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For a very long time, people had no reason to believe that an airless void could exist in nature at all, whether above the earth or anywhere else.

According to Descartes, in his 1633 work The World, the world is already full of matter, whether merely air or something more substantial:

By the same token, if you consider in this regard some of the experiments the philosophers have been wont to use in showing that there is no void in nature, you will easily recognize that all those spaces that people think to be empty, and where we feel only air, are at least as full, and as full of the same matter, as those where we sense other bodies.

He further elaborates on this idea with an illustration of wine flowing out of a cask, that it cannot displace the air outside until the air has somewhere to go, namely, into the space left by the wine inside the cask.

When did we get from Descartes' position to the one we hold now, that there is an airless void naturally occurring above the atmosphere?

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  • $\begingroup$ It depends... "void" or "airless"? The aether was considered "airless", but not "void", and this was the opposing theory that lasted longer. For "airless", I would say the limit would be Bernoulli's experiments. For "void", you would have to wait for Maxwell and Einstein. $\endgroup$ – SJuan76 Nov 14 '14 at 11:32
  • $\begingroup$ I'm looking for airless. The distinction between the aether and vacuum is a different question entirely. $\endgroup$ – Joe Nov 14 '14 at 16:29
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    $\begingroup$ I think this is pretty much the same question: history.stackexchange.com/questions/17163/… $\endgroup$ – fdb Nov 21 '14 at 23:51
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The absence of air in the interplanetary spaces (to a very high degree of exhaustion) was appreciated by Newton: he may have been the first. His demonstrations in the Principia are heavily bound up with the combined effects of gravitation and atmospheric resistance on the motion of bodies, a subject that attracted his interest and study, from the earliest 'De Motu..' of 1684, through Book 2 of the 'Principia'.

In book 2 of the Principia, Newton made it a point to study at what rate the combination of gravitational and (de)compressive effects should cause the density of the earth's atmosphere to decrease with distance above the earth's surface (esp. Book 3 Prop. 10, [https://books.google.com/books?id=6EqxPav3vIsC&pg=PA230], (applying Book 2 Prop.22 Scholium) [https://books.google.com/books?id=6EqxPav3vIsC&pg=PA73 up to PA76]). He calculated that at an altitude of even 200 miles up, the air should be 'rarer' than at the earth's surface in a ratio of roughly 75 x 10^12 to 1. This is practically a vacuum. In Book 3 Prop.10 Newton went on to conclude that there should be at most no appreciable atmospheric-type drag on the motion of Jupiter.

In the General Scholium Newton afterwards wrote: [https://books.google.com/books?id=6EqxPav3vIsC&pg=PA388] (translation slightly amended here, closer to the Latin original): "Bodies, projected in our air, suffer no resistance but from the air. Withdraw the air, as is done in Mr. Boyle's vacuum, and the resistance ceases. For in this void a bit of fine down and a piece of solid gold descend with equal velocity. And the same reasoning applies to the celestial spaces which are above the Earth's atmosphere".

Near-contemporaries saw the interplanetary void as a feature of Newton's theories (and sometimes as an attackable one, even absurd). Voltaire, with characterstic dry humour, included it in his contrasts between Newton and Descartes (1733): "A Frenchman arriving in London finds things quite changed in philosophy as in everything else: he left the world full, he finds it empty. In Paris one sees that the universe is composed of vortices of subtle matter: in London one sees nothing of that." &c. (Voltaire, 'Lettres Philosophiques', 1733, Lettre XIV. 'Sur Descartes et Newton'.)

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