Yes to all of these. Much of human nature (and certainly not limited to humans) is the preference to rationalize the truth we find convenient rather than rationally seek actual truth. Think of all the people with contradictory philosophies who are nevertheless completely convinced that they're the ones in the right, with everybody else being wrong. They're all lying to themselves, and believing the lies. Not lying that their view is the correct one, but lying that it must be the correct one.Aren't there believable lies and unbelievable truths? I guess my question is: can we know that we aren't believing in falsehoods? Can the liars you mention, be believing in falsehoods that they misinterpret as truths? — FlaccidDoor
Prove to who/what? Would not you need to know that I exist in order to prove your knowledge of something to me?Can I then prove that I know this? — Cidat
Not claiming to be one, so I'll let them answer that. I make no claims of the unreality of anything.What would the phrases, "living under a rock", or "living in a bubble" mean for an anti-realist? — Harry Hindu
I favor a relational stance (Rovelli), so I'd say that other people exist to me, and I to them. We measure each other, so each exists relative to the other. This has nothing at all to do with people, mind, consciousness or epistemology. I exist relative to my keyboard because it measures me (I have a causal effect on it). I do not exist relative to the current state of Betelgeuse since that 'system' has not measured me. I suppose I exist to some future state of Betelgeuse, but not necessarily any future state.Are there other minds, or other bodies?
That's their claim it seems. They give meaning to the property of existence, but claim nothing has that property. I see little point in positing a property that nothing has, but other than that (and your wonderfully worded argument from incredulity aside), I see no contradiction in the stance, even if it isn't my stance.so anti-realism defeats itself by rejecting it's own existence as a belief? A non-existent nihilist? :lol: — Harry Hindu
No relation specified, so the statement is meaningless in my view. For something to exist objectively, it would have to exist in relation to, what?... something more encompassing than the universe at least. The proverbial view from nowhere it seems. Is a member of the set of all that exists, except the set cannot list itself for the reason given above.What do you mean by, "'existence of an objective reality" to say that it is meaningless?
It goes a bit beyond my expertise, but density affects overall gravitational effect to the extent that sufficient density suffices to overcome the effects of dark energy. The gravitational epoch epoch ended some billions of years ago and the expansion reached a minimum. The average density is now low enough that dark energy has the greater effect. The Hubble 'constant' will eventually settle on an actual constant of about 57 km/sec/mpc which corresponds to exponential expansion as opposed to the nearly linear expansion of the last several billion years.I am curious as to how the current density would have any influence on either the physical possibility of expansion, or the degree to which it occurs. In what way then are these two factors correlated, in particular? — Vessuvius
You mean a cyclic model? I'm not familiar with any such model that matches empirical evidence at the level of the accepted FLRW tunings. So I think you can make up any rules you want about what properties are preserved from one bang to the next.Good thought. Add to that, if you would; What does the vision of "multiple" contractions and expansions do if we focus on the velocity of (light in space) during these periods. — Don Wade
I've never heard of a model that posits contraction that doesn't accelerate to some kind of crunch singularity. Doesn't mean such a model doesn't exist, but I've never heard of it.Then the question of; how far does the universe contract before it starts to expand. Lots and lots of questions about the model.
Unsatisfied in the case of uniform distribution everywhere. The level of compression has nothing to do with it. The current density of the universe (about 6 protons per cubic meter) is enough to prevent expansion if it was that mass expanding into empty space. None of the material would have sufficient recession speed to exceed the escape velocity of the bounded mass that comprised the occupied part of the universe.unsatisfied in the case of a mass subject to an arbitrarily high-degree of compression — Vessuvius
The rate of increase in proper separation of a sufficiently distant (and visible) galaxy does indeed increase at a rate greater than c, but this still isn't superluminal since the light emitted by that galaxy in a direction away from us is moving away from us even faster. Nothing is outrunning any local light as you know.but as seen from the perspective of a fixed observer, relative to some far off point which is of so large a scale as to make the effects of such expansion dominate, for all intents and purposes it does appear to the observer as though a superluminal velocity is attained. — Vessuvius
I did, but there's not much appearance to it. We see redshift and brightness, both of which approach infinity and zero respecitively with subluminal local motion, and from that glean the speed. If we wait long enough, we see the object get smaller over time, but not so much that it appears to move super fast. Take GN-z11 which at redshift z=11 is the most distant galaxy know. Yet it subtends an angle that places it only about 3 billion light years away, making it appear to move quite slowly actually. Speed from appearances is a calculation relative to a model and a coordinate system, not something that can be directly measured just by looking at it.Do notice how I qualified my statement with likening its chosen object only as appearance, rather than an absolute.
Good grief, I never caught a suggestion of that in your posts.As my argument certainly wasn't that this reference frame is somehow privileged, or the only one of merit.
