Why did I, again pure Zetetic observation, feel the acceleration?
I've said this before, but I feel you misunderstood. The term "feeling acceleration" is extremely vague - it's a term you've created to make a sensation seem intuitive. What you actually perceive is your acceleration relative to the air around you. Because motion is always relative, this is exactly the same as the air accelerating relative to you - there is no universal frame of reference from which you could distinguish the two. That is the sticking point - you feel "the acceleration", but there is no objective answer as to what's accelerating relative to what.
Because motion is relative, you could also completely rephrase UA to mean something like "anything other than sufficiently massive celestial bodies is accelerating downwards at 9.81m/s2 relative to the otherwise stationary bodies". Physically, the two are one and the same. All that changes is the frame of reference you chose.
Perhaps a different thought experiment will help here. Try to imagine the sensation of your body being held down in a river, well under the surface. Imagine how the water would feel against your body. Now, imagine a separate situation. You're submerged in water which is not flowing, like a lake, and you're being pulled through the water.
Without external information, you would not be able to tell the difference by the sensation alone. This is exactly the same here.
And yes, your comment about Einstein is correct. According to the Equivalence Principle, it MUST be the case that you won't be able to tell the two apart. Basic physics would break if this wasn't the case.
Thanks for the thoughtful response. Due to the obvious climate we live in, I am just done with arguing but a polite debate is always welcome.
I did not create the term, I paraphrased it... from the Wikipedia on Falling (sensation)
A sensation of falling occurs when the labyrinth or vestibular apparatus, a system of fluid-filled passages in the inner ear, detects changes in acceleration
To be more clear I should have said "detecting changes in acceleration" instead of "feeling acceleration".
I have googled and not found Einstein's direct quote but I see a lot of interpretations. One is the Elevator cable breaking. I submit from my direct observations that you would indeed sense the acceleration. One almost all of us have experienced is turbulence in an airplane. A common turbulence situation is an aircraft loses lift and you feel it. No air movement. Not external references. You just feel it. As part of pilot training, learning to recover from a stall is standard practice. If you have ever been in a stalled aircraft you felt it too.
https://en.wikipedia.org/wiki/Falling_(sensation)
you feel "the acceleration", but there is no objective answer as to what's accelerating relative to what
What we sense is a velocity change relative to our current velocity vector. The inner ear is made to do just that, without that you couldn't walk, jump or do much else besides lay there. People with inner ear problems sometimes report that feeling of falling, for the ear to falsly report that would suggest that it is a real feeling for a real purpose.
So no, I am not convinced. Again not from youtube videos, or literature, but direct observation.