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There are no such mistakes to fix.

In case 2 it's similar, but all the galaxies are moving through the expanding space fabric at relativistic speed. It takes longer for them to evolve due to their slowed functionality, but again they all reach the same stages of development at the same time because they all have the same amount of slowed functionality.…The correct coordinate system to use for this is one that expands with the universe.

You should not be attempting to use one in which we are fixed in place while other galaxies are moving and where some (outside the observable universe) are moving through that grid at superluminal speeds.

But with case 2 you get a very different result because it's the galaxies that are moving fast while all the travellers moving in one particular direction are at rest, so for them the journeys take vast amounts of time and they arrive at galaxies where very little has had a chance to happen due to their almost completely frozen functionally.

QuoteThose are objective (not coordinate system dependent) observations, so that will be observed in case 2 as well. You don't seem to realize that.No - it can't be the same in case 2.

Those are objective (not coordinate system dependent) observations, so that will be observed in case 2 as well. You don't seem to realize that.

If STR can't apply to this, it has no business being applied to our universe at all.

With this thought experiment though, we show that it is the absolute frame of the kind which objects can either be at rest in or moving through and where they have absolute speeds of motion through it which determine how fast their clocks tick. That's the bit that's news

This is about pinning down the absolute frame at a location. It isn't merely about pinning down a coordinate system.

akin to a twins paradox and that's traditionally done by sending a person

In case 2 they are all moving at the same speed through space and in the same direction, so their clocks must remain in sync so I'm not making any mistake.

Light does not propagate relative to an object!

The propagation speed of light in space is constant and INDEPENDENT of its source.

The big word being the most significant, meaning light does not acquire the speed of the source. This distinguishes light motion from material object motion.

This demonstrates the equivalence of inertial motion and rest, and an example of SR postulate 1, the same description of physics is valid in all inertial frames.It also shows a need for a definition of 'rest' different from that of Newton. There is only motion and 'rest' is a special case when two systems A and B, have identical velocities.Thus each can be in motion while at rest relative to each other.

The MGP experimentThe motion can be represented as a cylinder with the ct axis through the origin, and d equal to the circumference. The cylinder is unrolled to a flat surface with only constant velocities, the origin (black) and light (blue). Light speed is constant in SR. The rotation is absolute motion, with the origin approaching in the cw direction and receding in the ccw direction.

Are those effects included in your simulations?

When considering motion, light speed is c, object speed is v.It is necessary to use the forms of c-v and c+v in calculations, as closing speeds, rates of change for a spatial separation. There is no physical thing moving at those speeds.

Quote from: David Cooper on 29/08/2020 05:56:48There are no such mistakes to fix.In that case you’re talking about your own new theory where simultaneity isn’t frame dependent.

That’s consistent for an absolutist, but having the galaxies being the thing moving is not consistent with the view. So you’ve alienated every view I can think of. If you find an inconsistency, it just means the new theory doesn’t work so well.

QuoteThe correct coordinate system to use for this is one that expands with the universe. This is what I mean. I cannot think of any known coordinate system where this is the case, which is why I’ve said case 2 doesn’t exist. FLRW metric is such a solution, but that metric does not have frame rotation operators defined like SR does with Minkowski coordinates, so there’s just the one frame.You’re free to find a solution to Einstein’s field equations that satisfies all these conditions, but until then, there’s little to discuss about it.

The correct coordinate system to use for this is one that expands with the universe.

]FLRW metric does not have anything moving at superluminal speeds.

QuoteBut with case 2 you get a very different result because it's the galaxies that are moving fast while all the travellers moving in one particular direction are at rest, so for them the journeys take vast amounts of time and they arrive at galaxies where very little has had a chance to happen due to their almost completely frozen functionally.This is wrong. You’re using a Minkowskian property on a non-Minkowskian coordinate system. You’re also denying Minkowskian RoS above, but still attempting to apply dilation with Minkowskian rules. You’re not being self consistent.

QuoteNo - it can't be the same in case 2.It must be. If objective observations are different from one case to the other, then one of the cases is wrong, which is what I’ve said from the beginning.

No - it can't be the same in case 2.

QuoteIf STR can't apply to this, it has no business being applied to our universe at all.Much better. And yet you’re trying to use it above, but incorrectly.

QuoteWith this thought experiment though, we show that it is the absolute frame of the kind which objects can either be at rest in or moving through and where they have absolute speeds of motion through it which determine how fast their clocks tick. That's the bit that's newsIt’s not news. The general idea has been known for 90 years. It still doesn’t foliate all of spacetime, which suggests that there is no absolute frame at all. This is just a special one, but not necessarily absolute. If you want to demonstrate the latter, you need to find a valid way to falsify the view that there isn’t one.

QuoteThis is about pinning down the absolute frame at a location. It isn't merely about pinning down a coordinate system.A frame has a location? If not, what’s the difference between a coordinate system and a frame? They’re the same thing to my knowledge.

What are the absolute coordinates of our solar system? Seems funny to call it absolute if you can’t answer that. “2nd star to the right and straight on till morning” is a relative reference for example.

Quoteakin to a twins paradox and that's traditionally done by sending a personEvery physical demonstration of the twins scenario has been done with atomic clocks, never people.

QuoteIn case 2 they are all moving at the same speed through space and in the same direction, so their clocks must remain in sync so I'm not making any mistake. Ouch. Why do I bother if this is your understanding?