# The history of science

How humans learned to question nature: Greek natural philosophy, the optics of Ibn al-Haytham, the Scientific Revolution from Copernicus and Galileo to Newton's Principia, the chemistry and biology of the 1800s, and the modern upheavals of relativity, quantum mechanics, DNA, and plate tectonics.

*This story parallel: How Islam began and spread*
*This story parallel: How technology remade the world*
*This story parallel: The Catholic Church as a world power*
*This story parallel: The Renaissance: the rebirth of antiquity*
*This story part of: Science and technology*
*The history of mathematics parallel this story*
*Science and technology parallel this story*

## c. 1601 BCE — Egyptian medicine and the Edwin Smith papyrus

The surviving papyrus, copied from a much older text, treats injuries by observation and prognosis rather than by magic alone. It shows early empirical medicine sitting side by side with spells and ritual. Historians caution against reading it as fully rational science; healing in Egypt mixed careful observation with religion.

## c. 701 BCE — Babylonian astronomers record the sky as numbers

Scribes in Mesopotamia kept centuries of records of the moon, planets, and eclipses on clay tablets, and reduced their motions to arithmetic rules. This was proto-science, not modern science: the goal was omens and calendars, not physical laws. Yet the data and mathematical methods later fed directly into Greek astronomy.

## c. 586 BCE — Thales and the first natural philosophers

Thales and the Milesian thinkers began to explain the world through natural causes rather than the acts of gods, asking what everything was made of. The famous story that Thales predicted a solar eclipse is likely later legend. The lasting shift was the idea that nature follows understandable principles.

## c. 401 BCE — Hippocratic medicine separates disease from the divine

The texts gathered under the name of Hippocrates argued that illness had natural causes and could be studied through observation of the patient. The works were written by many hands over generations, not one man. Their theory of four humors was wrong, but the method of careful bedside observation endured.

## c. 351 BCE — Aristotle's physics, four elements, and Earth at the center

Aristotle built a vast system in which everything on Earth was made of earth, water, air, and fire, and the heavens turned around a motionless Earth. His work was a huge advance in systematic reasoning and biology, based on real observation of animals. It also fixed several wrong ideas, like geocentrism and objects needing a constant push to move, that would take almost two thousand years to overturn.

## c. 241 BCE — Eratosthenes measures the size of the Earth

Using the different noon shadows cast at Alexandria and Syene, Eratosthenes estimated the Earth's circumference by simple geometry and got close to the true value. The exact figure depends on the length of his units, which we cannot pin down. The point stands: Greek science already knew the Earth was a globe and roughly how big.

## c. 150 — Ptolemy's Almagest codifies the geocentric universe

Ptolemy gathered Greek astronomy into a mathematical model that predicted planetary positions using circles upon circles. It was geocentric and, in hindsight, wrong about the structure of the cosmos. But it worked well enough to guide navigation and calendars for over a thousand years, which is why it was so hard to displace.

## c. 830 — The House of Wisdom gathers the world's learning in Baghdad

Under Abbasid patronage, scholars in Baghdad translated Greek, Persian, and Indian works into Arabic and pushed them forward. The picture of a single grand library called the House of Wisdom is partly a modern simplification of a broader translation movement. Either way, this era preserved and advanced knowledge that Europe had largely lost.

## c. 1021 — Ibn al-Haytham and the experimental study of light

In his Book of Optics, Ibn al-Haytham (Alhazen) showed that we see because light reflects from objects into the eye, overturning older Greek theories. He insisted on testing ideas against controlled observation, and many historians credit him as an early champion of the experimental method. The claim that he invented the scientific method single-handed is an overstatement, but his stress on evidence over authority was real and influential.

## c. 1025 — Ibn Sina's Canon of Medicine

Ibn Sina (Avicenna) organized Greek and Islamic medicine into a single encyclopedic work that became a standard text in Europe and the Islamic world for centuries. It combined real clinical insight with the inherited humoral theory that was later abandoned. Its long reign shows both the strength and the danger of a single authoritative textbook.

## 1543 — Copernicus places the sun at the center

In On the Revolutions of the Heavenly Spheres, published the year he died, Copernicus put the sun at the center and set the Earth in motion. His system still used circular orbits and was not obviously more accurate than Ptolemy's at first. Its real power was conceptual: it made the sun-centered cosmos a serious scientific proposal.

## 1543 — Vesalius corrects the anatomy of the human body

Vesalius published On the Fabric of the Human Body based on his own dissections, correcting many of Galen's long-accepted errors. His insistence on looking at the body directly, rather than trusting ancient texts, marked a turn toward evidence in medicine. The lavish illustrations spread the new anatomy across Europe.

