The reality of time, Lee Smolin lecture.

[ollypenrice]

I watched this, rather than his lecture on the trouble with String Theory, by accident but I'm glad I did. He returns, via a different route, to his earlier ideas about evolution in physics and cosmology.

Olly

[Rodd]

2 hours ago, ollypenrice said:

I watched this, rather than his lecture on the trouble with String Theory, by accident but I'm glad I did. He returns, via a different route, to his earlier ideas about evolution in physics and cosmology.

 

I am not yet through watching the lecture, but I do have a comment about what is said regarding what he says about Max Tegmarck's concept early on.  He claims that if the universe is a mathematical construct (which he now does not believe), then reality is in actuality a formula and that time must not exist.  However, just because reality is a formula, hypothetically, it does not follow that time, per se, can't exist.  For example, the movement of a ball through space can be described completely in Newtonian calculus.  Ballistics, is completely understood from a mathematical approach.  But that does not mean that it does not take the ball, or missile, 5 30 seconds to land.  In fact, calculus has time built into it...."change over time"   So I do not understand, or agree with, the notion that just because we are are mathematical constructs and the future is determined (not saying I believe that), that that precludes the existence of time.  I mean, time is built right into the statement "the future is determined".

Secondly, with respect to the existence of time, we are irrelevant.  Our biology, our perspective, our minds, etc.  Lizards age, rocks weather away.  We do not matter.  So tying the concept of time into our perceptions is unnecessary.

Lastly, I was under the impression that most scientists do not think that the future is determined and that free will does not exist.  He says early on that most scientists currently hold these things to be true.  I find that hard to believe.  As far as I can remember, time has always been about change, and the universe is constantly changing (entropy) because there is heat...temperature.  At absolute zero, all change ceases (except maybe the decay of neutrons...which is only believed to happen).  Without change, can there be time?  That has always been the fundamental question of time, because change happens OVER TIME.

Anyway....I will finish watching this later today.   

Rodd

 

[ollypenrice]

21 minutes ago, Rodd said:

 

I am not yet through watching the lecture, but I do have a comment about what is said regarding what he says about Max Tegmarck's concept early on.  He claims that if the universe is a mathematical construct (which he now does not believe), then reality is in actuality a formula and that time must not exist.  However, just because reality is a formula, hypothetically, it does not follow that time, per se, can't exist.  For example, the movement of a ball through space can be described completely in Newtonian calculus.  Ballistics, is completely understood from a mathematical approach.  But that does not mean that it does not take the ball, or missile, 5 30 seconds to land.  In fact, calculus has time built into it...."change over time"   So I do not understand, or agree with, the notion that just because we are are mathematical constructs and the future is determined (not saying I believe that), that that precludes the existence of time.  I mean, time is built right into the statement "the future is determined".

Secondly, with respect to the existence of time, we are irrelevant.  Our biology, our perspective, our minds, etc.  Lizards age, rocks weather away.  We do not matter.  So tying the concept of time into our perceptions is unnecessary.

Lastly, I was under the impression that most scientists do not think that the future is determined and that free will does not exist.  He says early on that most scientists currently hold these things to be true.  I find that hard to believe.  As far as I can remember, time has always been about change, and the universe is constantly changing (entropy) because there is heat...temperature.  At absolute zero, all change ceases (except maybe the decay of neutrons...which is only believed to happen).  Without change, can there be time?  That has always been the fundamental question of time, because change happens OVER TIME.

Anyway....I will finish watching this later today.   

Rodd

 

My grasp is that in normal scientific equations there is nothing special about 'now,' it is just one point arbitrarliy chosen on a continuum.  But do finish the video, it's worth it. I've just downloaded the book onto my Kindle and will get stuck in as soon as I've ploughed my way through a biography of one of the twentieth century's most odious people. (No politics on SGL but I don't think much of this guy's taste in shirts... )

Olly

[Rodd]

26 minutes ago, ollypenrice said:

My grasp is that in normal scientific equations there is nothing special about 'now,' it is just one point arbitrarliy chosen on a continuum.

True.  Though there is one aspect of "now" that IS special......and that is, "now" is not "then".  No moment in time is exactly like any other moment....there are differences in chemistry, particle positions, etc.  Unless we are at absolute zero--in which case, there IS no difference between now and then.  Other than one is spelled with 3 letters and one is spelled with 4.

