In an interview with Physics Today, physicist Richard Muller hints at his work on a new theory of time.(See the interview) http://physicstoday.scitation.org/do/10.1063/PT.5.3047/full/
I found a couple of his statements questionable, and here I’d like to look at them in greater detail.
“Time flows. Choose any coordinate system and you can stand still in space but not in time. That different behavior breaks the otherwise glorious spacetime symmetry.”
The claim that you can stand still in space needs to be qualified (as Muller does) with the addition “relative to a particular coordinate system”. Through his relativity theory Einstein demonstrated that motion and rest must always be relative quantities, and those quantities can change with changing observers. This is as true for time as it is for space. If you wish to claim that time flows, then you must admit that it flows at different rates for different observers. From this you can infer, contrary to what Muller says, that in some coordinate system relative to me time’s flow is zero. Einstein found that coordinate system by imagining himself straddling a beam of light traveling, as beams of light are wont to do, at the speed of light. From this perspective all clocks stop. At the terminal velocity of the universe time comes to a standstill.
This is not just a theoretical thought experiment. For a mass-less particle like a photon traveling at the speed of light, it is the fundamental nature of the universe. For example, say the sun emits a photon, the photon travels the 93 million or so miles to my living room where it enters my eye, its energy absorbed and converted to an electrochemical impulse that I interpret as the perception of sunshine. In my coordinate system it takes about seven minutes for the whole process to complete, but from the perspective of the photon the process is instantaneous. In other words, emission and absorption take place simultaneously. There is a further consequence of this that is rarely if ever brought up. That is, the reality of the photon is not only time-less, it is space-less. What I see as here (my living room) and there (the sun) are seamlessly one to the photon, as simultaneous in space as emission and absorption in time. We can see that it becomes difficult to talk about these things without thumping along on the crutch of our common sense notions of space and time. Nevertheless the math is clear.
Muller may be appealing to some common sense perception of time and space when he attempts to make his distinction, but he does so at the expense of a rigorous accounting of the nature of either. This also might be the loose talk of an interview versus the rigors of experimental physics. The question I would pose to Muller: Can we truly “stand still” and still observe the flow of time? I will examine that question at length in a later essay, but first a few words on another of Muller’s statements:
“[T]here is a special moment in time we call “now.” No such special location exists in the dimensions of space.”
If there is a special moment in time I call “now,” then there certainly is a special location as well, and I call it “here.” The two are inextricably linked. But what’s so special about this moment in time we call “now?” As I noted above, two observers (Richard Muller and J. Lee Strickland, for example) traveling at different speeds relative to one and other will also have clocks running at different speeds. If they start from a single origin, the clocks will gradually go out of sync. Richard’s special “now” will become different from J. Lee’s. In fact in the larger picture of the entire universe Richard’s “now” isn’t very special at all. I’d venture it’s not worth two Federation Credits to some sadsack spacer hauling ore across a distant star system on the back side of the Andromeda Galaxy.