If time is just the measurement of change, and not some kind of 'thing' that literally exists, or that 'flows' or has an arrow or what have you.... would it still make sense in Einsteins special relativity? — ChatteringMonkey
I'm looking to do away with what might be a mistaken metaphysical notion of time, as a thing... — ChatteringMonkey
To be clear, I have no problem with abstractions or relations etc... they are usefull to be sure, as long as we don't forget they are abstractions. — ChatteringMonkey
What is the difference you ask? The idea of timetravel for instance is nonsensical if time is not real. — ChatteringMonkey
Your title mentions spacetime, not time. Time is the same sort of thing as space, so if space is a measurement of separation, then so it time. It does not measure change since a slower process needs more time to produce the same change, but it would be the same time if it was a measurement of change.If time is just the measurement of change, and not some kind of 'thing' that literally exists, or that 'flows' or has an arrow or what have you.... would it still make sense in Einsteins special relativity? — ChatteringMonkey
The above description is effectively fusing them together. The two are the same thing.And would there still be a need to fuse it together with space into spacetime to make the theory fit?
They do not influence time, but mass is a function of speed, and time is a component of a specification of a speed.In special relativity high speed and mass influences time.
Yes, it influences the rate of change, but per what I said above, time is not a rate of change. An object does not have speed or velocity as a property, but only as a relation to an inertial frame. So the same object in its own inertial frame has normal mass and rate of change of any process. The rate of change is not a real property, and so isn't objectively different than the rate of change for an object of different velocity. SR says that given two objects moving at vastly different velocities, there is no local test that would determine that change is taking place faster or slower for one than for the other. This is a consequence of the principle of relativity which goes back to even before Galileo.If time is a measurement of change, in special relativity this then would mean that high speed and mass influence the rate of change.
To be clear, I have no problem with abstractions or relations etc... they are usefull to be sure, as long as we don't forget they are abstractions. — ChatteringMonkey
Well, anything we contemplate becomes an abstraction in our mind. This goes for "things" as well as not-"things". — SophistiCat
What is the difference you ask? The idea of timetravel for instance is nonsensical if time is not real. — ChatteringMonkey
Why not? We travel forward in time, obviously, and that makes perfect sense. We also can orient and move in space in any directions, and space is just as "abstract" as time, isn't it? The question of why we cannot (easily) travel backwards in time both makes sense to ask and not trivial to answer. — SophistiCat
Space is real, so time is real, but things don't 'travel' in spacetime. Take just space: A boat is 100 meters long, so does the boat travel for 100 meters? No, the whole thing just exists for 100 meters, and the point at the bow and the point at the stern are considered different points of the same boat. Likewise, I do not travel through time despite the fact that I exist in 2008. That younger-me is considered to be the same 'me' as the 2018 me, any only because of that designation is it said that I travel through time. Nothing actually 'moved' through spacetime to do that. The 2008 version of me cannot be elsewhere than 2008 any more than the bow of the boat can be at the stern (except the Titanic which attempted that feat).The idea of timetravel for instance is nonsensical if time is not real. We maybe don't believe it can be done practically, but we sure theorise about the possibility — ChatteringMonkey
Well, you interpret it that way. You (here at a moment in time) can't see objects that are not here, only the light that reaches you from past objects, and only when that light gets 'here', just like you (now) don't experience times other than 'now'. Spacetime is more of a view-independent model that does not have a privileged here or now, so isn't particularly compatible with an idealistic definition of existence being dependent on perception.noAxioms, there's a lot to consider in your posts, so let's start at the beginning.
What is real to me is what can be percieved. I can see 'space', or rather i can see distances and objects in three dimensions. I suppose space is real in that sense. — ChatteringMonkey
Yes The units to measure time are similarly abstractions.The units we use to measure that, or x,y,z axis in geometry are abractions, these are not real. We invented those.
You can measure it, so isn't that perception of it? By your definition, it is real then. I cannot make a physical measurement of an abstract circle, so abstract circles are not real in that sense.So then why is time real? I have never seen time.
Yes, if you define time as temporal separation. That's what it means to be a definition. Different words for the same thing. You don't have to accept the definition. The flowing time model (with 3D space, no spacetime) would probably word the definition differently, but perhaps now.Also is defining the measurement of time as the measurement of temporal separation not merely a tautaulogy? I don't get it.
I thought about this some more, and technically this is incorrect.What is real to me is what can be percieved. I can see 'space', or rather i can see distances and objects in three dimensions. — ChatteringMonkey
Relativity theory IS a non metaphysical theory, so it doesn't render an opinion on say what is real. Like any scientific theory, it makes predictions about what to expect when observing the world, and that is not really metaphysics.If i'd have to put a label on my views, it would be materialism (what exists is the physical). I do try to refrain from metaphysics as much as possible. My goal in this thread was figuring out what kind of view of time physicist are assuming in special relativity, and if the theory is compatible with a non-metaphysical view on time. — ChatteringMonkey
Yes, Minkowski spacetime is a 4-dimensional structure best described by B-series descriptions, and it is really hard to work with relativity if you have to convert to a different model. Everything is confusing and unintuitive in A-series, but is clean and symmetrical in B-series.And additionally, figure out if we still need a notion like spacetime then... That's why i named the thread "SpaceTime?" (questionmark).
