Does the Block Universe Theory Affect Our Understanding of Time and Reality?

[bobc2]

4D spacetime consists of events. Events are the buiding blocks, permanantly available to be part of a 'now'world. A 'now' world is your world at a specific point in time.
How one's worldline runs through spacetime determines which events out of total spacetime you will select as being 'simultaneous'. Our 3D world is a construction (made by ourselves) of a limited collection of in spacetime permanently available events. This collection is your world during a split second in your life. In spacetime there are no 'simultaneous' events as such, because 'simultaneity' is something we stick onto the events that we consider happening the same time. Other people will put the simultaneity sticker to oher events.
Whether a world at a specific point in time (= per definition made of simultaneous events) is 'physical' or 'real' is not that important (this gets philosophical), BUT if you consider one world 'real', then all other now worlds of all other 'moving' systems are also to accepted as 'real'. Therefore: all events of spacetime are 'real', or none is 'real'.
Every day I find it mindboggling that this is so difficult to understand by people juggling with Einstein's formulas. Relativity of simultaneous events is so easy, but apparently for many a too great mental step to take...?
I have not read every post of bobc2, but I think bob took that step.

A very nice and efficient summary of the situation, Vandam.

 

[Dale]

Every day I find it mindboggling that this is so difficult to understand by people juggling with Einstein's formulas. Relativity of simultaneous events is so easy, but apparently for many a too great mental step to take...?

Translation: "I have an untestable philosophical position that I have good reasons for liking. Therefore everyone who doesn't like it as strongly as I do must be mentally deficient."

 

[Vandam]

Translation: "I have an untestable philosophical position that I have good reasons for liking. Therefore everyone who doesn't like it as strongly as I do must be mentally deficient."

Wow, Dale, that's definitely not my way of seeing it.

May I ask you following question:
If you only consider your world of simultaneous events as real, but not the world of simultaneous events of somebody moving relative to you, do you accept that that other person will say to you: "Mr Dale, my world of simultaneous events is real, but not your world of simultaneous events" ?
What do you answer him? Do you think he will not consider his world of simultaneous events as real? Why not? He's using exactly the same procedure (lightspeed information into his eyes) as you do to make up his world of simultaneous events. And both worlds are different. So what's the problem, or where's the problem?

 

[PeterDonis]

4D spacetime consists of events. Events are the buiding blocks, permanantly available to be part of a 'now'world. A 'now' world is your world at a specific point in time.

But this "world" is a construction, as you yourself say just a bit later on:

Our 3D world is a construction (made by ourselves) of a limited collection of in spacetime permanently available events.

But the "permanently available events" you use to make this construction are outside your past light cone, so you have no direct information about them. In order to construct your model of those events, you must extrapolate from the information that is in your past light cone, and that information is not sufficient to determine what happens at those spacelike separated events. So your model of those events may be wrong.

Therefore, as I've pointed out to bobc2 before, by asserting that those events are "real" or "permanently available" or whatever phrase you want to use, you are putting yourself in the position of asserting the reality of events that may not actually happen. This seems like a very odd position to take. I've commented along these lines in this thread before, but there was also another thread (I think the one that was linked to a few posts back) where this was hashed out.

 

[PeterDonis]

He's using exactly the same procedure (lightspeed information into his eyes) as you do to make up his world of simultaneous events.

This procedure doesn't tell you, or him, what is in either of your simultaneous spaces. It only tells you what's in your past light cone. You have to extrapolate from that information to construct your simultaneous spaces, and that extrapolation is not determinate--the information in your past light cone is not sufficient to nail down exactly what happens in your simultaneous space.

So I would say that both of your simultaneous spaces--and in fact both of your models of any events that are spacelike separated--are tentative constructions; they're in your heads, not in reality. You won't know what's in reality until you get direct information from those events.

 

[Dale]

Wow, Dale, that's definitely not my way of seeing it.?

