2

I think this is not the first time this question has been asked. Nevertheless, I ask it.
Often when asked if there was a time before the beginning of time, the North pole analogy is put forward. It's useless to ask because it's the same as asking what is north of the North pole. The flaw in this analogy is that in this analogy there is already a two-dimensional space (surface of the Earth)in which you can move to the north, and even a three-dimensional space in which you can go higher up. This is obviously not the case for time. There is not yet a time before time is supposed to come into being. You can imagine a static block universe (in which time exists in spacetime points but not in a transitive, thermodynamical way) to exist but that merely shifts the problem. How can a motion in this block universe get started?

So, how can anything start to move in time if there wasn't time yet to move? Does this impossibility prove that time in fact was there forever? Assuming the universe was not created, which would also shift the question: what moved the first mover?

3
  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Geoffrey Thomas
    Jun 19 at 7:42
  • 1
    It is also possible that the big bang was a vacuum metastability event: the previous phase state of vacuum suddenly transitioned to another phase state and released energy that became all the matter. en.wikipedia.org/wiki/False_vacuum_decay
    – Anixx
    Jun 20 at 10:35
  • That's more like it indeed!
    – user52804
    Jun 20 at 10:36
2

As you stated in your opening sentence, "this is not the first time this question has been asked." The Ancient Greek Philosophers of Science were asking this very question 2400-2500 years ago. Thinkers, such as Zeno of Elea, Heraclitus of Ephesus, Democritus of Abdera and Aristotle, were probing into this question...though with very different answers and conclusions.

Let's presuppose that Time, is infinite and has no beginning or foreseeable end-(this, incidentally, was a view held by Democritus). If it is true that Time has no start or finish, then the notion of a Naturally based Creation story-(no matter how sophisticated it may be), could not possibly work. Yet, the Big Bang THEORY, appears to be gaining more and more factual validity and legitimacy.

If the Big Bang is a convenient and comprehensible starting point for ALL physical reality, then it begs the question, what "moved" and helped form this infinitesimal proto point? The answer, still continues to mystify the Scientific community to this day. There are two possible cosmological answers:

  1. The Multiverse Theory: Perhaps the Big Bang, was an explosion which marked the beginning of our existing Universe and that an older Universe-(or series of earlier Universes), predate the Big Bang, thereby expanding the time continuum.

  2. Metaphysical/Supernatural explanation(s): The traditional position of nearly every society in History, was to associate the origin of the Universe, with the Divine. It is a nonphysical entity/entities who was/were responsible for causing or creating the Universe.

Which answer is correct? Well, I am neither an Astrophysicist, nor a Theologian; however, I too am interested in the process of time....primarily from a historical point of view.

Historians and History Teachers-(such as yours truly), are fascinated with antecedents, origins and causes. When did Human Civilization really begin? Did the earliest civilization originate in Iraq/Mesopotamia 6000 years ago? or should we go back to the earliest origins of humankind in East Africa dating back 5 million years ago? Whichever approach one takes in trying to better understand our human origins, the fields of History and Archeology, are constantly wondering about the distance of time and how it can relate to our present-day reality. Perhaps humankind's antecedents date back more than 5 million years and our human origins are much, much older than we originally believed.

In other words, the understanding of Time-(whether as a Historian, an Archeologist, an Astrophysicist, a Theologian, a Philosopher of Science or just as an everyday thinking civilian), has and will continue to mystify and fascinate us. Even with our contemporary advancements in space technology and exploration, as well as our ability to understand the tangible origins of our existing universe; the age old question about whether time is infinite or created, will probably remain, unresolved and a mystery.

3
  • The historical approach is a nice one! It doesn't need a physical view indeed. Maybe I become a historian too, instead of a physicist (yours truly)!
    – user52804
    Jun 18 at 20:20
  • Actually, I had a book that was called, "two millions year of history", in which only time was considered important insofar people were living.
    – user52804
    Jun 18 at 20:27
  • Thanks for the comments; they are greatly appreciated.
    – Alex
    Jun 18 at 20:31
1

One way to think of a beginning in time is, as you rightly say, in terms of a block universe, more or less what philosophers call the B-theory of time. Perhaps think of it this way. Natural numbers have a beginning (0 or 1, depending on who you ask), but that beginning would not be a natural number without the rest of numbers. All numbers are created equal, but one of them is the first one.

You can imagine a static block universe ... but that merely shifts the problem. How can a motion in this block universe get started?

