AbstractDreamer

12 hours ago, swansont said:

How would you test for non-constant time?

How would you test for constant time?

32 minutes ago, swansont said:

No, because GR has evidence to support that it works.

But GR works. Tests of the equivalence principle don’t show any problems. Clocks that are supposed to agree, agree.

There is no evidence that "non-constant function of time over time" doesn't work.

GR, experimentally, works with "non-constant function of time over time" too.

Would you agree with the above statements?

3 hours ago, MigL said:

As the EH is not an 'edge' to space-time, but rather a 'threshold', any curvature continues along with the global geometry through the threshold; BHs do experience gravity from external objects.

So "Schwarzschild spacetime is entirely empty vacuum everywhere", but Schwarzschild spacetime is not necessarily uniform or symmetrical?  For example a source of significant curvature on one side, external of the blackhole would create asymmetry of the spacetime beneath the EH?

So in a circumstance when spacetime is significantly asymmetric under the EH around the singularity, and when spacetime is significantly asymmetric above the EH around the black hole; would a non-rotating Schwarzschild blackhole still appear perfectly spherical?

2 hours ago, MigL said:

Then why do you think it would make a difference ?

A Einstein based GR on the assumptions of homogeneity ( same in all locations oruniformity of structure ) and isotropy ( same in all directions or uniformity of properties ) of the universe.

Because is it possible that a "non-constant time function over time" could model observed space expansion?   It would remain experimentally untestable, unless your experiment spanned a volume of space time that contained such expansion, yet somehow remained unaffected by the expansion.   

I cant really grasp the scale that expansion works on, but I would wildly guess that it appears to me to break homogeneity at least on a scale reasonable local to expansion.  Of course the argument for homogeneity is to choose a larger scale.

If spacetime is a continuum, then homogeneity in space is also homogeneity in time.  How do we can reconcile homogeneity in time, when we have a universe that apparently expands locally or globally, or at least inflated globally?  It's appearance and properties shortly after t=0 is much different that today.

2 hours ago, swansont said:

AFAIK there are none. Certainly none with evidence to support them.

In the same way that GR has no evidence to support that time is constant over time?

2 hours ago, swansont said:

Einstein’s equivalence principle

Not sure how this relates at all.

What is the principle in GR that assumes time is constant over time?  I don't think there is one.  Indeed it doesn't need one... experimentally.

However it does assume this, right?

On a similar notion, what evidence do we have that any unit is constant over itself?  Take distance for example.   At a large enough scale that experiences significant expansion, something that measures D units using measurements within that expansion, might measure D+E relative to observations from without that expansion.

What is the principle of realism that states non-theoretical units are uniform from zero to infinity?  

So anything crossing into the EH joins/shares its charge, mass, angular momentum with the single entire entity of the blackhole?

Does a black hole experience gravitation from objects outside its EH? If some nearby spacetime is curved by some other object, does this curvature extend beyond the EH?  As a graviton wave crosses into the EH, does the black hole grow in energy?  Which if any of its properties will change?

If the black hole was of sufficient "volume? surface area?" where the external curvature at one location was significantly different from the other "side?", and taking the blackhole as a single non-quantisable entity, would this cause one part of the black hole to "move" in a different direction to another part of the black hole?  Would this cause pressure or stress within the black hole?

On 9/10/2022 at 9:30 PM, MigL said:

Absent other variables which influence it, how would you be able to tell if time is constant over time ?

GR, a geometric theory of gravity, tells us that gravity is mostly due to time axis curvature.
IOW, time progresses differently in flat space-time, as opposed to curved space-time, and is definitely not constant.

I don't think you could tell experimentally.  But my question is really: If we assume that time is constant over time, WHY do we assume that?  What evidence is there?  I'm guessing there is no evidence, hence my questions here.  As physics is based on evidence, why is this one assumption exempt?  What are the theories in the scientific community that considers time over time as non constant?

I'll posit again that motion or potential changing the experience of time is missing the point.   In a thought experiment, take two volumes of spacetime, both identical in motion and gravitation potential, and identical all other properties EXCEPT in the property of time.  One volume is close to t=0, and the other volume is close to t=infinity.

