For example. A star is 8B light years away, we’re told that that the light has taken 8B years to get to us.
BUT the universe is constantly expanding therefor was the star not much much closer to us therefor making it’s light younger?
In: 10
Light is really that old.
There is may distance to an object in space, let’s look at [https://en.wikipedia.org/wiki/GN-z11](https://en.wikipedia.org/wiki/GN-z11) that in 2016 was one of the farthest away when it was discovered. I use it because I know of what is listed.
The present proper distance is 32 billion light years. That is how far it is from us right now.
The light-travel distance is 13.5 billion light years. That is how far the light has traveled to reach is and if you remove the light from it you get how long time ago it was emitted 13.5 billion years.
The last number is how far away it was then the light that was emitted. That is usually not listening, it is in the notes and why I pick this object. That distance is 2.66 billion light-years.
The expansion of the universe does not make the light younger. It was emitted 13.5 billion years ago and during its travel to us the distance in between expanded so the initial distance of 2.66 billion light-years got longer and the result was the travel distance was 13.5 billion light-years.
compare it to if you walk on a conveyor belt that we tend to call a moving walkway or something similar for human usage. Start 10 meters from the start and try to walk back against its motion. If you walk faster it moves you can reach the star but you will have walked longer than 10 meters. A buddy that did says still on it will have been moving farther away by it without walking.
So you have the distance to your body that is like the resent proper distance.
The distance you walks is the light-travel distance
The distance at the start is the distance at the time the light was emitted.
It is not a perfect analog for the expansion of the universe. The space between objects grows faster if they are farther apart it is not independent of distance like the conveyor belt. The distance to the buddy will be equal to your walking distance. You could modify it with multiple moving walkways when each will move a bit faster than the previous to get a distance difference.
But it does illustrate the different measurements with something a bit like the expansion that is simple to grasp.
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