Look at the picture below, from the Wikipedia article on equations of motion. Here you have a motion, which is just a change in some quantity (velocity, in this case) across time. Something changing across time is compatible with all those times existing (in some sense) on a par. They are all there, laid out on the x-axis, after all.

nakulll, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons

7
  • Motion is possible if you find yourself in a region where t is bigger than zero. But how can the initial motion take off? There are no previous spacetime points. How do you apply a force, which comes before the motion?
    – user52804
    Jun 18 at 8:46
  • What you have in mind is the "growing block" theory, where times start existing at a rate of, well, 1 second per second. The block universe does not work like that. All times exist (from a certain metaphysical stand point) equally, from the get go. Let me know if the edit to my answer helps.
    – Schiphol
    Jun 18 at 8:52
  • @More or less. No, more! But... How can particles at time zero get their motion? That is if there is no time before time zero? How can they come into existence?
    – user52804
    Jun 18 at 8:59
  • You need to think differently about this. All creation and destruction of particles, and all other motions, are just events that happen at different points of the time axis. If there are three particles at t=n and four particles a t=n+1, a particle has been created. That's all there is to it. t=0 in particular is populated by a very dense and hot, very small region of space.
    – Schiphol
    Jun 18 at 9:04
  • But particles can't just be created from nothing. There must be virtual ones first. How can they be there before t=0, when the real ones appeared? By the way, do you teach at the VU? I have looked at Schiphol when studying there. We were supposed to look at the sky, but it got cloudy. So we turned to Schiphol. The planes were pretty close and landing upside down... If so, is prof. Radder still there?
    – user52804
    Jun 18 at 9:06
1

The problem of "taking time" to travel through time in the block universe is an old one. It was given a thorough wringing-out by JW Dunne in his An Experiment with Time, published in 1927. He proposed that there had to be a second time dimension, from which we could measure the passage of base physical time. There are two big problems with this approach.

The first is that such theories do not produce viable mathematical models; they tend to break causality or offer false predictions in other ways.

The second, as Dunne found, was that the new time then demands a third Time in which to measure the passage of the second Time, and so on in an infinite regress.

The Hartle-Hawking model instead changes the nature of the time dimension so that at the Big Bang it is what mathematicians call "imaginary". In his Imaginary Time universe, the initial moment, their equivalent of the North Pole, spacetime simply runs smoothly across. There is no "outside the Universe", no "North of the North pole". As the Universe expanded, Time became the "real" number we know it as today. (as far as I know no mathematical model for this transition were ever offered, but a complex rotation during the inflationary era is an obvious conceptual candidate).

1
1

There might only be one 'place' and one 'time', fundamentally. With time and space as we understand them, as emergent symmetries from differentiation of that oneness. This is an old idea in philosophy, monism, and it's found for instance in Hindu thought, and Liebniz's monadology.

Time can be pictured as emergent from an underlying order, like in Loop Quantum Gravity. Rovelli describes there as being a crowd of possibilities jostling around events, with the one in some sense closest happening next, creating time emergently from the iteration of descriptions of spin lattices.

E8 is a higher dimensional mathematical structure, of the ways that a fundamental symmetry can break - one type of particle into particles & force carriers (fields), and then one force into other forces. Like a fracture plane fixing a certain irregular sub-dimensional 'place' in a higher dimensional symmetric space of all possible laws of physics. It's increasingly not a popular model among physicists, but I bring it up as illustrative.

Penrose developed the Conformal Cyclic Cosmology largely from the observation photons don't experience time. Wheeler's 'one electron universe', where all electrons are actually one moving backwards as antielectrons then forward again (the wavefunction of antiparticles has a symmetry that at least looks like they are their particle equivalent moving backwards in time, though Feynman rejected that as being literally true).

What is time? A way of organising events, geometrically (spacetime). Observation of change (like of oscillators, ie clocks). The thermodynamic arrow of time. Working memory, or statespace limitations on the iteration of a mental model or wavefunction. These, and more.

We need time to be emergent, along with space, to get a theory of gravity that integrates with the rest of physics. If the cosmos has existed for 'infinite time', that removes the question of what happened before, but leaves How is it possible for an infinite number of moments to have elapsed prior to now?

I'd say it's likely in some sense physics will have to recover a kind of monism, to reconcile this. Personally I would find that satisfying, I like the idea 'other times' are just special cases of 'other universes', that is all part of how all possibilities are found in 'now', to different degrees.

3
  • I think there is a difference between emerging time (or emerging space) and time (space) as it exists on a spacetime manifold. Emerging time (space) is relational, while the existence of time points (or space points) is not. So emerging spacetime is different from spacetime itself. Emerging spacetime is relational (the arrow of thermodynamic time) while spacetime itself can be seen as non-relational (maybe its appearance is relational though when considering its relation to our mind).
    – user52804
    Jun 19 at 14:18
  • The last question you link to seems to be answerable from the perspective of non-relational spacetime. Infinite in extension this spacetime can accommodate infinite moments of relational spacetime. Do you think of the MWI when considering other times and other universes? Is this a kind of monism?
    – user52804
    Jun 19 at 14:20
  • Yes MWI, that other worlds need not be 'out there', but only present here, eg as possible futures. "emerging spacetime is different from spacetime itself" I don't understand what this means. I look to Noether's theorem, to understand how space-time like other fields can be understood as emergent local symmetries under translation
    – CriglCragl
    Jun 21 at 11:33
0

One way to look at this is that infiniteness or finiteness of time is subject of interpretation (or rather, choice of the coordinate system).

