According to presentism, only the present exists. But according to special relativity, which events occur simultaneously (and thus co-presently) is relative to a frame of reference. So something can both exist and not exist, depending on which frame of reference you are looking from. But this is absurd.
An example: Suppose that from reference R1, events A and B occur simultaneously, and C later. But from reference R2, A occurs earlier, whereas B and C are simultaneous.
Now, suppose event B is presently occuring, and thus the objects it involves truly exist. Do the objects of A and C exist? By R1, A is occurring presently, and thus its objects exist. But by R2, A is in the past, and so its objects no longer exist. Contradiction. Ergo, presentism is false.
Or, put more formally:
1. Simultaneity is relative.
2. Existence is not relative.
3. Therefore, existence cannot depend upon simultaneity.
4. Presentism implies that existence depends upon being simultaneous with the present.
5. Therefore, Presentism is false.
Is there any response left for the Presentist? (Could they deny #4, perhaps?)
Posts
Sometimes Richard , I wish you would not post such interesting topics. Even this apparently innocuous one makes my brain 'twang' with questions.
ReplyDeleteI guess the 'presentist' could say .. "yes, but as far as an individual is concerned there is, even in the scientific relativistic meaning, ONLY the local time frame, and in that frame there exists only the 'present'. This would apply in all circumstances, for everyone across the whole univers. "
Actually, that would not even work, since the brain/self itself in a single instant would experience nothing since there could be no complete thought/perception process. Come to think of it, in one 'instant' there could not even be time for a sub atomic particle to complete a 'wave function.'
okay .. existence requires time 'spread out'.
I like the idea of this 'eternal' time/ space continuum of all that has ever been and will be 'existing'.
Presumably, our own sense of existing simply tracks with the changes inside us along this eternally existing .. thing .
Like a fairly large (universe through all time ) sized CD upon which we are a tiny track!
or something
david L.
I know Craig has been out there trying to reconcile presentism and relativity. I tend to agree that it just doesn't work. I've brought this up on my own blog relative to the free will debate. (I should add that it is amazing how many things I disagree with Craig on - especially those related to science or mathematics)
ReplyDeleteProbably the best paper arguing against presentism being compatible with relativity is Balashov's and Janssen's "Presentism and Relativity" up at the Philosophy of Science repository. I think I linked to it on my blog a couple of months back. It does a good job with the issues.
On the other hand, here is a paper arguing that things are different in quantum gravity. "Presentism and Quantum Gravity". I'm not convinced in the least I should add.
Just to add - there are lots of other papers on the subject up at the repository. Including a few that argue fairly convincingly that the whole debate is pointless.
ReplyDeleteClark, thanks for the resources, I'll be sure to read them in the next few days. My guess is that it wont be long before I cease to be a presentist. I suppose one of my weaknesses is my ignorance of Einsteinian physics. I'm still stuck in a Newtonian world, and haven't had any scientific training since high school. I'm going to have to make serious strides towards rectifying that.
ReplyDeleteQuentin Smith--who, by the way, claims to have invented the term 'presentism', and is notably distraught that the term has been usurped by philosophers like Craig--uses 'presentism' in a completely different way. In any case, the second to last chapter in his book is a discussion of his idea that Einstein's Special Theory of Relativity doesn't actually characterize time. This is worth a read for anyone interested in the topic.
ReplyDeleteThis is the Presentist's reply.
ReplyDeleteThe difference between the 2 R is but a illusion due to the fact that infomation cannot be sent faster then the speed of light.
1: Simultaneity is not relative, it only seems so because of the speed limite of informations, due to the fact that nothing can be faster then light.
2. Everything exists at the present. Any differences in each's experience of time, such as those in SR, is due to either the delay in information (as the above example of ABC and the 2 Rs) or, a result of the change in due to the fact that matter is stationary energy (hance E=mc2), and therefore moving matter will experience an acceleration/ deceleration of change (time dilation), together with all other phenomenon mentions in SR.
3: Things flow from the past to the present, and to the future because of change. In fact, time dose not exist, it is only a concept. All perceptions of time are actually to changes. Changes are what give us the illusions of time.