Theoretically or mathematically, but not experimentally, comparing the progress of time in each volume relative to the other volume, why do we assume they are the same?

2 minutes ago, swansont said:

Your state of motion or your potential can change over time.

Thank you for this, but I'm not talking about motion or potential. Or either of them changing over time.

1 minute ago, swansont said:

Both of the ones I quoted in my previous post, both of which asked if time was constant. (the third statement wasn’t actually a question)

 

I stated no such thing. Once you know that time depends on certain factors, it answers the question of whether time is constant. Whether there are more variables is a completely different question.

The first question was whether GR is premised on time being constant 

The second question was if there is any basis that time is constant.

Both questions are about time being constant over time, which I believe you have either misunderstood or ignored, hence your answer about time being dependent on your motion relative to another observer, and on your gravitational potential.

With respect, you are repeatedly selecting only some of my questions, and then providing answers that do not relate to those questions.

48 minutes ago, swansont said:

As I said earlier, we know time depends on your motion relative to another observer, and on your gravitational potential.

 

 

So you are saying categorically it (time) cannot depend on anything else, such as for example a function of itself?

53 minutes ago, swansont said:

To the extent that the question makes sense, we know that the answer is no.

 

Which of my questions is "no" the answer to?

How do the equations in GR allow for Proper Time that has a world line that spans two manifolds between which have observed space expansion?

So do the equations of General Relativity premise on the propagation of time being constant since the Big Bang?  That is, the premise that the axes of time are uniform between t=0 and t=infinity.

Is there any logical or reasonable basis upon which to assume that the propagation of time is a constant since the Big Bang?

If we accept that the spacetime continuum experiences a stretching of its axes when observing space expansion, why should we assume that its only the axes of space that is stretched, and that the axes of time remain uniform?

I have read that Blackholes have properties Mass, Charge and Angular Momentum, and that the Event Horizon is the boundary between where spacetime is curved so much that all paths converge, and between where there are some paths that could diverge.

Putting aside Hawking Radiation, apparently "nothing?" can leave the EH.  As far as I understand, the "nothing" refers to anything with mass and any form of electromagnetism such as light, and perhaps categories of other things.

So if electromagnetic waves cannot exit the EH, how does the charge of the Blackhole create the electromagnetic effect that propagates around the black hole due to that charge?

Likewise with mass and curvature, how does the density of the mass "inside" the black hole's EH manage to curve the space time outside the EH, if the EH is a boundary where all paths converge?  If you were a bit mass under the EH, and you tried to emit your gravitational wave through the EH, that wave would have a geodesic that remains within the EH.  If that wave never exits the EH, and if ALL waves never exit the EH, what is causing the gravitational effect of the blackhole as experienced by objects outside the EH?

17 hours ago, swansont said:

But if this rate changes for everything, why does it matter? Everything that changes is referenced to that rate. And of it's static, it doesn't matter at all.

 

Then it's tied to something that's not measurable. If you use an arbitrary rate, it will be some constant multiplicative of the rate we observe, which is just a constant of proportionality that gets lumped in with any other constants of proportionality. It's meaningless from a physical point of view.

It didn't think it does matter.  That's why I'm asking questions. If learned minds can also agree it doesn't matter, I'll take it as a reasonable basis to continue using it as a premise to my end question about dark energy.

It's meaningless perhaps today from anything directly measurable within spacetime.  But theoretically, would you agree there if there is a conceptual idea of the rate of change of time, that there is no basis to assume it is constant at different moments/periods in time?

Something is seemingly stretching the axes of spacetime.  With a leap of faith, it is possible this entity is outside of time?  What if this entity was not directly measurable, but its effect on the measurable universe CAN be observed.  We can observe space expansion occurring in the measurable universe, it is possible that we cannot directly measure what is causing it?

Can we directly measure a singularity? I don't think so.   A singularity exists outside of spacetime as its gravitational potential is undefined.  Can we observe the effects of a singularity?  Maybe not.  What exactly does a singularity do?

Perhaps we cant measure dark energy directly.  Perhaps dark energy is outside of spacetime as it's motion is undefined.  Perhaps its effect can be observed through spacetime expansion.

