Physics and Philosophy of Time

(I have aged. Linda has not.)

(I'm re-posting this for a friend.)

I am seventy-four years old. Where has the time gone!? And what, anyway, is "time?" 

Here are some thoughts. For more you might read Now: The Physics of Time, by Berkeley physicist Richard Muller, and Why Time Flies: A Mostly Scientific Investigation, by Alan Burdick. Especially helpful is God and Time: Four Views. 

Scientific American as published several essays on the nature of time -  A Question of Time: The Ultimate Paradox. One of my favorite physicists, Paul Davies, has an essay called "That Mysterious Flow." Here are some of his thoughts on time.

"Nothing in known physics corresponds to the passage of time. Indeed, physicists insist that time doesn’t flow at all; it merely is."

Our commonsense view is that time is "slipping away." It feels like there is a "flow" to time. However, Einstein said, “The past, present and future are only illusions, even if stubborn ones.”

Davies writes: "Physicists prefer to think of time as laid out in its entirety— a timescape, analogous to a landscape— with all past and future events located there together. It is a notion sometimes referred to as block time. Completely absent from this description of nature is anything that singles out a privileged, special moment as the present or any process that would systematically turn future events into present, then past, events. In short, the time of the physicist does not pass or flow."

Time is just as real as space, but "the flow of time" is unreal. 

Time is unidirectional. For example, an egg dropped on the floor will break into pieces. But the reverse process - a broken egg spontaneously assembling itself into an intact egg - is never witnessed. "Nature abounds with irreversible processes." But there is no "arrow of time." Yes, time is unidirectional, but...

..."this does not imply, however, that the arrow is moving toward the future, any more than a compass needle pointing north indicates that the compass is traveling north. Both arrows symbolize an asymmetry, not a movement. The arrow of time denotes an asymmetry of the world in time, not an asymmetry or flux of time. The labels “past” and “future” may legitimately be applied to temporal directions, just as “up” and “down” may be applied to spatial directions, but talk of the past or the future is as meaningless as referring to the up or the down."

Remember - this is physics. We may feel some flow of time, but in reality time is not something that moves or flows. 

Note this: We do not really observe the passage of time. "What we actually observe is that later states of the world differ from earlier states that we still remember. The fact that we remember the past, rather than the future, is an observation not of the passage of time but of the asymmetry of time." Think of individual movie frames. As we watch a movie we experience individual states of affairs that are different from previously experienced states of affairs. That's all.

Think again of the "broken egg" example. Imagine a movie of the egg being dropped on the floor and breaking. Then imagine the film sequence being run backwards. We would see that the backwards sequence was unreal, even though there would seem to be a "flow" to the backwards series. This shows the illusion of the "flow of time." Yes, time is asymmetrical, but "time’s asymmetry is actually a property of states of the world, not a property of time as such."

When I remember the past and the many birthdays I have already celebrated, but do not remember the future birthdays that (hopefully) are forthcoming, this is "an observation not of the passage of time but of the asymmetry of time." Note: only conscious observers register the "flow of time." "Therefore, it appears that the flow of time is subjective, not objective."

I think the biblical distinction between chronos and kairos may help us here. Chronos is "clock time," and the experience of a flow of time. But kairos is more like a discrete, individual frame in a movie isolated from all other events. Kairos is the "right time," or the "appointed time." 

All of this is good news for me. Time has really not "passed me by." Time is not "slippin', slippin', slippin'... into the future."  

Davies writes: 

"What if science were able to explain away the flow of time? Perhaps we would no longer fret about the future or grieve for the past. Worries about death might become as irrelevant as worries about birth. Expectation and nostalgia might cease to be part of human vocabulary. Above all, the sense of urgency that attaches to so much of human activity might evaporate."


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Here's a review of some philosophical ideas about time. (Special thanks to Manuel Velazquez's excellent Philosophy: A Text With Readings, 11th edition)

PLATO (Ancient Greek philosopher, 429-347 BCE)

• "Time" exists independently of events that occur in time.
• "Time is like an empty container into which things and events may be placed; but it is a container that exists independently of what (if anything) is placed in it." (SEP) 

ARISTOTLE (Ancient greek philosopher, 384-322 BCE)

• Time does not exist independently, contra Plato, of the events that occur in time.
• This view is called "Reductionism with Respect to Time."
• This means that "all talk that appears to be about time can somehow be reduced to talk about temporal relations among things and events." (SEP)
• The idea of a period of time without change is seen as incoherent.
• Thus "time" cannot exist independently of what is placed in it. Apart from events, no time exists.