4: It is due to this fact that effect cannot precede cause, because the effect is in the past, it's gone. All things changes, this is the mechanism behind causality.
5: Externalism at least violates causality and the second law of thermodynamic. Since if the future and past actually exist, there is currently no known mechanism to drive us moving only towards the future. There is also no mechanism for causality. The only possible natural mechanism, which does not require any higher being (IE: GOD) to preplan every event in time to take place in accordance to causality and the second law of thermodynamic, is presentism, together with the idea of changes. You cannot have a theory in which the past exist yet dose not violates causality. You can either chose causality or eternity, but not both.
6: We don't see things moving at high velocity, even those close to the speed of light, disappearing into the future or past, same goes for non moving object, If we were all actually moving in a dimension of time. This is blatant evidence that there is a universal time, there is just no universal experience of time, due to the effects of gravity and movement on matter's experience of changes.
Typo Error.
ReplyDeleteWe don't see things moving at high velocity, even those close to the speed of light, disappearing into the future or past, same goes for non moving object, which will be the case if we were all actually moving in a dimension of time.
If a universal time dose not exists and we are moving in time, then the above will happen.
However, it dose not, therefore, there is a universal time, the question is if it is dynamic or static.
In Eternalism, time is though of as static, and we exist throughout all time and changes, together with the idea of 'now' is an illusion.
The problem is that not only is there no law of physic or natural mechanism for us (and everything else) to experience time the way we do if this is the case, causality, which is the most fundamental concept in science is an illusion under the idea of eternalism. This can only be true if there is a intelligent, higher being. Which until today no evidence of it's existence can be found.
We cannot have anything forming naturally without causality, can causality demands presentism and changes, demands an dynamic time.
Therefore, you can either throw eternalism into the trashbin, or start calling yourself a priest or pastor.
I contend essentially that the present moment and only the present moment exists. I may make minor exceptions to this, but on the whole, the notion that what happened 5000 years ago on Earth is still happening off somewhere in another dimension is ludicrously absurd and confusing. Does this make me a presentist? I don't know. I guess it does, but I do not like the label, not that I am hung up on not identifying people, I just think its meaning is ambiguous. For instance, one straw man against presentism is that presentism is irrational (or rather anti-realist) because it implies that the future AND the past are not real. Just because something is (currently) non-existent does not make it unreal! While some so-called presentists might take this position, that the past and future are fiction, since only the present is experienced (which by the way IS indeed solipsistic), generally those labeled "presentist" hold a realist view of the universe in which the past is no more or less real than the present, but it does not currently exist. For instance the typical presentist (non-solipsist) does not deny that past objects DID exist or that the future WILL exist (but perhaps specific futures only MIGHT exist). For example dinosaurs are not unreal. Dinosaurs definitely did (operative word being did) exist and are therefore real (as they are connected to reality), but they no longer do (except of course as fossil remains) exist, therefore even though dinosaurs do not exist, they are not fictional. Likewise, I did not exist in 1900, but I do now. Existence is a time-dependent property. Our existence is defined over an interval of time, thus we are said to endure from one moment to the next (hence why "presentism" is often referred to "endurantism"). This is my take and I am sure Son of Light agrees. Eternalism seeks to eliminate tense from all thought. More examples, Socrates DID exist, even though he currently does not (If he does exist, where is he? He once lived in Athens but I did not see him when I was there.) I DO exist, but I WAS NOT in existence in the year 1492. Bazilor the Space King WILL (or WILL NOT) exist perhaps in the year 4000 AD, even though he DOES NOT exist now. Existence is temporary. Makes sense, as existence is temporally dependent. Even an eternal entity exists at specific instants (it just endures for an infinite time). WHY IS THIS SO FREAKING HARD TO UNDERSTAND? Another problem I have with use of the presentist label is that many might pigeon-hole "presentists" as those who reject that time exists (or at least as temporal relationalists). First of all, since presentism is defined as a perspective on time, i.e. the presentist concept of time, then while one who claims time does not exist would agree on essential points with presentists, they would not have a view of time, which to them does not exist, so how could they be presentists? I must say that I am not certain whether or not time actually exists or not and if it does, whether this existence is absolute or relational (if everything stopped, would time stop?), but I contend that time does exist. Son of Light appears to hold that the existence of time is relative (though its passage is absolute), and I tend to disagree partially with him on this, as I lean towards the view that time is tangible, but this is a whole other debate and I am not so confident in this stance. For more on the ontological and epistemological problems on time, I would suggest Hume.
