Horror vacui (physics)
In physics, horror vacui (commonly stated as "Nature abhors a vacuum."), or plenism ("fullness", from Latin plēnum, English "plenty", cognate via Proto-Indo-European to "full"), is a postulate attributed to Aristotle, who articulated a belief, later criticized by the atomism of Epicurus and Lucretius, that nature contains no vacuums because the denser surrounding material continuum would immediately fill the rarity of an incipient void. He also argued against the void in a more abstract sense, (as "separable"), for example, that by definition a void, itself, is nothing, and following Plato, nothing cannot rightly be said to exist. Furthermore, in so far as it would be featureless, it could neither be encountered by the senses, nor could its supposition lend additional explanatory power. Hero of Alexandria challenged the theory in the first century CE, but his attempts to create an artificial vacuum failed. The theory was debated in the context of 17th-century fluid mechanics, by Thomas Hobbes and Robert Boyle, among others, and through the early 18th century by Sir Isaac Newton and Gottfried Leibniz.
[In a void,] no one could say why a thing once set in motion should stop anywhere; for why should it stop here rather than here? So that a thing will either be at rest or must be moved ad infinitum, unless something more powerful get in its way.
Further, things are now thought to move into the void because it yields; but in a void this quality is present equally everywhere, so that things should move in all directions.
Further, the truth of what we assert is plain from the following considerations. We see the same weight or body moving faster than another for two reasons, either because there is a difference in what it moves through, as between water, air, and earth, or because, other things being equal, the moving body differs from the other owing to excess of weight or of lightness.
Now the medium causes a difference because it impedes the moving thing, most of all if it is moving in the opposite direction, but in a secondary degree even if it is at rest; and especially a medium that is not easily divided, i.e. a medium that is somewhat dense.Now there is no ratio in which the void is exceeded by body, as there is no ratio of 0 to a number. For if 4 exceeds 3 by 1, and 2 by more than 1, and 1 by still more than it exceeds 2, still there is no ratio by which it exceeds 0; for that which exceeds must be divisible into the excess + that which is exceeded, so that will be what it exceeds 0 by + 0. For this reason, too, a line does not exceed a point unless it is composed of points! Similarly the void can bear no ratio to the full, and therefore neither can movement through the one to movement through the other, but if a thing moves through the thickest medium such and such a distance in such and such a time, it moves through the void with a speed beyond any ratio. For let
A, then, will move through
G, and through
D, which is thinner, in time
E(if the length of
Bis equal to
D), in proportion to the density of the hindering body. For let
Bbe water and
Dair; then by so much as air is thinner and more incorporeal than water,
Awill move through
Dfaster than through
B. Let the speed have the same ratio to the speed, then, that air has to water. Then if air is twice as thin, the body will traverse
Bin twice the time that it does
D, and the time
Gwill be twice the time
E. And always, by so much as the medium is more incorporeal and less resistant and more easily divided, the faster will be the movement.
Zbe void, equal in magnitude to
D. Then if
Ais to traverse and move through it in a certain time,
H, a time less than
E, however, the void will bear this ratio to the full. But in a time equal to
Awill traverse the part
A. And it will surely also traverse in that time any substance
Zwhich exceeds air in thickness in the ratio which the time
Ebears to the time
H. For if the body
Zbe as much thinner than
A, if it moves through
Z, will traverse it in a time inverse to the speed of the movement, i.e. in a time equal to
H. If, then, there is no body in
Zstill more quickly. But we supposed that its traverse of
Zwas void occupied the time
H. So that it will traverse
Zin an equal time whether
Zbe full or void. But this is impossible. It is plain, then, that if there is a time in which it will move through any part of the void, this impossible result will follow: it will be found to traverse a certain distance, whether this be full or void, in an equal time; for there will be some body which is in the same ratio to the other body as the time is to the time.—Aristotle, Physics, Book IV, section 8
The idea was restated as "Natura abhorret vacuum." by François Rabelais in his series of books titled Gargantua and Pantagruel in the 1530s. The theory was supported and restated by Galileo Galilei in the early 17th century as "Resintenza del vacuo." Galilei was surprised by the fact that water could not rise above a certain level in an aspiration tube in his suction pump, leading him to conclude that there is a limit to the phenomenon. René Descartes proposed a plenic interpretation of atomism to eliminate the void, which he considered incompatible with his concept of space. The theory was rejected by later scientists, such as Galileo's pupil Evangelista Torricelli who repeated his experiment with mercury. Blaise Pascal successfully repeated Galilei's and Torricelli's experiment and foresaw no reason why a perfect vacuum could not be achieved in principle. Scottish philosopher Thomas Carlyle mentioned Pascal's experiment in the Edinburgh Encyclopedia in an 1823 article titled "Pascal". The Magdeburg hemispheres used by Otto von Guericke in 1650 were seen by some as proof that the theory was not correct.
Astrophysicist Neil deGrasse Tyson has explained that nature does not actually abhor vacuums, as the nature of them pervades the universe. The difficulty of creating or observing such a phenomenon here on Earth is more attributable to gravity than anything else, as the fundamental force is what is responsible for attracting the atmospheric gases toward the earth's surface, thereby filling any voids no differently than water filling the shape of a container, rather than the gases flying out into space. The commonly cited misconception, therefore, may owe more to its colloquial usage in modern times than anything else, as the phrase is commonly used to demonstrate the fleeting nature of opportunity as it is recognized and quickly seized by an opportunist before another opportunist beats them to it. This is sometimes referred to as 'finding a niche'.
- Casimir effect
- Lamb shift
- Spontaneous emission
- Quantum fluctuation
- QCD vacuum
- QED vacuum
- Vacuum permittivity
- Vacuum Rabi oscillation
- Vacuum state
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