First, I will give you a spatial analogy. Is space finite or infinite?

  • In proper coordinates, the space is infinite. Wherever a warrior would stay, he can push his spear further. If you travel the universe in a spaceship, you will never hit a wall that prohibits you going further.

  • In global coordinates though, space is finite. At the distance of roughly 5 GPc from us in all directions there is impenetrable boundary: the cosmic event horizon. This is because our space expands, and the spacetime is close to de Sitter solution. The faster the space expands, the closer the event horizon is to us. The horizon has de Sitter temperature of T=2.67x10^(-30) K.

So, how it can be the case that the universe is at the same time infinite, but has impenetrable boundary with finite radius and temperature?

The answer is that from the point of view of stationary observer, everyone approaching the cosmic event horizon, has the radial dimension shrinked and the time slowed down, about the same way as near a black hole.

No one can cross the event horizon, because as they approach it, they become radially compressed (in the coordinates of stationary observer) and their time slowed down. They remain "sticked" and redshifted at the cosmic boundary.

So, when we consider space, the proper space is infinite, the coordinate space is finite.

With time, it is similar, but the opposite: the proper time is finite as the world lines of all objects end in the past at Big Bang singularity. At the same time, the global, coordinate time is infinite in the past.

The speed of time depends on the density of mass-energy. Near massive objects the time is slowed down. And the early universe had greater density. If we account for this effect, we would conclude that time was going much slower in the past due to higher matter density. Of course, no one would notice it because everything was slower at the same proportion, so the proper time went just at the same visible speed.

But if we see it in global coordinates, the further we go into the past, the slower were all the processes. In fact, the Big Bang point occurs at the infinite past, so the universe was just slowly accelerating from a stationary highly-dense state with nearly no time going, but its density was slowly reducing and time becoming faster.

1
0

It possible that the big bang was a vacuum metastability event (vacuum decay event): the previous phase state of vacuum suddenly transitioned to another phase state and released energy that became all the matter we know.

5
  • Is this seen in the light of quantum field theory? (I haven't read the article yet)
    – user52804
    Jun 20 at 10:45
  • 1
    @Methadont yes.
    – Anixx
    Jun 20 at 10:46
  • I have read that a "bounce" comes about in this decay. Do you think that there is a relation with the big bounce theory? Which actually talks about a pre big bang time.
    – user52804
    Jun 20 at 10:52
  • @Methadont no, these are different theories. Big bounce theory is a GR solution/explanation. Has nothing to do with vacuum.
    – Anixx
    Jun 20 at 10:54
  • I think modern versions include quantum gravity (quantized spacetime). In these theories, particles are not concentrated at a point in spacetime, because spacetime itself prohibits this. The result is a pre-big-bang universe. Time would be even larger than infinite. It nicely circumvents the problem of time having a start.
    – user52804
    Jun 20 at 11:02
0

This is a third answer of mine.

Another my answer looks at the problem from the point of view of general relativity. And this is another answer, from the point of view of quantum mechanics.

It is well known that all physical laws except the second law of thermodynamics are time-reversible. It says that entropy of a closed system can only grow.

In quantum mechanics all systems in absence of an observer undergo time-reversible unitary evolution, the entropy of the system does not change in this process and no wave function collapse happens.

This in fact means that all visible entropy growth is due to the interaction with the observer.

If we assume the existence of universal wave function as in some interpretations of quantum mechanics, we would conclude that visible entropy growth is entirely due to entanglement of the observer with a branch of the universal wave function.

At the same time, the universal wave function as a whole undergoes unitary evolution and does not exhibit entropy growth.

Since the second law of thermodynamics is what defines the arrow of time, this leads us to the conclusion that the universe as a whole remains in the same (statistical) low-entropy state, and all evolution of the universe is an illusion due to interaction with the observer.

In other words, the universe eternally remains in low (maybe, zero) entropy state and undergoes time-reversibe, time-symmetric evolution, similar to statistical fluctuations without distinguished arrow of time.

All visible entropy growth is due to the fact the observer can see only his own branch of the universal wave function.

6
  • And his own part is just a statistical fluctuation?
    – user52804
    Jun 20 at 12:07
  • Ah, the MWI. The number of branches is not fixed. One branch (where the superposition finds itself) will break up in two after the measurement. In a unitary way, which is in fact the reason why the MWI was developed in the first place. The overall wavefunction does stay the same, but its structure inside varies, so time is present.
    – user52804
    Jun 20 at 12:25
  • @Methadont the universal wavefunction undergoes unitary (time-symmetric) evolution, so there is no distinguished arrow of time. The entropy also stays the same (zero).
    – Anixx
    Jun 20 at 12:27
  • @Methadont There is no Big bang, there is no universe expansion, there is no formation of atoms, etc. These all are manifestations of entropy increase, that is, wavefunction collapse, that is entanglement of the observer. The universe remains highly dense and uniform and globally unchanging.
    – Anixx
    Jun 20 at 12:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy