Henry Cevendish

Personal details: Born on 10 October 1731 in Nice, France – Died on 24 February 1810 in London, United Kingdom.

Education and Specialisation: Educated at Newcome’s School in Hackney and studied at Peterhouse, University of Cambridge. Qualification: Natural Philosopher, Chemist, and Physicist.

Major Discovery: Discovery and isolation of hydrogen gas (which he called “inflammable air”) as a distinct element in 1766, and the accurate measurement of the density and mass of the Earth through the famous Cavendish Experiment (1797–1798).

Henry Cavendish, born in Nice to a high-ranking British aristocratic family in 1731, was a man of extreme wealth, immense intellect, and extraordinary eccentricities. Inheriting a vast fortune that led French physicist Jean-Baptiste Biot to call him “the richest of all the wise, and the wisest of all the rich,” Cavendish lived an almost monastic life entirely dedicated to scientific precision. Suffering from social anxiety bordering on severe pathological shyness—leading modern biographers to suggest he may have been on the autism spectrum—he shunned nearly all human contact. He avoided public life, communicated with his household female servants solely through written notes, and frequented only the meetings of the Royal Society, where he would quietly slip into rooms and engage in conversation only if addressed strictly on scientific matters.

Despite his profound reclusiveness, Cavendish achieved groundbreaking scientific milestones. In 1766, he isolated hydrogen gas (which he called “inflammable air”) and demonstrated it was a distinct element far lighter than atmospheric air. Decades later, in 1797–1798, using a delicate torsion balance apparatus originally designed by John Michell, he carried out the famous “Cavendish Experiment”. By measuring the minuscule gravitational attraction between small lead spheres and larger lead masses in his laboratory, he calculated the mean density of the Earth with astonishing precision—a result that allowed subsequent scientists to deduce the Universal Gravitational Constant ($G$) and calculate the exact mass of the Earth. True to his famously elusive character, Cavendish left a vast body of major discoveries—including Ohm’s Law and the inverse-square law of electrostatic force—completely unpublished in his personal notebooks; they were only revealed to the world decades after his death when James Clerk Maxwell edited and published his manuscripts.

Johan August Arfwedson

Personal details: Born on 10 October 1731 in Nice, France – Died on 24 February 1810 in London, United Kingdom.

Education and Specialisation: Educated at Newcome’s School in Hackney and studied at Peterhouse, University of Cambridge. Qualification: Natural Philosopher, Chemist, and Physicist.

Major Discovery: Discovery and isolation of hydrogen gas (which he called “inflammable air”) as a distinct element in 1766, and the accurate measurement of the density and mass of the Earth through the famous Cavendish Experiment (1797–1798).

Johan August Arfwedson was born in 1792 into a wealthy Swedish aristocratic and merchant family. Displaying exceptional academic promise, he entered Uppsala University at an extraordinarily early age, earning degrees in both law and mineralogy. Combining his knowledge of legal affairs with his passion for natural sciences, Arfwedson briefly worked for the Swedish Board of Mines before moving to Stockholm, where he joined the laboratory of the renowned chemist Jöns Jacob Berzelius.

In 1817, while analyzing samples of the mineral petalite from the Utö iron mine in Sweden, Arfwedson noticed an anomaly: the quantitative analysis consistently yielded a missing fraction of about 4% in weight. Investigating further, he isolated a new alkali metal salt whose chemical properties differed from sodium and potassium. Together with Berzelius, he named the new element lithium (from the Greek lithos, meaning “stone”) to highlight its origin in the mineral kingdom, unlike potassium and sodium which were first isolated from plant ashes. Although Arfwedson was unable to isolate pure metallic lithium itself—a feat achieved later by electrolysis—his discovery added a foundational element to the periodic table. Later in life, Arfwedson devoted much of his time to managing his family’s industrial estates, remaining a respected figure in Swedish science until his death in 1841.

Sir Joseph Norman Lockyer

Personal details: Born on 17 May 1836 in Rugby, United Kingdom – Died on 16 August 1920 in Salcombe Regis, United Kingdom.

Education and Specialisation: Self-taught in the sciences, later appointed Professor of Solar Physics at the Royal College of Science. Qualification: Astronomer and Physicist.

Major Discovery: Identification of the element helium in the solar atmosphere (1868), even before it was discovered on Earth.

Sir Joseph Norman Lockyer was born in Rugby in 1836, but his scientific career truly took off after moving to London in 1857. Initially working as a civil servant at the War Office, he taught himself astronomy from his home in Wimbledon. His breakthroughs eventually earned him a professorship in Solar Physics at South Kensington, a role from which he orchestrated eight scientific expeditions across the globe—including to India and Egypt—to study solar eclipses. In 1911, eager to escape London’s notorious smog, he retired to Salcombe Regis in Devon, where he established the observatory that he would work in until his death in 1920.

Lockyer’s name is forever linked to the extraordinary double discovery of helium in 1868. On 20 October that year, peering through his spectroscope from England, Lockyer spotted an unfamiliar yellow line in the solar spectrum. Unbeknownst to him, the French astronomer Pierre Janssen had captured the very same line just a couple of months earlier, in August, whilst observing an eclipse in India. Entirely unaware of each other’s work, both men posted their findings to the French Academy of Sciences. In a staggering twist of timing, their letters arrived on the exact same day, 26 October, just hours apart. To avoid a massive row over who got there first, the Academy gracefully chose not to pick sides; they awarded the discovery ex aequo to both men, immortalising their joint triumph on a single commemorative medal.

