Time: A-series or B-series?

GeorgeDishman

It's difficult to avoid implying a temporal model just because the concept is ingrained in our language.

That's how I view it too. You've probably seen sci-fi films where something is "scanned" by having a laser swept to form a plane of light which then moves across it. If the block universe is a glass paperweight with the big bang at one end and the heat death of the universe at the other, the "Moving Spotlight" is like that laser plane moving through it. Our present (the location of consciousness) is the point where the plane intersects our individual worldline and the time of cosmology is a measure of how far through the glass the plane has moved (13.7 billion years so far). In that model, the past is the section that has already been scanned and the future lies ahead of the spotlight plane.

Our perception of a "flow of time" in this model is like looking out of a train window and seeing the countryside flow past, but in fact the landscape ahead is already set in stone and the flow is an illusion. "Change" is the sequential variation of the intersection of the plane with the worms of our lifelines.

Your distinction is rather subtle, I see our awareness of the passage of time as emergent, an interpretation of the accumulation of seemingly ordered memories. However, that gets us into the complexities of neuroscience and I'm far from up on that topic!

lmoh

I just want to hammer in your last point here. Memories are necessary for a perceived change, are not necessarily required for changes in perception. I can be an animal with virtually no memory of my life, yet I can still experience t1, then t2, then t3, even if at t2, I have no perception that time has passed from t1 to t2 (because I barely have an ordered memory of it).You can say that neuroscience can deal with the former well, but as for the latter, it is a bit more complicated. In fact, if we are going to have a block universe scenario, then as I said before, the emergence of this kind of "passage of mind" may be entirely unrelated to the issue of matter. But with that said, it is possible to view our changing experiences as the byproduct of having brain states in different parts of the block universe, especially if you take in entropy as a description for why our experience moves from t1 to t2.

mangaroosh

Just a question about the A-theory of time, and presentism in particular: I thought the concept was fairly well understood, but in a discussion on this site, it appears that it might not be that well understood.

I'm just looking for a fairly concise explanation of presentism. I would say that it is the idea that there is a single, universal present moment, common to all observers. I would see this as being incompatible with the relativity of simultaneity, which I think leads to the B-theory of time, and the idea that there is no single, universal present moment, but that the present moment is relative to each individual (although it can be shared).

I was also under the impression that Lorentz Ether Theory incorporates presentism, I'm just wondering if anyone knows if this is true or not?

p.s. I don't want to get into a philosophical discussion about the accuracy, or otherwise of LET, I'm just wondering if it incorporates the concept of presentism [as I outlined above]

GeorgeDishman

Presentism is the belief that only the present moment exists. This is a basic article on it:

http://en.wikipedia.org/wiki/Present...osophy_of_time)

This is more comprehensive and introduces relativity too:

http://plato.stanford.edu/entries/temporal-parts/

From the SEP page:

"If STR thereby rules out presentism, and if endurantism requires presentism in order to explain change (see section 3), then STR rules out endurantism: things have temporal parts. But not all endurantists agree that they must be presentists, and not all presentists agree that their view is undermined by STR."

This article should give you a clearer idea of the A and B theories:

http://www.iep.utm.edu/time/#H1

This is a paper on B-theory by Pruss which might also give you some background:

http://www9.georgetown.edu/faculty/a...s/BTheory.html

What I suggested in the other forum was that it is difficult to start from a presentist philosphical approach and not be driven to an aether-style theory but the converse need not be true. It is possible for example to assume clock effects caused by an aether within the philosophy of a block universe, but much of the motivation for the block view is then removed.

The accuracy or otherwise of theories is not a philosophical topic anyway and would probably be inappropriate here.

lmoh

Presentism is basically the idea that only the present exists. However, what is meant by "present" can vary. The present moment may consist of a single moment in time or consist of multiple moments or an "extended present" (Luigi Acerbi advocated this earlier in the thread) for example, and if you want, you can even extend presentism to include something like the moving spotlight view (which George Dishman mentioned in the other thread).

I would not necessarily say that the B-theory would follow, and there are some people would follow me on that point as George . As for myself, I would at best say that it may suggest a block time, but that does not necessarily vindicate the B-theory, and I would still hold on to an A-theory for my own reasons mentioned earlier.

I would not necessarily say that LET incorporates presentism, but is compatible with it, just as SR does not necessarily rule out presentism (assuming that you can assume an undetectable present that is not the same as an ether theory). Scientific theories are indfferent on philosophical issues such as this.

The only person that I can recall that uses LET to support presentism is William Lane Craig, who opts for a "neo-lorentzian" interpretation (and he is the only person to do so apparently according to a paper I've read a while ago). I am not a fan of his work though, but you can look him up if you want.

mangaroosh

Thanks for the reply lmoh.

That would be my own general understanding also, but with the added qualification that there is only one present, common to all observers.


I suppose it depends on what is meant by RoS; if it refers to the mutual simultaneity and non-simultaneity of events, then I think it would have to lead to a B-theory, because it would mean that there is no universal present.



