I did a search on the site to see if this question had been covered, and although the subject was breached, the thread drifted off leaving what seemed to be the original intent in its wake.
Tucson_Tim's post triggered my Google Alert and I initially posted the question there. He suggested - in the kindest way - that it might be suited better elsewhere on the site, and I have taken his advice. So...
Some might consider this nit-picking, but in the spirit of Eddington, sometimes it is the minor discrepancies (Mercury's orbit, eclipse displacement of stars) that make for new directions...
Galileo's rolling balls work fine, but over distance drag from air resistance would mean that the larger, more massive ball arrives first.
The famous Hammer and Feather on the Moon demonstration also works, but dropped from an altitude of 300 miles, the feather would be subject to interference from solar wind and would - unless driven directly by the wind - arrive after the hammer.
Even in the thinnest intergalactic space, any given cubic centimeter is awash in activity. Virtual particles spontaneously come into existence, then blink out again. Radiation permeates this thinnest of space. Whole atoms, unhindered, reach such high velocities that a plethora of them pass through a given cubic centimeter at any given time.
ALL space appears to be a fabric of interference, so the laws of pressure are just as relevant in outer space as within the boundaries of our own atmosphere, just on a much bigger scale.
...so my question - in the strictest sense - is there a problem with our present reasoning about the behavior of mass and motion, if the experiments upon which we base our reasoning show discrepancies? Or am I just being too nit-picky?
Addendum: In my original posting, a senior forum member named George was kind enough to send me this intriguing link which - if this topic is of interest - you might enjoy.