Introducing Laws of Physics

As announced in October’s blog post, several volumes from the Wenner Collection are now available online in our digital repository . In Part 1, we looked at texts popularizing natural philosophy to the general public. In Part 2, we are going to look at how texts in the collection present scientific discoveries.

Part 2: Introducing Laws of Physics

In modern physics textbooks, we often learn about named laws of physics in the form of simplified equations. However, when they were first published, they often looked quite different. Here are some examples from the Wenner Collection showing how these familiar physics laws were first introduced.

Hooke’s Law

Hooke, Robert. Lectures de potentia restitutiva, or, Of spring : explaining the power of springing bodies : to which are added some collections (London, 1678)
Catalog Record | Digitized Book

If you’ve ever tried to stretch a Slinky, you’ve probably witnessed Hooke’s law of elasticity in action. It states that the force required to stretch (or compress) a spring is proportional to the distance that spring is extended, thus the more you stretch a spring, the harder it is to continue stretching it. Physics textbooks generally teach it as F=-kx where F is the force required to restore a spring to its natural state, k is a constant representing the stiffness of the spring, and x is the distance the spring is stretched or compressed.

In 1678, English natural philosopher Robert Hooke published this treatise on the nature of springs to introduce and explain his theory of springs to the public. Hooke had actually published this theorem secretly two years earlier by hiding it in a Latin anagram in his book on the Descriptions of Helioscopes (1676), but did not reveal it in full until Lectures de potenetia restituvia. It was a common 17^th century practice for scientists to insert ideas they were working on through coded means like anagrams and ciphers into other published works to prove date of discovery in case someone else got around to publishing first and claim the patent to it.

The two anagrams presented in the Descriptions of Helioscopes later revealed in Lectures de potenetia restituvia are:

These Latin anagrams unscramble to “ut tension sic vis” and “ut pondus sic tensio,” which translate to “as with tension, so too the force” and “as with the weight, so too the tension” respectively. Hooke’s maxims observed that the more tension you apply to a spring, such as through extending or compressing it, the greater the force that is required to do so. His theory on weights similarly observed the proportional relationship between the amount of weight hung from a spring and the amount of extension.

Hooke uses his Lectures de potentia restituvia to explore these ideas in more detail and illustrate them with examples from his observations. The treatise is rather short, only 20 pages, so Hooke also took the opportunity to fill out the volume by including other accounts related to erupting bodies in nature (such as natural water springs, fountains, and volcanoes) by other scientists of the day that complimented his theory.

Included are French physicist Denys Papin ’s description of a wind-fountain and spring pump made for Robert Boyle; Plymouth Royal Navy surgeon James Yonge ’s observations on the nature and source of natural fountains and springs in his travels; Captain Samuel Sturmy ’s observations of natural springs and exploring a subterranean cavern near Bristol in 1699; and Hooke’s retelling of the observations from a friend (only known as “Mr. G. T.”) of a 1674 trip to the Pike of Tenerife and the volcanic eruption on the Island of St. Michael de La Palma (in the Canary Islands) on November 13, 1677.

Pascal’s Law

Pascal, Blaise. Traitez de l’equilibre des liqueurs, et de la pesanteur de la masse de l’air. Contenant l’explicaton des causes de divers effets de la nature, qui n’avoient point esté bien connus jusques ici, particulièrement de ceux quel’on avoit attribuez à l’horreur du vuide. (Paris, 1664)
Catalog Record | Digitized Book

This 2^nd edition of French physicist Blaise Pascal’s book on hydrostatic equilibrium and air pressure was a major work in the early science of fluid mechanics. The work was initially published in 1663, a year after Pascal’s death, by his brother-in-law, Florin Périer. It contains an account of the experiments Pascal conducted a decade earlier on the nature of atmospheric pressure and the vacuum, inspired by the work of Torricelli and Galileo. The experiments also demonstrate the relationship between the pressure in liquids and pressure in air.

The text is now best known for introducing “Pascal’s Law” or “Principle,” that any change of pressure in an enclosed incompressible fluid (like water) is transmitted equally to all points within the fluid. This concept, and its application to air pressure, is the basis for how hydraulic lifts and the power brakes in your car work.

In addition to the two main tracts on liquid equilibrium and the weight of air, at the end of the volume are a selection of papers, unpublished works, and letters by Pascal on his experiments related to atmospheric pressure and the vacuum.

Absolute Zero

Boyle, Robert. New experiments and observations touching cold, or, An experimental history of cold, begun : to which are added An examen of antiperistasis, and An examen of Mr. Hob’s doctrine about cold by the Honorable Robert Boyle, fellow of the Royal Society ; whereunto is annexed An account of freezing, brought in to the Royal Society, by the learned Dr. C. Merret, a fellow of it. (London, 1665)
Catalog Record | Digitized Book

This book contains the first published account of the modern concept of absolute zero, or the temperature where all motion of atoms ceases and entropy is at its minimum (-273.15 °C). Earlier theories from the Greeks and Atomist philosophies thought the source of cold was a hypothetical substance called the Primum Frigidum — translating to “the first cold” — that all cold in the world drew from. Boyle expresses his doubt for this concept in this text and instead proposes that there be an absolute minimum temperature that any body can obtain as a quality.

At nearly 1,000 pages, this is one of the longest books we digitized for this project. This edition is also particularly rare. As was common with texts at this period, it includes other accounts on the concept of cold by members of the Royal Society.

Osmosis

Hoff, J. H. van’t. Lois de l’équilibre chimique dans l’état dilué, gazeux ou dissous, (Stockholm, 1886)
Catalog Record | Digitized Book

Jacobus Henricus van’t Hoff (1852-1911) was a Dutch chemist who did pioneering work in the fields of physical and theoretical chemistry. He is particularly known for his discoveries that osmotic pressure obeys the ideal gas law and that chemical reactions are governed by molecular kinetics, which earned him the honor of being the first person ever awarded the Nobel Prize in Chemistry in 1901.

The text that has been digitized here is the first published French edition of van’t Hoff’s theories on osmosis from 1886. In the 1870s, German botanist Wilhelm Frederich Phillipp Pfeffer developed a method to measure the osmotic pressure for various solutions – that is the pressure that occurs while two solutions are trying to reach equilibrium separated by a semi-permeable membrane. In this text, van’t Hoff used Pfeffer’s experimental results to show that osmotic pressure obeys the ideal gas law so that the pressure of a dilute solution is proportional to the absolute temperature and concentration of the solute. In addition, van’t Hoff proposed that osmosis occurred by the motion of solute molecules bounding off the membrane, which was the first time molecular kinetics was applied to understanding osmosis.

Van’t Hoff later published an English edition of his work, but it was more condensed, so this original French version is the most complete version of his Nobel Prize winning theory.

Wave-Particle Duality

Broglie, Louis de. Ondes et mouvements (Paris, 1926)
Catalog Record | Digitized Book

Wave-particle duality is foundational in understanding light and quantum mechanics. The idea that light had properties of both a wave and particulate matter was first proposed by French physicist Louis de Broglie (1892-1987) in 1923 at a meeting of the Paris Academy of Sciences. A graduate student at the time, it soon became his PhD thesis, and finally in 1926 he wrote this treatise, Ondes et mouvements, to explain his theories more fully. Just a year later the results of the double-slit experiment devised by Clinton Davisson and Lester Germer proved his theory and the three of them were awarded the Noble Prize in Physics in 1929.

The Wenner Collection contains copies of de Broglie’s earlier papers . However, this treatise explaining the theory to the public was chosen to be digitized as it is less widely known.

Stay tuned for one more post on the recently digitized Wenner Collection books in the new year!