Is it possible that singularities are the source of dark energy?

7 minutes ago, swansont said:

There is no theoretical or experimental evidence that this is the case. If there was some universal change in time and it affected everyone, how would we notice it? And if it was not universal, we should notice it.

 

Right, we can't notice it!  We are all "trapped" in the same rate of change of time.   The unit of time could be doubling, halving, exponential, logarithmic.  We would not be able to observe it, and it would have not consequence to anything within our spacetime.   If there is no theoretical or experimental evidence that this is the case, then why should there be theoretical or experimental evidence that this isn't the case?  What basis do we have to assume the rate of time is constant?

So it doesn't really break any theories to consider the rate of time as non-constant, as it is not measurable.  So why not pick an arbitrary function of this rate of time and tie it into dark energy with undefined motion, to explain space expansion?  What are the main arguments that oppose this approach?

19 hours ago, MigL said:

Are you really asking whether the 'unit' of time is getting larger, or smaller, as time progresses ?

And further, does it really matter ?

Yes, I think that is my question.  And no, I don't think it matters at all to the standard model.  Which is why I'm asking the question... if it doesn't matter, what are the theories that follow if the "unit" of time does or does not change, as time progresses.  And can dark energy exist outside of time.  And in the possibility that dark energy can exist outside of time, could it cause or be caused by time accelerating?

3 hours ago, swansont said:

As I pointed out before, time passes at different rates in different frames of reference, and this has been shown empirically.

Regardless of whatever conjecture you might have, you need to start out from what we have already shown.

I don't know what "undefined motion" means

I accept that the passing of time is relative, and therefore it changes. That is, time dilates.  But this argument does not refute my question.

My question is more:  For a situation where the effect of time dilation due to relative motion is zero, is there no possibility that the rate of change of time is variable -  specifically, a rate that has a denominator value "outside" of time.

Undefined motion akin to gravitational potential at a singularity.  Do singularities have undefined gravitational potential?  Would this mean singularities exist "outside" of time?  Black holes will eventually decay, but what happens to the singularity?

10 hours ago, Sensei said:

Speed is distance in meters divided by time in seconds. So it does apply to time curve f(t')=t.. If time at some point, goes faster or slower, then you need another clock, which will tell how much they differ, when they try to synchronize their clocks once again after re-meeting.

My choice of the word "speed" is poor.   I should have said "rate of change per something else".

Density is mass/volume.  If mass increases, it is denser.

Speed is distance/time.  If distance increases, it is faster.

"rate of change of time per Gap" is time/Gap.  If time increase, it is more "rate of change of time per Gap"

But I don't think it needs to be another clock.  It just needs to be another unit, measureable or not.   But for conceptual purposes, lets call it Imaginary Time or iT, where iT is orthogonal to T.

16 hours ago, joigus said:

Feynman bitterly complained about ideas like this: Maybe time is not continuous. Maybe there are other dimensions. Maybe spacetime is a fractal...

Yes. But how does it relate to everything else we know? What the auxiliary hypothesis that gets you out of this arbitrariness/circularity?

 

It relates via my wildly speculative question about variable rate of time and space expansion -  that is, whether it is possible that the unit of time changes over time with respect to a unit of something else outside of time. And, if there are entities that exist outside of time (such as an imaginary entity with undefined motion), could they be linked to dark energy somehow.  And ultimately, could something like a variable rate of time be the cause or the effect of space expansion.

23 hours ago, joigus said:

what exactly is the "speed of time"?

You cannot define things in a vacuum. How do you measure that speed?

In order to measure a speed, you need a quantity changing. And then you need something else changing in a way regular enough from the perceptual POV to serve as a standard clock.

What is the standard clock against which time is seen to change?

Well I deliberately avoided any precision in its definition because I really don't know myself.  I have an idea that time propagates.  And if this propagation is with respect to something else, then we can define the rate of propagation (relative to that something else).  Of course, if we cant find anything else, we cant define the rate of propagation.  But that doesn't mean the propagation is constant, it just means it is undefined (possibly meaningless but also possibly meaningful). 