You're talking about objects outside the visible universe? A few will become visible as that radius expands, but most never will. As a non-realist, I cannot say that any of those objects specifically exist relative to us, but someone positing an objective state of the entire universe would say that these distant objects do exist, any one of which is receding from us at an arbitrarily high rate.The purpose for which I cited it was instead to highlight how ideas of causality are meaningless in these cases because the light-cone of the observer is forever prevented from accessing the image of such distant point-sources, and nothing more.
Again, the expansion rate is expressed in different units and thus is not a speed and cannot be meaningfully compared using a word like 'superluminal'.Under all circumstances then, and unless the rate of expansion slows considerably enough to no longer appear superluminal — Vessuvius
A reasonable definition, but still dependent on serveral assumptions such as your chosen interpretation of QM. An MWI guy for instance might say that the universe is the one universal wave function. Any follower of a realist interpretation (MWI being one of them) might say that the universe is all that is. I learn towards the RQM side, but I'm hesitant to say the universe is all that I measure since that confines it to the visible universe, and it needs to be meaningful to talk about more distant things, however much those things don't relate to us.Then what is the universe? That is, something other than it started with a big bang. — Don Wade
No model supports that. It is a naive interpretation that is quickly falsified.Does the universe exist in space
Time as well since it is the same thing. Few can get their heads around time being part of the universe rather than the universe existing in time, which reduces its ontology to that of a mere object.or does space exist in the universe?
Great example of trying to think of the universe as being contained by time. The universe is not an object. Spacetime is part of the structure that is the universe.Which came first, space, or the universe?
The big bang theory does not posit an explosion into space from some point in that space. Any simple description on the web will tell you this. The expansion of the universe is not a speed, and is measured in different units. Pfhorrest seems to know the physics.If we first assume the universe started with a Big Bang, then there should have been a shock-wave extending out from the center. — Don Wade
Science says no such thing. It makes no mention of a shock wave, which is something you get from say a star exploding in space. The universe isn't an object in space like a star.Science tells us that the shock-wave could not move faster than the speed of light. Did it?
The diameter of the visible part of the universe is about that. That volume includes all the material that can possibly ever have had a causal effect on us today. It doesn't mean we can see that far. Any light that has ever reached Earth up until the present has never been further from us than a proper distance of under 6 billion light years. Measured that way, the size of the visible universe is under a 6 BLY radius. We can only see these really distant galaxies because they were much closer than that distance back when they emitted the light that we're seeing now.the diameter of the universe is about 90 billion light years — T Clark
What light can or cannot do is irrelevant to my point. It is similar in other ways, which is why I brought it up. My arguments have not been based on light signals.The Rindler horizon's similarity to the event horizon is only insofar as any light travelling from the negative x direction cannot reach the x=0 worldline. That seems to be the entire basis for your argument that the space the photon travels in does not exist in the Rindler frame. — Kenosha Kid
Either car can say what the other is doing 'now', whether they can reach each other or not, so it is not the same at all. You continue to either not get my point, or you're deliberately evading it because its implications make you uncomfortable. So address the question I asked and not another:This is exactly the same as saying the car behind does not exist in the frame of the car in front because it can never reach it. It's the same argument.
I do not think this any more than I think the distance to a black hole EH is infinite because light from it will never reach an orbiting object. Pilot at x=1, RH at x=0. That's a constant finite distance of 1 (as I've said above), not an infinite distance as you suggest here.[At location x=0 in the ARF,] Time is infinitely dilated, and there is no light cone if there is zero time for light to get anywhere.
...
Nothing can ever get closer to it in its own proper frame. That's what I've been repeating in the last several posts.
— noAxioms
Yes, I know. And this is why your argument is incorrect. You seem to think that somehow, in the accelerating observer's frame, the distance from x=0 to x>0 is infinite in the proper frame because nothing from x<0 can reach x=0 — Kenosha Kid
I never said one car cannot be represented in the frame of the other. That's partly because they're the same car, the front and rear bumper, moving by definition at the same speed in the rigid car's own frame. But the rear bumper must accelerate harder than the front one. The car on the other side of the RH is what cannot be represented in the Rindler frame of the accelerating car. It cannot be keeping up with the accelerating (but stationary) car in the ARF. (Please tell me if any of these acronyms are confusing. I tire of typing the full words).akin to saying that if two cars were travelling in the same direction at the same speed, the car behind can't be represented in the rest frame of the car in front because it cannot reach it.
Yes, and the math says the acceleration cannot be finite at the RH, and which is why I said the length of my object extended almost 1 to the rear, but not all the way, because I wanted to avoid the infinite acceleration required there, with yes, infinite time dilation, just like at the EH of a black hole.For all finite accelerations within finite times, there is no infinite time dilation, no infinite length contraction, and any light approaching from the negative x-direction is getting closer, even if it cannot intersect the accelerating body's worldline in finite time. None of this is new: you can do all of the math in standard SR.
