In one person’s reference frame the event is in the present (or past), and in the other person’s reference frame the event is in the future. I find this peculiar. — Michael
The galaxies you are moving towards would have come into view regardless of your motion, only at a later time as measured by your clock. Similarly, the galaxies you are moving away from will also come into view, but at a later time — Pierre-Normand
I only talked about the Rietdijk–Putnam argument itself and how it didn't make much sense to me. — Alkis Piskas
the edge of the visible universe is receding from us faster than the speed of light. Although individual galaxies are much slower than light their apparent movement adds up radially away from us. Over billions of years we would see fewer galaxies spread further apart in ever darkening space. — magritte
If you want to be very precise with the terminology, the Andromeda Paradox shows that some spacelike separated event in my present is some spacelike separated event in some other person's causal future even though that person is also a spacelike separated event in my present. I find that peculiar. — Michael
Some event (A1) in my (A0) future is spacelike separated from some event (B0) in someone else's (B1) past, even though this person is spacelike separated from my present. It might be impossible for me to interact with B1 (or for B1 to interact with A1), but Special Relativity suggests that A1 is inevitable, hence why this is an argument for a four-dimensional block universe, which may have implications for free will and truth. — Michael
(1) Relativity of simultaneity + all observers’ 3D worlds are real at every event = block universe
This is a non sequitur. That an event cannot be predicted with certainty isn't that the event isn't certain. Or to phrase it another way, even if we cannot know (with certainty) whether or not "there is intelligent alien life in the Andromeda Galaxy" is true, it doesn't follow that it isn't true (or false). — Michael
The "elsewhere", e.g. anything outside my frame of reference, is incoherent to be talking about as it doesn't exist for me. — Benkei
Also known as the block universe, or eternalism, a view that goes back to at least the 11th century.About the Rietdijk–Putnam argument, to which the above link refers to, we read the following:
"In philosophy, the Rietdijk–Putnam argument, [...] uses [...] special relativity – to support the philosophical position known as four-dimensionalism." — Alkis Piskas
Would be more helpful to name a part that isn't a temporal part. If it doesn't exist in time, then it hasn't a location in spacetime, and it effectively doesn't exist."In contemporary metaphysics, temporal parts are the parts of an object that exist in time. A temporal part would be something like 'the first year of a person's life', etc." — wiki?
Yes, quite easily. It being an object only becomes problematic if its identity is challenged, but must such challenges don't apply to a human, at least not significantly beyond a few days from conception. A human life is bounded by a couple meters of space most of the time and several decades of time. That's what a worldline is.But can a person's life be considered an "object"?
Why, because you don't consider thoughts to be a physical process, or because you don't consider a physical process to be an object. I would probably agree only with the latter. Given other parts of the post, I think you mean the former, in which case it is your choice or not to work with a model compatible with this 4 dimensionalism or not.And if we accept that to be true, should we also consider thoughts as objects too?
That's like saying you're ok with bread having width but you can't see how it can have length.We say that an object occupies space. I really cannot see how it can also "occupy time".
For one thing, when you reference a statement like that, at least quote the statement. Anyway, I just don't see how the statement indicated seems to assume any privileged FoR.Your [Michae;'s] statement ["it's about that thing actually happening for one person before another person."] assumes a privileged frame of reference. It's not coherent within the context of relativity theory. — Benkei
I agree, SR does not imply a block universe. The wording of it pretty much assumes it, but it is quite trivial to change that wording to more empirical wording. So for instance, instead of light moving at constant c relative to any frame, you say that light is measured to move at constant c relative to any frame. The later papers (and GR in particular) are worded more in this fashion.
