If you want a proper example of the "light getting brighter" then you can do no better than look at the scientific method.
It is very rare nowadays for something to come along that completely changes an existing theory. So much is verified and peer reviewed that new information simply adds more detail, exposes something previously unknown or verifies a prediction that previously could not be proven.
If you were to take something like gravity or general relativity and go back through the evolution of our current understanding you will find it like the layers of an onion, each modification building on previous knowledge. There will be an "eureka" moment where it burst onto the scene and wiped out some superstitious teaching (usually dogmatically supported by the Church) but after then it's about increasing knowledge not flip-flops, u-turns, complete change to understanding.
The way we understand the world around us through science is a true analogy for the light getting brighter. The changing doctrine of Jehovah's Witnesses with contradictory teachings replacing previously establish "truths" is the shite getting shite-er