If that was not your intention then you should avoid comments like

"this is so difficult to understand" and "for many a too great mental step to take"

Which appear to presume that your philosophical position is undeniably correct and that the only possible reason for disagreement is a lack of understanding or some other mental deficiency.

May I ask you following question:
If you only consider your world of simultaneous events as real, but not the world of simultaneous events of somebody moving relative to you, do you accept that that other person will say to you: "Mr Dale, my world of simultaneous events is real, but not your world of simultaneous events" ?
What do you answer him?

I give him the same answer I give anyone who asks a question about what is "real". I ask him to provide an experiment which could be performed to determine whether or not a given event is "real" according to his concept of "real". If he provides an experiment then I use standard physics to predict the outcome and reply accordingly. If he does not provide an experiment then I tell him that his idea of "real" is unscientific and so I couldn't care less which events he chooses to label "real" and which he chooses not to.

I myself would never assert that my world of simultaneous events is "real" for exactly this reason.

 

[harrylin]

[..]Therefore: all events of spacetime are 'real', or none is 'real'.
Every day I find it mindboggling that this is so difficult to understand by people juggling with Einstein's formulas. [..]

"Mindboggling" you say? What I find "mindboggling" is that it is so difficult to realize that the above conclusion is wrong after this has been explained already in this thread and the other thread. For example Bell (who taught SR and QM) argued for the QM interpretation that the events of a single space-time are "real", only we cannot know which one. But his interpretation must be impossible (erroneous) if your understanding is correct; thus, according to you he did not understand Einstein's formula's and must have made a logical mistake. Which one?

 

[bobc2]

But this "world" is a construction, as you yourself say just a bit later on:



But the "permanently available events" you use to make this construction are outside your past light cone, so you have no direct information about them. In order to construct your model of those events, you must extrapolate from the information that is in your past light cone, and that information is not sufficient to determine what happens at those spacelike separated events. So your model of those events may be wrong.

Therefore, as I've pointed out to bobc2 before, by asserting that those events are "real" or "permanently available" or whatever phrase you want to use, you are putting yourself in the position of asserting the reality of events that may not actually happen. This seems like a very odd position to take. I've commented along these lines in this thread before, but there was also another thread (I think the one that was linked to a few posts back) where this was hashed out.

Hi, PeteDonis, it's always good to exchange views with you. On this point, as I've pointed out in other threads, Einstein would be revulsed. He often cautioned against being led into solipsism, as your logic would lead us.

The thing about it is that you may argue that logically you cannot present a proof that solipsism is not the correct reality--and that's the problem. But there seems to come a point in pursuing a concept of physical reality that you simply reject concepts that seem absurd on the face of it.

Nevertheless, there are those who would cling to solipsism and defy you to prove them wrong.

Vandam has manifestly presented better logic than any solipsist could offer.

 

[Vandam]

But this "world" is a construction, as you yourself say just a bit later on:

If its a construction, all the worlds are a construction, also yours! Why should your world NOT be a construction?

But the "permanently available events" you use to make this construction are outside your past light cone, so you have no direct information about them. In order to construct your model of those events, you must extrapolate from the information that is in your past light cone, and that information is not sufficient to determine what happens at those spacelike separated events. So your model of those events may be wrong.

Therefore, as I've pointed out to bobc2 before, by asserting that those events are "real" or "permanently available" or whatever phrase you want to use, you are putting yourself in the position of asserting the reality of events that may not actually happen. This seems like a very odd position to take. I've commented along these lines in this thread before, but there was also another thread (I think the one that was linked to a few posts back) where this was hashed out.

whatever, inside or outside lightcone, als you like, but so do the events that you use to make up your now world... Don't you realize this? Think about it.
So why should your world be real and not the other?

 

[Dale]

He often cautioned against being led into solipsism, as your logic would lead us.

How so? I don't see how his comments lead to solipsism.

