2

Time is treated in Relativistic Physics as a pattern of events laid out in a continuum. In philosophy it is usually related to change which physicists partly understand as "time's arrow".

McTaggart, a philosopher, pointed out that if time were a fixed, ordered set of events then nothing that was in time could move through time. This objection is valid but it does not obviate time as a fixed, ordered set of events. It implies that anything that were to move along these events would need to be outside of the fixed order.

McTaggart's point is resolved if we abolish time as an ordered list but the Presentism that results does not have any time within it to permit change and is inconsistent with the copious evidence for a physical spacetime continuum.

Perhaps time contains two concepts, the ordered list and the moving observer who witnesses change. Perhaps we should use terms such as "dimensional time" and "motion through time" to distinguish the two.

A subsidiary question then arises: can change occur without an observer?

Is time a fixed, ordered list of events, is it changes somehow linked to the present instant or both or something else?

Some clarifications:

I now realise that the skimpiness of the the way that the question is put above may have been misleading. I am new here :)

A dimension is a direction in which things can be arranged. This page is a spatial arrangement in two dimensions. If time is a dimension in a 4D manifold then there are arrangements of things that are in time so being a more complex, but still fixed, pattern.

The second part of the question asks that IF time contains an existent ordered list of events does change depend upon an observer moving along the list? If you had a list on a page you could move a cursor over the list but if the cursor were in the list (ie: an image of a cursor) it could not move.

Reference: McTaggart, J. M. E., (1908) “The Unreality of Time.” In Mind 17: 457-73.

1
  • 1
    Give details of McTaggart. Full name, when active, publications etc. More clarity needed.
    – Meanach
    Commented Nov 21, 2023 at 18:16

3 Answers 3

1

Time is neither an arrow nor a pattern. According to our current best mainstream theories of physics, time is a dimension in a four-dimensional spacetime. I cannot begin to imagine how you might suppose change is dependent upon there being at least one observer. Do you believe that if all sentient life was snuffed out this instant, then the Universe would freeze? How do you account for the fact that the Universe, according to the astro-physics boffins, evolved for billions of years before anything remotely resembling an observer came about?

11
  • Thank you for your comment. A dimension is a direction in which things can be arranged. This page is a spatial arrangement in two dimensions. If time is a dimension in a 4D manifold then there are arrangements of things that are in time so it is a pattern. Commented Nov 22, 2023 at 9:55
  • If time were a pattern in "four-dimensional spacetime" all sentient life would not be snuffed out by the absence of the hypothetical observer in the question. The question asks whether change could occur without an observer somewhere - without something that moves through time. Commented Nov 22, 2023 at 10:07
  • I think you will find that the things form the pattern, not the dimension along which they are arranged. Commented Nov 22, 2023 at 10:31
  • True, however, if you rotate an arrangement of events off the time axis (by changing your velocity relative to the events) the order of the events in time is still preserved. The events constitute a fixed, ordered list in time. I am not sure how your comment affects the discussion of ordered lists in time and how change occurs. Commented Nov 22, 2023 at 11:01
  • I am afraid that I consider McTaggart to be guilty of triggering an epidemic of unhelpful thinking about time, and if you have his book I would urge you to throw it out of the nearest window. The view of mainstream physics (by which I mean physics as currently taught at Universities) is that at any instant you have a position in 4d spacetime, and at any subsequent instant you have a different position in 4d spacetime- you are, in effect, continually moving along your own personal time axis... Commented Nov 22, 2023 at 11:52
0

Here’s an excerpt of what Robert Lawrence Kuhn has to say about time:

“To many physicists, while we experience time as psychologically real, time is not fundamentally real. At the deepest foundations of nature, time is not a primitive, irreducible element or concept required to construct reality.

“The idea that time is not real is counterintuitive. But many ideas about how the world works that humanity had taken for granted have required a complete rethink. As [MIT physicist Max] Tegmark puts it, ‘There've been so many things in physics that we thought were fundamental that turned out to be mere illusions, that we're questioning everything — even time.’”

8
  • Well, ... time is not real, is too far-fetched! Commented Nov 21, 2023 at 21:37
  • @IoannisPaizis, as Neil deGrasse Tyson wrote in Astrophysics for People in a Hurry, “The Universe is under no obligation to make sense to you.” Commented Nov 21, 2023 at 21:47
  • ok, but you responded to something I wrote some minutes ago and soon I will go to sleep, do I live in an illusion? Commented Nov 21, 2023 at 21:58
  • 1
    The way I’d describe it is that our everyday experience is, to a surprising extent, created by our minds and does not correspond in a highly accurate and precise way with physical reality. If you want to call that illusion, I won’t object. Perhaps a more useful way to think of it is that our experience constitutes a model of objective external reality and, like most models, is sometimes useful and at other times misleading. We didn’t evolve to understand Nature perfectly, but to stumble along well enough to get our genes replicated. Commented Nov 21, 2023 at 22:04
  • Why did you quote selectively from an article in which some of the people quoted claimed time was not real and others that it was real? Commented Nov 21, 2023 at 22:25
0
  1. According to the Special and also the General Theory of Relativity time has to be considered in the broader context of spacetime. The latter is a 4-dimensional structure of events. There does not exist a canonical splitting of the four dimensions into 3 space-dimensions and 1 time-dimension. Instead, each splitting of spacetime depends on the reference system chosen by the observer.

    As a consequence there is no intrinsic concept of time, independent from the choice of the coordinate system. Two events, which are simultaneous with respect to one coordinate system, can relate to each other in an arbitrary time order with respect to a second coordinate system.

  2. In physics time is an observable, which each observer measures by his clock. Due to the observed irreversibility of events, we speak about the flow of time and the direction of this flow. How to explain its direction? There is one distinguished cosmological process with a fixed direction: The expansion of the cosmos.

    Hence one can speculate that the arrow of time is linked to the cosmic expansion.

2
  • Good summary of the reality of time. Given that time is real there is an ordered list of events along the time axis, a pattern. A bit like a pattern in space. Change is then like moving a cursor along the pattern. However, the cursor cannot be a part of the pattern. McTaggart spotted this problem. If time is a dimension the observer must be outside time. Commented Nov 22, 2023 at 10:22
  • The arrow of time is the mixed physical concept of dimensional time+causality+change. Entropy is due to the existence of a time dimension that allows events in space to be more random with displacements along the time axis. The manifold then contains a fixed four dimensional pattern that has events that are more randomly placed with distance along the time axis. Dimensional time in itself does not explain change - something would need to move over the fixed pattern for change to occur. Commented Nov 22, 2023 at 10:31

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .