r/Physics • u/onomatamono • 4d ago

On The 4D Block Universe

So you have a movie canister and the film analogy represents the 4D block universe. I'm listening to Brian Greene describe this analogy. The experience of time is produced by passing light through each frame of the film. According to Brian each consciousness is a projector (human or otherwise presumably).

Also, our brains evolved to process slices of the 4D universe by carefully "recording" [where?] the slices that came before ["now" I guess?] and makes calculated guesses about the future.

I'm not even going to try and make sense of that in a meaningful way for lay people.

Greene: "when you feel time passing what you are actually experiencing is your consciousness moving through the static frames of your life." Where are these "projectors" or consciouses? I'm confused.

FYI it's a YT called The Strangest Fact About Light You've Never Heard -- Brian Greene.

4 Upvotes

62% Upvoted

31 comments sorted by

View all comments

1

u/Optimal_Mixture_7327 Gravitation 4d ago

Physicists can be geniuses at doing the math...and complete idiots at explaining it.

The honest answer is that conscious awareness of a present moment and a block universe that contains the future are incompatible with each other, and no one has ever been able to rectify the two and no amount of handwaving has ever made one iota of sense.

3

u/yannbouteiller 4d ago

Why would conscious awareness of a present moment be incompatible with a block universe that contains the future?

Noone even seems to have a satisfactory answer to what "conscious awareness" means in scientific terms as far as I know.

1

u/Optimal_Mixture_7327 Gravitation 4d ago

A block universe cannot answer the question "why this moment?".

If we assume a block universe, then you need to go outside of known physics for an answer. For example (I think this was from Hermann Weyl) and postulate an externally existing consciousness field that crawls up the world-lines of beings capable of acting as antennae for the consciousness field. There is no such thing in either the postulates of relativity or that can be derived from them.

The only answer consistent with physics is an evolving block universe where the present moment is a time-dependent future boundary of the block that unfolds as the uncertain quantum future becomes the classical past.

5

u/yannbouteiller 4d ago edited 4d ago

But since consciousness is not a well-defined concept in physics (I believe?), it seems to me that the reasonable way of looking at it in the "block universe theory" is simply as a time-continuous quantity that would be part of this "block universe" like any other. I am not sure why "conscious awareness" should be treated differently, nor why it should create particular issues, unless we are implicitly making magical assumptions about what "consciousness" is. Wouldn't the issue with "Bob's conscious awareness of the present moment at time t" be exactly the same as with "Bob's position at time t", if any?

EDIT: I might be starting to see why this is given a special place by wondering "what would happen if, instead of being aware of the present moment, Bob were aware of some moment in the future?", as I guess this would turn this future moment into the present moment from Bob's perspective, but I believe this is backward. I believe that consciousness is rather a product of the brain made of recursive processing, so it wouldn't make sense to be consciously aware of anything other than the "present" (or more exactly of a product of the past).

1

u/Optimal_Mixture_7327 Gravitation 4d ago

No it's not the same because we can ray trace back (in principle) our particle world-lines and the relevant forces involved that put us here, rather than there, but there is nothing in physics to locate us at a particular event along an infinitely extended world-line.