One clock runs slower than the other. Neither of them tracks the pace of the advancement of the present. If there was a device that could do that, you'd have your empirical evidence for the view.How about doing a simple time dilation experiment? Synchronise atomic clocks, and take one on a flight around the world. When the clocks are reunited, they no longer agree on the time. How is that possible under presentism? — Inis
Yes they do, all other factors being equal.Clocks in different time zones don't run at different rates. — Inis
Well, I buy into neither presentism nor time travel, so I'm trying to imagine how a presentist would envision travel to a time that is no longer existent. Somehow you need to find yourself in a world with the state being some prior state except for you being in it, which sort of seems to require a physical rewind of all state (except the part where 'you' appears in it), thus dragging the present back to that prior time. It really makes no sense to me, but it makes no sense in the block view either, so go figure.What do you mean "they rewind"? — SophistiCat
Well relativity gets you that, and it even looks normal to the 'travelling' person.The idea of time travel is that someone (or something) is moving in time (at a different than normal rate), while everyone and everything else goes on as if nothing happened.
I don't think it makes sense for a presentist to propose a divergence of time. A divergence of worlds, sure. That avoids some paradoxes, but time going forward for Fred but backwards for me in my machine, no. If my machine does that, then it just creates a new world now that looks like my old world did X years ago, without actually alter the course of 'the present'.But how this divergence is possible if there is only one now is something I can't wrap my head around. It would make sense if now diverged as well.
If the "Present" existed, then the clocks would read the same. — Inis
Hey, we actually agree on a point...I don't see how the reading on the clock has anything to do with whether or not the present exists. — Metaphysician Undercover
I don't see how the reading on the clock has anything to do with whether or not the present exists. — Metaphysician Undercover
Perhaps you don't, but you cannot explain, given an objective present, why the clocks diverge. — Inis
Perhaps you don't, but you cannot explain, given an objective present, why the clocks diverge. — Inis
How about doing a simple time dilation experiment? Synchronise atomic clocks, and take one on a flight around the world. When the clocks are reunited, they no longer agree on the time. How is that possible under presentism? — Inis
The question that bothers me is why are there no instances of time travel? Why is it difficult? We see travel in 3D space - it's so commonplace that no one even notices it. What is so special about the 4th dimension? — TheMadFool
One clock runs slower than the other. Neither of them tracks the pace of the advancement of the present. If there was a device that could do that, you'd have your empirical evidence for the view. — noAxioms
The idea of time travel is that someone (or something) is moving in time (at a different than normal rate), while everyone and everything else goes on as if nothing happened. — SophistiCat
Even if there were no clocks, the present still "exists" and change still happens and therefore time (a derivative concept of change) passes. If there were no change there would no time. — prothero
One clock runs slower than the other. — noAxioms
Apparently I was responding to a different quote, the one just below the one quoted in that response. It is about how time dilation doesn't invalidate presentism.I'm not sure how this relates to what I've said. — Luke
Presentism and Eternalism are two different metaphyscial interpretations of the same empirical data. Since time travel would be an empirical experience, it should in principle make zero difference whether presentism or eternalism is assumed. Under current empirical physics, both metaphysical views forbid time travel to the past, and neither forbids forward travel. Hence I see little point in needing to assume one metaphysical stance when discussing if a physical act is possibility or not.Again, I think we need to assume presentism (or that "the A theory of time is correct") for the purposes of the topic of this discussion. However, if you all just want to discuss the failings of presentism then have at it.