Relativity theory IS a non metaphysical theory, so it doesn't render an opinion on say what is real. — noAxioms
Nope. SR works whether simultaneity is real or not, or if actual simultaneity is objective or relative. SR is an empirical theory, which makes it non-metaphysics in my book.Special relativity is a metaphysical theory. It renders an opinion on the reality of simultaneity. — Metaphysician Undercover
Nope. SR works whether simultaneity is real or not, or if actual simultaneity is objective or relative. SR is an empirical theory, which makes it non-metaphysics in my book. — noAxioms
For example:Not a lot of people in more 'popular' media keep the science (only predictive value) and possible metaphysical implications seperate... — ChatteringMonkey
No, it is just a way of relating two events. SR only says that the ordering of two non-causally related events is frame dependent. That is not a statement of what is. A statement that '7 is greater than 5' is not a metaphysical assertion despite the presence of the word 'is' in there.Simultaneous is a statement about what "is". — Metaphysician Undercover
Exactly. There is a "local" test that can be made to determine which direction the arrow of space-time takes. In other words, it's all relative. I could actually be off-planet and still have the directions of space that you speak of. The directions would be relative to me, instead of the planet, with things above my head being up and below my feet being down. In other words, when talking about perspectives, there seems to be directions flowing away from the present perspective in both space and time. But what is spacetime absent any perspectives? Is spacetime a mental construction of a perspective? Does it really exist outside of our perspectives?Under spacetime, time is just another dimension and does not flow. It is exactly as real as space, so it is real if you consider space to be real.
As for the arrow of time, it is just like the arrow of space: There is indeed a local test that can be made to determine which direction is 'future' from a given point, so an arrow is defined. On any planet, there is an arrow of space for all three dimensions, with a clear direction for 'down' which can be determined with a plumb line, 'north' which can be determined by looking at the way the stuff in the sky rotates, and 'east' which is the remaining dimension. Out in deep space, these methods don't work, so there is no objective direction that is 'up' for instance. Perhaps away from the most influential gravitational force, which might be something like the great attractor if you're not particularly near any specific galaxy. Time would still have an arrow so long as there is work being done where your point of measurement takes place. — noAxioms
SR is taught as 4D spacetime (one thing, not two separate things), but most of the examples (e.g. the train platform or barn-pole or twins 'paradoxs')are done in 2D spacetime (one each of space and time) to reduce the trigonometric overhead that is irrelevant to the points being made. Mass and length dilation are very much part of the teachings of SR. Gravity, acceleration, and non-locality are not part of the special case that is SR, and these topics are covered in GR teachings.One thing I noticed is space and time is always discussed when discussing SR. However, relativistic mass is rarely included in the discussion, even though it is part of the 3 part SR package. One may notice, SR is reduced to 2-D; space and time and not taught as 3-D; space, time and mass. This is the 2-D and 3-D clock problem in another guise. — wellwisher
Kinetic energy is definitely not absolute. An object has none in the frame in which it is at rest. Mass is completely frame dependent. Rest-mass is not, but you didn't say that. Spacetime on the other hand is invariant. Any event is the same event in any frame.Relativistic mass is connected to an energy balance; relativistic kinetic energy, which tells us that all references are not relative, but rather they are absolute at some level. Unlike space and time, Mass is an invariant.
This cannot be. If rocket R1 has a velocity V relative to R2, then R2 has velocity -V (not V) relative to R1. Each ship does not observe the same velocity when measuring the other.As an example, say I had two rocket ships in the dead of space with a relative velocity V.
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The same velocity is seen from either ship. — wellwisher
All this is ambiguous. Are you saying that one ship has twice the rest-mass of the other? No speed has been specified. For all I know, these ships are moving apart at a walking pace. So I cannot parse your example.If we add mass, such as one ship has mass M and the other side has mass 2M, the energy balance is not the same in both references, even with the same relative velocity. Reference preference will double or half the total energy. The references are made distinct by their relativistic mass and energy balance due to the impact of a common 2-D relative variable, on two different 1-D invariants.
Seems to be some asymmetrical claim concerning momentum and such, but again I cannot parse what exactly you imagine going on. I imagine two billiard balls (with masses 1 and 2) in a collision, doing Newtonian sort of inertial momentum exchange without loss from friction, but perhaps at (unspecified) relativistic speeds. Yes, SR would be wrong if total energy or momentum was different before than after the collision.This can be proven by collisions and how the system responds to the recoil. The 2M ship will always punt the 1M ship if it has the velocity. There will always be an absolute hierarchy in the recoil response. Relative reference is an illusion due to using 2-D SR, instead of 3-D SR.
Well that does seem to be a metaphysical question, and possibly doesn't have a correct answer even if it is unknowable. To me, spacetime seems not to be itself a thing that relates to other things, but is part of the relation itself between things that relate to each other in this universe. GR might have a good counter to this. If space is expanding and light has a speed relative to that space, then it is indeed a thing, despite it not being a thing under SR.But what is spacetime absent any perspectives? Is spacetime a mental construction of a perspective? — Harry Hindu
No, it is just a way of relating two events. SR only says that the ordering of two non-causally related events is frame dependent. — noAxioms
You seem to be confusing physical time (the thing measured in seconds or years in any physics equation) with metaphysical time (the assertion of a present time (or alternatively, a lack of it), and the unitless rate at which it moves if it exists).Right, and that's clearly a metaphysical statement, just like the opposing claim that there is an absolute ordering of events is a metaphysical statement. Whether the ordering of events is frame dependent or not, is an issue concerning the nature of being, existence, and is therefore an ontological question, thus metaphysical — Metaphysician Undercover
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