I've been through this before. I've bought the text books.

Can you give me a simple answer; In the relationship between the speed of light and the expanding space, which is the numerator and which is the denominator?

It should be very easy math.

Hint;

In classic redshift, when the source moves away, it doesn't affect the denominator, only increases the amount of it. So the denominator is the ruler and the numerator is the distance measured by this ruler.

Example; When the train moves away, down the train tracks, it doesn't stretch the train tracks, simply increases the distance along them.

My problem; The reason given for cosmic redshift is that the light takes longer to cross the space between source and receiver, so it would seem that in terms of the speed of of light, aka, lightyears, the distance increases, not the metric defined by the speed of light.

So it would seem that in this relationship, the speed is the denominator, aka, the ruler.

If the space between the source and the receiver were considered the stable distance and the speed of light was the variable, aka, "tired," then the speed would be the numerator and the space would be the denominator.

Now before you say they are unrelated, or some argument the expansion is global, while the speed is only measured locally, remember the expansion has to occur where the light is being measured, in order for it to redshift. Also, both metrics are based on the same intergalactic light, one on the speed and one the spectrum.

Safe to say, I've been through this debate a few times in the last thirty+ years.

The usual response has been to hand wave me off to, "do the math," with no apparent mathematical logic or effort included.