Presentism and Eternalism are two different metaphyscial interpretations of the same empirical data. Since time travel would be an empirical experience, it should in principle make zero difference whether presentism or eternalism is assumed. Under current empirical physics, both metaphysical views forbid time travel to the past, and neither forbids forward travel. Hence I see little point in needing to assume one metaphysical stance when discussing if a physical act is possibility or not. — noAxioms
No clock or other device measures objective time, so this doesn't follow. All clocks run slow, and some slower than others, so it is to be expected that they don't always agree.We know that an objective present cannot exist because the clocks disagree. All there can be are relative presents. — Inis
I don't think any of those theories assert it, despite the typical interpretation of relativity. I know Einstein held eternalist views due to the implications of the theory, but that's mostly because it is the simpler view, without a needless addition that adds nothing to the theory.Eternalism isn't metaphysical if it's part of our best physical theories. — Inis
I actually don't follow what you're trying to say here. I don't know what it would mean to say that the universe is not at rest (has a nonzero velocity???), so there doesn't seem to be any meaning to saying it is at rest.Both general relativity and quantum mechanics tell us that the universe as a whole is at rest. This was realised early on in GR but took a while to be understood in QM.
This means that presentism isn't metaphysical either, it's just wrong.
Yes, that would be a metaphysical claim, and one independent of the eteralism/presentism debate. The latter concerns the nature of the universe (is it 3D or 4D?), but the former is something deeper, and seems to rest on a sort of undefined meaning of 'exists'. Being a relativist, I don't make sense of something being said to just 'exist'. It exists in relation to something (which need not be an observer), and I'm not sure in relation to what the universe might be said to exist or not exist. So such statements need to be defined by those that makes such statements.What is metaphysical, however, is the claim that an objective observer-independent Reality exists.
If 'I' am an observation, that observation is taken at some event, and that means 'I' am an event, in relation which 'the present' very much has meaning. If 'I' constitutes a defined series of specific events, then those events are not simultaneous and none of the events is more special than any of the others, except perhaps the two endpoints. 'The present' could still be defined as the last event of the series of events that defines 'I'. Presentism is not wrong there, and the cost doesn't seem too high.If you take the view that reality is observer-dependent, then presentism may be rehabilitated, but at what cost?
Eternalism isn't metaphysical if it's part of our best physical theories. Both general relativity and quantum mechanics tell us that the universe as a whole is at rest. This was realised early on in GR but took a while to be understood in QM.
This means that presentism isn't metaphysical either, it's just wrong.
What is metaphysical, however, is the claim that an objective observer-independent Reality exists. If you take the view that reality is observer-dependent, then presentism may be rehabilitated, but at what cost? — Inis
A presentist need not deny observer-independent reality. Instead they are describing reality from a preferred reference frame - their own — Andrew M
- time simply elapsed at a different rate for each clock. — Andrew M
What do you think "time elapsed at a different rate" means? Suppose you and I meet. It is the present when we meet. Then we go our separate ways, and meet again later. It is still the present when we meet the second time, and it was the present for each of us during the entire intermediate period. But for each of us, there is a different amount of time passed between the two meetings, if we take differing spacetime paths. — Metaphysician Undercover
Doesn't this just mean that there is not a fixed quantity of time between any two distinct points of the present? So we can say that for any two points in time, there is not a fixed amount of time between those two points, because the quantity of time between them varies according to the spacetime path that a person or thing takes to get from one to the next. — Metaphysician Undercover
Can you give an example of a factual disagreement? — Andrew M
Suppose Alice and Bob are twins. On the day they both turn 20 years old, Bob travels into space at high speed and returns on the day that Alice turns 30 years old (according to Alice's clock on Earth). But Bob is 26 years old (according to the clock on his spaceship) and has only aged 6 years. Less time has elapsed for Bob than for Alice. (Example here.) — Andrew M
Can I make the further, more generalized conclusion, that the amount of time between any two points in time, is indeterminate? — Metaphysician Undercover
It's indeterminate because from every different frame of reference there is a different amount of time between the two points. Therefore there is no fixed value for that time period. — Metaphysician Undercover
Get involved in philosophical discussions about knowledge, truth, language, consciousness, science, politics, religion, logic and mathematics, art, history, and lots more. No ads, no clutter, and very little agreement — just fascinating conversations.