Is the speed of light really the speed of causality? Would the effect of gravity (the lack of) affect Earth earlier than us perceiving the lack of light.
Nope. All physical effects are bounded by the speed of light. (As far as anyone knows, anyway.)
The only weird one is quantum entanglement, but even then information transfer doesn't travel faster than light and that's about all I know on that subject.
In short, the only information you gain is about the outcome of the other side's measurement. They cannot introduce information into the particle, and thus can't transmit information. The only thing you learn is what you already knew: the other particle had a 50% chance of being in one state or another, with the added fact that it's now correlated to your particle with a 75% (depending on experiment) chance. This is information that didn't exist until that moment, so it couldn't have been sent out and reach you before you measure your particle, which would inform you with 75% certainty how your particle would act and break causality.
The universe expanding is a property of space itself. And "faster than light" is only because miniscule space expansion in any quantum of space adds up with distance, e.g. 1 picometer per kilometer per second, add enough trillions of kilometers and you get that faster than light expansion. There is no mass, particle or information moving THROUGH space faster than the speed of light, which is what the said limit concerns.
Well the other way to look at it is: gravity travels at maximum possible speed in this universe. Light in vacuum can also reach same maximum speed. I guess we would say the light travels with speed of gravity if we measured them in other order.
