Is the speed of light constant throughout the galaxy?

[Mohika]

Why are there exactly 12 inches in a foot?

Could this number be different in the center of the galaxy?

Again, I was not asking about 12 inches in a foot.

But why is the value what it is and could it be something behind the value, something that determines our measurement of it, something that causes light to have that speed? It would be the same as I asked why the speed of light is not twice what we measure or a half, but exactly what we measure and how do we know that its the same value across the galaxy.

Its quite a different question.

 

[Mohika]

You guess wrong. Nothing physical has changed because you specified $\alpha$ not to have changed. All you have done is changed your units.

This has nothing to do with the speed of light. People have produced various modified gravity models, some of which have been quite successful on the galactic scale. However, none has come close to predicting any cosmological measurement, as far as I'm aware, so they remain less well thought of than dark matter.

Gravity is modeled as spacetime curvature, not density. I'm not aware of any formal mathematical model that uses "density of spacetime".

"Density of spacetime" is in quotes.. I wouldn't know how different to call it. Maybe different excitation of a field that gives particles a mass. I am not a physicist.

 

[Ibix]

Its quite a different question.

It really isn't, as we've explained several times. $\alpha$ having a different value would have consequences, but active searching has not found any evidence for it. $c$ having a different value is just a unit change - very much like changing the number of inches in a foot.

 

[berkeman]

Thread is closed temporarily for Moderation...

 

[Dale]

Again, I was not asking about 12 inches in a foot.

But why is the value what it is and could it be something behind the value, something that determines our measurement of it, something that causes light to have that speed? It would be the same as I asked why the speed of light is not twice what we measure or a half, but exactly what we measure and how do we know that its the same value across the galaxy.

Its quite a different question.

We are just going in circles here. We have already answered this question. Repeatedly.

Here is a good overview of the topic from John Baez: https://math.ucr.edu/home/baez/constants.html

The dimensionful parameters, like c, or h, or e, do not tell us about physics, they tell us about our units. There is no physical meaning to their values beyond describing our units. The physically meaningful parameters are the dimensionless ones, like the fine structure constant.

This thread will remain closed. Once you have fully internalized the above, please feel free to open a new thread to discuss variations in the fine structure constant or other dimensionless parameters.