But the topic presumes a different view than the one you presume, so your personal beliefs are inapplicable. Your statement here seems outright solipsistic. What exists is determined by you and you alone.The "elsewhere", e.g. anything outside my frame of reference, is incoherent to be talking about as it doesn't exist for me. — Benkei
The thing is, the way the story is worded seems to presume everybody uses the inertial frame in which they are stationary to consider what is going on. It simply isn't true. Almost everybody uses the same frame from day to day, which is the frame of the ground under you, which just happens to be an accelerating rotating frame, but pragmatically, it works for almost all uses. So the two people passing in the street don't have an opposing view of what time it is in Andromeda.According to special relativity some of these events happen in your future even though they are happening in my present. This is what I find peculiar. — Michael
Careful. The Andromeda scenario is supposed to assume 4 dimensional spacetime in which you don't have a present. So relative to a given event at which you are present, these different inertial frames with minor velocity differences translate to significant time differences at large distances.If you want to be very precise with the terminology, the Andromeda Paradox shows that some spacelike separated event in my present ... — Michael
Under relativity, the point is irrelevant. Under QM, it is very relevant, and given a non-counterfactual interpretation of QM, the statement " there is life on <really distant planet X>" is not truth-apt any more than the statement "Schrodinger's cat is alive".even if we cannot know (with certainty) whether or not "there is intelligent alien life in the Andromeda Galaxy" is true, it doesn't follow that it isn't true (or false). — Michael
There's no such thing as a moving observer without establishing a frame. I suppose 'shifts' can describe the difference in the motion of things when the frame changes (the observer accelerates?). So in my frame, the tree gains velocity relative to me when I run towards it, but that's very different from the tree itself accelerating.What the Andromeda Paradox implies is that the observed universe apparently shifts in its entirety towards a moving observer. — magritte
Your velocity doesn't change what you see. OK, it can blueshift it a bit, but nothing comes into view that wasn't already there regardless of your velocity. Of course given enough time, you'll separate yourself from a observer left behind, and that separation (and not the velocity) will change which galaxies are in view.Which means that in the forward moving direction many more of the most distant galaxies come into possible view
That's just silly. It's not about the respective rate of time passage at all.It's the notion that a few seconds on Earth could mean fifteen minutes in distant galaxies. — jgill
Yes, and if the two observer walking past each other simultaneously send signals to Andromeda, and then another signal a minute later, they'd get to Andromeda at the same time, and the second signal a minute later, separated by the time it takes light to go however far apart the guys got in that minute.If we send two signals to the Mars Rover, spaced at exactly 10 seconds apart, does the Rover receive them in that same time spread?
Yes, and yet galaxies become visible over time as our expanding visible universe overtakes them. These newly visible galaxies are also receding faster than c (proper distance, constant cosmic time), but not as fast as the 'edge'.the edge of the visible universe is receding from us faster than the speed of light. — magritte
More galaxies actually, but our capacity to see them diminishes as they indeed redshift into less detectable frequencies and lowed brightness due to increasing distances.Over billions of years we would see fewer galaxies spread further apart in ever darkening space.
What? Hubble is in fairly low orbit, hardly 3 light days away. Light from the supernova reaches Earth in the same second as it reaches Hubble, presuming Hubble's view of it isn't blocked by Earth. It has nothing to do with the motion of Hubble, and nothing to do with this topic, which is about Relativity of Simultaneity, not about when things get measured. Hubble most certainly does not see a whole different view of distant things when it is approaching them vs 45 minutes later when its orbit takes it the other way.The Hubble space telescope orbits Earth. Let's suppose that when flying at maximum approach speed in the direction of Andromeda it sees a quickly brightening supernova star. Mission control decides to keep the telescope pointed there to record continuously for 10 days. From Earth we will not discover that supernova for another 3 days — "magritte
If we send two signals to the Mars Rover, spaced at exactly 10 seconds apart, does the Rover receive them in that same time spread?
Yes, and if the two observer walking past each other simultaneously send signals to Andromeda, and then another signal a minute later, they'd get to Andromeda at the same time, and the second signal a minute later, separated by the time it takes light to go however far apart the guys got in that minute. — noAxioms
:roll:By the time the light reaches her, she's simply closer to it. She's been walking millions of years towards it already. Once Bill sees the decision happening, for Ann at that point, having walked at 5 m/s for all that time, the light reaching her then is 15 days later and the armada is already on its way. — Benkei
Why do you aplogize? I was not expecting a response from you but from the OP of this discussion, @Michael, who seems not to know what a discussion is and/or he lacks communication basics, esp. when he is the OP of a discussion.Apologies for responding to stuff sometimes days old, but some of them needed comment. It turned into a long post. — noAxioms
Thanks for letting me know.Also known as the block universe, or eternalism, a view that goes back to at least the 11th century. — noAxioms
Then we are not speaking about the basic meaning of the term "object", which is anything that is visible or tangible and is relatively stable in form, but about is secondary and more general meaning, i.e. anything to which thought and action is directed, related or referred. The first is clearly physical. The second one not necessarily physical.Re "But can a person's life be considered an "object"?
Yes, quite easily. It being an object only becomes problematic if its identity is challenged ... — noAxioms
Most probably you mean a "human body". (A life occupying space is just absurd.)A human life is bounded by a couple meters of space — noAxioms
I don't consider thoughts to be a physical process. There's nothing to prove this. The brain reactions that neurobiologitsts and other consider as thought are just that: reactions. The brain is a stimulous-response mechanism, And as such it reacts to thoughts, in various ways. That's all it does and can do. It cannot originate, create, imagine a thought from scratch.Re "And if we accept that to be true, should we also consider thoughts as objects too?"
Why, because you don't consider thoughts to be a physical process, or because you don't consider a physical process to be an object. — noAxioms
"Width and length refer both to space. They have nothing to do with time.Re "But both are concepts that cannot exist in space! How can we include them in 4 dimensions when they do not exist even in 3 dimensions?"