Rodd

 

[andrew s]

I have read the book and was not convinced by it. He sets up a view of current thinking which is not sustainable. He stick to the Newtonian view of absolute space and time when describing what science takes as it view on time. He discusses knowing all the initial condition and being able to predict the future.

This is impossible in SR and GR due to the lack of simpeltaneity and that there are regions of spacetime that are not casually connected. 

He does make some good points on how limited some current theories are but I am unaware of any evidence for the evolution of the laws of physics he proposes.

In my view now is special but it applies to an "event" as it only meaningful as the point defining the "event" and it is where it past and future light cones meet.

I am here and now, my past is behind me my future in front!

Regards Andrew 

[Rodd]

13 minutes ago, andrew s said:

I have read the book and was not convinced by it. He sets up a view of current thinking which is not sustainable. He stick to the Newtonian view of absolute space and time when describing what science takes as it view on time. He discusses knowing all the initial condition and being able to predict the future.

This is impossible in SR and GR due to the lack of simpeltaneity and that there are regions of spacetime that are not casually connected. 

He does make some good points on how limited some current theories are but I am unaware of any evidence for the evolution of the laws of physics he proposes.

In my view now is special but it applies to an "event" as it only meaningful as the point defining the "event" and it is where it past and future light cones meet.

I am here and now, my past is behind me my future in front!

Regards Andrew 

Agreed.  My main point that I would like to say, and get his reaction to is...just because we can (if we could) predict exactly what would happen in the future, does not mean that time does not exist.  I do not see the connection between knowing what will happen and time.  If I were to go into the future (if I could) and watch the ball fall and hit the ground, I would know it was going to happen.  But time would still pass between now and then.   In short--even if reality is one big formula, it does not preclude the existence of time. This brings me to a point that has significance to what he is trying to do.  there is a major difference between the statements

"My work shows that time may not exist", and

"My work shows that time can't exist", which is what he must do, really, in order to be convincing.  Like most (if not all) aspects of nature, if it exists it is because it must exist (this does not necessarily hold for evolutionary biology--but the physical laws of nature).

Rodd

[andrew s]

I agree with you Rodd. If it were as he said then why do we not experience the retrodicted world as well as we do the predicted. The equations are just as valid.

In my view time is just as important  an element of our model of reality as space is. Just as Einstein demonstrated in SR.

Regards Andrew 

[vlaiv]

I don't agree with some views presented in video, but on the other hand, there are couple of interesting points - hopefully falsifiable, like that of evolution of laws of nature (not whole black whole = big bang thing - that is a bit far fetched in my view).

Here are some questions about time though that have been bothering me:

1. I don't hold that time is illusion - as Andrew pointed out it is essential part of space-time, and therefore exists. Question is: is passage of time, or apparent motion in one direction an illusion? We all agree that we are "moving" along temporal direction, and we agree that we are moving along temporal line in same direction. I think that we also agree on rate of movement in temporal direction (locally in terms of SR/GR).

2. Time is not dimension in 4d space-time that is on equal footing - we can go left or right, we can accelerate or move in relation to something else. We don't have absolutely no control over motion in time, nor can we move at different speeds thru time unless separated by distance in space time. Two objects can be very close and move at different speeds in space - this is not true for time. Also motion in different directions is not possible.

3. Matter of probability. Very fundamental for QM, depends so much on time. If we subscribe to relativity and time being one of coordinates of space-time, we are reducing probability to ensemble interpretation. Propensity does not play a role any more.

Also, to add - I have no problem with idea that time is element of reality (created at the big bang - so there is no time prior to big bang), but also have no problem with the realm of abstract and laws of universe being "set" - these are just properties of universe.

Asking a question why universe has such and such property is same as extending causality (related to concept of time) beyond of existence of time - prior to big bang.

[Rodd]

28 minutes ago, vlaiv said:

Two objects can be very close and move at different speeds in space - this is not true for time.

Unless you subscribe to the multi-world hypothesis--the multiverse, in which two universes could be juxtaposed very near to one another, each supporting different cosmological constants, including time (they are different universes after all).  Then, an object in one can literally be occupying the same region of space--but in a different universe and traveling through time at different rates.   