 

[PeterDonis]

On this point, as I've pointed out in other threads, Einstein would be revulsed. He often cautioned against being led into solipsism, as your logic would lead us.

I don't see this at all. Where have I said that I am the only thing that exists? I am simply trying to draw a distinction, which you repeatedly refuse to see, between what is known and what is only extrapolated. I really don't see why the distinction is so hard to grasp.

 

[PeterDonis]

If its a construction, all the worlds are a construction, also yours! Why should your world NOT be a construction?

You are missing the point. I'm not saying that your world is constructed and mine is not. I agree that "all the worlds are a construction" (assuming that by "worlds" you mean "simultaneous spaces").

Pick an event E where two observers in relative motion, A and B, meet. The past light cone of event E is invariant, so A and B both agree on which events are in that past light cone. Those events are known to A and B at event E.

A and B can each *construct* their simultaneous spaces at event E; these will be different spacelike surfaces, SA and SB, that each contain event E. But of *all* the events in either SA or SB, the *only* one, strictly speaking, that is known to A or B at event E is event E itself. *Every* other event in SA *and* SB is constructed; all those events are spacelike separated from E, so they are outside E's past light cone, so they are not known to A or B at event E. So both "worlds", yours and mine (A's and B's) are constructed.

But there's more to it than that. First, *nothing* that happens at any event in SA or SB, other than E, can have any effect on what A and B observe at event E. So whether you call the events in SA and SB, other than E, "real" or not, the actual observations of A and B at event E are the same. (You'll notice that I didn't use the word "real" at all in what I said above.)

But more important than that, when A and B construct their simultaneous spaces, SA and SB, the only information they can use for the construction is the information contained in the past light cone of E. They have to extrapolate from that information to construct SA and SB, and their extrapolations could be wrong, because the information in E's past light cone is not sufficient to determine what actually happens at the events in SA and SB other than E (or indeed at *any* that's event spacelike separated from E). So if you insist on calling all the events in SA and SB "real", you are claiming that there are "real" happenings that might not actually happen. (bobc2 and I went through this in detail in the other thread.)

 

[Dale]

So why should your world be real and not the other?

Why should either be "real"? I notice that you have not proffered an experiment by which we can experimentally determine the "real"-ness of any event.

 

[bobc2]

How so? I don't see how his comments lead to solipsism.

In the sketch below you see a representation of space-time with observers A, B, C, D, and E moving through time. You can ask whether there is an external objective real world for observer A. For the solipsist relying on ideas from special relativity, he has no external world for his present instant. He is forever moving forward in time at the apex of his past light cone. No information from his otherwise "simultaneous space" is available to him, so he is obliged to affirm that he is the only thing that exists, whether it be at his instant t1 or t2, t3, t4, t5, t6, etc.

Einstein rejected solipsism and would affirm the existence of reality in the external simultaneous space, "...Physics is an attempt conceptually to grasp reality as it is thought independently of its being observed. In this sense one speaks of 'physical reality' ."

 

[Vandam]

You are missing the point. I'm not saying that your world is constructed and mine is not. I agree that "all the worlds are a construction" (assuming that by "worlds" you mean "simultaneous spaces").

Pick an event E where two observers in relative motion, A and B, meet. The past light cone of event E is invariant, so A and B both agree on which events are in that past light cone. Those events are known to A and B at event E.

A and B can each *construct* their simultaneous spaces at event E; these will be different spacelike surfaces, SA and SB, that each contain event E. But of *all* the events in either SA or SB, the *only* one, strictly speaking, that is known to A or B at event E is event E itself. *Every* other event in SA *and* SB is constructed; all those events are spacelike separated from E, so they are outside E's past light cone, so they are not known to A or B at event E. So both "worlds", yours and mine (A's and B's) are constructed.

But there's more to it than that. First, *nothing* that happens at any event in SA or SB, other than E, can have any effect on what A and B observe at event E. So whether you call the events in SA and SB, other than E, "real" or not, the actual observations of A and B at event E are the same. (You'll notice that I didn't use the word "real" at all in what I said above.)