Good. I wasn't sure given your posts.Do you accept that the accelerating object is always stationary in its own frame?
— noAxioms
If you'd read me carefully, I not only accept it, I asserted it.
In the Minkowski frame, we know where the x=0 point is at t=0. It is at X=0, T=0, right? Think wiki picture if you don't know what I mean. Our object extends from X=2 back to X=0. It is effectively a long meter-stick in a rail gun, with a clock at each end and in the middle.This is all x=0 is in the rest frame of the moving body: a coordinate of the origin of that frame. It is not a singularity by any definition.
You continue to make erroneous assumptions about what I'm saying, so of course you think I'm getting something wrong. No, I never claim a pair of cars following each other are not in each other's reference frames. You totally don't get my point if that's your take.The problem is you don't understand the framework you're trying to use to make your point, so don't understand why your point is invalid.
I'm asking you to do some legwork in the example above, to compute which event corresponds to the cessation of acceleration at the rear of the object, and where that event falls in the original Minkowski diagram. I can do the same mathematics if you like, but the picture already shows the event in question.You have to do the legwork, not just try and jump to the crazy conclusions of some impossible edge cases and mistake that for the theory as a whole.
That's the same as the wiki picture, but with far less detail. Yes, in an arbitrary inertial reference frame as depicted in all these drawings, that entire line is the Rindler horizon. Under Rindler coordinate time (not shown in this new picture), the horizon is a coordinate singularity and is not comprised of a line like that. Time is infinitely dilated, and there is no light cone if there is zero time for light to get anywhere.If the above is indeed your source, I hope this convinces you that it is the entire x=0 (or t=infinity) line that is the Rindler horizon, not the X=x=0 point. — Kenosha Kid
Similarly, you can accelerate away from Earth to push the distant event horizon further away in the coordinate space of the thing accelerating away, but that just pushes it off. You can't turn off the acceleration of expansion like you can turn off the ship engine. Yes, I agree, the Rindler horizon exists for a continuously accelerating thing, and it ceases to exist when that condition goes away.Of course, this is not the same as a black hole’s event horizon in two very important respects. Firstly, it’s always possible to stop the spaceship accelerating
Nothing is inherently damaged by free-falling through a black hole event horizon. Are you under the impression otherwise? As I said, a small black hole will 'damage' you before you even get to the event horizon, but that's not the event horizon doing it to you. Orbit close enough to a neutron star and you're dead, no event horizon needed at all.Secondly, there is nothing corresponding to a black hole’s singularity to do any actual damage to anything passing through the horizon.
I was unaware of there being a boundary of the universe. In the ship case, yes, you have the option of turning off the acceleration. In the dark energy case, you do not, so no matter what you choose to do, there are points in space in no significant gravity well from which light can never reach you. This is not true in Minkowski spacetime.This is not a real event horizon like the boundary of the universe or that of a black hole.
No. My bold. This is where you're wrong. Nothing can ever get closer to it in its own proper frame. That's what I've been repeating in the last several posts.It is an artificial horizon based on the decision of the ship to constantly accelerate away from everything else. Things effectively cannot reach it (cannot reach x=0) because it moves away from them. However, things can get closer to it (move toward x=0) in its own proper frame.
No argument.Because lightspeed is not observer-independent in non-intertial frames
Do you accept that the accelerating object is always stationary in its own frame? I know it's not an inertial frame, but if you take any event on the ship (say the pilot at x=1 at time t=2, his clock), and you reference the one inertial frame in which the pilot is momentarily stationary at that event, then every location along the ship is simultaneously (relative to that IRF) stationary. In that frame, the Rindler horizon is still a distance of 1 behind the pilot, regardless of the time that has passed.It is equivalent, in inertial motion, to saying that an object that is following me with the same speed as me doesn't reach me. Or, in my rest frame, an object to my left is not occupying the same space as me.
