Why was the observational link between the AU and Earth's position severed?

Answer

Relying on an observed measurement that was slightly variable became problematic for high accuracy

As astronomical precision increased, relying on a constantly observed and slightly variable value derived from Earth's position became problematic for the most accurate scientific work.

Why was the observational link between the AU and Earth's position severed?

#Videos

What Does AU Mean In Astronomy? - Physics Frontier - YouTube

measurementastronomyscienceAUabbreviation