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I have known this perspective on time for quite some time but never really thought about it much further until now reading this article. Doesn't this imply tha

I have known this perspective on time for quite some time but never really thought about it much further until now reading this article. Doesn't this imply that presentism is the right view or at least the one Occam's razor would suggest and not one of the block universe models? One could say without a fundamental time dimension there are not enough dimensions for a block universe to begin with. All of the universe would really exist in the same moment, a kind of true now, while each observer could invent his own frame-dependent time dimension and assign time coordinates to events in the normal way so that the laws of physics formulated in time become simple. Not withstanding this the evolution of the state of the universe could be fixed - ignoring the complications of non-determinism or probabilistic laws for simplicity - by the laws of nature so that one could still think of the universe as a block universe once one has established a time dimension. It still feels very weird to me to think about the evolution of the universe without any time. I understand that I can rexpress a circular motion x(t) = (r cos x, r sin t) as r² = x² + y² without reference to time but how do we recover the ordering of positions as time progresses without time? Just saying that from position X you will end up in position Y given some specific velocity at position X seems somewhat problematic to me as the velocity is a time derivative and time we do not have. On the other hand it doesn't really matter because the idea alone of the state of the universe changing without any time for the change to occur in doesn't compute in my brain. And if there was such a time, wouldn't a time for the universe to involve in have to be a different time then the one we can invent inside of the universe to write simple equations? But couldn't we then link those times and arrive at a unique global time within the universe after all, some kind of preferred foliation of spacetime?

platz 6y ago
> It still feels very weird to me to think about the evolution of the universe without any time. It's not that time doesn't exist in the block universe, it's just a free parameter in the block.
- danbruc 6y ago
  That's not what I meant. I meant if time is not fundamental, then there must be a time-free formulation of the laws of physics and also the universe itself must fundamentally work without time. I can somewhat - but certainly not fully - wrap my head around a time-free formulation of physics for specific situations and recovering time from that as an emergent phenomenon. But thinking about the universe as fundamentally time-free just breaks my brain, I can not overcome the thinking that change happens over time while the truth is probably closer to time emerges from change, roughly speaking. I guess because we are so used to reductionism, thinking about things as the sum of their parts and how they work, we or at least I struggle when something is not decomposable. But time seems to fall into this category - if there is a single isolated particle, then there is no time, it only shows up once there is a composite system and relations between its parts can change.
  - platz 6y ago
    The term "Arrow of Time" is something that might be relevant to what you're considering; which is a somewhat unsolved problem but generally thought to be caused as a statistical consequence of there being a very low entropy state in the past.
    - danbruc 6y ago
      This is a different problem - the laws of physics when formulated in the usual way with a time dimension are mostly symmetric or reversible, i.e. there is no obvious difference between past and future. As you said, one of the proposed solutions is a low entropy initial state that can break this symmetry and help to explain the perceived difference between past and future.

platz 6y ago

> It still feels very weird to me to think about the evolution of the universe without any time. It's not that time doesn't exist in the block universe, it's just a free parameter in the block.

danbruc 6y ago
That's not what I meant. I meant if time is not fundamental, then there must be a time-free formulation of the laws of physics and also the universe itself must fundamentally work without time. I can somewhat - but certainly not fully - wrap my head around a time-free formulation of physics for specific situations and recovering time from that as an emergent phenomenon. But thinking about the universe as fundamentally time-free just breaks my brain, I can not overcome the thinking that change happens over time while the truth is probably closer to time emerges from change, roughly speaking. I guess because we are so used to reductionism, thinking about things as the sum of their parts and how they work, we or at least I struggle when something is not decomposable. But time seems to fall into this category - if there is a single isolated particle, then there is no time, it only shows up once there is a composite system and relations between its parts can change.
- platz 6y ago
  The term "Arrow of Time" is something that might be relevant to what you're considering; which is a somewhat unsolved problem but generally thought to be caused as a statistical consequence of there being a very low entropy state in the past.
  - danbruc 6y ago
    This is a different problem - the laws of physics when formulated in the usual way with a time dimension are mostly symmetric or reversible, i.e. there is no obvious difference between past and future. As you said, one of the proposed solutions is a low entropy initial state that can break this symmetry and help to explain the perceived difference between past and future.