Re: "We say that an object occupies space. I really cannot see how it can also "occupy time""
That's like saying you're ok with bread having width but you can't see how it can have length. — noAxioms
My wait was also in vain.I was not expecting a response from you but from the OP of this discussion, Michael, who seems not to know what a discussion is and/or he lacks communication basics, esp. when he is the OP of a discussion. — Alkis Piskas
OK, we differ here. A body might continue after life, but I see no better way to interpret 'a life' than 'a body, while it is alive'. That makes it an object in any scientific sense. If you have a non-scientific definition of such things (and apparently you do), then yes, perhaps your definition isn't compatible with some of the concepts expressed in relativity theory as well as other theories.Then we are not speaking about the basic meaning of the term "object", which is anything that is visible or tangible and is relatively stable in form, but about is secondary and more general meaning, i.e. anything to which thought and action is directed, related or referred. The first is clearly physical. The second one not necessarily physical.
Most probably you mean a "human body". (A life occupying space is just absurd.) — Alkis Piskas
Do you have a reference for the consensus view of neurobiology that a brain cannot 'originate, create, imagine a thought from scratch'. I mean, there are probably some that hold such beliefs for supernatural reasons, but I'm speaking of the scientific consensus.The brain reactions that neurobiologitsts and other consider as thought are just that: reactions. The brain is a stimulous-response mechanism, And as such it reacts to thoughts, in various ways. That's all it does and can do. It cannot originate, create, imagine a thought from scratch. — Alkis Piskas
Under the spacetime view, they're just different dimensions of the same thing, so every 'object' has a series of 4D points (events) that it occupies and the rest of the events which it does not. This is the same as a 3D table in space occupying some points and not the rest."Width and length refer both to space. They have nothing to do with time.
Indeed, how do you imagine an object "occupying time"? I'm very curious ... — Alkis Piskas
Obviously.I see no better way to interpret 'a life' than 'a body, while it is alive'. That makes it an object in any scientific sense. — noAxioms
What things? And what do you mean by "non-scientific definition"?If you have a non-scientific definition of such things ... — noAxioms
How can I have such a ref? This is an impossible question for a philosophical discussion. It can be asked only and maybe among scientific communities. For out purposes, one can only know about the prevailing views of neuro(bio)logy on the subject. You can google if you like things like "Thoughts are created", "Thoughts are located", etc. You will see that almost all the results refer to the brain.Do you have a reference for the consensus view of neurobiology that a brain cannot 'originate, create, imagine a thought from scratch'. — noAxioms
This isn't what I asked. I asked "how do you imagine an object 'occupying time'?" And I added that I'm very curious. Well, I'm not anymore! :smile: In fact, I wasn't curious at all. It was a manner of speaking. Because an object occupying time is a totally absurd idea.Under the spacetime view, they're just different dimensions of the same thing, so every 'object' has a ... — noAxioms
This is called argumentum ad hominem, i.e. "argument against the person". And it's a bad thing.so if you don't understand it, you're not particularly qualified to critique it. — noAxioms
My mistake I think. I looked at your comment to which I was reacting and thought it said that the neurobiologists say that thoughts do not originate in the brain. It is only you that asserts this about where thoughts do or don't originate. My mistake.How can I have such a ref? This is an impossible question for a philosophical discussion. It can be asked only and maybe among scientific communities. — Alkis Piskas
The same way it occupies space, since time and space are just different dimensions of the same thing under the spacetime view. Under the 3D view, objects and the entire universe are contained by time. I'm not sure if that would be considered 'occupying time' or not, since the term isn't typically used that way.This isn't what I asked. I asked "how do you imagine an object 'occupying time'?"
Because an object occupying time is a totally absurd idea.
It's not against you personally. Anybody sufficiently unfamiliar with a given subject is unqualified to meaningfully critique the subject. You seem to attempt to demonstrate this unfamiliarity with statements like the above one where you consider it absurd. It happens to match empirical observations perfectly, so there's nothing absurd about it at all. That alternate views also match empirically indicates that there's no positive evidence one way or another. Somebody familiar with both views would realize that. Somebody positing the impossibility or absurdity of one view or the other only demonstrates ignorance of the subject. I'm ignorant of plenty of subjects, and it isn't anything against me to point out that I'm unqualified to critique them. But I'm quite familiar with this subject, which isn't very complicated at all. It gets more complicated when general relativity sets in and the 3D presentist view gets some real (but not insurmountable) challenges.so if you don't understand it, you're not particularly qualified to critique it.
— noAxioms
This is called argumentum ad hominem, i.e. "argument against the person". And it's a bad thing.
Saying "the same way it occupies space" is wrong because space and time are not "just different dimensions of the same thing"; they are two totally different things and concepts. Look them up! Besides, I already mentioned that we can undestand how an oblect occupies space, but we cannot say the same about time. So, you have avoided the question for the nth time.This isn't what I asked. I asked "how do you imagine an object 'occupying time'?"
