Special Relativity: A or B Series of Time?

[cezalinho]

Hi everyone.

Does the theory of Special Relativity determine whether time follows the A or B series? In other words can we show that either eternalism or presentism are true? How about the http://www.bbc.co.uk/news/world-south-asia-13264301" theory; is that supported by special relativity?

I spoke to a professional physicist and he said he does not believe in eternalism and is a presentist; although he says the growing block model is possible. Now I am a bit of a noob in in this subject so I didn’t ask him to explain his reasoning. I heard that lots of physicists believe in the block universe model.

So how can we justify any of the models using special relativity?

 

[bcrowell]

Hi,

You haven't defined "A series" or "B series." Your "growing block universe" link currently leads to an article titled "India's unwanted girls." However, WP does have an article, http://en.wikipedia.org/wiki/Growing_block_universe , which presents it as a philosophical concept, not a physical theory. Eternalism and presentism are also philosophy, not physics.

So how can we justify any of the models using special relativity?

When a physicist says "model," it means something that makes testable predictions. The philosophical ideas you're referring to aren't models in that sense.

I'm not saying that nothing interesting can ever happen at the interface between physics and philosophy, but you do have to distinguish between the two. They are different fields with different methods. Scientific theories don't typically settle philosophical questions.

-Ben

 

[Bill_K]

So how can we justify any of the models using special relativity?

I'd say these ideas are all inconsistent with special relativity. Aside from the philosophical challenge of defining the word "exist," there is not even a way to define the word "present." You could define the present of point P as the points on a spacelike hypersurface through P, but this is not unique. And so to claim that events not on this hypersurface do not exist is not unique either. Or you could define the present of P as the exterior of P's light cone. But then by taking all points Q in the present of P and considering their presents, you have filled the entire spacetime.

 

[bcrowell]

I'd say these ideas are all inconsistent with special relativity. Aside from the philosophical challenge of defining the word "exist," there is not even a way to define the word "present." You could define the present of point P as the points on a spacelike hypersurface through P, but this is not unique. And so to claim that events not on this hypersurface do not exist is not unique either. Or you could define the present of P as the exterior of P's light cone. But then by taking all points Q in the present of P and considering their presents, you have filled the entire spacetime.

Your definitions in terms of physics are reasonable, but there are many other definitions that could also be reasonable, and could lead to the opposite conclusion. For instance, I could take the word "present" to be shorthand for some notion involving a Cauchy surface. I seriously doubt that the philosophers who developed ideas like the "growing block universe" were even interested in defining their terms in a way that would be considered a valid definition in physics. That's not the business they're in. Their profession has different criteria than ours for what constitutes a valid definition, a true theory, valid modes of reasoning, or an important or interesting result.

 

[bobc2]

Of course the Block Universe model (not the "growing" block universe) was specifically motivated by special relativity when it was realized that different instants of 3-D space for observers moving at relativistic speeds with respect to each other implied a Block Universe as one possible model. That of course does not prove the model actually represents reality, but that model is at least consistent with SR.

 

[bcrowell]

Of course the Block Universe model (not the "growing" block universe) was specifically motivated by special relativity when it was realized that different instants of 3-D space for observers moving at relativistic speeds with respect to each other implied a Block Universe as one possible model. That of course does not prove the model actually represents reality, but that model is at least consistent with SR.

"Growing block universe" does actually seem to be standard terminology. There is a WP article with that title, and, e.g., this paper: Merricks, Trenton, 2006, "Good-Bye Growing Block" in Dean Zimmerman (ed.) Oxford Studies in Metaphysics. Oxford University Press

I thought this paper

George Ellis: Physics in the real universe: time and spacetime, http://www.mth.uct.ac.za/~ellis/SpaceTime.pdf

was worth looking at, since the author is a very well known relativist, so we at least know he knows his physics. But I think he's full of crap when he claims that "the results of human agency are unpredictable even in principle from initial physical data," and in general it's not obvious to me that there is anything to it beyond a sketch for non-physicists of how relativity and quantum mechanics work.

 

[bobc2]

"Growing block universe" does actually seem to be standard terminology.

I was trying to make a distinction between "Block Universe" and "Growing Block Universe." I was assuming that the "Block Universe" represents the frozen 4-D space populated by frozen 4-D objects and the "Growing Block Universe" allowed a future to evolve with passing of time, leaving a frozen static 4-D universe in its trail (which doesn't make any sense to me). But my interpretation is probably misplaced.

There is a WP article with that title, and, e.g., this paper: Merricks, Trenton, 2006, "Good-Bye Growing Block" in Dean Zimmerman (ed.) Oxford Studies in Metaphysics. Oxford University Press

I thought this paper

George Ellis: Physics in the real universe: time and spacetime, http://www.mth.uct.ac.za/~ellis/SpaceTime.pdf

was worth looking at, since the author is a very well known relativist, so we at least know he knows his physics. But I think he's full of crap when he claims that "the results of human agency are unpredictable even in principle from initial physical data," and in general it's not obvious to me that there is anything to it beyond a sketch for non-physicists of how relativity and quantum mechanics work.

Good assessment, Ben. I sure agree with that. Excellent references that I was not aware of. Thanks.