ReplyDeleteAnother issue with presentism-endurantism vs. block universe models is that once one accepts a block universe concept, they are forced to become fatalist. With a presentist-endurantist perspective, one may be a strict fatalist/determinist or a strict indeterminist or anything between. (Consider that LaPlace, presumably a presentist-endurantist, thought that the universe was theoretically deterministic because of fixed mechanistic causation.) The issue depends on the nature of causal relations and not time itself. This poses a problem. Consider the following conflict between Relativity and Quantum Physics.
A-2. The Theory of Relativity is actually composed of two theories. Special Relativity and General Relativity.
A-3. Special Relativity is actually a subset of General Relativity, one in which gravity is ignored (or in free fall, or in cases involving infinitesimal masses). General Relativity is Special Relativity + gravitation (not a force between masses but a force exerted by mass on the STC).
A-3. Therefore, special and general relativity are compatible.
B. (Assumption) Relativity requires a block universe model in which time is a geometrical dimension no different from space. All events occur in a 4-D continuum. This implies eternalism.
C. Quantum theory describes indeterinistic systems described by probability. Though the past is fixed, the future is unwritten. (Consider Heisenburg's Uncertainty Principle)
Therefore, going by the a-priori assumption that relativity negates endurantism, relativity and QM, the two keystones of modern physics, are inherently incompatible. UNLESS, for every possible future there is a space in the temporal continuum. Therefore, given the deterministic nature of a block universe (where future moments coexist with earlier ones), and the indeterministic behavior of quantum physics, the only possibile reconciliation is that there is a universe for every possible outcome. This idea, known as the multiverse interpretation of QM might reconcile a block universe with the potential for multiple outcomes, as opposed to the Copenhagen interpretation which necesitates indeterminacy and thus contradicts eternalism. Problem is, you must modify your precious 4-D Minkowski space-time into a 5-D space-time, having 2 dimensions of time to fit a potentially infinite number of diverging timelines. Given Richard's assumptions and strawmen, his options are:
* Accept relativity as interpreted by the block model, and reject quantum mechanics, maintaining Einstein and Minkowski's 4-D STC (or rather Richard's conception of it).
* Accept the standard (Copenhagen) interpretation of quantum mechanics but reject relativity, since according to Richard, relativity necesitates the fatalist block universe, thus contradicting the indeterminacy of QM.
* Postulate a five dimensional "Ultra-verse" consisting of three spatial dimensions and two temporal dimensions consistent with the (predetermined) block universe but allowing branching time lines on the temporal plane reflecting the chaotic causation inherent in QM, a universe for each and every outcome.
It is no wonder why so many physicists buy into this multiverse/parallel universe/alternate reality BS. They stick to a misunderstanding of time, and must reconcile their fatalist block universe model with the data from quantum mechanics. If you apply Occam's Razor, it is apparent that the 3rd option is the least feasible. But then why choose one theory over the other. Saying presentists are stupid because they reject the findings of relativity (a strawman btw) is not only ignorant but hypocritical, because it is you block theory proponents who reject the findings of presentist QM on the basis of its indeterminacy (assuming you eliminate the 5-D Ultraverse on the basis of Occam's razor, you are left with a single fatalist 4-D universe). (Some might insist on neither endurantism/presentism on the one hand or eternalism, but instead on the growing block model (as Chris seems to have settled on) that the past and present exist but not the future, but the obviously irrational nature of this view is apparent since the past is simultaneous with the present, our present is the future to some past moment, so why does are future not exist. It makes even less sense than eternalism!) There is one way out however. Reevaluate your inane arguments to reconcile relativity with presentism and thus indeterminacy and QM. Here are some suggestions:
1. Take an absolutist view of time's passage consistent with classical mechanics. Absolute universal time is obviously consistent with presentism. You can in turn hold to a concept of time which is (a) absolute in its existence and passage (Newton's absolute universal time, presumably incompatible with relativity) or (b) a concept of time whose existence is relational (Leibniz's relational universal time, perhaps more compatible with Galilean-Newtonian mechanics including Galilean relativity than with Lorentz-Einstein relativity, but more flexible) Son of Light appears to have taken a somewhat similar approach.