Not the one at the rear. Time is stopped there in that coordinate system, and the photon makes no better progress than one at a black hole horizon trying to get out. A photon anywhere forward of that does indeed make progress and will eventually reach any part of the ship.The photon is still in the moving observer's coordinate system
The accelerating observer goes off the right side at about t=1.25, where proper distance to the horizon is still exactly x=1 behind him, unchanged. In another frame, the ship is moving, so of course the distance is length contracted, which would be true if the thing was accelerating or not. As I said, you don't need to wait for it's speed to change. Just do a Lorentz transform to a different arbitrary frame and you can contract that distance as much as you like, even at T=0.Follow that worldline to the edge of the diagram. Now, tell me, is it closer to the horizon or further away? — Kenosha Kid
Only in a frame different than the ship frame. That frame is thus arbitrary, and irrelevant to our observer's measure of the distance to the event horizon.Yes, the worldline is bending to the right (increasing X). But the horizon is always moving to the right more quickly
It is a singularity, so this does not follow. Suppose the ship extends all the way back to the horizon. Where is the rear of the ship at t=1 (as measured by our observer at x=1)? Follow the t=1 line-of-simultaneity back to x=0 in the diagram. Where does it go? It goes to the same event where it was at t=0, the left-most event in the picture. That shows which event is approached as you move backwards in the accelerating frame. The actual event there is a singularity, with undefined time, so asking which horizon event is simultaneous with our observer at t=1.25 is meaningless, but I can point to the event in your arbitrary Minkowski frame that is approached.The Rindler horizon is not X=0. X=0 lies on the horizon at T=0.
Unclear what you mean by this. Acceleration is continuous, not something that is 'simultaneous'. At all times in ship frame, all parts of the ship are moving at the exact same speed, and thus the entire ship is always stationary in its own accelerating frame. The ship is said to be Born-rigid.So what you mean is that we choose a frame of reference where the acceleration is not simultaneous
I don't 'think' that. It is a coordinate singularity, just like the one 16 billion light years away, and just like the event horizon of a black hole. The center of a black hole on the other hand is an example of a physical singularity. A coordinate singularity only exists in certain coordinate systems, and there's nothing actually physically weird going on at them. Hence people can drop into a sufficiently large black hole without really noticing any obvious immediate change, not even if they're looking out of the window. A small one of course will kill you before you get there.Your interpretation is still erroneous though, because you still think the Rindler horizon is a spatial horizon.
Only to the right in this case, not the left. Can't go past x=0. For the same reason, I cannot have a rigid rod much longer than about 27BLY with us stationary at the midpoint. It is an interesting exercise to figure out how to position a rod of twice that length without strain. It can be done. I digress.The length of the ship may for all intents and purposes be infinite in the origin's rest frame.
I assume 'more rapid' means higher acceleration (and associated rate of change in rapidity) and not high-speed since the ship is always stationary along its entire length in its own frame (the frame in which rapidity is meaningful), so there is no different frame of reference between one part and another. There is a variable rapidity change rate that is dependent on the different parts of the ship. Over at x=1, acceleration is 1, so the rapidity there is a function of how long it's been doing that between two times as measured by a clock there. At higher acceleration parts of the ship, the same time interval results in a greater rapidity change over the same interval on again a local clock. The rapidity of light is infinite, but I don't know what 'rapidity of photon emission' means.As you move to more rapid parts of the ship through one part's frame of reference, you approach but never reach the rapidity of photon emission
It contains all events in the Minkowski frame, but in real spacetime, light should be able to get here from far away given enough time, but it doesn't in reality, so the Minkowski model fails to describe the large-scale structure of our universe. It is, and always has been, a model of local spacetime.You cannot map out an entire Minkowski space from the light cone of one event. That's fine because that's not what a Minkowski space is: it is a frame of reference containing all events, not just one.
Nonsense. Show me the definition that says this.You cannot, by definition, "accelerate away from the Rindler horizon". — Kenosha Kid
It is not. It, like any other event horizon, is a boundary in spacetime separating events that can have a causal effect on a given worldline and those events that cannot. So there is an event horizon currently about 16 billion light years distant beyond which no event can ever have a causal effect on Earth (the worldline in question here). This is due to the acceleration of Earth away from locations more distant than that. The only reason that is technically not a Rindler horizon is that Earth's acceleration is not constant, but is instead increasing.That horizon is an acceleration limit.
Lemme dig out a pic to explain.
The picture depicts the Rindler coordinates of one body, one worldline. Yes, other bodies to the left and right, at different accelerations, would trace those other worldlines, but their times would not correspond to the times plotted for the one object at X = proper distance of 1. The t= values are for that body and are not shown for any of the other worldlines.X here is position, T time in a Minkowski frame. The hyperbola are worldlines of bodies undergoing constant proper acceleration. t here is the proper time of the accelerating body.
After any amount of time, the proper distance between our accelerating body and the Rindler horizon remains 1. It is a constant. Sure, if you choose an inertial frame where this whole setup is moving fast, you can length contract it down to any size you like, but you don't need to wait a long time for that. Just choose a different frame. From the perspective of our constantly accelerating observer, the horizon remains at a fixed distance behind him (in the direction opposite his acceleration vector).As the body is accelerated for longer and longer, T and t increase. At infinity, they converge at the event horizon
You are unaware of acceleration not being constant along the length of an accelerating rigid object? This is a simple consequence of special relativity. Read up on Bell's paradox (the two ships accelerating while attached by string). It illustrates most of the concepts involved.So it's difficult to make sense of what you're saying. I get that you're trying to simulate gravity here. If you have a long ship pointed radially outward from a black hole, the bottom undergoes more acceleration than the top. I can't envisage, in the absence of gravity, how you can make a single object do the same.