Short of this far-fetched notion....maybe things can move at different rates.  A rock ages much more slowly than a fruit fly.  maybe they are moving through time at different rates.  Its hard for us to know, for I believe that all of human knowledge amounts to a thimble full afloat on an intergalactic sized ocean.  Or, in a more vernacular manner..."You know nutt'n, John Snow"

Rodd

[vlaiv]

1 minute ago, Rodd said:

Unless you subscribe to the multi-world hypothesis--the multiverse, in which two universes could be juxtaposed very near to one another, each supporting different cosmological constants, including time (they are different universes after all).  Then, an object in one can literally be occupying the same region of space--but in a different universe and traveling through time at different rates.   

Short of this far-fetched notion....maybe things can move at different rates.  A rock ages much more slowly than a fruit fly.  maybe they are moving through time at different rates.  Its hard for us to know, for I believe that all of human knowledge amounts to a thimble full afloat on an intergalactic sized ocean.  Or, in a more vernacular manner..."You know nutt'n, John Snow"

Rodd

I have a problem distinguishing multiple universe and multiverse - those two, as far as I can tell are different things.

Multiple universe is supposed to handle / explain probability outcome: each time "die is cast" and there is definite outcome that has been only probability prior to "now" - universe branches of into as many copies as there are possible outcomes. Don't subscribe to that at all - don't know if it is testable at all, and once we split there seem to be no causality connection between the two (or multi) - from our standpoint of view - it's like it did not happen (if there is no picture on instagram - it did not happen ). It also tremendously violates Occam's razor (in my view).

So while two copies of same object (is it different object then?) can travel at different speeds - maybe there is pink unicorn instead out there traveling at super luminal speed

Multiverse is much closer to above discussion (again if I understand it correctly) - different regions of universe, causally disconnected due to speed of light and expansion of universe have "evolved" different laws of physics and are totally different. It's still single "universe" encompassing everything, but again - no way to tell if its true - not sure if it's testable.

[andrew s]

1 hour ago, Rodd said:

A rock ages much more slowly than a fruit fly.  maybe they are moving through time at different rates. 

The lesson of special relativity is that all motion through space and time is relative. I am currently doing 0.9999...c relative to a neutrino heading my way and - 0.9999...c relative to the one that just passed through me. In addition, a few km/s relative to the car on the road outside my house and  probably any other allowed velocity you can imagine. 

On my time like world line I am doing 1 second per second through time and 0 m/s through space as I always have and always will do!

However, my travel along my geodesic is currently interrupted by the easy chair I am sitting on and the earth it stands on. It is this that give the illusion of a gravitational force!

It is hard to think about SR/GR and its implication as we are blocked on are free fall by the matter under our feet and the EM force that binds it together.  Were we normally weightless in free space we might find it more intuitive though difficult to breath.

Regards Andrew

[saac]

9 hours ago, ollypenrice said:

My grasp is that in normal scientific equations there is nothing special about 'now,' it is just one point arbitrarliy chosen on a continuum.  

Olly

Olly from what I recall there are only a few, what you call normal physics equations , in which the past, present and future are delineated, in other words in which the direction of time is described in the relationship.  The second law of thermodynamics springs to mind  ds = dQ/T .  This is such a simple looking equation but it describes so much .  I was first introduced to it 30 years ago studying engineering and I must admit it has taken as long to really appreciate its significance. 

Jim  

[ollypenrice]

10 hours ago, saac said:

Olly from what I recall there are only a few, what you call normal physics equations , in which the past, present and future are delineated, in other words in which the direction of time is described in the relationship.  The second law of thermodynamics springs to mind  ds = dQ/T .  This is such a simple looking equation but it describes so much .  I was first introduced to it 30 years ago studying engineering and I must admit it has taken as long to really appreciate its significance. 

Jim  

Yes, though does the arrow of time specify any particular 'now,' or does it just describe the general trend which must apertain before and after any particular moment? The second law is indeed astonishing in its range of implications.

Olly

[andrew s]

58 minutes ago, ollypenrice said:

Yes, though does the arrow of time specify any particular 'now,' or does it just describe the general trend which must apertain before and after any particular moment? The second law is indeed astonishing in its range of implications.