If we create a theoretical unit of something, lets just say its called Gap, which is a measurement of time but from outside of time.  We can calibrate Time and Gap arbitrarily, so we can take any moment in time and any period of time as equal to 1 Gap.  So lets take right now as the moment, and a period of 1 hour = 1 Gap.  So we can ask will 1 hour=1 Gap tomorrow, next year, next 13 billion years, 13 billions years ago?  (Lets define 1 hour as something which exists unchanging in all time moments, like some probability of emission decay of some particle.)

We might never be able to empirically show that the speed of time is constant or changing (it might be meaningless).  Whether it is variable or not, it wont ever affect any experimentation as everything we do is "trapped" in the same time and subject to the same changes in the speed of time.   So does it break anything if we assume or not that time has a speed and that this speed is variable?  What if space expansion today, and the inflation model 13 billion years was a manifestation of this?  Could dark energy exist outside of time?

On 8/24/2022 at 2:37 PM, swansont said:

We know time depends on your motion relative to another observer, and on your gravitational potential 

Do singularities have infinite or undefined gravitational potential?  Would this mean singularities exist "outside" of time?  Black holes will eventually decay, but what happens to the singularity?

Is there anything (theoretical or otherwise) that has undefined motion relative to another observer?  Space expansion/dark energy?   Would something with undefined motion necessarily exist "outside" of time?  Would that thing need to have undefined motion relative to ALL observers concurrently at one moment in time, or is it enough to be undefined relative to just one observer? If a thing has undefined motion at one moment in time, will it always have undefined motion?  

Whether Time is linear or cyclical or something else, is the speed of time constant?

What basis do we have to extrapolate time back to t=0 (or very close to 0) and assume it's speed is the same as it today?

I read descriptions of the early universe describing things like "A few millionths of a second (after the big bang), quarks aggregated to produce protons and neutrons"

https://home.cern/science/physics/early-universe

How would an observer in the early universe measure time when there are only quarks, protons and neutrons?

Is it possible the speed of time is variable?  Could 1 millionth of a second in the early universe be equivalent to a few million years today, relative to that early universe?

If time is accelerating universally, would this not affect any empirical evidence of any experiments performed to date, unless we can time travel?

If time is accelerating, could that explain dark energy and space expansion?

On 9/18/2021 at 9:23 AM, Markus Hanke said:

Think back to your math lessons in high school - remember how you drew simple graphs such as y=x^2. No question that the graph is globally curved. But now imagine you were to choose some point (eg x=2), and zoom into the graph there. What happens? The more you zoom in, the flatter it will begin to look. It’s just like that.

If you zoom OUT far enough, and assuming you zoom out at the same rate for the X and Y axes, then y=x^2 approaches a straight line.  Does this mean anything?  Is it possible that eventually that no global curvature can be measured from the equation?  How is it a global curvature if its not truly global and only local?

What does it mean if you zoom IN at different rates?  What if this rate itself was not a constant but another function of something.  Is it possible it may not look flatter?

Is there a loose analogy between the zoom-ratio of axes and tensors?

If you had two or more clones that were absolutely identical in that there was no way to practically (not theoretically) identify one from another, how do you know you have two or more clones to begin with?

The identification of multiple clones confirms they were not identical.  The absence of identification of multiple clones, suggests you only had one clone to begin with.

You either have only one clone until you identify another, or you have many clones that are not identical.  And anything that you do not know only exists as a probability, subjectively.

Thanks for the visuals.

So Simultaneity is just subjective.  But what about concurrency?

Lets presume both you and I exist.    Is the star shining concurrently for you and me, or sequentially?  That is, my detection of photons are registered sequentially by me, and your detection of photons are registered sequentially by you.  But are our combined detection of photons registered collectively sequentially, or could some be registered concurrently?

Not a single unexpected macro event that violates GR in this universe, other than singularties.  Is that not rather odd, considering all the random branches of possibilities that MIGHT occur with every quantum observation  everywhere since the beginning.

If the fundamental essence of the universe is random, chaotic, unpredictable, then surely there cannot be any fundamental laws or principles or constants.

Conversely if the essence of the universe is determinate, ordered, and predictable, then surely there must be a fundamental laws/principles/constants.