And connect them with string, yes. Unfortunately, the clock of only one of those ships will correspond to the times depicted in the picture above.Perhaps a fleet of ships would be better. Non-rigid bodies were among the original hypothetical objects of the equivalence principle for this very reason.
What?? The body is accelerating away from the Rindler horizon. It's not approaching it. That's why I call the direction of it 'down'.in the latter it is the coordinate approached by an accelerating body as t goes to infinity. — Kenosha Kid
You have links where this wording is used? I'm trying to make sense of it.All accelerations lead to the horizon at eternity.
Not sure what worldlines have to do with this. Yes, the (constant) proper distance to the Rindler horizon of a small object undergoing continuous proper acceleration is a function of the magnitude of that acceleration. An extended object such as I described doesn't have a worldline so much as a 'world-swath' of sorts (the accelerated coordinate system of which I spoke) since each part of the object traces different worldlines, none of which intersect the worldlines of other parts.The Rindler horizon can be reached one of two ways. As the worldline of a body undergoing acceleration, it is reached as that acceleration becomes infinite. — Kenosha Kid
Sorry, I'm unfamiliar with that term. Google was no help.This is the light-line (e.g. photon creation).
Acceleration must be greater further 'down'. Less in the 'up' direction, so the 'ship' can be as long in that direction as required to serve its purpose as a coordinate system for an accelerated reference frame. It is somewhat equivalent to my weight being greater on the ground floor of a building than it is at a higher floor. Clocks run faster in the higher low-acceleration portions of the object than the clocks in higher-acceleration locations further down.Why is your apparently infinitely long ship accelerating more the further away from x=0 you go?
The product of the distance to the horizon and the inverse acceleration will equal c^2. So c^2 / 9.8m/sec^2 = ~9.2e15 meters which is not quite a light year.And why do you think it is infinitely accelerating one LY from x=0?
Let me put it this way:If someone outside the hole applies the appropriate transformations to their forever-falling astronaut, they will find that form the astronaut's perspective the fall is finite.
If the astronaut applies the appropriate transformation, they will find that for someone outside the hoel the fall takes forever - or more.
I don't see any inconsistency. What did I miss? — Banno
No such transformation exists since the astronaut never crosses the event horizon, so there can be no transformation of events beyond that from either frame to the other.If someone outside the hole applies the appropriate transformations to their forever-falling astronaut, they will find that form the astronaut's perspective the fall is finite. — Banno
He cannot apply the transformation, which is what is meant by events that cannot be consistently assigned a spot on the outside observer's timeline. His events do not exist at all on that outside timeline.If the astronaut applies the appropriate transformation, they will find that for someone outside the hoel the fall takes forever - or more.
Exactly, which is why I say that inertial frames do not describe the universe.That is a limitation of inertial frames, not of the physical universe. — Kenosha Kid
The material/energy from which they are comprised very much did.Also, you seem to think that if we see light from a star 13.4B LY away, there must have been a time when that star was very close to us. That is not right. It didn't have to "move 13.4 BLY away and then send a signal back". Stars did not emerge from the big bang.
A coordinate system doesn't propagate. You mean light propagates at c in a coordinate system. This is more or less true for an intertial coordinate system, with variation on speed due to changes in gravitational potential. So light from another star often gets to us at slightly greater than c due to most of the trip taking place in space at higher gravitational potential than we have here.the current inertial frame of Earth won't do: There are objects beyond our event horizon (events from which light can never reach us even in infinite time).
— noAxioms
I don't see why an absolute coordinate system would be obligated to propagate that the speed of light. — Banno
They do in some coordinate systems, but they don't have a particular position in our inertial frame.Hence, those events that are beyond our event horizon nevertheless might have a particular position in an absolute coordinate system.
No coordinate system works. That's been my point. Every choice leaves parts of spacetime unordered. As Enai puts it: There are always events that cannot be consistently assigned a spot on any choice of objective timeline.The answer to your question seems to me to be that any coordinate system might be set up as absolute; relativistic physics specifies how we translate from any frame to any other frame, so calling any frame of reference absolute becomes simply irrelevant.
