A 3D part in Eternalism is equivalent to a 3D object at a time in Presentism. Both describe the mug on my desk at time t. — Luke
the Eternalist part at t and the Eternalist part at t' cannot be considered to be the same part (by Eternalists) — Luke
Are you wanting to argue that the 4D object moves? — Luke
Moves with respect to what? Time is one of the four dimensions. — Pfhorrest
An object moving in three dimensions with respect to the fourth will just look like a 4D object to you, though. — Pfhorrest
You're arguing against something that nobody is defending. — Pfhorrest
Eternalists don't think that the universe is motionless. — Pfhorrest
They think motion has to be with respect to something. 3D objects move with respect to a fourth dimension of time, tracing out a 4D shape as they do so. — Pfhorrest
not the motion of 4D objects with respect to... what exactly? — Pfhorrest
This underlies my whole view of the matter (although somewhat vaguely): that Eternalism is all position and Presentism is all momentum. — Luke
Motion implies that the same object moves from t to t'. This is a Presentist assumption which makes no sense in Eternalism. — Luke
I don't understand your use of the word "redundant" here. — Luke
Motion implies that the same object moves from t to t'. This is a Presentist assumption which makes no sense in Eternalism.
— Luke
As defined, yes. — Kenosha Kid
Wait... Are you saying you are satisfied that Eternalism logically precludes motion (according to our agreed upon definition of motion)? — Luke
Eternalists don't think that the universe is motionless. — Pfhorrest
There is something that turns the cup at t into the cup at t'. — Kenosha Kid
Motion still falls out: dx/dt = (dx/dc) x (dc/dt) — Kenosha Kid
So as long as x, c, and t are continuous, i.e. so long as objects don't disappear then later reappear, motion is still possible. — Kenosha Kid
Space is present in both, so therefore momentum is possible in both. — Kenosha Kid
If motion were impossible, then x(t) = x, which a constant. We could write a position as (x, y, z, m, n, t). But since (x, y, z, t) fully determine position, i.e. (m, n) don't do anything, this is merely describing a 4D something in a 6D space for no reason: it is still 4D. Likewise if nothing moved, (x, y, z) cannot change thus those coordinates define everything. — Kenosha Kid
1) Eternalism does not say that the cup at time t is a different cup at time t', so the above is unnecessary — Kenosha Kid
2) Is still yields motion, just via an additional variable.
There is something that turns the cup at t into the cup at t'. — Kenosha Kid
Momentum requires only space? — Luke
Eternalism logically entails that the cup at time t and the cup at time t' both co-exist as separate objects/parts. They exist as different 3D parts of the same 4D cup, but always as different parts. You can call them the same cup if you like, but you can also say that time passes if you like. — Luke
The additional variable is motion? That is, what is this "something"? — Luke
The momentum of a quantum mechanical body at a particular time is a feature of its wavefunction's geometry at that time. Precisely, it is, in a given direction, proportional to the number of wave peaks per metre in that direction. It is still related to time, but indirectly, via something called the dispersion relation, which is energetics not kinematics. — Kenosha Kid
If it is irrelevant in eternalism whether consider the cup at time t' to be the same cup as the cup at time t, then it cannot form part of your argument one way or the other. (So here we agree.) — Kenosha Kid
No, just whatever it is that connects the cup at t' to the cup at t. It's not something I postulate. — Kenosha Kid
I know the cup at t' is the same as the cup at t, that they are different cross sections of the same 4D object. But if you want to postulate they are not, then there needs to be some explanation for why, if I stare at a cup for a given interval of time, the cup at the end not only appears indistinguishable from the cup at the start, but appears continuously. — Kenosha Kid
If you want to refer to them as the same part, then you are ignoring the Eternalist reality and may as well be a Presentist — Luke
An Eternalist can just reject that and attribute it to something else with an identical effect? — Luke
What you need to account for as an Eternalist, which you have simply assumed here, is how you, or your consciousness, moves from one temporal cross section to another. — Luke
There's no "you" to get from one point to the other (presentism). — Kenosha Kid
So it's the same cup from t to t', but not the same you? — Luke
No you don't, that is precisely what the eternalist viewpoint doesn't need. You don't need to account for how you get from an event at time t to one at time t', because it's all just laid out there and real. The continuity of 4D objects purely as geometric objects is sufficient, and that geometry is sufficient for motion. — Kenosha Kid
Unless you main one must account for the subjective human experience of presentism in an eternalist universe. But understand that is not needed for motion: motion is geometric in 4D just as shape is in 4D. — Kenosha Kid
"there needs to be some explanation for why, if I stare at a cup for a given interval of time, the cup at the end not only appears indistinguishable from the cup at the start, but appears continuously" — Kenosha Kid
The impression of presentism when you are laid out in 4D is a different question that does not bear on whether or not motion is possible. — Kenosha Kid
The continuity of 4D objects purely as geometric objects is sufficient, and that geometry is sufficient for motion. — Kenosha Kid
Or are you saying that "history is laid out there and real" somehow provides this motion? If so, how? — Luke
If you're just going to assume that motion is possible because it's "in the model", then I suppose there's nothing to discuss. I guess your model contains no assumptions. — Luke
Why is it sufficient? — Luke
As I've said before, motion is the geometry of the 4D object. Any point on that object will have a coordinate (x, y, z, t). If two points (x, y, z, t) and (x', y', z', t') on the same 4D object have different time coordinates (t' != t) but the same spatial coordinates (x'=x, y'=y, z'=z), the object is not in motion. Otherwise it must be by definition, since its position is different at different times — Kenosha Kid
Motion in 3D + time = geometry in 4D. — Kenosha Kid
doesn't the very concept of motion assume that a 3D object moves from t to t' in some fashion akin to temporal passage? — Luke
the concept of motion is based on Presentist assumptions, I would argue. — Luke
What is motion in 3D? How does that work without time? — Luke
Motion in (3D + time) = geometry in 4D. — Kenosha Kid
To support this thought, they define "motion" in very strange ways, as Kenosha has demonstrated. This makes the thing described as "motion" something completely different from what we commonly refer to as motion. — Metaphysician Undercover
doesn't the very concept of motion assume that a 3D object moves from t to t' in some fashion akin to temporal passage?
— Luke
No, it just depends on position being a continuous function of time. What you're talking about is a kind of propagator. That can be made consistent with kinematics, but not derived from it. — Kenosha Kid
Isn't such a "propagator" being implicitly assumed when you talk about deriving motion from the geometry? — Luke
No, not at all, as per the mountain example. You don't need a hiker to have a gradient. You don't need a temporal hiker to have a gradient either. — Kenosha Kid
We ordinarily talk quite readily of motion or change with respect to a dimension other than time as we usually experience it. Hence the mountain that gets smaller with altitude even though it stays the same size with time; the pipe along its side that gains altitude as it moves westward, even though it’s not moving with respect to time; the abstract line that moves in a y-ward direction over the x-ward direction, even though it too doesn’t move with respect to time. — Pfhorrest
Would you not say that a cone is smaller at the point than at the open end? — Pfhorrest
Is that really such a weird way to speak to you? — Pfhorrest
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