I've noticed that most of the very successful formulas in physics, once you break them down, contain several references to quantities of time. And it has really begun to bother me that once you start poking around and asking a few questions, it quickly becomes apparent that nobody actually knows what time truly is at the most basic level. For me, "time is what clocks measure", does not seem like a scientifically nor logically rigorous definition, yet it is (basically) what the currently accepted definition is, and most physicists (the loop quantum gravity guys might be an exception... I'll have to check on that...) don't ask if time is truly fundamental.

So, have you guys heard any good theories on the true nature of time lately?

  • Physicists consider McTaggart's B-Theory of Time to be the most suitable for physics. See also McTaggart's A-Theory of Time. There is also the C-series, but wiki doesn't have a page.
    – nwr
    Jul 5, 2018 at 3:57
  • I made an edit which you may roll back or continue editing if I misrepresented your question. Jul 5, 2018 at 3:59
  • Thanks for the links explaining McTaggart. I guess I'm looking for something more... Testable. I'm personally not a fan of the block universe. I guess I'm more of an A series guy, but and I'm not sold entirety on that idea either. What's the C-series?
    – Thor
    Jul 5, 2018 at 4:25
  • Like, what (specifically) causes the percieved flow of time? I'm willing to wager that it's not cesium atoms. Does the Holographic Principal have anything to say on the matter?
    – Thor
    Jul 5, 2018 at 4:27
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    @NickR A, B and block universe theories rely on classical intuitions and are essentially irrelevant in modern fundamental physics despite their continued popularity with some philosophers and popularizers. The emergence of time is a constant theme in quantum gravity proposals, but really understanding them requires some mathematical prowess and for obvious reasons they are very far from experimental testing. Isham-Butterfield's On the Emergence of Time in Quantum Gravity is a good review for non-experts.
    – Conifold
    Jul 5, 2018 at 17:50

4 Answers 4


General relativity is currently our theory of time, and of course space. Any integration of time into quantum field theory and the standard model is going to have to involce a unification with general relativity. This looks to be on the Planck scale, and so be way outside our foreseeable experimental reach. Orbital gravity-wave observatories may really help with observations of relevant events out in the universe though. Gravity space & time are undoubtedly intimately linked.

Carlo Rovelli has interesting things to say from the quantum loop gravity perspective https://www.theguardian.com/books/2018/may/05/the-order-of-time-by-carlo-rovelli-review

In brane theory, other forces are carried by open strings, but gravity is carried by closed loop strings which are not limited in the same way to this dimension. It explains the relative weakness of gravity nicely. It seems like we can think of a larger space, in which our timeline is just a slice or surface, with a 'thickness' related to the scale of the rolled up higher dimensions https://www.universetoday.com/48619/a-universe-of-10-dimensions/

Have a look at the Axiom Of Purification idea, which seems to provide a satisfying and plausible account of the arrow of time arising in a quantum world https://plus.maths.org/content/purifying-physics-quest-explain-why-quantum-exists

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    OMG! I finally read some of Rovelli! I've obviously heard of loop quantum gravity before, but I didn't realize how it dealt with time. I don't know how this fact escaped me for so long and I can't believe I'd never even heard of the Wheeler - DeWitt Equation: en.wikipedia.org/wiki/Wheeler%E2%80%93DeWitt_equation
    – Thor
    Jul 7, 2018 at 17:58
  • Wheeler is a boss. It from bit, geons, supervised the PhD that presented the many-worlds interpretation, more-or-less named black holes that, the one-electron-universe that led to the idea antiparticles go backwards in time. Wheeler was a boss. I still think he was really on to something about quaternions and octonions too.
    – CriglCragl
    Jul 8, 2018 at 18:31

Time is a composite of position within 3 dimensions. If an object exists, occupies space, then its position is described using time. It is impossible to describe any object without reference to time. Time separates the position of an object from another position held at another time.

We measure time by using objects that are moving at a regular rate, so their observed position relates to the passing of time.

Philosophically you can try to say time is just a subjective observation except the very process of thinking, going through ideas requires the movement of energy, electrons, blood, oxygen in the brain of the person thinking it.