But more important than that, when A and B construct their simultaneous spaces, SA and SB, the only information they can use for the construction is the information contained in the past light cone of E. They have to extrapolate from that information to construct SA and SB, and their extrapolations could be wrong, because the information in E's past light cone is not sufficient to determine what actually happens at the events in SA and SB other than E (or indeed at *any* that's event spacelike separated from E). So if you insist on calling all the events in SA and SB "real", you are claiming that there are "real" happenings that might not actually happen. (bobc2 and I went through this in detail in the other thread.)

Why should either be "real"? I notice that you have not proffered an experiment by which we can experimentally determine the "real"-ness of any event.

I'm happy you agree that all worlds are constructed, but I never said that at one specific event (your event E, where A en B meet) somebody knows what the world (sim events) is at that moment. But that doesn't mean there was no world!
One receives information over a certain time, and based on length, time measurements, speed of light, he concludes what his world was at (f.ex.) event E.
If the two observers do this exercise, they will not agree on their world (sim events).

The real/unreal discussion is indeed philosophical, bus IF you call one world real, THEN all worlds are real.

If for you the world is nothing real, but only a subjective/conscious dream, then all worlds are dreams. But SR tells you there's also total spacetime of dreamevents. And A's dreamworld is a section trough dreamspacetime. And B's world is a section through dreamspacetime. That's logic.

Maybe you don't accept that there exists a 'somebody else with consciousness' to 'construct' his own (dream)world. Then you are really a hard solipsist ;) Are you?

 

[nitsuj]

If for you the world is nothing real, but only a subjective/conscious dream, then all worlds are dreams. But SR tells you there's also total spacetime of dreamevents. And A's dreamworld is a section trough dreamspacetime. And B's world is a section through dreamspacetime. That's logic.

And that commentary greatly degrades the "quality" of this topic.

"total spacetime of dreamevents" what on Earth is that?? (Rhetorical)

 

[Vandam]

In the sketch below you see a representation of space-time with observers A, B, C, D, and E moving through time. You can ask whether there is an external objective real world for observer A. For the solipsist relying on ideas from special relativity, he has no external world for his present instant. He is forever moving forward in time at the apex of his past light cone. No information from his otherwise "simultaneous space" is available to him, so he is obliged to affirm that he is the only thing that exists, whether it be at his instant t1 or t2, t3, t4, t5, t6, etc.

Einstein rejected solipsism and would affirm the existence of reality in the external simultaneous space, "...Physics is an attempt conceptually to grasp reality as it is thought independently of its being observed. In this sense one speaks of 'physical reality' ."

As I answered to Peter it is feasible to make out what your world WAS at a previous event.
And what will the real solipsist then say? Everything of the past is not part of my now, so I don't know wheter it existed or not. Gotcha ;)
Solipsist only believe in ther own now event.

 

[Vandam]

And that commentary greatly degrades the "quality" of this topic.

"total spacetime of dreamevents" what on Earth is that?? (Rhetorical)

Please read al the posts of this tread. Then you will understand why I wrote this.

 

[bobc2]

As I answered to Peter it is feasible to make out what your world WAS at a previous event.
And what will the real solipsist then say? Everything of the past is not part of my now, so I don't know wheter it existed or not. Gotcha ;)
Solipsist only believe in ther own now event.

Solipsists only believe in ther own NOW event You've got it for sure, Vandam. And Einstein did not like solipsism and warned against being led into that trap.

 

[PeterDonis]

I'm happy you agree that all worlds are constructed, but I never said that at one specific event (your event E, where A en B meet) somebody knows what the world (sim events) is at that moment. But that doesn't mean there was no world!

And I have never said "there was no world". Nor have I said there was a world. I don't think either statement has meaning, for the reasons DaleSpam has already given--there's no experiment you can do to tell whether "the world" as you define it is "real" or not.

