> Though there is a key difference – Galileo could see through his telescope the same way, every time. Actually this is a really critical error- a core point o

> Though there is a key difference – Galileo could see through his telescope the same way, every time. Actually this is a really critical error- a core point of contention at the time was that he didn't see the same thing every time. Small variations in the lens quality, weather conditions, and user error all contributed to the discovery of what we now call "instrument noise" (not to mention natural variation in the astronomical system which we just couldn't detect with the naked eye, for example the rings of Saturn). Indeed this point was so critical that it led to the invention of least-squares curve fitting (which, ironically, is how we got to where we are today). OLS allowed us to "tame" the parts of the system that we couldn't comprehend, but it was emphatically not a given that telescopes had inter-measurement reliability when they first debuted.