The 3D Earth doesn't move from t1 to t2; two different parts of the 4D Earth each exist at those times. — Luke
Exactly as I described. — Kenosha Kid
I'm perfectly happy with the description of the Earth moving through time. I am happy with that in an everyday, subjective, pseudo-presentist, practical sense. — Kenosha Kid
The 3D Earth doesn't move from t1 to t2; two different parts of the 4D Earth each exist at those times. — Luke
Exactly as I described.
— Kenosha Kid
I never claimed that you said it; I said I thought that you agreed to it. — Luke
Even a stoopid frog can figure out where a fly will be such that it can fire its tongue out and catch it. — Kenosha Kid
Yes, but changes with time, i.e. has different positions at different times. I recall that the Moon was there. Now it is there. It has moved. — Kenosha Kid
That's contradictory, to say that it is moving, and that it is at a place.
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No, motion is not having different positions at different times — Metaphysician Undercover
Being bigger than the fly, that's an easy thing for the stoopid frog, it merely has to get in the fly's way. — Metaphysician Undercover
Okay, I was agreeing with the emboldened part. — Kenosha Kid
The first part does not enter an everyday, Gallilean idea of motion, — Kenosha Kid
Light, for instance, moves through space — Kenosha Kid
What I've been asking you to do is stick to one definition of motion and not change the definition as one moves from a presentist picture to an eternalist picture, or from an eternalist picture with a spotlight to one without, etc. — Kenosha Kid
You said you meant by 'motion' the typical, everyday, kinematic idea of different positions at different times: dx/dt, dy/dt, dz/dt for instance. Is this present in eternalism? Yes, because things exist at different positions at different times. — Kenosha Kid
Yes, because again a continuous worldline through x, y, z, and t is defined, and so is the proper time T of the body under consideration. dx/dT, dy/dT, dz/dT and dt/dT are all there, and motion according to this definition is evident. — Kenosha Kid
Another way of moving through time might be, as SophistiCat suggested, to posit a second temporal dimension, call it ? — Kenosha Kid
To be clear, you disagree that "3D Earth doesn't move from t1 to t2"? That is, you believe that 3D Earth does move from t1 to t2? — Luke
...which change temporal position. Of course this isn't a Gallilean or Presentist idea of motion; it's an Eternalist description.
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Where have I been inconsistent on this? — Luke
But when I ask you to explain what the motion in your model represents, you can only do so in "pseudo-presentist" terms. — Luke
You might be able to calculate motion, but how does that make it Eternalist rather than Presentist motion? — Luke
Again, I've never suggested anything about a second temporal dimension. — Luke
I'm okay with the fact that 4D objects don't move, whether that makes sense or not. — Luke
It is not to kinematics, which accords with my everyday experience of motion: the thing is not where it once was. — Kenosha Kid
If you define motion to be impossible, then I agree it is impossible. — Kenosha Kid
It cannot do that if it only knows where the fly is now, and not where it is going. — Kenosha Kid
I am satisfied that, in Einsteinian motion, a body moves from one time to another. I am satisfied that, in Gallilean motion, this is not held. — Kenosha Kid
But you must have a consistent definition, and not say on the one hand that motion is e.g. Gallilean and on the other than, in the eternalist universe where by definition Gallilean motion is nonzero, that motion is not possible by definition. — Kenosha Kid
If "change temporal position" means, as it should, "is defined for more than one time", there is no inconsistency: that holds true in an eternalist universe. — Kenosha Kid
In Gallilean motion, a body does not move from one time to another? — Luke
I can't say that motion is impossible by definition, but you can say that motion is possible by definition? That's hardly sporting. — Luke
What "is defined for more than one time" in a 4D universe? ... Instead, you have one part of 4D Earth existing at one temporal position and another part of 4D Earth existing at another temporal position. — Luke
What "is defined for more than one time" in a 4D universe? ... Instead, you have one part of 4D Earth existing at one temporal position and another part of 4D Earth existing at another temporal position.