One receives information over a certain time, and based on length, time measurements, speed of light, he concludes what his world was at (f.ex.) event E.

If you mean the "world" is constructed after the fact--after the observer has already received light signals from all the events in his "world" at some instant--then that's something different than what we've been discussing up to now, because the observer will have to wait for some time *after* a given event before he can construct his "world" at that event. (In fact, if he wants to construct his *entire* "world" at a given event, he might have to wait an infinite amount of time--to the best of our knowledge, the universe is spatially infinite.)

On this view there is no reason to claim that the "world" is "real" at event E; you're only claiming events are "real" after you've received light signals from them, so you know what happens in them. In other words, you are limiting your claims to what's actually known--what's in your past light cone.

If the two observers do this exercise, they will not agree on their world (sim events).

Only if they insist on identifying their "world" with their simultaneous space at a given event. But since no events spacelike separated from a given event can affect what any observer observes at that event, their different choices of simultaneous space have no observable consequences, as DaleSpam has pointed out. So there's nothing that *requires* them to disagree. They could both just say that the entire set of spacelike separated events is "elsewhere" (Roger Penrose's term), and defer making any claims about them until they receive more information (as discussed above).

Or, if either one wants to extrapolate from what's known, what's in their past light cone, to *predict* what might be happening at some event that's spacelike separated from them, why would either one need to restrict his predictions to just his own simultaneous space at a given event? Why couldn't observer A make a prediction about what might be happening at an event that is simultaneous with observer B at event E? Why must each one restrict their predictions to their own "world"? Or even to the other's "world"? Why couldn't either of them make a prediction about *any* event that's spacelike separated from them? There's nothing stopping them; they have the same amount of information (in the past light cone) to extrapolate to *any* spacelike separated event. So there's nothing that even picks out either one's "world" as being any different from any other set of spacelike separated events.

The real/unreal discussion is indeed philosophical, bus IF you call one world real, THEN all worlds are real.

I haven't called any of the worlds "real", so this doesn't apply to me.

If for you the world is nothing real, but only a subjective/conscious dream, then all worlds are dreams.

I have never said the world is only a dream. How are you getting that out of what I said? Are you actually reading what I post? You seem to be making a lot of assumptions about what I am saying that are invalid.

Maybe you don't accept that there exists a 'somebody else with consciousness' to 'construct' his own (dream)world. Then you are really a hard solipsist ;) Are you?

Of course not. If you had actually read what I posted, it would be obvious; I talked explicitly about multiple observers and what each one observes, constructs, etc. I never said that any observer, including me, was "privileged" in any way; they are all on an equal footing.

 

[PeterDonis]

As I answered to Peter it is feasible to make out what your world WAS at a previous event.

A finite portion of it, yes. But to know what your entire "world" (meaning simultaneous space) was at a previous event, you need to wait for an infinite time after that event, since the universe is spatially infinite (to the best of our knowledge).

And what will the real solipsist then say? Everything of the past is not part of my now, so I don't know wheter it existed or not.

I have never said this or anything like it. I don't know where you are getting this from. In previous threads I have explicitly said that I have no problem with viewing every event in the past light cone as "real". I realize you weren't in those previous threads, but bobc2 was, and he should know better than to reinforce you on this point.

 

[Vandam]

And I have never said "there was no world". Nor have I said there was a world. I don't think either statement has meaning, for the reasons DaleSpam has already given--there's no experiment you can do to tell whether "the world" as you define it is "real" or not.If you mean the "world" is constructed after the fact--after the observer has already received light signals from all the events in his "world" at some instant--then that's something different than what we've been discussing up to now, because the observer will have to wait for some time *after* a given event before he can construct his "world" at that event. (In fact, if he wants to construct his *entire* "world" at a given event, he might have to wait an infinite amount of time--to the best of our knowledge, the universe is spatially infinite.)

