The Physics of Diving & Laws

The Physics of Diving

Diving physics are the aspects of physics which directly affect the underwater diver. Physics explain the effects that divers and their equipment are subject to underwater while diving. These effects usually differ from the normal human experience out of the water.

The effects are mostly consequences of immersion in water, the hydrostatic pressure of depth and the effects of the pressure on breathing gases, the diver and the diving equipment.

An understanding of physics is useful when considering the physiological effects of diving and the hazards and risks of diving (full article).

Archimedes’ Law

Archimedes of Syracuse (287 – 212 BC) was a Greek mathematician, physicist, engineer, inventor and astronomer. Archimedes anticipated modern calculus and analysis by applying concepts of infinitesimals and the method of exhaustion to derive and rigorously prove a range of geometrical theorems, including the area of a circle, the surface area and volume of a sphere, and the area under a parabola (full article).

Archimedes’ law or Archimedes’ principle states that a body immersed in a fluid experiences a buoyant force equal to the weight of the fluid it displaces.

Read more about buoyancy and Archimedes’ principle in the following post: Let’s Talk About Buoyancy.

Boyle’s Law

Robert Boyle (1627 – 1691) was an Anglo-Irish natural philosopher, chemist, physicist, and inventor. Boyle is largely regarded today as the first modern chemist, and therefore one of the founders of modern chemistry, and one of the pioneers of modern experimental scientific method (full article).

Boyle’s law sometimes referred to as the Boyle–Mariotte law, or Mariotte’s law is an experimental gas law that describes how the pressure of a gas tends to increase as the volume of the container decreases.

Read more about pressure volume relationships and Boyle’s law in the following post: Pressure Volume Relationships in Diving.

Charles’ Law

Jacques Alexandre César Charles (1746 – 1823) was a French inventor, scientist, mathematician, and balloonist. Charles wrote almost nothing about mathematics, and most of what has been credited to him was due to mistaking him with another Jacques Charles, also a member of the Paris Academy of Sciences. Charles and the Robert brothers launched the world’s first unmanned hydrogen-filled gas balloon in  1783. Charles and his co-pilot Nicolas-Louis Robert ascended to a height of about 1,800 feet (550 m) in a manned gas balloon. Their pioneering use of hydrogen for lift led to this type of balloon being named a Charlière (full article).

Charles’s law, describing how gases tend to expand when heated, was formulated by Joseph Louis Gay-Lussac in 1802, but he credited it to unpublished work by Jacques Charles.

Charles’s law also known as the law of volumes is an experimental gas law that describes how gases tend to expand when heated.

Read more about pressure volume temperature relationships and Charles’ law in the following post: The Ideal Gas Law and the General Gas Equation.

Dalton’s Law

John Dalton (1766 – 1844) was an English chemist, physicist, and meteorologist. He is best known for introducing the atomic theory into chemistry, and for his research into colour blindness, sometimes referred to as Daltonism in his honour (full article).

In chemistry and physics, Dalton’s law also called Dalton’s law of partial pressures states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases.

Read more about partial pressures and Dalton’s law in the following post: Partial Pressure Implications.

Gay-Lussac’s Law

Joseph Louis Gay-Lussac (1778 – 1850) was a French chemist and physicist. He is known mostly for his discovery that water is made of two parts hydrogen and one part oxygen, for two laws related to gases, and for his work on alcohol-water mixtures, which led to the degrees Gay-Lussac used to measure alcoholic beverages in many countries (full article).

This law is often referred to as Gay-Lussac’s law of pressure–temperature. The pressure of a gas of fixed mass and fixed volume is directly proportional to the gas’s absolute temperature.

Gay-Lussac’s law can refer to several discoveries made by the French chemist and other scientists in the late 18th and early 19th centuries pertaining to thermal expansion of gases and the relationship between temperature, volume, and pressure.

Read more about pressure volume temperature relationships and Gay-Lussac’s law in the following post: The Ideal Gas Law and the General Gas Equation.

Henry’s Law

William Henry (1774 – 1836) was an English chemist. He was the son of Thomas Henry and was born in Manchester England. He developed what is known today as Henry’s Law (full article).

In chemistry, Henry’s law is a gas law that states that the amount of dissolved gas is proportional to its partial pressure in the gas phase.

Read more about dissolution of gases in liquids and Henry’s law in the following post: Decompression Theory Basics.

 Snell’s Law

Snell’s law is also known as Snell–Descartes law or the law of refraction.

Although named after Dutch astronomer Willebrord Snellius (1580–1626), the law was first accurately described by the Persian scientist Ibn Sahl at the Baghdad court in 984. In the manuscript On Burning Mirrors and Lenses, Sahl used the law to derive lens shapes that focus light with no geometric aberrations.

The law was rediscovered by Thomas Harriot in 1602, who however did not publish his results although he had corresponded with Kepler on this very subject. In 1621, Willebrord Snellius (Snell) derived a mathematically equivalent form, that remained unpublished during his lifetime. René Descartes independently derived the law using heuristic momentum conservation arguments in terms of sines in his 1637 (full article).

The index of refraction of water is similar to that of the cornea of the eye, one third greater than air. This is the reason a diver cannot see clearly underwater without a diving mask with an internal airspace.

Read more about refraction of light and Snell’s law in the following post: How We See Things Underwater: It’s All About Light.


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