Hi AstroRockHunter

You said with respect to my expanding spacetime illustration the following,
You're not breaking a postulate, you're breaking your clocks. If you are going to use your clocks as a standard, then you cannot let the mirrors move apart with the expansion of space.

It was proposed or postulated that spacetime has structure, and that clocks, (such as a light clock composed of mirrors “floating” in space), expand with that structure, If that occurs, than intervals of time described by the light clocks become dilated with the expansion. Your objection is with the postulates.

Snowflake