## c. 1576 — Tycho Brahe builds the best pre-telescope observatory

Tycho Brahe gathered decades of extremely precise naked-eye measurements of the planets and stars from his observatory at Uraniborg. He kept the Earth at the center in his own hybrid model, so he was not a Copernican. But his data, more accurate than anything before, became the raw material for a revolution he did not intend.

## 1609 — Kepler's laws break the spell of the perfect circle

Working from Tycho's data, Kepler found that planets move in ellipses, not circles, and sweep out equal areas in equal times. His third law, linking orbital period to distance, followed in 1619. He reached these results through years of grinding calculation, and mixed them with mystical ideas about cosmic harmony that historians are careful not to airbrush out.

## 1610 — Galileo turns the telescope on the heavens

In Sidereus Nuncius, Galileo reported moons circling Jupiter, mountains on the moon, and countless unseen stars, all through a telescope he did not invent but greatly improved. These sights were hard to square with a perfect, Earth-centered heaven. He became the loudest public voice for the Copernican system.

## 1620 — Francis Bacon argues for knowledge from experiment

In Novum Organum, Bacon called for building knowledge from careful observation and experiment rather than from ancient authority. He was a promoter and organizer of method more than a working scientist, and did little experimenting himself. His vision of collective, evidence-based inquiry helped inspire later scientific societies.

## 1633 — The trial of Galileo

The Roman Inquisition tried Galileo for defending the sun-centered system and forced him to recant, sentencing him to house arrest. The clash was tangled up in Church politics, personality, and how he argued, not simply science against religion. It became a lasting symbol of the cost of challenging authority, and later a caution against reading all of history as that one story.

## 1637 — Descartes and reason as the path to knowledge

In the Discourse on Method, Descartes argued for doubting everything and rebuilding knowledge on clear reasoning and mathematics. His mechanical picture of nature as matter in motion shaped how the next generation thought. Some of his specific physics was wrong, but his push for systematic method left a deep mark.

## 1687 — Newton's Principia unifies the heavens and the Earth

In the Principia, Newton set out three laws of motion and a law of universal gravitation that governed both falling apples and orbiting planets. It fused Kepler's and Galileo's findings into one mathematical system and became the model of what a scientific theory could be. The tidy apple story is mostly legend; the work rested on years of hard mathematics and drew on many predecessors.

## c. 1752 — Franklin and the electric nature of lightning

Benjamin Franklin's experiments argued that lightning is electrical and introduced ideas like positive and negative charge. The dramatic kite story is probably exaggerated, and flying a kite in a storm as usually pictured would be deadly. His real contribution was a clear theory of electricity and the practical lightning rod.

## 1789 — Lavoisier and the chemical revolution

Lavoisier named oxygen, discredited the old phlogiston theory of burning, and showed that matter is conserved in chemical reactions. He built much of his work on careful weighing, and on results from others such as Priestley whom he did not always credit. His wife Marie-Anne was a real collaborator, translating and illustrating the work. He was executed in the Terror in 1794.

## 1824 — Carnot lays the ground for thermodynamics

Sadi Carnot analyzed the ideal steam engine and found deep limits on how much work heat can do, seeding the science of thermodynamics. He still thought of heat as a fluid, a picture later abandoned, yet his core result survived. His work was largely ignored until Clausius and Kelvin built the first and second laws on it decades later.

## 1831 — Faraday discovers electromagnetic induction

Michael Faraday showed that a changing magnetic field produces an electric current, the principle behind generators. Largely self-taught and weak in mathematics, he thought in terms of invisible fields of force filling space. That intuition, later given equations by Maxwell, reshaped physics.

## 1839 — Cell theory: all life is made of cells

Schleiden and Schwann proposed that plants and animals are all built from cells, the basic unit of life. They got some details wrong, such as how new cells form, corrected later by Virchow's rule that cells come from cells. The core claim became a foundation of modern biology.

## 24 November 1859 — Darwin publishes On the Origin of Species

Darwin argued that species change over time through natural selection, offering a natural mechanism for the diversity of life. He rushed the book into print after Alfred Russel Wallace independently reached the same idea, a shared credit often forgotten. It reshaped biology and set off a long argument with religion that continues in places today.

## c. 1861 — Pasteur and the germ theory of disease

Louis Pasteur's experiments argued that microbes, not spontaneous generation or bad air, cause fermentation and disease. His public swan-neck flask demonstration was carefully staged to win the argument. The germ theory transformed medicine, surgery, and public health.

