And futhermore, if the speed of light in the vacuum of free space is not a constant after all, then we once again have to ask the question as to the constancy of the radiometric decay rates.. and it has been challenged that these radiometric decay rates are not quite the universal constant that early 20th Century Physics had held them to be... that they can in fact be changed by a number of different forces and techniques.

If so, this even changes the radiometric dating techniques used to date the 'oldest rocks on Earth'...

What seems so certain as to these things in your high-school or college classes now is once again considerably up in the air... again, Science advances one funeral at a time.