Why is this particular instance of a universe reliable to such a degree that we have not witnessed someone who lived forever; we have not witnessed a variable speed of light; we have not witnessed a single star or planet propelled by a means other than gravity; we have not witnessed an exception to time dilation; we have not seen a single star spontaneously appear anywhere in the our universe, as they inevitably must do in some universes.

Why is this particular instance of a universe so predictable that sentient beings have evolved and developed mathematics called General Relativity to model how things behave so accurately?

If Many Worlds interpretation describes infinite branches of worlds of possibilities, why is this world so predictable?  Or is it?  Why don't random macroscopic events happen in our universe?  Or is variance of possibilites limited in all universes to the quantum scale only?  Is it beyond even the power of infinite universes for one universe to exist where a star is spontaneously created in the sky within the next 24 hours?

On 9/3/2020 at 5:49 PM, swansont said:

If the observer gets the signal at the same time, they are simultaneous for that observer. They would not necessarily be simultaneous for other observers.

 

So if two stars supernova, and are recorded as simultaneous by an observer equidistant to each, then let me say (for the remainder of this thread) the supernovae were "objectively" simultaneous.  That is, there is more than one coordinate where, had a recording been made, then a simultaneous reading would have been obtained, and that all such coordinates lie on a plane perpendicular to the line between the two events.

Are there any other points or locus that is not equidistant from the two stars that might read a simultaneous reading for two "objectively simultaneous" events, either though some specific non-inertial frame or other condition?

If the two stars supernova objectively non-simultaneously (that is, any equidistant observer would not observe simultaneity), what would the shape of the locus of simultaneity of  look like for non-inertial frames as a function of degree of non-simultaneity?  That is, there would be some point where two objectively non-simultaneous supernovae would be seen as simultaneous. 

Lets say the supernovae were separated by 1light year and by 1 hour.  Each produces an expanding sphere of observables.  What does shape of the intersection of the two spheres look like over some time, and does this shape change with the degree of event separation (either distance or time).  Does this shape have a pattern?  Is it still plane-like with curves, or something else?

Moving away from simultaneity, i think my original post is more about concurrency.  Interactions throughout the universe all occurring concurrently, but not observably simultaneously.  Or is there not such thing?

3 hours ago, swansont said:

These are not inertial frames. Time is relative in all of them, but identical clocks can’t be synchronized between these frames.

I don’t think the words you are using mean what you think they mean. “interactions between star B and C are mutually simultaneous” makes no sense. You say non-relative for something that is relative. 

“interactions between star B and C are mutually simultaneous”

By this i mean Star B is affected by Star C at the same time while Star B is effecting Star C.  They are simultaneously (and not sequentially - not even by an infinitessimal small increment in time - true simultaneity - not mathematical equivalence through granularity of calculus) interacting with each other.

I do not mean inertial frames, in this instance.

If time is relative in all of them, how can any two events separated by either a space value or a time value ever be truly simultaneous?  If you cannot compare two events because time is relative to each event, by deduction, the only that can be simultaneous with an event is the event itself, no?
 

2 hours ago, swansont said:

Simultaneity is a binary condition - either two events are simultaneous in your frame, or they aren’t. This doesn’t change over time.

What do you mean by non-relative frames? 

 

OK non-relative frames.  Not really sure what I mean to be honest, but let me try and blurt out something coherent.

We have star A,B,C mutually, simultaneously interacting with each other, lets say gravitationally affecting their velocities.    The relative frame we choose as star A.    So the gravitational "force?" between A and B can be calculated and its effect on the velocity of star B as observed from star A can be calculated.  

Star C also has a gravitational effect on and affect by both Star A and B, this too can be calculated.

So the interactions between star B and C are mutually simultaneous (presumably) but not in the same frame of reference as star A.  So that is non-relative frames.  What is happening between star B and C are non-relative to measurements or observations from star A, but presumably they are still simultaneous and might even be synchronisable with frames of observations from star A.

I have to read your stuff a dozen times, and then see how what it means for me

I'm having trouble formalising my thoughts at the moment.  Need some time to ponder what I really mean.