This assertion is false in General Relativity. In GR, all of space-time exists forever. The past still exists and the future already exists. In GR time is kind of like space. My father died when I was young, but in GR, he's still there, just at a different location in time than I am. It's kind of like he's in California, only in time there's less freedom of movement than there is in space. So, while my father is alive and well in California (or actually 1969), I just can't get to California from where I am currently located.
In GR, I am not located below my feet or above my head, and likewise, I am not located before I was born or after I die. But I exist always between the bottom of my feet and below the top of my head and for the time between when I was born and before I die. — Douglas Alan
Let me be more clear with a more specific example. Let's say that we build or find a closed timelike loop. And now let's say that we have a million people traverse this timelike loop, but traverse it differently so that they all end up in different times in the past. And at each of these times, let's say that each of these million people is causally connected to billions of other people.
So, we now have a million different people who were here earlier today but are now spread across the past. Did they cease to exist? Or do only the locations surrounding these million people exist in spacetime? What about all the billions of people that are causally connected to them?
I'm sure that someone could come up with some crazy explanation for this which doesn't entail eternalism, but it sure to be ad hoc and completely violate Ockham’s razor. — Douglas Alan
I've presented a thought experiment where a million people use a closed timelike curve to all travel to different times. As far as I understand things, these types of thought experiments are generally taken by physicists to entail eternalism, assuming GR is true enough that closed timelike curves are actually possible.
Though even Special Relativity makes presentism difficult to defend. See the Stanford Encyclopedia of Philosophy for more details.
I went to a Philosophy conference at MIT filled to the brim with professional philosophers. In one of the talks, the moving spotlight theory was given a quick refutation as part of the argument. Here's a longer discussion. Though this author actually defends the moving spotlight theory as not being incompatible with Special Relativity:
https://web.mit.edu/bskow/www/research/timeinrelativity.pdf
There was Q&A after the talk. Not a single philosopher spoke up to question the implicit eternalism that was presented, nor to support the moving spotlight theory. My natural conclusion is that eternalism is not hugely controversial. Or at least not amongst the philosophers who might come to MIT for a conference.
In any case, eternalism is a simple and natural explanation for what happens in the thought experiment. It is also in my experience how virtually all scientists who talk about GR, talk about GR.
I consider eternalism prima facie true, assuming the thought experiment is actually possible.
I think that anyone who wants to reject eternalism without rejecting the possibility of this thought experiment has a lot of work to do! And I find it highly improbable that whatever theory is presented as an alternative would be widely accepted as more likely.
As for who is better equipped to address such questions, I don't consider philosophers better equipped than scientists. Particle physicists used to consider virtual particles just a mathematical convenience, rather than virtual particles being real. Now virtual particles are universally accepted as real. I don't consider philosophers to be better equipped than particle physicists to determine the metaphysical status of virtual particles wrt existence, and in the unlikely case that philosophers come to a different conclusion than physicists on this issue, I would most likely side with the physicists. — Douglas Alan
I've presented a thought experiment where a million people use a closed timelike curve to all travel to different times. As far as I understand things, these types of thought experiments are generally taken by physicists to entail eternalism, assuming GR is true enough that closed timelike curves are actually possible. — Douglas Alan
I went to a Philosophy conference at MIT filled to the brim with professional philosophers. In one of the talks, the moving spotlight theory was given a quick refutation as part of the argument. Here's a longer discussion. Though this author actually defends the moving spotlight theory as not being incompatible with Special Relativity:
https://web.mit.edu/bskow/www/research/timeinrelativity.pdf
There was Q&A after the talk. Not a single philosopher spoke up to question the implicit eternalism that was presented, nor to support the moving spotlight theory. My natural conclusion is that eternalism is not hugely controversial. Or at least not amongst the philosophers who might come to MIT for a conference. — Douglas Alan
Although it seems that most philosophers who take a position on the matter are B‐theorists, nevertheless, A-theorists have made up a significant proportion of the metaphysicians actually working on the A‐theory–B‐theory debate during the past ten or fifteen years. We A‐theorists might be inclined to explain this as a case in which the balance of opinion among the experts diverges from that of the hoi polloi. There is an alternative explanation, however. I have the impression that there is a much larger proportion of incompatibilists (about free will and determinism) among those actually writing on free will than among philosophers more generally. A similar phenomenon may be at work in both cases: The B‐theory and compatibilism are regarded as unproblematic, perhaps even obviously true, by a majority of philosophers; they seem hardly worth defending against the retrograde views of A‐theorists and incompatibilists. Philosophers sympathetic to A‐theories or incompatibilism, on the other hand, are more likely to be goaded into defending their views in print precisely because they feel their cherished doctrines are given short shrift by most philosophers. — Dean Zimmerman, Presentism and the Space‐Time Manifold[/url], The Oxford Handbook of Philosophy of Time (2011)
As for who is better equipped to address such questions, I don't consider philosophers better equipped than scientists. — Douglas Alan
So a presentist walks into a spacetime bar, and the wormhole behind the counter asks: "Why so tense?"
This is a split of a side discussion in another thread (starting here), which I thought merits its own topic. I will just quote from some posts and continue here.