Olly

I don't know of any law of physics that defines a specific "now" nor any one that defined a specific place as in here and now. 

Some theories predict a specific time as in the BB cosmological model. It would be counter to modern cosmology, GR and SR if they did. Now only has meaning at a specific event and separates the events past and future light cones. 

Even if you are having a conversation in your living room you are currently aware of the  past as all the information took time to get to you.

Regards Andrew 

[Rodd]

2 hours ago, andrew s said:

I don't know of any law of physics that defines a specific "now" nor any one that defined a specific place as in here and now. 

Some theories predict a specific time as in the BB cosmological model. It would be counter to modern cosmology, GR and SR if they did. Now only has meaning at a specific event and separates the events past and future light cones. 

Even if you are having a conversation in your living room you are currently aware of the  past as all the information took time to get to you.

Regards Andrew 

For those who subscribe to the idea that the universe IS the equations, then this question is indeed important.  For those who believe that the equations DESCRIBE the universe, it I not as vital.  "Now" does not have to be included in the formulae, as there is only 1 now, and it only exists for a period of time equivalent to the shortest possible duration (I would assume the time it takes light to traverse the smallest definable distance). "Now" is EVERY point in the continuum at some time, and no point is ever "now" more than once.   Time is the mid point between the past and the future.  So in some Feynman diagrams, if I remember correctly, there are particles depicted traveling backward in time.  In order to travel backward in time, they by definition must pass through "now"--unless one holds to the theory that the future exists and that time is not unfolding from moment to moment.  I suppose Einstein falls into this category if, in fact, he was the source of the famous saying "the past, present, and future are happening simultaneously".  Finally, just because the equations do not define "now" does not mean that "now" is unreal.  Now is not particularly important, remember.  In Newtonian physics, it is irrelevant.  The equation that describes the path of a non powered ballistic object is applicable regardless of when the object is hurled.

Regarding being aware of the past--not necessarily so.  We are aware of a construct of how we remember the past.  memories are not equivalent to the past--they are inherently unreliable because they are formed by our brains through electro-chemical reactions.  They are constructs.

We might as well talk about string theory...I am getting dizzy.

Rodd

[vlaiv]

Relativity postulates that there is no universal "Now". Now is localized and very intimately connected to space.

We can think of now as being an event in 4D space time. It has place and it has time when it happened (or will happen). Problem is of course that simultaneity depends on observer. So for some observer thing that is happening now can already have happened for someone else, and might be yet to happen for third observer (depending on their state of motion to one another).

Just by acceleration you are changing what is known as "now" slice - all space time points that you can say are simultaneous for you.

This combined with QM has very interesting implication - I did not ponder enough on it to start to understand what it may mean, but here it is:

Entanglement. Let's say that there are two entangled photons and there is setup where Bob and Alice measure polarization at some distance to each other. From QM we know that hidden variables are excluded and that prior to measurement there is no, even in principle, way of knowing which way measurement will go for Bob and for Alice. All we know is that they are 100% correlated. But there is one more thing - one who measures first causes "collapse of state" - here in quotes to emphasize that there is no actual collapse of wavefunction, but rather decoherence to environment and settling in single state (whether by splitting into multiple universes - each one carrying one possible outcome, or pure random event). 

Now interesting part comes. There exist three observers Claude, Debby and Forest, each one of them in such motion in respect to Alice and Bob as to measure: Alice doing measurement first, Bob doing measurement first and Alice and Bob doing measurement simultaneously.

Now if we say polarization is correlated - that is ok, but why is there consistency between Alice measuring first and Bob measuring first? Only way that it can work A causes B and B causes A is if both A and B were predetermined, but QM postulates random event. So contradiction.

[andrew s]

There is a lot to un-pick in this Rodd but I will give it a go.

1 hour ago, Rodd said:

For those who subscribe to the idea that the universe IS the equations, then this question is indeed important.  For those who believe that the equations DESCRIBE the universe, it I not as vital.

To be clear I am in the camp that there is an objective reality independent of us as observers and that our physical theories seek to model it.

1 hour ago, Rodd said:

there is only 1 now, and it only exists for a period of time equivalent to the shortest possible duration (I would assume the time it takes light to traverse the smallest definable distance). "Now" is EVERY point in the continuum at some time, and no point is ever "now" more than once.