2. State that time is relative both in regards to its passage and its existence. This is not so different from Leibniz's position, but it is adjusted to relativity.
3. State that time exists independently from motion, but that its passage is relative. This need not imply eternalism. See below.
Son of Light put forth a very persuasive argument for presentism. First off, only presentism is consistent with the laws of thermodynamics (admittedly, thermodynamics have little say in the subatomic realm, but it is through these principles that we identify the arrow of time). Second, causality depends on a dynamic universe, not a block model. In fact, eternalists essentially reject the existence of time because in their worldview, time is another dimension like space. Therefore movement, change, any sort of transformation, does not occur. Nothing happens! Everything merely is there. Time and velocity are illusions. Furthermore, Son of Light seems to understand relativity better than eternalists. (See the sixth point in his first post!)
One other possible compromise to reconcile presentism-endurantism with relativity is to loosen the definition of presentism, and allow small local deviations from a general present moment. Even so, this implies that time changes from a 0-D point consisting of the present instant to an infinitesimally short line segment extending from the latest time an object or frame of reference with the least time dilation to an area with the most time dilation. This is still a far cry from a line or rather a ray extending from the Big Bang indefinitely forward or a line segment from the Big Bang to the Big Crunch. Perhaps the answer is a compromise (similar to a different time-related question, whether time's existence is independent of or related to motion), but I still lean towards presentism. Besides, for every inertial frame, only the present moment exists, which means that time may just be relational. So in short, the equivalence of space and time in relativity may be simplified as a collection of four primary vectors. Three of which, are geometrical and manifested spatially (the static aspect of the STC) and one which is a vector, purely agebraic and manifested temporally (the dynamic aspect of the STC). This vector (in classical mechanics) is a 0-D point, which is constantly moving from past to future, but this motion is not in any way geometric or associated with any navigable direction. Modified for relativity, this movement may be slowed in regions of increased gravity or in frames of reference of higher velocity. As such, there might be a difference in time, but, here is the catch, this difference varies through 3-D space, not some pretend t-axis. As such, this "dimension of time" does not satisfy any geometric definition. So all relativity says is that time has space-like properties!
HI RICHARD
ReplyDeleteJust found this topic, and I felt like leaving my 2 cents. I happened to find many of the comments ammusing. Also, I had a crabby day, so please excuse my arrogance.
David L. says:
"Sometimes Richard , I wish you would not post such interesting topics. Even this apparently innocuous one makes my brain 'twang' with questions. ..."
Something about this tone reeks of pseuso-intellectualism. DUDE!
..."Actually, that would not even work, since the brain/self itself in a single instant would experience nothing since there could be no complete thought/perception process. Come to think of it, in one 'instant' there could not even be time for a sub atomic particle to complete a 'wave function.'..."
So, what, is continuous motion/change impossible? Then the eternalist has the same problem. If this is so, then there exists a non-zero minimum interval of time. Time thus can not be infinitely divisible, for it is LOGICALLY impossible to divide time into smaller units then this fundamental atom of time (presumably the amount of time for a subatomic particle to complete an entire wave function). Does this mean that presentism is false? Not necessarily, since this interval of time is indivisible, the entire moment could be regarded as present. (Some theories of quantum gravity, notably loop quantum gravity and string theories argue that space and time are discrete.) Of course, if you argue that time is in fact continuous, then this is irrelevant. David's argument is a retread of Zeno's Paradoxes, which were thought up nearly 3000 years ago, when the ancient Greeks did not understand zero or infinity very well. For more on this, I recommend Zero: Biography of a Dangerous Idea by Charles Seife. The wave function or a human thought is essentially a transformation, a form of motion or change, and as such could be described in terms of rate or speed. Instantaneous rate of change (movement in a 0 interval) is a basic aspect of differential calculus. He probably never took a calculus course yet. My advice David? Come back when you finish highschool.
