My question is: How is light passing through different gravitational densities affected?
The value of "c" is constant in a vacuum. I'm curious about if various time frames have any effect.
This is the thought experiment that occurs to me.
Suppose we are doing a test in two different regions of the universe. In the first region, we have an observer in a place in between two galaxies. This is a region that should have the least amount of gravitational influence, being many thousands or millions of light years between centers of mass.
The second region is a place of high mass, thus high gravitational density. Suppose, for the sake of argument, that our second observer is in the middle of a Sol-sized star. Additionally, this star is transparent so we can shine light through it and it can come out the other side. Also, our observer is sufficiently protected so as not to be cooked and turned into heavier elements via nucleosynthesis.
The passage of time in each region will be different, where the observer inside the star will experience time moving slower relative to the observer in between the galaxies. Higher gravity, slower time passage.
To setup the model of the thought experiment:
We would measure the distance of a laser beamed between points A and B, where it passes through the exact center of the two spatial regions previously described.
The distance between points A and B is exactly one light second, or 299,792,458 meters.
Visually, it would look something like this:
A -------> CENTER -------> B
In the low-gravity region, it is expected that a laser pulse fired from point A will arrive at point B in exactly one light second, as expected.
In the high-gravity region, will a laser pulse passing through the center of the star arrive at point B in exactly one light second, or will it be delayed by passing through a region of space that has high gravity?
As I am thinking through this scenario, it occurs to me that there are at least a few ways of thinking about this in terms of perspective.
In the low-gravity location, I place points A and B in the same gravity as the center. However, in the high-gravity location A and B can exist in the same gravity as the center, or A and B might be points outside of the gravity region of the star's center.
There are also questions about where the passage of the laser is being observed from. In the low-gravity location, I put the observer in the same low gravitational field. However, in the high-gravity context the observer could be within the same high-gravity environment or could be observer the experiment from the low-gravity perspective. The high-gravity observer would see the experiment from the context of their time frame and might get different results than the observer from outside in the low-gravity time frame.
I am unsure how to reconcile these scenarios.