I am unclear what you mean by this.

I would say that every world line through spacetime is paramatised by its proper time.  To define "now"  I think requires an event on this line to be identified but I don't know how to do it other than for a sentient being i.e now is the event I am currently in. This is why I think now does not appear in Physical laws. 

1 hour ago, Rodd said:

So in some Feynman diagrams, if I remember correctly, there are particles depicted traveling backward in time.

This is one reason why I think the equations are not the real world. Feynman diagrams are a way of calculating integrals in QFT using perturbation theory as the equations can't be solved directly. They are a pictorial way of describing the terms in the expansion. They are not a picture of what actually happens (no virtual particles flying about) any more than a symphony is the components of the Fourier transform of the sound waves reaching your ears. 

1 hour ago, Rodd said:

I suppose Einstein falls into this category if, in fact, he was the source of the famous saying "the past, present, and future are happening simultaneously". 

I think he was highlighting the fact there was no absolute time and space as in Newtonian physics but depending on the frame of reference and event could be in the past, present or future.

1 hour ago, Rodd said:

We might as well talk about string theory.

In my view string theory is an exercise in mathematics or possibly metaphysics and will remain so until it makes testable predictions.

 

Time for a cup of tea and a lie down or have I already done it?

Regards Andrew

[andrew s]

2 minutes ago, vlaiv said:

Now interesting part comes. There exist three observers Claude, Debby and Forest, each one of them in such motion in respect to Alice and Bob as to measure: Alice doing measurement first, Bob doing measurement first and Alice and Bob doing measurement simultaneously.

As the photons were entangled they will all observe the same result irrespective of the order they observed them being measure. 

Regards Andrew

[Rodd]

 

11 minutes ago, andrew s said:

I don't know how to do it other than for a sentient being i.e now is the event I am currently in. This is why I think now does not appear in Physical laws. 

That's what I mean by that

 

12 minutes ago, andrew s said:

This is one reason why I don't think the equations are not the real world.

I don't know what You mean by this! (smiling imogi--I lost them for some reason)

 

15 minutes ago, andrew s said:

I think he was highlighting the fact there was no absolute time and space as in Newtonian physics but depending on the frame of reference and event could be in the past, present or future.

I think this is why "now" is not defined in physics.

 

17 minutes ago, andrew s said:

Time for a cup of tea and a lie down or have I already done it?

Define tea (another clever imogi)

[Rodd]

10 minutes ago, andrew s said:

As the photons were entangled they will all observe the same result irrespective of the order they observed them being measure. 

So entangling aligns reference frames.  However-there is no evidence to suggest that objects (or people) can be entangled.  Consciousness certainly can't be entangled.  Photons, or electrons have no use for the concept of now.  They just "are".

 

23 minutes ago, andrew s said:

I think he was highlighting the fact there was no absolute time and space as in Newtonian physics but depending on the frame of reference and event could be in the past, present or future.

Maybe he meant "all times are now".  So defining now becomes unnecessary.

[vlaiv]

42 minutes ago, andrew s said:

As the photons were entangled they will all observe the same result irrespective of the order they observed them being measure. 

Regards Andrew

Not sure how this follows. Entanglement means that there is single state of both photons, or shall we switch to electrons for convenience - and say that state is characterized as Spin Up + Spin down - with anti correlation between two electrons.

It only states that there is single state, and that state is mixed and when transition to pure state happens (eigen value) - or measurement is made, there will be anti correlation in electron spins. Problem is of course that we perceive state transition as an event - random in nature and that evolution of state function is causal - Interaction of systems coupled with decoherence causes transition to pure state. Here problem arises from the fact that causality is local in relativity, but with entanglement state function is spatially distributed.

We can say that outcome of measurement is determined prior to measurement (no single measurement event that causes probability to realize it self), thus we enter either hidden variable territory, or we can say that there is one global wave function and its evolution does not follow probabilistic "selection" - and then we go into pure determinism.

There is a way out of all of that, but I can't seem to find any justification for it other than convenience. Measurement that happens first in frame of reference where entanglement happened in the first place is the one that causes probability to realize.

