The mercury cannot drop if there's nothing to make it drop.
This is the entire point of atmosphere inside the tube.
But you have already said there is no atmosphere inside the tube.
So why does the mercury drop when there is nothing to make it drop in your model?
Yes but in indicating there was no air there I was also indicating why there would be no barometer to work to measure anything.
All you're doing is mixing yourself up.
No I'm not.
There is no air in there. Yet the barometer still works.
As such, your explanation does not hold. You do not need air in the top of the tube of a barometer for it to work.
(In fact, air makes it work a lot worse).
The weight of the mercury cannot pull anything down in your full scenario. There's no pull for starters but there's also no decompression inside the tube to create any movement, at all.
This was an explanation using mainstream science, not your model.
With mainstream science, lots of things are pulls.
But if you like you can consider it as a field which pushes or curved spacetime which pushes.
Regardless, that weight of the mercury (unless it is balanced) results in a motion of the mercury.
This causes the mercury to fall.
This leaves a void behind it resulting in a pressure differential which acts to push the mercury back up the tube.
The column equilibrates at a height which the pressure differential balances the weight.
So rather than just dismissing it, do you need anything explained?
It's got nothing to do with being long enough. It's all to do with the tube having atmosphere trapped in it for it to even work at all.
Again, all the evidence shows that to be wrong.
If you tube is short enough the mercury stays put.
Even without any air in there you can still get a void.
If there's no atmosphere in the void then there's no void.
No, it's still there.
The void is clearly observable and you have admitted that the air isn't there to begin with and no air went in.
So how does the air magically make its way to the void?
You can do that but then you lose the whole point of having a barometer.
No you don't.
It still works.
It still measures pressure.
This is what I'm trying to tell you because the barometer works of displacement of atmosphere by whatever pressure it displaces at any given time, measureable on a printed gauge on the tube.
And what I have been trying to explain to you repeatedly is that is not how they work.
A fluid filled barometer works based upon a pressure differential (usually at least approximately as some pressure outside, 0 inside) balancing the pressure due to the height of the column due to its weight.
I don't want you to just keep on asserting things. I want you to explain what occurs in reality using your model.
That's what I'm doing but you're trying to scupper it.
No you aren't. You are ignoring reality.
You can't just ignore reality to have me accept your explanation.
You need to provide an explanation of how the mercury filled barometer works based upon that inversion of the tube in which no air is at the bottom to begin with, no air appears to get in, there is no way for the air to get in (or else the void at the top would just fill with atmosphere and the mercury would drop all the way), and thus there is almost certainly no significant amount of air in the top.
And that is just to start.
Once you have an explanation for that, we then move on to other size tubes (where the mercury goes to the same height) and using other fluids (which have a different height).
So if you want it to be nice and simple, you start with the original setup, tube down, filled with mercury, no air.
You turn it upright.
No air gets in (at least not visibly), yet the mercury drops leaving behind a void.
Can you explain it?