I need your opinion then. OK a foliation based on the perspective some outside observer cannot account for events beyond the event horizon, and thus seems to not to be a viable candidate for an objective foliation of all of spactime. Is there some other coordinate system that is actually up to the task? If not, is this a valid falsification of objective space and time such as is proposed by Lorentz Ether Theory? This is not even including those interpretations that additionally posit a preferred moment in time.Worse, at the event horizon, time dilation becomes so extremely that, from the perspective of the outside observer, events there do not ever occur- not even after an infinite amount of time has passed. — Enai De A Lukal
There are at least six kinds of multiverses discussed. Tegmark enumerated them as Level 1 (other Hubble spheres), Level 2 (other bubbles in eternal inflation theory), Level 3 (other quantum worlds), and Level 4 (other unrelated structures). There is also the Smolin evolutionary thing where the interiors of black holes are considered to be other universes. If Level 1 is our universe but spatially 'not here', then there should be a Level 0 which is our universe but temporally 'not now'. That's six at least.could multiverse theories be an attempt to explain causation prior to the Big Bang? — 3017amen
Whether it is interpreted as block or not seems immaterial. Look into eternal inflation theory. Wiki has a terse entry on it. I found a more comprehensive description in Tegmark's Mathematical Universe with some illustrations that help with visualization. There are other 'universes' that have different number of spatial and temporal dimensions, and the vast majority of them cannot produce complex physical states.As a very rudimentary example, what in theory, would exist outside of the block universe?
GN-z11 is about 2/3 of the way to the edge of the visible universe. Immediately after inflation, the size of the visible universe was anywhere from a grain of sand to a city block, depending on your model. A 1 meter head start isn't going to get that object (or rather, the material that would eventually become it) out far enough to be 13.4 GLY away when that light is emitten only 400 MYr laterThe wiki site says it was emitted 13.4 billion years ago, but it could not have got far enough away in only 400M years for light to take that long. Of course, wiki isn't using inertial coordinates when making that statement, so kindly describe the situation in those terms. Where is the emission event?
— noAxioms
Right. So, first, there was a supposed stupendous inflation period in the early universe that cannot be described by any inertial frame. — Kenosha Kid
OK, you're allowed to give it more time, but how long do you want? It's going to take 13.4 billion years to get far enough away, at which point there's no time left to send the light back to us here.Second, it is unexpected that the galaxy would have formed 400M years after the big bang
Actually it does stop it. It's not a mystery, it's a physical impossibility in an inertial coordinate system for something to move 13.4 BLY away and then send a signal back, all in 13.8 BYr. Waving your hand around and spreading 'I don't know/it's a mystery' dust all over the place isn't a viable model.i.e. it is a cosmological and astronomical mystery but a) that doesn't stop it being 13.4 billion light years away from us when it did form
You don't comprehend my explanation, so I'll try to comprehend your vision.It's perfectly appropriate for that: that's just light further outside the light cone. It being further away just means its further away. Minkowski spacetime is not appropriate for gravity, though. — Kenosha Kid
There is no cosmic expansion under inertial spacetime. There is only an explosion of stuff from a point, with nothing moving at faster than c.I don't see how that is a consequence of a global inertial frame. Light may not reach us for other reasons unrelated to it, one of which is the cosmic expansion of the universe being faster than light. — Mr Bee
They are indeed not the same. The boundary of our inertial frame is much less than the 47 BLY radius of the observerable universe, and even less than the ~16 BLY distance to the event horizon. The current radius of our inertial frame must be 13.8 BLY because nothing outside that radius could have come from the big bang without moving faster than c, and nothing moves faster than c in an inertial frame.If there is a boundary to an inertial frame, then event outside that boundary do not exist in that frame.
— noAxioms
You seem to be mixing up the boundary of the observable universe with the "boundary" of an inertial frame, the latter of which I don't really understand. They are both not the same.
Your understanding here is fine. Nobody is proposing a closed timelike curve. Any foliation, objective or not, would preclude that.My understanding is that it is mainly spacetimes with closed timelike curves that preclude the existence of global hypersurfaces, but I haven't heard anything about black holes doing the same.
First of all, I meant dropping a clock, which seem more useful than dropping a glowing rock. I used a rock at first and neglected to change them all to 'clock'. But it moves like the rock: not under propulsion or anything.I got lost at:
The [clock] is dropped from a hovering location outside, which shines light down on the dropped clock.
— noAxioms
It's not clear what frame of reference we're in here. — Kenosha Kid
I've caused confusion. The rock and the dropped clock are the same thing. The space station can watch it fall in, but if it reads time T when it crosses the event horizon, then the space station will never see the clock read anything after T. It will appear from the space station to slow and approach but never reach T. Event B is that clock when it reads T+1.From the perspective of an observer outside the event horizon (with some magic blackholescope), the clock will accelerate toward the singularity and run slower and slower. Any photons emitted from the rock (which is getting further and further away from the clock) will still travel at the speed of light and catch up with the clock, because the clock cannot move at the speed of light.
