comment on Saving time: Physics killed it. Do we need it back?
It’s unfair to blame Einstein for the ‘fatal blow’ to the ‘flow of time’, which some physicists still find problematic. Lee Smolin argued recently (26 April 2013) that the blows were never fatal.
The source of the trouble is the time-reversible formulations of ‘laws’ of physics, such as Newton’s laws. Einstein’s special relativity showed clock-timing is not unique, but did retain the time-sequence that is essential for causality – a principle that Einstein stoutly defended.
Einstein also advocated the Faraday-Maxwell concept of space-filling fields, and extended the differential equations for their field-borne light waves to apply to field-borne gravity waves.
However, these time-reversible formulations are not the whole story. Light-rays reach us only from the past, not the future. The time-explicit formulation of light waves uses (Liénard-Wiechert) retarded potentials to form an integral over waves reaching each point from earlier times. This integral satisfies both Maxwell’s time-reversible equations and the Penrose criterion that a truly fundamental law of physics is irreversible.
Thus the difficulty of standard physics with the ‘flow of time’ arises because it tries to dispense with fields of force, presuming they can be represented by particles (‘photons’, ‘gravitons’) governed by reversible interactions. Physics has to return to fields, carrying waves at the speed of light (following Einstein’s special relativity) to recover common sense over passage of time.
Einstein’s much quoted phrase “the distinction between past, present, and future is only a stubbornly persistent illusion” was written 3 weeks before his death and months after he’d expressed doubts about his whole life’s work including gravitation “based on the field principle”. Evidently, the Einstein in 1955 was failing fast, had lost confidence and influence as a physicist, and his weak blow to the flow of time has proved non-fatal.