question4477

 

 

It just means that the predictions made by the theory match the measurements we make.

Please expand further - By that I presume you mean experiments such as Gravity Probe B lend support to the substantivalist (Space-Time as a Physical Entity) view as opposed to the relationist view?

I don't think that Einstein was greatly interested in metaphysics and so I would not be surprised if you can find differing quotes.

 

I know for sure that he was not impressed by some philosophical views on time.

 

 

He is free to hold that view. The problem is that as our understanding of space-time changes, and it must do at some level when we take quantum effects into account, will the classical view of space-time still be 'physical'?

 

I am not sure, other than mathematically we should have a good understanding of how the classical notion comes from the quantum one - otherwise we will be at a complete loss as to why classical general relativity has worked so well so far.

 

 

All the tests of general relativity tell us that the physical theory matches nature very very very well. I don't think one can really say much more.

By the tests of general relativity matching 'Physical Theory' do you mean the substantivalist view of Space-Time?

" ... In my opinion the answer to this question is, briefly, this: as far as the propositions of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality. ... "

Albert Einstein, "Geometry and Experience", 1921

I personally find this contradictory considering that he also seemed to subscribe to the block universe theory which implies substantivalism as opposed to relationism when he stated - "The distinction between the past, present and future is only a stubbornly persistent illusion." or am I missing something here.

Someone like Brian Greene for example in his book 'Fabric Of the Cosmos' makes it specifically clear that he regards space-time as a physical entity and not a mathematical abstraction which I guess would make him a substantivalist, in a recent documentary he expressed his belief that Gravity Probe B which measured an effect on space-time curvature provided evidence to support this view, how plausible is this claim?

The modern form of this question has been around since (and discussed by) Einstein in the form of the Hole Argument. TL;DR: The mathematical formalism leaves us with two options. Either GR is indeterministic, or spacetime points are merely mathematical convenience rather than anything ontologically real.

 

This problem goes from blurring-the-line-between-philosophy-and-physics to a big effing deal for physicists when it comes to quantum gravity theories, because it is the direct reason behind The Problem of Time.

Very interesting, so did Einstein himself have a substantivalist or relationist view of Space-Time?

As far as I know there are some Physicists who consider Space-Time to be an actual physical thing whereas others regard it as merely an abstract concept - Brian Greene expressed his belief that the results from Gravity Probe B confirm this. What is the general consensus of this?