Again, they are the same thing, so the clock indeed will eventually reach the abrupt end of time and tick it's last, so to speak. This is assuming the clock is a point device that isn't destroyed by excessive violence like tidal forces before it gets to the singularity.From the rest frame of the clock, it is in perpetual free fall. Eventually the rock will simply recede so far into the distance it cannot be detected.
I said it is a psychological choice when I decide what components comprise a system or not. The physics of the relationalism has zero to do with this choice.So your perspective is more psychological and related to our conscious experiences. Is this a Berkeley or Kantian strategy you are gleaning from in treating spacetime as a fundamental psychological process but nothing more? — substantivalism
I find the acquisition of new information to be a contradiction in the solipsistic idealist view. Say you find a tomb full of Egyptian writing and spend years trying to decipher it. You've memorized every character and could reproduce it at will from memory, yet you cannot read it. After years of study, you finally break the code and learn the language, and suddenly there is information that was always there, but suddenly is meaningful to you. That implies there is something out there that didn't come from you. I cannot dream of a coherent language that I don't yet understand. Something else has to have produced that tomb, which contradicts your experience being more fundamental than the noumena. That contradiction sinks the view in my opinion.I get that this philosophical viewpoint is not emprically well-founded and never could be (it would be consistent with any personal experience) but it always felt relatively possible. — substantivalism
Time slows (is more dilated) when deep in a gravity well, So clocks on Earth for instance run objectively slower than say GPS clocks (which are very high up and not moving fast). Those GPS clocks are slowed due to their orbital motion, but the gravity effect is greater at that altitude. Clocks on the ISS run slower than the ones on the ground due to minimal gravitational potential difference in low orbit, coupled with significant dilation from the higher orbital velocity. So at an altitude of 1.5 R (R being Earth's radius), the two effects cancel out and orbiting clocks can be synced indefinitely with those on the ground.Two quick questions:
1. Does black hole time travel increase or decrease Time ( I can't remember)?
2. Do black holes contribute to Multiverse theories at all? — 3017amen
You've drawn flat Minkowski spacetime (with arbitrary inertial frame) in which light from any spatial location will reach any other location. That makes it an inappropriate model of the large scale universe where light that is currently say 17 GLY away will never get here, not in 17 billion years or ever.As you can see, any event can be located in an inertial frame, but only those events within our past light cone can be detected by us now. Events outside that cone are still in the reference frame but cannot influence us. — Kenosha Kid
You can still foliate reasonable gravitation in 'bent' Minkowski spacetime, but not black holes. So for instance, a device measuring absolute time here on Earth would run apparently faster than one on the surface of Saturn due to the lower gravitational potential here on Earth. The same device on a ship with relativistic absolute speed would similarly appear to run faster (than the clock next to it) than it would if the ship had low peculiar velocity.Gravitation can't be accurately described by inertial frames but require curvilinear coordinate systems. — Kenosha Kid
There's no requirement for light to reach any location from any other since there are very much cases where that does not occur. My point was that in an inertial frame, light can reach location X from Y given enough time, and thus such a model is not a model of our universe.I don't get this. Why would they have to reach us? — Mr Bee
If there is a boundary to an inertial frame, then event outside that boundary do not exist in that frame. An inertial frame does support cosmic expansion, but it does not support acceleration of that expansion. So given no such acceleration, there would be no event horizon and light will eventually get from location X to Y given time. And even locally, an inertial frame cannot foliate the interior of black holes, so it fails twice.The light will never reach us because of cosmic expansion, so the fact that we don't see them doesn't mean they don't exist.
There are indeed ways to do it with a single black hole, but you must assume the black hole is at some kind of privileged location. So consider 3 events: A clock is dropped into a black hole. Event A is that clock 1 second (measured on that clock) after passing the event horizon. The black hole is big enough that it survives at least one second. The rock is dropped from a hovering location outside, which shines light down on the dropped clock. At some point the last light is emitted from this location that will catch up to the dropped clock before it hits the singularity. Event B is that hovering location 1 second after that last light goes out.I'm not sure about that. As far as I know, any spacetime that doesn't allow for closed timelike curves is open to being sliced into global hypersurfaces.
None perceived. I agree with your comment that there is a general aversion to solipsism among philosophers, and I was just pointing out that the aversion itself is a poor reason to reject any view. I personally find the view self contradictory, and reject it for that reason.I mean no disrespect — substantivalism
Yes, but again, I identify that as a personal bias, and therefore not good grounds for rejection. Who knows, maybe the universe is made for us. That possibility must be considered, but positing such doesn't seem to explain anything better than more plausible views.We see eye to eye on the geocentrism and anthropocentrism of view points as I also find metaphysics which make us highly centered in the grander scheme of things likewise also highly suspect.