## 1865 — Maxwell's equations unify electricity, magnetism, and light

James Clerk Maxwell showed that electricity and magnetism are two sides of one field and that light itself is an electromagnetic wave. His equations predicted radio waves before anyone had detected them. It was one of the great unifications in physics and set the stage for relativity.

## 1866 — Mendel's laws of heredity, ignored then rediscovered

The monk Gregor Mendel worked out the basic rules of inheritance by breeding pea plants, but his paper went almost unnoticed for decades. It was rediscovered around 1900, long after his death, and became the basis of genetics. Some later analysts have argued his data look suspiciously clean, a debate that has never been fully settled.

## 1869 — Mendeleev arranges the periodic table

Dmitri Mendeleev arranged the elements by weight and properties into a table, and boldly left gaps for elements not yet found. When those elements turned up with the predicted properties, his system won wide acceptance. Others were groping toward similar tables, but his willingness to predict set his apart.

## 1882 — Koch pins diseases to specific microbes

Robert Koch identified the microbes that cause tuberculosis and other diseases and set out rules, now called Koch's postulates, for proving a germ causes an illness. His rigorous methods turned germ theory into a working science of specific diseases. The bitter rivalry between his German school and Pasteur's French one drove much of the era's progress.

## 1905 — Einstein's special relativity

In his miracle year, Einstein argued that the speed of light is constant for all observers, so space and time stretch and shrink with motion. The same year he explained the photoelectric effect and Brownian motion. He built on work by Lorentz and Poincare, who had some of the pieces but not the full reinterpretation.

## 1915 — Einstein's general relativity reshapes gravity

Einstein recast gravity not as a force but as the bending of space and time by mass and energy. The theory predicted that starlight would bend around the sun, confirmed by an eclipse expedition in 1919 that made him famous overnight. It remains our best description of gravity and the large-scale universe.

## c. 1925 — Quantum mechanics remakes the rules of matter

In the mid-1920s Heisenberg, Schrodinger, Born, Dirac, and others built quantum mechanics, in which particles behave as probabilities rather than certainties. It was the work of many hands over a few intense years, not a single breakthrough. Its predictions are astonishingly accurate, yet physicists still argue about what it really means.

## 1929 — Lemaitre and Hubble find an expanding universe

Edwin Hubble's measurements showed that distant galaxies are rushing away from us, so the universe is expanding. The Belgian priest Georges Lemaitre had derived the expansion and proposed a primeval atom two years earlier, an idea that grew into the Big Bang. The name Big Bang was actually coined later by a skeptic, Fred Hoyle, as a jab.

## 1934 — Popper argues that science must be falsifiable

Karl Popper argued that a theory is scientific only if it makes predictions that could in principle be proven wrong. This drew a line between science and claims that explain everything and risk nothing. Later philosophers, including Kuhn, argued that real science rarely works as cleanly as Popper's rule suggests.

## 1953 — The double helix and the contested credit of Rosalind Franklin

Watson and Crick worked out that DNA is a double helix, revealing how genetic information is copied and passed on. Their model depended heavily on Rosalind Franklin's X-ray images, shown to them without her clear consent, and she received little credit at the time. She had died before the 1962 Nobel Prize, which does not go to the dead, and the fairness of the credit is still debated.

## 1962 — Kuhn and the idea of scientific revolutions

Thomas Kuhn argued that science does not just accumulate facts but lurches between paradigms, with old frameworks replaced in crises. His book made paradigm shift a household phrase and challenged the tidy story of steady progress. Critics warned his view could be pushed too far, into treating all theories as equally valid, which he did not intend.

## c. 1965 — Plate tectonics vindicates a drifting Earth

Alfred Wegener had proposed drifting continents back in 1912, but was dismissed for lacking a mechanism. In the 1960s, seafloor spreading and magnetic stripes on the ocean floor supplied the missing engine, and plate tectonics became the framework of modern geology. It is a clear case of a rejected idea proven right once the evidence caught up.

## c. 1970 — Peer review and science as a self-correcting process

Formal peer review, where experts vet a paper before publication, became standard in most journals only in the middle of the twentieth century, later than many assume. It is a filter, not a guarantee of truth, and it misses errors and fraud. The deeper strength of science is that findings must survive repeated testing by others, so it corrects itself over time rather than resting on fixed truths.

## c. 1975 — The Standard Model and the Higgs boson

Through the 1960s and 1970s physicists assembled the Standard Model, describing the known particles and three of the four fundamental forces. Its final missing piece, the Higgs boson, was predicted in 1964 and detected at CERN in 2012. The model is our most tested theory, yet it leaves out gravity and dark matter, so the work is unfinished.