[andrew s]

3 minutes ago, vlaiv said:

Not sure how this follows.

If it were not the case then there would be two sets of results for the same experiment which contradicted each other when the results were compared via exchange of messages. I would contend that while the observers would dispute which measurement came first (i.e which was cause and which effect) they must get the same net outcome. 

I found this when researching how to reply to Rodd about aligning reference frame which is too strong a statement in my view.

"Quantum entanglement does violate the classical notion of relativistic causality, if the wave function is considered real. This is the content of Bell's theorem. However, quantum entanglement does not violate signal causality, ie. it does not allow classical information to be sent faster than light."

Reference https://www.physicsforums.com/threads/how-does-quantum-entanglement-not-violate-causality.825292/

Regards Andrew

[vlaiv]

8 minutes ago, andrew s said:

If it were not the case then there would be two sets of results for the same experiment which contradicted each other when the results were compared via exchange of messages. I would contend that while the observers would dispute which measurement came first (i.e which was cause and which effect) they must get the same net outcome. 

I found this when researching how to reply to Rodd about aligning reference frame which is too strong a statement in my view.

"Quantum entanglement does violate the classical notion of relativistic causality, if the wave function is considered real. This is the content of Bell's theorem. However, quantum entanglement does not violate signal causality, ie. it does not allow classical information to be sent faster than light."

Reference https://www.physicsforums.com/threads/how-does-quantum-entanglement-not-violate-causality.825292/

Regards Andrew

Quite agree on that quotation - there is no way to pass any sort of information, nor causality between A and B.

But there seems to be some sort of paradox in it, arising, in my opinion in our notion of wave function evolution being causal in classical sense. It also questions probabilistic nature of wave function evolution. I have no problem with "regular" wave function evolution - but I think that all will agree that we have a problem with "collapse" part of it. Even if we can explain evolution to pure state due to decoherence - there is simply no mechanism that "decides" which one of pure states should wave function evolve to other than random choice and probability.

Probability is very intimately related to time - there is probability only forward in time, backward in time there is only certainty (in classical reasoning).

Relativity is giving us hint that time is not divided by hard division - past, now, future, but as Einstein put it - it is all time all the time. This example with entanglement just confirms this in my view.

Problem with all of the above are, as outlined in video - consciousness and free will.

I don't think that we examined these in great depth, or in relation to what is our physics telling us. Problem of course being that if all time is all the time, then there seem to be quite strong determinism in spite of apparent probability nature of universe. 

Strong determinism does not go very well with our notion of free will, nor our understanding of probability. Free will can't arise even in probabilistic picture. Not sure how consciousness goes into all of this, but I do have a following thought about it:

- given that we accept current world view as per physics description, consciousness is just byproduct of system complexity. I can't help but wonder - at what level of complexity does consciousness arise and by which mechanism? What would be gradients of consciousness? Can we say there is borderline - this system is conscious and one with one degree of complexity less is no longer conscious?

To use analogy from video - mathematics is a system, and probably one of ultimate complexity - is it conscious? I mean system can be system of atoms, or can be system of electric circuits (our brain?). There is no distinction between the two according to current physics and relation to consciousness. Electrical signals are just simulation of a system - a concept, and it's very close step to abstract and mathematics.

[saac]

7 hours ago, ollypenrice said:

Yes, though does the arrow of time specify any particular 'now,' or does it just describe the general trend which must apertain before and after any particular moment? The second law is indeed astonishing in its range of implications.

Olly

The "now" is surely just a particular value on a continuum of flowing time;  I don't believe it holds any particular significance to the universe.  Of course it tortures the human mind, it is fleet footed and ever elusive but it is of no concern to the universe. 

Jim 

 

[andrew s]

56 minutes ago, vlaiv said:

Problem with all of the above are, as outlined in video - consciousness and free will.

We have come full circle - personally I don't believe consciousness plays any role in physical laws.

As to free will I am not sure we have it and if we do it is constrained by biology and upbringing. However, I believe we should act as if we do.

56 minutes ago, vlaiv said:

in my opinion in our notion of wave function evolution being causal in classical sense

Whatever, ones interpretation of QM the equations work as far as we have probed.

I don't think I can add any more insights right or wrong!

Regards Andrew