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Viewing the universe as a timeless four-dimensional object - rather than the temporal evolution of a three-dimensional one - does not really buy you any "simplicity" - because then you need an additional explanation of why the four-dimensional object is structured in the way that it is.
In response to
Timeless Physics
you also need to explain motion which does not exist at all in a timeless 4d object. you need to explain how any static being can experience a present moment and moments leading up to it as past moments. and you need to explain how any perception is possible by a static being.
This is off the top of my head, so it may be total bullshit. I find the idea of memory in a timeless universe slippery myself, and can only occasionally believe I understand it. But anyway...
If you want to implement a sort of memory in your 2D space with one particle, then for each point (x0,y0) in space you can add a coordinate n(x0,y0), and a differential relation
dn(x0,y0) = δ(x-x0,y-y0) sqrt(dx^2 + dy^2)
where δ is the Dirac delta. Each n(x0,y0) can be thought of as an observer at the point (x0,y0), counting the number of times the particle passes through. There is no reference to a time parameter in this equation, and yet there is a definite direction-of-time, because by moving the particle along a path you can only increase all n(x0,y0) for points (x0,y0) along that path.
A point in this configuration space consists of a "current" point (x,y), along with a local history at each point. If you don't make any other requirements, these local histories won't give you a unique global history, because the points could have been visited in any order. But if you impose smoothness requirements on x and y, and your local histories are consistent with those smoothness requirements, then you will have only one possible global history, or at most a finite number.
one small problem, nothing is moving. how can you have an observer when every bit of that observer is part of the existing static universe... observer implies a moving entity and no motion exists in a static universe.
In response to
Timeless Physics
Timelessness is one of the first things I grokked after accepting physicalism. After removing magic from my ontology, but before encountering Kolmogorov/Solomonoff, I intuitively had the feel that the idea of a line called the 'present' that is constantly 'moving forward' and destroying everything before it and creating everything just ahead of it seemed astonishingly complicated and unnecessary. Minkowski spacetime doesn't need time to be 'moving'; that's an unnecessary additional hypothesis. Our brains can 'see' the past and not the future because of the way memories are constructed in brains, which are part of the timeless physics.
TIME is not moving, its the measure of stuff like matter and energy moving. to say we can see the past but not the future because of the way memories are constructed implies motion which your blockhead universe sorely lacks. timeless physics ignores the implicit motion required for anyone to notice anything changing. if all moments were equally real that there is no way to say any moment is the present moment, the past or the future. no one would be moving to notice any other changes because there are not any actual changes going on. if all moments are real, you would have to be outside looking in on them to make the required motion.
This can't be the right answer. Time does flow, whether or not you understand how that can be. This approach is like being troubled over why the universe exists - how can existence itself have a cause, when such a cause must already exist? - and obtaining relief by convincing yourself that nothing actually exists.
That things happen is bedrock knowledge about the world, up there with the knowledge that anything exists at all. You reject the idea that the present is a moving line which erases the past and creates the future? Fine, so do I. Past, present, and future coexist "in eternity", but they all have the character of "becoming", not just of "being". There is a flow of time inside each world-line; the experience of your life is the feeling of the flow interior to the world-line of the conscious part of your brain. There is no point of awareness that moves along the line, erasing the past and creating the future; the line itself is the flow that occurs within the "eternal now" of your consciousness, from the moment it begins to exist, until the moment that it ceases to exist.
Maybe this is what you already meant by timelessness, but I don't think so, especially since, in this post, Eliezer is advocating Julian Barbour's ontology, in which the very idea of a world-line is an illusion, because there is no notion of space-time history as such, just a set of static, mutually detached spatial configurations.
I think you are close but still wrong. past and future only exist in the mind, not in reality. the past is just data about where stuff got recorded by you and has moved on to where it is now. the future is just an educated guess as to where that stuff will move to from here. NOW alone is real, NOW alone contains mass and energy. the only way we can experience and evolving time is because stuff is in motion and we have the capacity to record and project its locations. Time is a measure of changing relationships between matter and energy that exists and is in motion. 5 years ago means that the stuff of the universe has changed relationships and one of those relationships was the rotation of our planet around our sun 5 times. if the past present and future all exists then there is NOTHING moving and no way to notice anything change unless by some entity beyond it all, like a person watching a static film that moves via an external projector. if you accept that possibility that we are part of reality and not beyond it, then you cannot explain our perception of motion without actual motion involved.
In response to
Timeless Physics
While I don't disagree with the main conclusion, I have a problem with the following quote: "The r never repeats itself. The universe is expanding, and in every instant, it gets a little bigger. We don't need a separate t to keep things straight. When you're looking at the whole universe, a unique function ψ of (r, t) is pretty much a unique function of r." The permanent expansion is just some property our universe happens to have, that one could argue is a function of your abstract time variable. Suppose there existed a physical clock somewhere (similar to our human clocks) that was created during the big bang, you could replace "The universe is expanding" by "The clock keeps changing"-- just as a proxy of abstract time. So the above paragraph does not add anything useful to the argument?
not to mention that the original t was a marker used by a sentient beings to order his experiences and by saying r contains all experiences and so we don't need t any more is false. r does not in any way replace or make redundant the original use of t.
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@Nick Tarleton, anyone questioning the value of this post Prior to this post, my understanding was that there wasn't one 'me' consciously observing the unraveling of our universe over time. Instead, there were many of 'me', each observing a different universe, and with every irreversible thermodynamic event, more universes and instances of 'me' were being created.
This post blew my mind.
@Julian "Whence comes the present moment?" Now I understand that "I" am not a consciousness traveling through time. Instead, my consciousness is represented in a sub-space of the immensely-dimensional configuration space. Time is an illusion. Everywhere that my consciousness is represented within the many-world many-moment configuration space; it will feel like it is traveling through 'time'. "I" feel like I am traveling through time because "I" am a structure that models both itself and the evolution of sensory data. At every point that "I" am represented in the configuration-state, "I" IS this model of itself and the 'previous' states of the world, thereby fooling "I" into modeling and experiencing 'time'.
@Everyone Manon de Gaillande asked "Where does this configuration come from?" Seeing no answer yet, I'm also intrigued by this. Does it even make sense to ask it? If it doesn't, please help Manon and I dissolve the question.
@Craig_Morgan2 At every point that "I" am represented in the configuration-state, "I" IS this model of itself and the 'previous' states of the world, thereby fooling "I" into modeling and experiencing 'time'.
everything you are writing implies motion which does not exist in a blockhead universe. sorry, but a static being by any rational definition is a dead being incapable of experiencing anything at all. there is no past nor present nor even anticipation of a future without motion and you cannot have motion in a static universe unless you believe you exist outside it.