Some background: — SophistiCat
Laying my own cards on the table, I am not a proponent of either A- or B-theory, eternalism, presentism or possibilism; rather, I suspect that there isn't a substantive difference between them. But I've only dipped my toes into this subject on occasion, so I haven't made up my mind. — SophistiCat
I do, in general. For one thing, scientists rarely consider the same questions as philosophers. Their approach tends to be instrumentalist; excepting those few who work on foundations (which is widely considered to be a philosophical subject among scientists, and thus widely discouraged), they favor questions that can be resolved empirically, rather than through conceptual analysis or other approaches employed by philosophers. Nearly all the literature on this subject that I have come across was written by philosophers, many of whom understand the relevant science very well (for such general questions the scientific underpinnings aren't that difficult or esoteric). And scientists who do opine on philosophical questions are subject to the same competence limitations as other laymen. — SophistiCat
OK, you didn't say 'demonstrate', but it very much suggests it anyway. The vast majority of non-religious physicists that know their relativity (many (most?) probably don't) hold a block view. The view is semi-incompatible with the promises of major religions, and thus meets significant resistance without actually admitting the reason driving the resistance. — noAxioms
To my limited understanding, Einstein based his theory of Relativity on the idea that we live in a block universe. — christian2017
But what's the relationship between the block universe (a physical model) and the metaphysical interpretation of time? — Echarmion
In what sense do virtual or real particles live outside the mathematical equations? — MathematicalPhysicist
No, relativity does not assume any of the questions that are at issue, such as whether the present is in some sense more "real" than the past or the future, or whether past, present and future tenses are objective properties and not merely indexical. Some argue that relativity makes anything but the block universe untenable, but not because that is already assumed by the theory.
To be clear, "block universe" in this context is not merely a visualization of the spacetime continuum (in Newtonian physics you can also visualize the space and time dimensions as a single block). Here it is a synonym for the B-theory of time or for eternalism, which are metaphysical positions. — SophistiCat
There is some truth to this, but if you haven't yet surveyed the extensive literature on the subject, then perhaps the review articles that I posted at the top will go some way towards disabusing you of the notion that this is a settled issue in philosophy. — SophistiCat
In what sense do virtual or real particles live outside the mathematical equations? — MathematicalPhysicist
Some background:
Kristie Miller, Presentism, Eternalism, and the Growing Block, A Companion to the Philosophy of Time (Wiley, 2013)
David Ingram, Presentism (Stanford Encyclopedia of Philosophy)
Steven Savitt, Being and Becoming in Modern Physics (Stanford Encyclopedia of Philosophy)
Dean Zimmerman, Presentism and the Space‐Time Manifold, The Oxford Handbook of Philosophy of Time (2011) — SophistiCat
That no inherent meaning can be assigned to the simultaneity of distant events is the single most important lesson to be learned from relativity. — David Mermin, It's About Time
I did some skimming of the references you provided that were actually available to me. One thing I noted that was of interest is that in a closed timelike curve, there can be no consistent entropy gradient that gives time its forward arrow. If there were such a gradient, you couldn't return in the loop to the same point in space-time, since that point must have the same entropy, and consequently it wouldn't be a closed curve. It seems that this would make traveling around one unpleasant. But, I suppose if it were large enough, you could refrain from going all the way around the loop, and I suppose there could be a gradient that does not change direction in the part that you stay on. Well, this is probably neither here nor there for this discussion, but I found it an interesting worry. — Douglas Alan
I think you're just saying that relativity doesn't entail an arrow of time, nor is it dependent on there being one. Nevertheless, relativity is consistent with there being an arrow of time. Relativity is not a theory of everything.a problem with relativity as a model of time: relativity does not have a concept of the arrow of time — SophistiCat
Eternalists, then, hold that the world as a whole is static in two senses: which events exist does not change, and there is no sense in which the present moves. — Kristie Miller, Presentism, Eternalism, and the Growing Block, A Companion to the Philosophy of Time (Wiley, 2013)
If what you are saying about closed timelike curves is correct, it appears that even as the physical time reverses its flow, the coordinate time does not notice the fact, merrily ticking along. (Another interesting question is what happens after the heat death or, in some models, at the Big Bang, where physical time may effectively disappear, even as coordinate time goes on. But that is a discussion for another time, as it were.) — SophistiCat
This is more evidence for eternalism if you ask me. E.g., why is it that "metaphysical time" just happens to agree with the arrow of time placed by the direction of increased entropy? What a fortunate coincidence, since it would be a crazy world otherwise.
For eternalism, there is no problem here. — Douglas Alan
For example, after extensive paraphrasing, the blogger ends up with the following thesis:
(1) Relativity of simultaneity + all observers’ 3D worlds are real at every event = block universe
I take it from the context that "observers" here are not meant literally, but rather as virtual probes that could potentially be dropped anywhere within the spacetime block. Oh, wait. Well, he does go on to state the obvious: that the second premise already presupposes the conclusion. — SophistiCat
But then for some reason he backtracks and adds that the first premise is needed as well, although he doesn't explain why. — SophistiCat
Case in point:As always, it's impossible to tell when someone claims to represent opponents' arguments made elsewhere, whether they are doing it accurately. — SophistiCat
I don't think the typical eternalist would assert a motionless landscape. An object is here at time zero, and over there at time 1, thus there is motion, spin, acceleration, velocity and all that.it always amazes me that proponents of Eternalism so readily accept the static , motionless nature of their own temporal landscape. I'm no scientist, but much of science appears to be reliant on a dynamic world involving rates of change, momentum, spin, acceleration, velocity, etc. — Luke
The block view does not lack dynamics. The arrow of time kind of assumes that view since I don't see how you can draw an arrow in a direction that is posited not to exist.Except that an arrow of time assumes a dynamic world? — Luke
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