Where I end (spatially, not temporally) is an interesting problem. It seems to be a purely abstract thing. The guy in the sci-fi show straps a time travel device to his wrist and it takes him and his clothes and briefcase to some other time, but doesn't take the nearby shrubbery. How does the device know what's you and what's not? It's intuitive to us, but in trying to tell a device how to do it, it turns out it isn't obvious at all.It's like a sorites problem of sorts to attempt to specify where you end and the greater worldly environment begins.
Just because it's distasteful doesn't mean it's wrong. But I think there are serious logical problems with the solipsistic view, coupled with a personal bias against any sort of geocentrism, anthropocentrism, or any other view asserting us having a privileged status.Yeah, solipsism really makes a philosopher run for the hills doesn't it. — substantivalism
If I want to be formal, I had to find a definition of 'me' that didn't violate the law of identity, and it pretty much makes a hash of the way 'me' is used in everyday language. Language is littered with unstated premises, all of which I question (hence my user name), and most of which I cannot justify.It was just the words being used by you such as 'me' that made me think you were taking a sort of idealist direction for you metaphysics but I was wrong there.
The same way my thermostat turns on the heat in the winter despite the fact that it's warm in mid-May. No need for a 'measurment' spotlight to crawl up the thermostat's worldline in order to allow it to function.How does that work if your consciousness is not crawling up a worldline? — Luke
If that's how it works, it is still a form of presentism, with the consciousness (not part of the block) acting as the spotlight and defining a present. Dualism doesn't fit well at all with eternalism under which the entire worldline of a person is conscious. It would be rather absurd to say that the 1997 portionAll that is left to account for is the motion of one's consciousness crawling upward along the worldline. — Luke
Eternalism does not suggest that every state of a person along his worldline experiences every time in the worldline. That would be empirically quite different, wouldn't it?Or alternatively we are stages which are located at a single instant and experience only that one instant of time while other counterparts experience the others. You know, cause experiencing every moment has the whole obviously wrong thing going on with us experiencing only one moment. — Mr Bee
If B-theorist eternalist are right, and we are beings that only experience one moment in time — ChatteringMonkey
Ouch. Under eternalism, we beings are worldlines, and experience every moment along that worldline. So iff I define 'me' to be my worldline, then I am present at some event in 1995 and also 2021, and I experience those events and all others. There is none of this 'privy to one moment', which again smacks of a preferred moment.we are only privy to one moment and so experience it as passage of time. — ChatteringMonkey
I'd say 'has equal ontological status'. There's a difference to us non-realists.The eternalist says that every point in time is equally real — ChatteringMonkey
They're interpretations actually, despite all the literature referring to them as theories. No, neither interpretation can be falsified since they do not make distinct empirical predictions. All attempts to discredit one or the other proceed along logical grounds, not scientific ones.Hate to butt in, however, these are all unproven theories? — Outlander
The spotlight defines a present (preferred) moment, which makes it presentism, just like all the other variants described in the OP. Eternalism asserts the lack of a present,and doesn't seem to have so many variants.If you perhaps fancy and have the time, could you explain in layman's terms. What differentiates eternalism from the moving spotlight theory?
Under eternalism, such words are only relations, like Earth, 1927 is in the future of Earth, 1925.Both have past, present, future.
Moving spotlight (and pretty much the rest of your list) has a preferred moment. Eternalism does not.Please enlighten me as to the difference between Eternalism and the Moving Spotlight theory. — Luke
I implied no such thing. I said there is movement. I made no reference to temporal passage, which again is a term only meaningful to views that posit a preferred moment.You seem to be implying that temporal passage is possible under Eternalism? How so?
I smell a begging argument coming on. You did this fairly large post, but then never actually get around to this point until the last couple sentences.I wanted to lay out my view of why Eternalism logically precludes motion. — Luke
You can add me to that list. At noon, the mug has coffee in it. At 1pm the mug is in the dishwasher. How is that not motion of the mug?Some members of this site, including SophistiCat and @Douglas Alan have previously claimed that Eternalism does not preclude motion.
Somewhere between noon and 1 obviously (in my example). Every moment of it in fact, since at no time is any object actually stationary, what with Earth spinning and accelearting and all.In that case, my question is: when does motion occur according to Eternalism?
There's the begging I smelled. Everything here are A-series references which assumes the conclusion you're trying to demonstrate.It cannot be at the present moment, because motion or temporal passage at the present moment implies the A-Theory, making it not Eternalism, but the Moving Spotlight theory instead. So, does Eternalist motion occur in the past or the future somehow?
I don't think there's anything 'being' me, so does that mean I shouldn't consider myself conscious?Firstly, I don't know if communication per se is an indication of consciousness meant here as the existence of an inner life - what is it like to be something. — TheMadFool