"...I like the idea of this 'eternal' time/ space continuum of all that has ever been and will be 'existing'.
Presumably, our own sense of existing simply tracks with the changes inside us along this eternally existing .. thing .
Like a fairly large (universe through all time ) sized CD upon which we are a tiny track!
or something"
More pseudointellectual musings... LOL dude, you've made my day!
Chris says:
"The past exists as much as the present does. The present exists in that we are experiencing it right now, and just as we experience something now we have experienced something in the past. They both exist. But the future? I do not know if that exists or not..."
Sorry, but that makes absolutely no sense! Well, obviously, if the past exists then so does the future. Either all of time exists or only one moment exists or no time exists. Anything else is internally inconsistent! Having experienced something does not mean it exists currently (unless now and before are the exact same thing, if you argue for a tenseless eternalist time, then the future necessarily always exists)...
"Quentin Smith--who, by the way, claims to have invented the term 'presentism', and is notably distraught that the term has been usurped by philosophers like Craig--uses 'presentism' in a completely different way. In any case, the second to last chapter in his book is a discussion of his idea that Einstein's Special Theory of Relativity doesn't actually characterize time. This is worth a read for anyone interested in the topic."
I am not sure of the origin and history of the term "presentism" but as far as I know, it has not been used any differently than the way Craig and everybody else use it. Meanwhile I am surprised Chris, that you have read Quentin Smith. I would say Terrence McKenna is the philosopher for you! As for Q. Smith's assessment on what relativity says about the nature of time, I will address that later.
Clark Goble says:
"I know Craig has been out there trying to reconcile presentism and relativity. I tend to agree that it just doesn't work."
Granted. This alone does not refute presentism however, as I shall explain. (It is important to understand why his approach does not work.)
"On the other hand, here is a paper arguing that things are different in quantum gravity. "Presentism and Quantum Gravity". I'm not convinced in the least I should add."
Why? I might add. Is it because you assume that the assumptions of general relativity should carry into quantum gravity? Are you a string theorist? Or do you merely reject presentism not for scientific reasons, but on the basis of association with the cult of eternalism? This deserves futher discussion!
"Just to add - there are lots of other papers on the subject up at the repository. Including a few that argue fairly convincingly that the whole debate is pointless."
Funny, it seems you sided with Richard in thinking that eternalism is the only valid view according to the theory of relativity. Now you say that there are some valid arguments that whether presentism or eternalism is true is irrelevant. In other words, neither of the two ontologies is refuted. I'm sorry to say, clark, but based on that (contradictory) statement I say you are full of ****! According to you, presentism is both false AND unrefuted?
Well that about sums up my beef with the anti-presentists. One thing for sure, I at least admire Richard for his integrity. While I obviously disagree with him on this issue, at least Richard could reasonably argue his case (on the basis of relativity theory). He does not parrot the typical pseudoarguments from the cult of eternalism. Such as misapplying McTaggart's horrendous arguments from that atrocious turd of a paper, "The Unreality of Time" (which btw has no relevance to the ontological nature of time becuase his notions of A-Theory, B-Theory, and C-Theory are purely semantical, not metaphysical). Or arguing on the basis of some moronically infantile and pedantic line of reasoning such as the truthmaker argument. Or resorting to circular reasoning, or personal incredulity (which makes no sense, because how is an ontology of time which not only counters our conscious experience, but reduntantly adds an entire dimension to reality more believeable than the fact of change?). Chris and David are clearly cultists of eternalism, unlike Richard on the other hand who at least admits that presentism is the 'common-sense view' of time, but that eternalism is the only valid alternative, and since presentism disagrees with relativity theory, eternalism is true. Interesting to note that the tensed concept of time was considered default prior to 1905. (Sure there were probably eternalists in the 1890's such as H. G. Wells, but in general...) Scientists however discovered relativity theory and since presentism seemed to be fading away, the cult of eternalism emerged with all its pseudo-intellectualism. Now, concerning my fellow presentists...
