Gribbin (1990: 190):
But what does the photon itself "see" as the arrow of time? We learn from relativity theory that moving clocks run slow, and that they run slower the closer they get to the speed of light. Indeed, at the speed of light, time stands still, and the clock stops. A photon, naturally, travels at the speed of light, and this means that for a photon time has no meaning. A photon that leaves a distant star and arrives at the earth may spend thousands of years on the journey, measured by clocks on earth, but takes no time at all as far as the photon is concerned.
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From the perspective of Systemic Functional Linguistic theory, time is a construal of experience of the non-semiotic domain as meaning, specifically: the dimension of the unfolding of processes. The "arrow" of time is the mathematical reconstrual of the dimension as a Euclidean vector, such that the dimension of time has direction as well as magnitude.
The notion that 'time stands still' when travelling at the speed of light confuses the dimension (time) with the process by which time is measured (a clock ticking). To be consistent with Einstein's model of time as a dimension, the relative slowing of a clock's ticking corresponds to the relative expansion of time intervals along the dimension. This is because the relative slowing of a process entails that the process takes relatively more time to unfold. This relative extension of the duration of the process is the relative expansion of intervals along the time dimension.
The relative stopping of a process, such as a clock ticking, corresponds to the expansion of time intervals to the point where no process can unfold for even the shortest time interval, the Planck time.
The notion of a photon "seeing" refers to Einstein's thought–experiment of an observer riding on a beam of light. In this case, as the observer approaches the speed of light, it is the unfolding of the observer's mental processes — including construing experience as time — that gradually come to a halt, relative to mental processes of other observers travelling at speeds slower than light.
The notion that 'time stands still' when travelling at the speed of light confuses the dimension (time) with the process by which time is measured (a clock ticking). To be consistent with Einstein's model of time as a dimension, the relative slowing of a clock's ticking corresponds to the relative expansion of time intervals along the dimension. This is because the relative slowing of a process entails that the process takes relatively more time to unfold. This relative extension of the duration of the process is the relative expansion of intervals along the time dimension.
The relative stopping of a process, such as a clock ticking, corresponds to the expansion of time intervals to the point where no process can unfold for even the shortest time interval, the Planck time.
The notion of a photon "seeing" refers to Einstein's thought–experiment of an observer riding on a beam of light. In this case, as the observer approaches the speed of light, it is the unfolding of the observer's mental processes — including construing experience as time — that gradually come to a halt, relative to mental processes of other observers travelling at speeds slower than light.
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