AB10B:
...Science is a "defined perspective" with the intent of producing a "reproducible observer". They commonly call this "objectivity", which is arguable but to make experiments "legitimate", all they really need is consistency. Therefore, it doesn't really need to be "objective", just consistent.
I think this part is well put.
The things which science searches for and from which it derives whatever predictive power it might have - symmetries, patterns etc. They are all about finding the things in a physical system that do not vary. The defining characteristic of that cornerstone of modern physics, symmetry, is constancy during a transformation. And, as you say, the concept of "objectivity" is one special case of a symmetry: the case in which the constant is the observer.
But I don't really understand the other stuff you're saying about expansion carrying light into the future. If I read your previous posts will it be clearer?
Happy recluse:
The speed of light is 299,792,458 meters per second. This speed is always the same, provided light travels in a vacuum. If that speed is always the same, then the length of a meter and the duration of a second is always the same. In fact, such is the case for every single observer.
I think the key thing to remember is that it only makes sense to define measured quantities like distance, speed and time with reference to the act of measurement. So the speed of light, the length of a metre and the duration of a second always have the same relationship to each other when measured
in the reference frame of the observer. It is when you try to measure something like a distance or a time interval in a different reference frame to your own that you have to be very careful about precisely what you are doing and how you are doing it.
The Lorentz transformations arise naturally as a consequence of very careful consideration of precisely what you have to do to measure, for example, the length of an object as it moves past you at high speed.
Two observers have different readings on each other's amount of time. By this I mean, the length of a second is longer or shorter for different observers. That's fine.
So, for example, you have to be careful to examine what you're saying when you say something like this. The length of a second, as measured by a clock travelling with him, is the same for one observer as it is for another observer using a similar clock travelling with
him. It is when one observer looks at the other observer's clock as it whizzes past and compares it with his own that the discrepancy arises.
However, all observers see light moving at the same rate because the length of a second for a beam of light is always the same.
And to examine this statement we'd have to define here what you mean by the length of a second "for a beam of light". Beams of light don't look at clocks. It might be clearer to say that the relationship between time and distance, when measured
using a beam of light, has been observed to be the same for two observers that are moving relative to each other but are using the same beam of light.
If the endurance of second is always the same for beams of light, then those seconds are absolute in the sense that they are always the same, and they are always seen to be the same. If you want to know how long a second lasts, you cannot look at your own clock.
What do you mean by "how long a second lasts"? A second always lasts for a second.
You cannot look at someone else's clock. You can look at the speed of light and always know how long a second truly lasts. Thus, the true and absolute length of a second is that found in the speed of light.
You can certainly emit a beam of light and measure, with a clock, how long it takes to reach a detector. But an observer who is looking at that same beam of light but moving differently from you will get a different result because they will see the path taken by the beam of light as being of a different length.
The clearest way to imagine this is to imagine a kind of clock that works by bouncing a beam of light backwards and forwards and registering whenever it bounces. If you imagine this "clock" moving relative to you, such that the beam of light moves perpendicular to the direction of motion, then you can see that, from your point of view, the path length of the light beam is longer than it is for somebody moving along with the "clock".