Son of Light says:
"The difference between the 2 R is but a illusion due to the fact that infomation cannot be sent faster then the speed of light.
1: Simultaneity is not relative, it only seems so because of the speed limite of informations, due to the fact that nothing can be faster then light.
2. Everything exists at the present. Any differences in each's experience of time, such as those in SR, is due to either the delay in information...therefore moving matter will experience an acceleration/ deceleration of change (time dilation), together with all other phenomenon mentions in SR."
I admire your attempt, but unfortunately it is not going to fly. Do you even fully understand relativity theory? Few people do. Problem is that this attempt (similar to the Neo-Lorentzian model) utilizes a nonstandard model of relativity theory. Do not worry because the compatibility of relativity and presentism is irrelevant to the truth of presentism. (See below.)
"4: It is due to this fact that effect cannot precede cause, because the effect is in the past, it's gone. All things changes, this is the mechanism behind causality.
5: Externalism at least violates causality and the second law of thermodynamic. Since if the future and past actually exist, there is currently no known mechanism to drive us moving only towards the future. There is also no mechanism for causality. The only possible natural mechanism, which does not require any higher being (IE: GOD) to preplan every event in time to take place in accordance to causality and the second law of thermodynamics, is presentism, together with the idea of changes. You cannot have a theory in which the past exist yet dose not violates causality. You can either chose causality or eternity, but not both."
Interesting take. I tend to agree. I argued a similar point with a poster on one of Richard's other blog entries. One eternalist might argue that causality is possible, but this type of causality is drastically different from the typical notion. (It is not cause and effect, but the intersection of world-lines.) The thermodynamical laws as far as they stand pose an even greater problem for eternalists.
"We don't see things moving at high velocity, even those close to the speed of light, disappearing into the future or past, same goes for non moving object, which will be the case if we were all actually moving in a dimension of time."
Yet another interesting point. Given that in a 4-dimensionalist (eternalist) view of time, motion does not occur, rather what we percieve as motion is actually a world-line. So your analogy is not as simple, but if you argue on the basis of GR that things would seem to disappear into the past or future depending on gravitational effects, your argument would work better. I did however use this line of reasoning on somebody who argued that eternalism and relativity are OBSERVED phenomena, not merely theoretical.
"Therefore, you can either throw eternalism into the trashbin, or start calling yourself a priest or pastor."
Gotta love his in-yo-face attitude. He is absolutely right in that there is a sort of cult of eternalism in philosophy circles. Richard at least argues on the basis of a scientific theory, but Son-of-Light, you need not worry! The challenge from the theory of relativity could be brushed aside, as there are viable theories of quantum gravity which are compatible with presentism.
Sup3rS@iyan says:
"I contend essentially that the present moment and only the present moment exists. ...Does this make me a presentist?"
Yes it does.
"I may make minor exceptions to this, but on the whole, the notion that what happened 5000 years ago on Earth is still happening off somewhere in another dimension is ludicrously absurd and confusing."
Just as the only valid 4-dimensionalist concept of time is eternalism, the only valid 3-dimensionalist concept of time is presentism. An extended present (unless you count 'time atoms') is internally inconsistent as is a growing block or shrinking block model of time. One need not alter the definition of presentism in light of relativity. (See below.)
"...but I do not like the label, not that I am hung up on not identifying people, I just think its meaning is ambiguous. For instance, one straw man against presentism is..."
There is really nothing ambiguous about the terms if you understand the definition. Seeing how many people abuse diffenrent terms and construct strawman arguments, and I am not naming names *Cough*Chris*Cough*! It is no wonder one would hold such a sentiment. From the looks of it however, you seem to understand the general ideas, you just seem to have written the above off the top of your head, and without planning.
"Consider the following conflict between Relativity and Quantum Physics. ...Relativity requires a block universe model in which time is a geometrical dimension no different from space. All events occur in a 4-D continuum. This implies eternalism. Quantum theory describes indeterinistic systems described by probability. Though the past is fixed, the future is unwritten. (Consider Heisenburg's Uncertainty Principle) Therefore, going by the a-priori assumption that relativity negates endurantism, relativity and QM, the two keystones of modern physics, are inherently incompatible."