Einstein showed time is relative to the speed of light and the speed of an observer relative to another observer. This embedded time as a reality of our existence rather than removing it.

There is a mathmatical concept called imaginary time. This poses a question. Which model of time is real in our universe and which is just mathematics. Some might argue both. https://en.wikipedia.org/wiki/Imaginary_time


Time is explained in the Perennial philosophy as a function of Mind. You might like Abhidhamma Studies: Buddhist Explorations of Consciousness and Time by the Venerable Nyaponika Thera. Time would not be fundamental and would be intimately entangled with the processes of Mind, much as Kant speculated.

I don't know any other theories of time that even begin to work. I'd say the only good theories are those for which time is not fundamental. Hermann Weyl talks much sense on the topic. His book on the Continuum and other writings are worth checking out. There's a blog article here by way of a general introduction https://dondeg.wordpress.com/2015/02/27/the-yogic-view-of-consciousness-7-the-absolute-according-to-hermann-weyl/

Here's another discussion of time, Weyl and Buddhism: https://philpapers.org/rec/JONTCE

  • Sometimes I wonder why there are not more people who believe in solipsism. But not all the time.
    – user34017
    Jul 6, 2018 at 3:19
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    The Buddhists and the followers of Copenhagen both fall into the same category, in my opinion. It all sounds good at fist, but when you try to pin them down on a point they tend to get rather vauge. That being said, I was wondering recently about the nature of computation. I'd always thought of computation as being very similar to information, just bits moving in time instead of spread out in space. But computation isn't just information, it's information that is both received and acted upon.
    – Thor
    Jul 6, 2018 at 4:32
  • Was there any information there before it was received? I think Shannon might say no... Perhaps it is the USE of the information (in the form of computation) and not "measurement" that causes the wave function collapse (if there even is a collapse).
    – Thor
    Jul 6, 2018 at 4:42
  • Buddhist hold a world view where consciousness is separation from the oneness of existence, which the individual should strive to stop and become one with everything. As a faith position it is not actually desiring to define time or how it effects us, because in effect the belief is time is part of this separation. This is a faith position not a theorem. As a philosophy, denying time, the very reality of our lives, is not a good starting point. And focusing a culture on self denial of existence is not going to solve anything.
    – PeterJens
    Jul 6, 2018 at 8:58
  • @PeterJens - I'd suggest you delve a little deeper into Buddhism.before setting your opinions in stone. At present they are poorly informed. The idea that it is a faith position is a serious misunderstanding.
    – user20253
    Jul 6, 2018 at 10:41

Time Is Not

Existence is the progression of events and the changes they cause. Matter and events define space and time, neither of which have any substance. Space and time are voids, which can cause nothing, but contain everything.

Space and time are those qualities of the universe that accommodate all objects of matter and energy and all conditions and events, no matter how close together, overlapping, or far apart. There is no substance to either space or time. Any effect upon, or by, objects is assumed to be communicated through space and during time, but these effects are caused only by other objects. Space and time are neither cause, nor effect.

Space is perceived and identified by the distance between the physical locations of objects. Empty space accepts objects in any place or attitude, and motion in any direction or around any axes. There are no favored or forbidden locations or angles of orientation. Space is without intrinsic feature, except for the objects it contains. Space is therefore non-discrete and continuous. There can be no space without objects.

Time is perceived and identified by the duration between occurrences. Time accepts any conditions and events without regard to when they occur. There are no favored or forbidden moments or durations. The occurrence, duration, and sequence of events are determined solely by the actions and reactions of the objects that create them. Time is without intrinsic feature, except for the events and conditions it contains. Time is therefore non-discrete and continuous. Continuous time is also the entirety of time, thus contains any and all discrete moments, however determined or selected. There can be no time without events.

Based on Natural Logic of Space and Time

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    Et quod vult, torquet. en.wikipedia.org/wiki/And_yet_it_moves
    – user34017
    Jul 6, 2018 at 3:23
  • This neglects a host of reasons to expect that both space and time are quantised, and have structure. It's just bias, not reasoning.
    – CriglCragl
    Jul 6, 2018 at 13:07

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