[Bill S]

Each physicist can see his own clock and the other’s with no time delay for information transfer.

If light speed is finite, there must be a time delay, which alters perception. Without a delay you can’t measure distance.

Of course, your comment is correct, but you seem to have overlooked the fact that this was a thought experiment.

….. which may not be the case.

Not the case

Could we be on the same page?

Time is not a causal factor. The time of an event is recorded after the event occurs, after awareness of the event. It's an historical account for a multitude of purposes.

Recall that I was trying to make sense of Barbour’s “Platonia”. 

[Bill S]

How could the Universe have a frame rate if time didn’t exist?

The mind requires a few milliseconds to register sensory input, which can be the duration of your snapshot.

Where would the few milliseconds come from if time didn’t exist?

[alancalverd]

The few milliseconds is what we measure with our laboratory clock between the sequential events of stimulus and response. If you poke about with an electrode, you can find a number of intermediate events as the electrochemical signal passes along the nerves.

You can't turn the light on by thinking about it, but your brain always registers the fact that someone has turned it on. So we say that the stimulus precedes the response: A => B. This determines the direction of time increasing. It's an arbitrary but convenient and universal convention.

[Bill S]

That makes good sense to me.  My sticking point was that Phyti seemed to find a few milliseconds without time.

[Bill S]

I don't buy the flow bit

That would seem to suggest “tensless” time, which I think equates, roughly, to John McTaggart’s “B series”. Have you read his “The Unreality of Time”?  It was a bit philosophical, not to mention pedantic, even for me. 

[yor_on]

Of course I could have made a treatise of it, I didn't. But what I say should hold even if you lift up accelerations as a special case Mike, and phyti, you will find more than me defining it this way. A acceleration is about displacements, and it will give you a red respectively blue shift. And you can talk about 'slices' of spacetime, which is not 'events' but just a 'slice' of it in time and space. Doing such a slice in a accelerating frame should keep the blue shift balanced relative the red shift as far as I see, expressed otherwise there is no energy added or lost in that slice. It's a equivalence to the idea of 'c' holding even in a acceleration, although the displacements make it look differently. And Halc, there is nothing like a privileged frame in relativity which put into question anyone talking about 'snapshots' as if the frame that represents that snapshot would be anything else than frame dependent.  We don't need to agree of course :) But that's the way I see it.
=

when it comes to me arguing that the local representation is the correct one :) Well, that's equivalent to someone arguing that 'repeatable experiments' works. When it comes to defining this 'slice' I used then it was from a observer being at rest with (inside) the 'black box', able to see the light bulb from both directions, aft and fore. It's a idealized situation naturally.

[Bill S]

Yes, otherwise your body would not decompose.

Of course, it’s not as simple as that.  If I’m a solipsist, does my body decay when I die?

The answer to that must depend on several possible factors. They are all philosophical, so I’ll not list them. Suffice to say that I would opt for “no”.

[alancalverd]

Since you could count microseconds between your milliseconds, the ticks of your millisecond clock are sequential events, separated by....time. Colleagues have rpoutinely counted femtoseconds between phases of chemical reactions, and AFAIK there is no essential granularity in the measurement of time,.

[Bill S]

The view is called eternal time, not tenseless time.

I tend to avoid the term "eternal time" because eternity and time are completely different concepts.  That's something which has probably been "flogged to death" elsewhere, without any resolution.   

[Bill S]

Alan, that's a good one to keep in mind for next time the question of the possible quantization of time rears its head.
It doesn't address the question of where any fraction of a second could come from if there were no time.

My feeling is that when we talk about time/timelessness, what we are really talking about is change/changelessness. Time is what we call the measure of that change.  If there were no change, we would not be able to take measurements, so a measurement system would be extraneous. 

[alancalverd]

A fraction of a second dooesn't "come from" anywhere. It's how we measure the gap between events. Just like a millimeter is the gap between the jaws of a caliper gauge.

[Halc]

The view is called eternal time (or block time), not tenseless time.

I tend to avoid the term "eternal time" because eternity and time are completely different concepts.  That's something which has probably been "flogged to death" elsewhere, without any resolution.

Agree, eternity and 'eternal time' are totally different concepts.  Not talking about boundless time.  I mean Minkowski spacetime: Time and space are one thing.  Time lacks a preferred moment in the exact same way that space lacks a preferred location.  That's my opinion, and I've on occasion defended the opposite view when somebody claims to have a proof against it.  I don't think there is any empirical way to settle the issue.

[Bill S]

If there were no calipers, that mm would have no meaning.
If there were no objects, distance would have no meaning.
If there were no change, time would have no meaning.

https://medium.com/the-physics-arxiv-blog/quantum-experiment-shows-how-time-emerges-from-entanglement-d5d3dc850933

Time is an emergent phenomenon that is a side effect of quantum entanglement, say physicists. And they have the first experimental results to prove it.

[Bill S]

Time and space are one thing.  Time lacks a preferred moment in the exact same way that space lacks a preferred location. 

I’ll have to ponder that a bit. My initial reaction is to wonder if it is just space that in influenced by relative motion, gravity etc. and that time – our measuring “instrument” – has to adjust to accommodate that change.

[alancalverd]

If there were no calipers, that mm would have no meaning.
If there were no objects, distance would have no meaning.
If there were no change, time would have no meaning.

Distance is the separation of points, not objects. Time is the separation of events.

It is arguably the case that if individual words have no meaning, their combination is also meaningless, but that is fatuous philology or, even worse, philosophy. Unlike philosophy, physical masturbation is at least pleasurable.

[Bill S]

Distance is the separation of points, not objects.

I can see that it is the separation of points, but isn't it also the separation of objects, places etc?  E.g. is there not a distance between London and Cambridge?

Time is the separation of events.

Are changes not events?

[alancalverd]

I'll take a short break from more pleasurable activities to explain that "London" and "Cambridge" are fuzzy patches on a map. Points within "London" and "Cambridge" are separated by all sorts of distances, mostly between 40 and 70 miles.You can define points within those fuzzy boundaries that are not associated with any particular object. In the absence of other data those points are conventionally located within Charing Cross and Great St Mary's respectively but if you want to navigate by dead reckoning from Cambridge airport to London City you  will need to choose two other points.

And the pedantry prize is awarded to the old fool who pointed out that the change from boyhood to manhood is not an event, nor two events, but it may be denoted by a single event, arbitrarily chosen at 13, 16, 18 or 21 years after birth

[Bill S]

Just like a millimeter is the gap between the jaws of a caliper gauge.

How small does something have to be to be a point rather than an object?

Are changes not events?

I really appreciate your taking a break from more pleasurable activities to answer possibly tedious questions.  Thanks.

[alancalverd]

A point is not a "something". It is by definition infinitesimal, and therefore smaller than any "thing".

[Halc]

Just like a millimeter is the gap between the jaws of a caliper gauge.

How small does something have to be to be a point rather than an object?

Small enough to be mathematically treated as one for the task at hand.

The lightning strikes in Einstein's train/platform thought experiment needed to be pretty precise and those events were as concise as Einstein could describe them.  But on the other hand, other events like the Chicago fire are quite large because they usually are not compared with more precise things.