When the level is level the highest point of the tube is in the middle so that's where the bubble goes.
When the level is tilted the highest point of the tube isn't in the middle so the bubble is to one side.
Obviously the curve is exaggerated in that diagram.
This is because of the force of gravity but if the force was replaced by the force of UA then why wouldn't it work just the same?
The point that you both seem to be missing is that gravity is not what makes the bubble move...it is what determines where the bubble lands when the level is stationary. In the RE model, gravity is what determines that the bubble lands at the highest point of vial. Why would UA do that? How does UA maintain the bubble in the middle?
And for the record, I am not saying that it wouldn't, I just don't see how it would and so far Pete has only attacked anything that I have said and deflected answering the question.
Try this as a thought experiment.
Imagine a spirit level at an angle accelerating upwards at an angle at the constant rate of UA. What happens to the bubble? Nothing. It will float at the top of the vial, but will never move to the middle. That would be true of both UA and gravity.
Then imagine accelerating the low end at a faster rate than UA What happens to the bubble? It moves to the middle.
Then imagine returning the low end to the original rate of acceleration (remember again this is a thought experiment
) With gravity, once you have it level, it stays that way until you move it. Once you move it and gravity determines where the bubble falls, it stays there. But what happens with UA?
One of two things...the low end falls again which would indicate that in order to maintain level a force greater than UA is required. How can that be?
Or it remains level. What causes it to remain level? The only thing I can think of is that because the whole thing is accelerating at the same rate, the UA force is equal along the whole spirit level and maintaining the bubble in the middle.
Two problems with this. First, if that is true, it is no longer analogous to gravity,
according to Pete, because in the RE model "level" doesn't mean that the force of gravity is equal across the whole spirit level. Something else is at work in both models apparently and so far, I haven't been offered any viable alternatives.
Secondly, if equal UA force across the whole spirit level is what maintains it at level, does that mean when it wasn't level, the force was not equal? How can that be if UA is a constant, consistent force that effects everything equally at all times?
Do you see the problem? I hope that we can all agree at least that in order for the bubble to land in the middle when the level is tilted, you have to move the level. In the RE model it lands in the middle and stays there because you have changed the level of gravitational pull across the length of the level and made it equal. In the UA model, you aren't changing the level of “gravitational” pull across the length of level and making it equal...because it already was equal.
Pete wants to have it both ways. Gravity and UA are analogous but one is a constant consistent force that effects everything equally at all times regardless of position or location and one is not a constant consistent force whose effect on anything is dependent on location and position.
That is not what analogous means.