I think it is a nice notion that scientific theories are indifferent on philosophical issues, but insofar as they are based on certain assumptions, they tacitly assume a philosophical position on certain specific issues.

LET appears to be founded on Newtonian assumptions about space and time, which was inherently presentism-friendly; while Einsteinian relativity doesn't appear to be presentism-friendly.

I don't mean to be facetious, but saying that SR doesn't necessarily rule out presentism, assuming that you can assume an undetectable present that is not the same as an ether theory, sounds a bit like saying, it doesn't rule out presentism as long as you can find an undetectable present that is compatible with SR.

If the above description of RoS is accurate, and SR incorporates it, then it is incompatible with the definition of presentism above.


I discovered as much, myself, after learning about LET on here, when trying to find out more about it. It is an unfortunate fact that it's WLC who happens to be trying to resurrect it, given his expressed motivation for doing so, but it might provide for healthy debate of the issue, to a certain extent that is.

GeorgeDishman

As has been said many, many times, the term "relativity of simultaneity" comes from SR and in SR it refers to the consequences of clock synchronisation. Since clocks in reality behave in one particular fashion RoS must apply to any theory that accurately describes that behaviour regardless of any philosophy.

However, SR also has a geometric interpretation (often attributed to Minkowski rather than Einstein) which is also carried forward to GR. That interpretation describes a 4-dimensional hypervolume we call spacetime. Within that, there is nothing intrinsic which uniquely distinguishes the basis vector of time. Since a surface of uniform time (isotemporal?) would be perpendicular the time vector, it too cannot be physically meaningful, thus the geometric interpretation of SR which is fundamental to GR supports the B-theory (and 4-dimensionalism in particular).

The effect known as "relativity of simultaneity" is irrelevant from the philosophical perspective.

petm1

Isn't the surface of matter a surface of uniform time, with every point of its surface perpendicular to its center of mass? If the act of being re/emitted only happens in the present then it only happens at what I see as the surface of matter, when coupled with the sun as the spotlight looks more like A=series.

GeorgeDishman

No, I wasn't talking about matter at all. Are you perhaps thinking of the geoid defining the surface of the Earth being a surface of uniform gravitational potential?

The rotation of the planet makes it slightly oblate so, other than at the poles and equator, a perpendicular to the surface doesn't pass through the centre.

I have no idea what that is supposed to mean, sorry.

None of your comment appears to relate to foliation of spacetime.

mangaroosh

Are the A- and B-theories of time linked to any scientific theories?

The impression that I get is that B-theory is linked to Einsteinian relativity, or that it is compatible with it, while A-theory is not compatible with Einsteinian relativity.

mangaroosh

EDIT: I don't want to derail this thread into a discussion about RoS, so I will just reply to this one post and leave it at that.

One of the consequences of that clock synchronisation appears to be that events that are simultaneous in one reference frame can be non-simultaneous in another; at least that is the definition that was supplied by some of the other posters on here. If that is the case, then it is incompatible with presentism, or the idea that there is a universal present, common to all observers, and therefore incompatible with the A-theory.

Again, if one of the consequences of the effect known as RoS is that events which are simultaneous in one reference frame are non-simultaneous in another - as mentioned by DaleSpam and Harrylin - then it preculedes the philosophical perspective of A-theory and favours B-theory.

harrylin

Quite to the contrary - the cited reference of the OP explains as one variant of the A-model:
"it can be plausibly argued that the theory [of relativity ] [..] has no bearing on whether there is such a phenomenon as absolute simultaneity."

Consistent with that (and despite the fact that I don't believe in a literal "flow of time"), I will now vote A.
A very hasty reading gives me the impression that I largely agree with Taggert, as I define time as being a measure of progress of physical processes - which implies change.

PS however, I now see that Taggert claimed that A is wrong, despite the fact that he largely agreed with my thinking; and like him I also hold that time doesn't really exist. And I definitely disagree with B. Thus perhaps I should change my vote to "other"?

harrylin

I now see that it's impossible to correct a vote; thus it's not a very good poll, regretfully. While I certainly disagree with B, I'm not sure that I fully agree with A.

lmoh

If by "literal flow of time" you are referring to some substance called time that flows from past to future, then I essentially agree with what you are saying. For me, what you are saying sounds more like the issue of whether or not time or change is fundamental (you can refer to Section 2 of my orignal link for more info). Many (including myself) would argue the same that time cannot exist without change, that it is simply a measure of change, but I don't see how that matches up with McTaggert's thinking.

Same here. I actually felt like changing my position to "A" from "I don't know" after some recent thought, but apparently I can't change my vote either.

harrylin

Did you not create this poll? I guess that it depends on how the poll is set up...
Still it gives a very rough indication about how participants think about time; it appears that there is no clear majority view!

GeorgeDishman

Do you think there is an aether which interacts with physical systems moving through it so that clocks (including radioactive decay) tick more slowly rather than the geometric explanation given by SR? If not, I may be able to give an example that sheds some light on the question.

It might be tomorrow, I have to go out soon.

lmoh

I am not sure what you are referring to, but in regards to your question, I am going to say no. Lets see where this goes.