# $c$ slowing down rather than universe expanding?

Can the Friedmann equations be reformulated with taking the universe as being rigid and instead have the vacuum-speed of light in the void decrease over time? So, not changing any equations, just interpreting them differently? Or does that way of looking at it not work for some reason?

• I know the concept of tired light, but that's a bit different and is solely an explanation for red-shift. What I ask is whether - without changing the friedman-equations, they can be interpreted as c decreasing simply by assuming another variable as being the constant (instead of c being the constant) – user1282931 May 31 at 11:59
• Proposals and papers are around. With no answers, look for "tired light" for one aspect and "light slowing down, Davies". Also in ArXiv .... – Alchimista May 31 at 12:03
• You want to know if there is a change in length scales over time so that the velocity of light decreases over time even though it is always "c" and that the cosmological redshift can, somehow I do not know how, be explained by this? – Agerhell May 31 at 12:22
• Possible duplicate: physics.stackexchange.com/q/73114/2451 – Qmechanic May 31 at 12:22