Yes, I just think it slightly arrogant to assume that human cosmological observations and assumptions are the only ones...Especially when it is widely assumed that life must exist elsewhere in the universe.
I agree with your above and always have thought what you state above.
My thoughts were about how someone living in galaxey that exists only 150 milllion years after the BIG WOW!, seeing redshifted light from us 13 Bil after the Big WOW!, how do cosmologist from each perspective who exists where on that time line. See what I mean Sarge.
Maybe they think were early Universe, even tho we think were older Universe. What is the mechanism by which each can determine the time line from Big W! that they each exist along?
If they existed only 150 million years after the Big Bang, they aren’t gonna see redshifted lights from us 13 Billion years after, they are going to see the light coming from us 150 million years after, minus the time it takes it to travel from here to there. But 150 million years after the Big Bang, there wasn’t any light coming from us yet, the Milky Way Galaxy didn’t even exist, the universe was still in its "Dark Age", and there is no light to see. We were on the verge of the “cosmic dawn" (Let there be light”. Gravity was causing clouds of hydrogen and helium to start to contract on their way to forming stars, so it's still the "Dark Age", no light to see.
But that's just a technicality, your question is really about how two different frames of reference see each other considering the time it takes light to travel. In 1905 Einstein was thinking about your question and that is what allowed him to develop the Special Theory of Relativity.
The question he asked himself was, “What does it mean to say two things happened at the same time”. He knew light traveled fast, but it was a finite speed, so if we observe something distant occurring at the same time something local occurs, then we know they didn’t actually happen at the same time, the distant thing happened earlier, it only appeared to occur simultaneously when the light arrived,
At the time, experimental evidence was that the speed of light was constant no matter how fast the source of the light \was traveling. This was perplexing, nothing else ever worked like that. Standing still with a train coming toward you at 60 miles an hour, you measure its speed as advancing by 60 miles an hour, if you are moving towards it a 60 mph, you measure it as advancing at 120 mph. With light though, it didn’t matter how you were moving relative to the thing being measured, light was simply defying the laws of physics.
Everybody else was thinking the measurements must be wrong (Albert Michelson got a noble prize for getting it right btw), maybe it was ether, maybe it was something else, but it just can’t be right. But nobody could understand how the speed of light could possibly be constant, no matter what the frame of reference was, except for this patent clerk with funny hair, While everyone else was thinking the experimental evidence must be wrong, Einstein was thinking that because every measurement said it was constant, let’s make that a principle of nature and see what happens. Then he mathematically worked through the physical ramifications of that new principle of nature.
He imagined two people at the front and back of an airplane that is moving very fast, a flash of light occurs in the center of the plane, the light traveled the same distance to both of them, and consequently, both observed the flash to have happened at the same time. But Einstein realized that somebody on the ground, with a stationary frame of reference, will necessarily observe it very differently.
Because the plane is moving fast, as the light travels, the front of the plane is moving away from the flash and the back of the plane is moving towards it, so the light traveling at a constant speed, travels a greater distance to the guy in the front of the plane and a shorter distance to the guy at the back of the plane. The guy on the ground observes the light arrive to the guy in the back before it arrives to the guy in the front, so to the person on the ground the light did not arrive to both guys simultaneously. WTF
He decided the solution to WTF was to simply accept the experimental evidence and consider the constant speed of light to be a principle of nature. When he applied that new principle to the traditional physics formulas, out popped the Special Theory of Relativity. If the speed of light stays the same in all frames of reference, then in the physical formulas, it’s the "distances" and "times" that have to change, hence, you get the Special Theory with its “length contraction” and “time dilation”. The mathematics is hard, but the idea is simple and straightforward, and it all happened because Einstein asked the kind of question you are asking ebuc.
He was a theoretical physicist; other scientists did the experiments and produced the evidence for him to work with. What made Einstein so great is that he had an insightful knack for asking the right questions about the evidence the experimental physicists were producing.
To come up with the General Theory of Relativity, the question he was trying to answer was “Why are gravitational mass and inertial mass equal”. Experimentally, the two were always measured to be precisely the same, other physicists didn’t wonder about it, it was just the case, but Einstein asked “why” that is the case. Once again, he accepted the experimental evidence, considered it a principle of nature, and worked through the physical formulas.
He reasoned that, since a guy falling in an elevator appears to be weightless in the elevator, and how much he weighs in that elevator depends on how fast he is accelerating or decelerating, that gravity (gravitational mass) and acceleration (inertial mass) must be two aspects of the same thing. He made the equivalence of gravity and acceleration a principle of nature, worked through the physical ramifications, and out popped the General Theory of Relativity.
So, there you go ebuc, it’s obvious to everyone that you don’t think like the rest of us, but in the end, it turns out you do think like Einstein :)
