You keep confusing uncertainty of knowledge with uncertainty of measurment.
Let me put it this way: what specific means of measuring cosmological distances do you believe unreliable, and why do you believe them to be unreliable?
Using telescopes and assuming our measurments are correct. We have no idea how deep space actually works having never been through it. For all we know light could travel much faster in empty space, or slower.
Using telescopes and assuming our measurments are correct.
Q: What specific means of measuring cosmological distances do you believe unreliable?
A: assuming our measurments are correct.
That's not an answer to the question. Please name specific means of estimated cosmological distances that you believe unreliable.
For all we know light could travel much faster in empty space, or slower.
We're just about as sure as one can be that it isn't the case. If the speed of light weren't constant there would be a lot of side effects that would be pretty noticeable.
For example, time dilation wouldn't happen even though we can confirm it happens and measure it with GPS satellites. It just so happens that it matches the values predicted by Relativity.
Another example is the famous Michelson and Morley experiments. They "released" two beams of light at right-angles. One beam was in the direction of Earth's travel and the other perpendicular to Earth's travel. If light's speed weren't constant, the two beams should have had different speeds. They did not.
Kennedy and Thorndike showed that the speed of light is independent of the velocity of the test apparatus, and also confirmed time dilation.
That takes care of the speed of light being independent of inertial reference, but what about in other places in the Universe. Can light have a different speed in different places? Not likely. If it did, the appearance of the Universe would differ depending on which way we looked. Some directions might have regions where light travels faster, and some slower. We don't see that. The Universe, and cosmic background radiation, are remarkably constant no matter which way we look.
>No matter which way we look.
But we've only ever looked from inside the solar system. We don't know because we can't until we can go out and check. You keep beating the same point that the measurments are consistent while ignoring that there could be major flaws in our assumptions.
Edit: You admit the stars would "look different" if the speed of light was not constant, which is exactly my point, they would look like they were closer or further away.
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