The Barometer and The Vacuum Myth
The experiment of Torricelli in 1642 was generally accepted as demonstrating that a perfect vacuum existed in the space above the mercury in a barometer.
As a result Gassendi four years later resurrected kinetic theory and an inter-atomic vacuum and since then the concept of vacuum has been an essential part of theoretical physics.
Subsequent experiments by Pascal were also believed to indicate that above a finite atmosphere, extending to an altitude of around 80 Km, space was a perfect vacuum.
Newton however asserted around 20 years later:-
“That gravity should be innate, inherent and essential to matter, so that one body may act upon another at a distance through a vacuum – is to me so great an absurdity that I believe no man who has in philosophical matters any competent faculty of thinking can ever fall into it.”
But today it is still stated unequivocally in textbooks that an absolute vacuum exists in a barometer, despite some commentators acknowledging the presence of gas atoms there.
However it is now observed that mercury freely and rapidly evaporates at STP, as this video clearly shows:-
http://www.youtube.com/watch?v=JABbofwD3MI
Therefore in a Torricellian mercury barometer, where in the conditions of low pressure at the top surface of the column of the liquid, generated by gravity acting upon it during the progressive elevation of the tube to vertical, it will evaporate at an even greater rate than at STP and fill the space above the liquid with mercury vapour.
According to current kinetic atomic theory mercury vapour is composed mostly of a vacuum, and in the vapour above the liquid mercury a pressure would be generated by the collisions of gaseous atoms.
As is observed in practice the top surface of the liquid will remain at a height of 760 mm at STP, and if a longer tube were filled and used, say 1.5 metres in length then, during the elevation of it to vertical, the mercury will remain at the same level above the external surface that is exposed to atmospheric pressure.
This would demonstrate that the vacuum component of the gas cannot influence the mercury atoms in any way, or resist its own volumetric expansion.
Accordingly the vacuum component of this kinetic atomic gas alone can have no effect whatever on the level of the liquid mercury, and this raises a serious question.
This is that, as mercury evaporates freely in these conditions of low pressure and the vacuum component has no influence, then it should continue to evaporate rapidly into this low pressure region and, under the influence of gravity on the liquid in the tube, the internal liquid level should accordingly subside to that of the external surface exposed to the atmosphere, and the pressure within the tube would equal that of the atmosphere.
Clearly this does not happen and at 760 mm the liquid ceases to evaporate, but in terms of the kinetic atomic theory of gases, where the mercury atoms can only apply a positive pressure by means of collisions through a non-interactive vacuum, the maintenance of this altitude above the exposed surface cannot be explained
And if any minuscule proportion of inter-atomic or sub-atomic vacuum were present here, which by definition could not resist its own expansion, as discussed it would do so.
This observed result is therefore an absolute disproof, and a complete contradiction of the 375 year old belief that an absolute vacuum occupies any part of this volume, and accordingly is a refutation of the kinetic atomic theory of gases.
And this rather obvious contradiction is the reason why the myth of an absolute vacuum in the barometer is maintained in the literature.