On this view there is no reason to claim that the "world" is "real" at event E; you're only claiming events are "real" after you've received light signals from them, so you know what happens in them. In other words, you are limiting your claims to what's actually known--what's in your past light cone.
Only if they insist on identifying their "world" with their simultaneous space at a given event. But since no events spacelike separated from a given event can affect what any observer observes at that event, their different choices of simultaneous space have no observable consequences, as DaleSpam has pointed out. So there's nothing that *requires* them to disagree. They could both just say that the entire set of spacelike separated events is "elsewhere" (Roger Penrose's term), and defer making any claims about them until they receive more information (as discussed above).

Or, if either one wants to extrapolate from what's known, what's in their past light cone, to *predict* what might be happening at some event that's spacelike separated from them, why would either one need to restrict his predictions to just his own simultaneous space at a given event? Why couldn't observer A make a prediction about what might be happening at an event that is simultaneous with observer B at event E? Why must each one restrict their predictions to their own "world"? Or even to the other's "world"? Why couldn't either of them make a prediction about *any* event that's spacelike separated from them? There's nothing stopping them; they have the same amount of information (in the past light cone) to extrapolate to *any* spacelike separated event. So there's nothing that even picks out either one's "world" as being any different from any other set of spacelike separated events.
I haven't called any of the worlds "real", so this doesn't apply to me.
I have never said the world is only a dream. How are you getting that out of what I said? Are you actually reading what I post? You seem to be making a lot of assumptions about what I am saying that are invalid.
Of course not. If you had actually read what I posted, it would be obvious; I talked explicitly about multiple observers and what each one observes, constructs, etc. I never said that any observer, including me, was "privileged" in any way; they are all on an equal footing.

Peter,
you say you're not a solipsist, but the way you expose things you are...
To be honest, I'm lost. I can't get your vision on things.

What's is the state of a tree you see in front of you?
Does the tree exisited the moment the light started going your way?
Or will you ask me "what do you mean with 'exist'"?

 

[Dale]

For the solipsist relying on ideas from special relativity, he has no external world for his present instant. He is forever moving forward in time at the apex of his past light cone. No information from his otherwise "simultaneous space" is available to him

The same is all true for the non-solipsist also.

, so he is obliged to affirm that he is the only thing that exists

The solipsist affirms that regardless of the above. Furthermore, since all the above is true for the non solipsist also, if the solipsist's conclusion follows from the above (it doesn't imo) then the non-solipsist must make the same conclusion.

A non-solipsist can certainly assert that any event in his past light cone was not merely a figment of his own imagination. He does not need to make assumptions about any events outside of his past light cone in order to not be a solipsist.

You are confounding two unrelated concepts, nobody here is promoting solipsism so your comments are very much a straw man argument.

 

[Dale]

The real/unreal discussion is indeed philosophical

Then it doesn't belong here, and since it is central to your premise, then neither does your premise.

If for you the world is nothing real, but only a subjective/conscious dream, then all worlds are dreams. But SR tells you there's also total spacetime of dreamevents. And A's dreamworld is a section trough dreamspacetime. And B's world is a section through dreamspacetime. That's logic.

Maybe you don't accept that there exists a 'somebody else with consciousness' to 'construct' his own (dream)world. Then you are really a hard solipsist ;) Are you?

You are also committing the same straw man logical fallacy that bobc2 is.

No I am not a solipsist, I am a scientist. If you were to make this absurd claim then I would issue the same challenge which you avoided earlier: what experiment could you perform to measure the "dream"-ness of a specific event or the universe as a whole?

The scientific content of your posts appears to be 0.

 

[PAllen]

New definition for the OED: solipsist: n : someone who disagrees with me, esp. over something not verifiable.

 

[George Jones]

There is no science content being added to this thread, so I have closed it.

The Special & General Relativity is a science forum, not a philosophy forum, so do not discuss philosophy here.