward and backward directions of time. Thus the distinction between the future and the past we observe in our everyday life is not readily explained by the most fundamental theories in physics, such as Newtonian mechanics, Heisenberg’s quantum mechanics, or Maxwell’s electromagnetism. All of these three fundamental theoretical systems are invariant under time reversal. Any future revisions of fundamental theories, which are inevitable with new discoveries, will probably involve new insights at the issue of time flow and the future versus the past distinction.
Although not explicitly discussed by Leggett, another distinction between fundamental physics theories and real life experience should be stressed. In addition to the future and the past, we are aware of a special moment in time, which we call “present time”. It is a point on the axis of time to which our perception is connected. We remember the past, we do not know the future, and we directly sense or experience the present. Thus the present moment of time is a very distinct point on the axis of time, and this point runs from the past to the future. Physics theories do not have any singular “present time”. In other words, any point on the axis of time can be assumed to be the present time. In real life, there is no option of “choosing’ the present moment of time. It is given to us. Those moments of time which are in the past can not be taken and con not become the present time. In physics theories or models, on the other hand, any moment can be chosen as the present time. In the theory it is not even necessary to select a particular time as the present time. Thus it seems that in real life there is some physical phenomenon, which converts the future into the past. This conversion is the time flow, as we know it from our experience. Interestingly, all humans seem to be in agreement about which moment of time is to be called the present time. If you think that the year now (at present) is 2010 and you ask your neighbor, he will probably tell you that he agrees with you, that the year now is 2010. At this time, physics does not seem to be able to explain such future-past conversion process, or the always forward flow of time, or the existence of the singular moment, i.e. the present time. One interesting philosophical guess is that the apparent distinctions between the past, present, and future are generated by our consciousness. Thus the phenomenon of time flow can be fully understood only after we understand our consciousness and self-awareness. Our consciousness seems to be a point on the axis of time, which runs consistently forward along this axis. What is even more puzzling is that all humans seem to have corresponding time points at the same location on the time axis. Presently these concepts are far from being understood within physics.

Source: NSF

Time paradox. Nobel Prize winner Tony Leggett speaks about time’s “forward motion”.

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