Pierre Jules César Janssen

Personal details: Born on 22 February 1824 in Paris, France – Died on 23 December 1907 in Meudon, France.

Education and Specialisation: Educated at the Faculty of Sciences of the University of Paris (Doctorate in Physical Sciences, 1860); later appointed Professor of Physics at the École Architecture and Director of the Meudon Astrophysical Observatory. Qualification: Astronomer and Physicist.

Major Discovery: Co-discovery of helium in the solar spectrum during the total solar eclipse of 18 August 1868 in Guntur, India, and the simultaneous invention of a spectroscopic technique to observe solar prominences without waiting for an eclipse.

Pierre Jules César Janssen was born in Paris in 1824 into a cultivated family. A severe childhood accident left him permanently lame, preventing him from attending regular schools during his early years. Undeterred, he pursued higher education independently and at the University of Paris, earning his doctorate in physical sciences in 1860 with a thesis on optics and the eye. Janssen quickly established himself as a master of observational astronomy and spectroscopy, traveling tirelessly across the globe to study solar phenomena—often under extraordinary conditions, such as escaping the Siege of Paris in 1870 in a hot-air balloon (“Le Volta”) just to observe a solar eclipse in Algeria.

Janssen’s legacy is forever tied to the historic total solar eclipse of 18 August 1868 in Guntur, India. Observing the brilliant red solar prominences with a spectroscope, he noticed a bright, unidentified yellow emission line near the sodium D lines. Crucially, Janssen realized that by opening the slit of his spectroscope and tuning it to specific wavelengths, he could observe these solar prominences in full daylight without an eclipse. He dispatched his report to the French Academy of Sciences, where it arrived on 26 October 1868—the very same day as a letter from Norman Lockyer describing the exact same solar line. Recognizing both scientists’ genius, the Academy awarded them a joint honor, cementing Janssen as a co-discoverer of helium and a founding figure of modern astrophysics.

Antoine Laurent de Lavoisier

Personal details: Born on 26 August 1743 in Paris, France – Died on 8 May 1794 in Paris, France.

Education and Specialisation: Educated at Collège Mazarin and studied law at the University of Paris (earned his licentiate in law in 1764, though he never practiced) while studying natural sciences under leading French scholars. Qualification: Chemist, Biologist, and Natural Philosopher (widely recognized as the “Father of Modern Chemistry”).

Major Discovery: Formulation of the Law of Conservation of Mass (“Nothing is lost, nothing is created, everything is transformed”) and the discovery of the role of oxygen in combustion and respiration, overthrowing the long-standing phlogiston theory.

Antoine Laurent de Lavoisier was born in Paris in 1743 into a wealthy bourgeois family. Though he completed a law degree at his father’s urging, his true passion lay in the natural sciences. Inheriting a massive fortune at a young age and expanding it through his involvement with the Ferme Générale (the royal tax agency), Lavoisier used his wealth to build the most sophisticated, state-of-the-art chemical laboratory in Europe. His work was transformed into a collaborative genius through his marriage to Marie-Anne Paulze, who translated English scientific papers, illustrated his apparatus, and kept meticulously detailed laboratory records.

Lavoisier’s scientific revolution replaced centuries of qualitative alchemy with rigorous quantitative measurement. By introducing sealed glass vessels and precise balances to measure the exact weight of reactants and products before and after chemical reactions, he proved that mass is always conserved. In 1774, after meeting Joseph Priestley—who had isolated an unusual gas—Lavoisier conducted crucial experiments demonstrating that this gas (which he named “oxygen”) was the active agent in both combustion and animal respiration.

Tragically, Lavoisier’s position as a tax collector made him a prime target during the Reign of Terror at the height of the French Revolution. Arrested along with 27 other members of the Ferme Générale, he was tried and guillotined on 8 May 1794. Popular legend holds that when appeals were made to spare his life for his scientific genius, the revolutionary judge declared, “La République n’a pas besoin de savants” (“The Republic has no need for scientists”). The day after his death, the famous mathematician Joseph-Louis Lagrange lamented: “It took them only a moment to cause this head to fall, and a hundred years will not suffice to produce its like.”

[01] The Molecular Cloud

It all begins in the vastness of space, where a gigantic cloud of gas and dust drifts through the freezing darkness, dense with mystery and potential.

[02] Gravitational Collapse

Then, the balance is broken. Gravity pulls the cloud inward, drawing its material toward the center and causing it to spin faster and faster.

Driven by this rapid rotation, the cloud flattens into a wide, spinning disk. At its center, matter continues to gather and become increasingly concentrated.

[03] The Protoplanetary Disk

[04] The Protostar

At the heart of this swirling cloud, a protostar begins to take shape. It is the first spark: pressure and temperature begin to rise dramatically.

[05] The Birth of the Sun

The core becomes an immense furnace. Once the critical temperature is reached, nuclear fusion ignites — and our Sun is born.

[06] Dust and Pebbles

Meanwhile, within the disk surrounding the newborn star, a chaotic dance begins. Dust particles collide and stick together, gradually forming grains and small rocky bodies.

[07] Planetesimals

The process continues. Through collisions and the force of gravity, these small fragments grow into planetesimals — solid building blocks of rock and ice orbiting the young Sun.

[08] Protoplanets

The planetesimals continue to collide and merge, giving rise to protoplanets — the embryos of the worlds that will eventually form.

[09] Planet Formation

The system gradually takes shape. In the regions closest to the Sun, where temperatures are higher, rocky planets begin to form, including Earth. Farther out, where it is much colder, gas and ice giants begin to take shape.