The same way it occupies space, since time and space are just different dimensions of the same thing under the spacetime view. Under the 3D view, objects and the entire universe are contained by time. I'm not sure if that would be considered 'occupying time' or not, since the term isn't typically used that way. — noAxioms
I personally can't see how the horizontal clock would be synchronized with the vertical one — Gampa Dee
The way I see this is simply the length the path of light will have for the first leg would be increased
(L + vt) and the second leg would be foreshortened (L- vt) which, as you mentioned, seems to cancel the effect.
What happens during the first leg which gives the gamma factor is what I still don't understand.
However, this was only part of the problem as S.R. would identify the path itself as being contracted by a factor of gamma, giving (gamma L+vt) + (gamma L - vt) = 2 gamma L. With c being constant,...this seems to give us a time contraction cancelling the effect of the vertical clock.. — Gampa Dee
Yes, you're right that the Lorentz contraction of the path must also be taken into account. The Lorentz factor, gamma, is always greater than 1, so the contracted length is L/gamma. — Pierre-Normand
The time required for the light ray to reach the receding mirror is therefore t1 = d/v1 — Pierre-Normand
Similarly, the time required for the light ray to return to the source is therefore t2 = d/v2 where v2 = c + v. — Pierre-Normand
The total time elapsed is therefore t1 + t2 = L/(gamma(c - v)) + L/(gamma(c+v)). To simplify, you can multiply the numerator and denominator of the first term by c + v and the numerator and denominator of the second term by c - v. — Pierre-Normand
You get
t = L(c + v)/(gamma(c^2-v^2))+L(c - v)/(gamma(c^2-v^2)) = 2Lc/(gamma(c^2-v^2))
Since gamma = 1/sqrt(1-v^2/c^2), 2Lc/(gamma(c^2-v^2)) simplifies to 2L*gamma/c which is the same time registered by the vertical light clock. — Pierre-Normand
(Note that c/(gamma(c^2-v^2) = c*sqrt(1 - v^2/c^2)/c^2-v^2 = sqrt(c^2 - v^2)/(c^2-v^2) = 1/sqrt(c^2-v^2) = 1/(c*sqrt(1-v^2/c^2) = gamma/c.)
Intuitively, as v tends towards c and taking into account the Lorentz contraction of the clock, the duration of the return travel tends towards zero. Meanwhile, the duration of the forward travel tends towards infinity despite the shortened distance, as c - v approaches zero faster than sqrt(1-v^2/c^2) does. — Pierre-Normand
I have a problem understanding this though; I rather see the time light displaces any distances as being d / c; I would instead claim that v would be responsible for the length contraction instead, being d or L/ gamma + or - some other distance being vt .Also, isn’t the relative velocity between the source and the mirror 0? Therefore, I, for now, understand the 1st path as being
t1 = d / c or (L/gamma +vt) / c — Gampa Dee
2L*gamma /c was what I had in my first response to you :)
however you correctly pointed to me that gamma was a factor which increased the original value, where I needed one which would reduce the outcome ( length contraction).
Now, what I have is in stead 2L/gamma c.
I will try to clarify a bit my point. Since the velocity remains c, I think that all we need is the distance for the light to travel in order to calculate the time.
In the first case, (the vertical light clock) the distances the outside observer calculates are the two hypothenuses SQRT L^2 + (vt)^2, the total being 2 * SQRT L^2 + (vt)^2
In the second case,for the horizontal clock, I have L/gamma. + vt one way, and the return path being L/gamma – vt.
If L/gamma +vt = L* [SQRT 1 –v^2/c^2] +vt ..and.the second path is even shorter.
Here’s my problem...as v tends to c, in the vertical clock the path tends towards L^2 +ct^2 ...a very long path,if not infinite, whereas for the horizontal path , it seems the path tends towards 0.
I seem to have two extreme opposite situations.
In the case of the horizontal clock you indeed have d1 = L/gamma + vt for the first path and d2 = L/gamma - vt_2 for the return path. I use "t_2" since the time for traveling the return path is different (shorter). Since in both cases the distance is travelled at c, we have the two equations:
d1 = L/gamma + vt = ct
d2 = L/gamma + vt_2 = ct_2 — Pierre-Normand
T = L/((gamma(c - v)) + L/(gamma(c + v)) with is the same result I had obtained more directly by considering the relative velocities of the light pulse and clock. — Pierre-Normand
In the case of the horizontal clock you indeed have d1 = L/gamma + vt for the first path and d2 = L/gamma - vt_2 for the return path. I use "t_2" since the time for traveling the return path is different (shorter). Since in both cases the distance is travelled at c, we have the two equations:
d1 = L/gamma + vt = ct
d2 = L/gamma + vt_2 = ct_2 — Pierre-Normand
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