BINGO! You have gotten to the heart of what I shall argue shortly.
"One other possible compromise to reconcile presentism-endurantism with relativity is to loosen the definition of presentism, and allow small local deviations from a general present moment."
Sorry, this just would not work. There is a way out for the presentist however.
"As such, there might be a difference in time, but, here is the catch, this difference varies through 3-D space, not some pretend t-axis. As such, this "dimension of time" does not satisfy any geometric definition. So all relativity says is that time has space-like properties!"
Sorry, Sup3rS@yian. You repeatedly misunderstand the theory of relativity. Attempts to reinterperate the theory amount to changing it. The Minkowski space-time model IS standard. As far as the theory of relativity is true, Richard's argument stands. The good news is, the theory of relativity is NOT the most fundamental theory. It is potentially false, as a theory of quantum gravity is expected to replace it.
Which brings me to my final point. Son of Light, Saiyan, please just give it a rest already. Do not even bother to defend presentism at the level of Relativity (the way William Lane Craig and Mark Hinchliff have tried). The issue is irrelevant. The question is whether presentism is compatible with quantum gravity, and as it stands, canonical quantum gravity and other QG theories utilizing a fixed foliation of space-time are readily compatible with presentism. This fixed foliation of events eliminates the relativity of simultaneity. I recommend that you read a document on this thesis by Bradley Monton (which Goble posted above), but for those of you who do not have a .pdf reader, you could find it here thanks to the Google cache. It provides a useful introduction to presentism, eternalism, and their compatibility with relativity. Son-of-Light, Saiyan, I highly recommend you read it. David L. too, (though he should probably wait until he is grown up though, because the concepts are a bit challenging and the average high school student will not understand it). Never mind that Goble summarily and uncritically dismissed the paper.
Indeed, if the the relativity of simultaneity is true, it implies that presentism is false.
ReplyDeletePushing things a bit further, we can show that even our "instant" perception of a three dimensional world is a percetual illusion. We just have to assume that there is indeed a maximum speed limit in the universe and that the speed limit is the speed of light in a vacuum.
Let us take the image formed on an observe's retina at a given "instant". That image is composed of all the photons strinking the retina at that instant. If the observer sees what appears to be a 10.4 meters rod with its midpoint located at exactly 3 meters from him, the image on the retina of the midpoint is 10 to the power -8 seconds old while the image of the endpoints is 2 X 10 to the power -8 second old. What he sees, even though it appears to be a three dimensional object, is a four dimensional object extending 10.4 meters in the space dimensions and one hundreth of a microsecond in the time dimension.
but even that is an oversimplification, since the retina itself is extended in space, signals from different parts of the retina reach different neurons at different times. those signals are processed and in the end, there is a subjective image of a rod that is constructed.
Given all that, how could we even define the "now" of presentism?
But anonymous, delay of a signal is NOT an instance of relativity of simultaneity. Neither is time dilation. Presently seeing something a lightyear away (which means it happened after a delay of a year) does not mean that that event which took place one year hence is currently occuring. This is a mere delay. You got it backwards. An "instant perception" is not a "perceptual illusion." It is our delay which is in fact illusory. Correcting for distance (and thus time delay) shows us that the perception is outdated, not merely a different time. When one argues for the relativity of simultaneity they do so on the basis of Minkowski spacetime, not the speed of light itself. This problem is circumvented if spacetime has a fixed foliation however. Even so, a time of 10^(-8) seconds is so minute it is nearly instantaneous to the perception of most instruments. Thus the effects of the finite speed of light only become apparent on the astronomical scale.
ReplyDeleteRenegade,
ReplyDeleteI may have expressed myself ambiguously.
What I meant by the rod example was that we never perceive a 3 dimensional object in space. Astronomical examples are better. When I look at the night sky, I see the moon as it was a little more than a second ago, and stars as they were years ago. I meant to say that the image of my retina is not a projection of a 3d world, but a projection of a 4d world, since I see through time as well as space.
If there's a proper past and future, how could I see the light from a star that has already passed me, and the light that didn't arrive yet?
ReplyDelete