AUGUSTINE (Augustine of Hippo, 354-430)

• Time, in a sense, does not exist.
• The past no longer exists.
• The future does not yet exist.
• Only the present moment is real.
• But the present moment has, in itself, neither a past nor a future.
• The present moment is timeless.
• "Time," from God's perspective, is different from our perspective.
• God is outside of time.
• Time is like a line of events stretched out before God.
• Every moment - past, present, and future - lies on this line. Everything on the "line of time" is fixed. This is God's perspective. (Cmp. C.S. Lewis who, in Mere Christianity, employed Augustine's view of time.)

McTAGGERT (British philosopher M.E. McTaggert, 1886-1925)

• Compare McTaggert to Davies, who cites McTaggert in his essay.
• The flow of time as we experience it is unreal.
• "Time" is a fixed series of moments, each moment either "before" or "after" the other moments. This is "objective time."
• We can also think of "time" as a sequence of flowing moments. Each moment changes or flows from "future" to "present" to "past." This is "subjective time."
• "Past," "present," and "future" are incompatible with each other. Therefore it is impossible for the same thing (viz., the same "moment") to be simultaneously future, present, and past.
• But if time did "flow," then every moment would have to be future, and then present, and then past.
• So the idea of subjective time as a sequence of flowing moments is unreal.
• Subjective time is unreal. Our experience of time as "passing" is an illusion.
• Following this McTaggert said, "I believe that nothing that exists can be temporal, and that therefore time [subjective] is unreal." (The Nature of Existence)
• "Time" is an unchanging, fixed series of events frozen onto the "line of time" that makes up the series. But this is not really time, because there is no flow or change here. And, since subjective time is unreal, time cannot be real.

KANT (German philosopher Immanuel Kant, 1724-1804)

• Time - whether subjective or objective - is simply a construct of the human mind.
• "Time" and "space" are categories of the mind that the mind uses to organize the flow of changing sensations.
• Kant said, "Time is therefore given a priori." "Time" as a mental category is "prior to experience" and organizes or categorizes experience.
• Time is not real but is a mental construct.

HUSSERL (German phenomenological philosopher, 1859-1938)

• See Husserl's The Phenomenology of Internal Time Consciousness.
• Husserl is in the Kantian stream of thinking. He is not interested in the metaphysical status of time, but time as transcendental, as lying at the base of consciousness, and giving shape to our experience. 
• Husserl "considers the present, past, and future as modes of appearing or modes by which we experience things and events as now, no longer (past) or not yet (future)." (IEP)

BERGSON (French philosopher Henri Bergson, 1859-1941)

• "Objective time," the "time" of the scientist, is just a conceptual abstraction, a construct of the mind.
• The image of time as a line is simply an image; the concept of objective time is only a concept. Neither images nor concepts can get at the reality.
• Only what we directly experience is real; viz., what we "intuit."
• We directly experience or intuit the flow of time. Bergson says we have the "intuition of duration."
• Real time is subjective time. This is the "flow of time" that I experience moving from future, through present, and into the past.
• Objective time is an intellectual reconstruction and thus is an illusion."Time" does not actually exist "out there" in the world (it's not a reality transcendent to human subjectivity).

WILLIAM LANE CRAIG (Christian theist, 1947 - present)

• Apart from events time does not exist.
• Prior to creation time did not exist.
• A personal God need not experience a temporal succession of mental events. "God could know the content of all knowledge - past, present, and future - in a simultaneous and eternal intuition." (See Craig, "God, Time, and Eternity")
• "The proper understanding of God, time, and eternity would be that God exists changelessly and timelessly prior to creation and in time after creation."
• There are no "events" prior to creation. Therefore, since God exists prior to creation and is an "eventless" being, "time" does not exist prior to creation. At the creation of the universe time begins. On a relational view of time God now relates to the universe, "and God subjects himself to time by being related to changing things."

STEPHEN HAWKING (Physicist, author of A Brief History of Time, 1942-present)

• Time is understood in relation to events. Hawking writes: 
• 
  
• "Since events before the Big Bang have no observational consequences, one may as well cut them out of the theory, and say that time began at the Big Bang. Events before the Big Bang are simply not defined, because there's no way one could measure what happened at them... [T]he universe, and time itself, had a beginning in the Big Bang, about 15 billion years ago. The beginning of real time would have been a singularity at which the laws of physics would have broken down." (See here) 

(For diagram + explanation, see here.)

FOR MORE READING: God and Time: Four Views. 

And: W.L. Craig, "God, Time, and Eternity"

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In my book Praying: Reflections on 40 Years of Solitary Conversations with God I write about hearing and discerning the voice of God and not much about time. But subjectively praying brings us into kairos moments, felt timeless experiences that are nondirectional because one's heart has arrived in the presence of God.