— Luke
You have answered your own question: the geometry of the Earth. There is still time in 4D, it is just a dimension, the other 3 of those 4 dimensions being spatial. The spatial coordinates of an object are defined for a continuum of temporal coordinates, i.e. the geometry of a 4D object is a path through 4D space. — Kenosha Kid
I think that's ridiculous. My tea cup is sitting on the table right now, and it used to be on the counter. So you say my cup is in motion because it's not where it used to be. — Metaphysician Undercover
To be in a position is not to be in motion, the two are contradictory. — Metaphysician Undercover
Sure it can, because it's bigger than the fly. A big thing doesn't need to know where the small thing is going, to get in the small thing's way. — Metaphysician Undercover
Does this imply that the 4D Earth moves? But that would reintroduce the problem that a second temporal dimension is required. — Luke
No, because motion is differences of spatial positions over corresponding differences in temporal positions, and both spatial and temporal positions are present in 4D. — Kenosha Kid
I've argued that no 3D part is defined for more than one time. — Luke
You've replied that what is defined for more than one time is the 4D whole. — Luke
You can't measure just a part of that whole to derive a value for motion, because the part is neither defined for more than one time nor what changes temporal position. — Luke
That was our agreed definition of motion. — Luke
Right, I think I see what you're saying. If the path of the 4D object could be written as something like P(x,y,z,t), i.e. whether the object is present at a given spatial+temporal 4D position, you're saying that essentially P(x,y,z,t)=P(x,y,z), i.e. time is irrelevant in 4D. This would be like the Earth in Huw Price's picture. If every object were like this, this would be a 3D universe with a pointless fourth dimension added with no purpose. It would not correspond to motion as we perceive it or mean it in a Galilean sense. — Kenosha Kid
The second ridiculous thing applying this straw man to: "My tea cup is sitting on the table right now, and it used to be on the counter" to imply that it did not move. — Kenosha Kid
My everyday experience of something moving now is based on recent and current sense data on the positions of the thing. — Kenosha Kid
I didn't say it was, but their not contradictory. Unless knowledge stalled millennia ago. — Kenosha Kid
no clue there? — Kenosha Kid
That's not quite right. I like it, but it's not really what I'm getting at. — Luke
If a 3D part cannot be defined for more than one time (per Eternalism), then change in temporal position cannot be calculated and neither can motion. — Luke
That's the problem with your kinematic definition, kinematics deals with the effects of motion, not motion itself. — Metaphysician Undercover
When I see a thing moving, such as a car going past me on the road, I see it as moving. I do not see it as having been in one position, and now in another position. — Metaphysician Undercover
But I don't believe that you really experience motion in this way. So I think you are either lying about how you experience motion, for the sake of supporting some metaphysical position, or you haven't ever really thought about how you experience motion, and so you are just fabricating this claim. — Metaphysician Undercover
It does not follow that the position of an object at a point in the future must equal the position of the object at a point in the past. — Kenosha Kid
It's not the spatial position which is at issue but the object itself. — Luke
The same temporal part of a 4d object cannot be "defined for more than one time", so cannot change temporal position. — Luke
To consider it the same object is a Presentist notion. — Luke
To borrow Kenosha Kid's definition, to change temporal location means "is defined for more than one time". This makes sense in Presentism where the same 3D object moves through time from t1 to t2. It does not make sense in Eternalism where different 3D parts exist at t1 and t2. — Luke
...so cannot change temporal position. — Luke
As I've repeatedly asked: what is it that changes temporal location? — Luke
It has to be considered the same object to meet the definition "is defined for more than one time". — Luke
However, in Presentism it is considered to be the same object that changes temporal location from t1 to t2. — Luke
Why would you think that lines that are arbitrarily drawn by us humans, that the language we choose to use, would have consequences for the nature of reality? — ChatteringMonkey
As I've repeatedly asked: what is it that changes temporal location?
— Luke
I think you need to reword the question then. I can't make sense of something "changing temporal location" beyond "existing at multiple times". They means the same thing to me. Can you differentiate them for us? — Kenosha Kid
As I've repeatedly asked: what is it that changes temporal location? It has to be considered the same object to meet the definition "is defined for more than one time". You can't determine the change of temporal location of an object if it's not the same object that changes temporal location. — Luke
Yes but it is not the same object, even in presentism. — ChatteringMonkey
It has to be considered the same object to meet the definition "is defined for more than one time". You can't determine the change of temporal location of an object if it's not the same object that changes temporal location. — Luke
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