In 1543, Nicolaus Copernicus proposed his heliocentric model of the universe.

As Nicolaus Copernicus said in his book On the Revolutions of theCelestial Spheres,moons and planets orbit more than one center. Only the moon orbits the earth. The celestial spheres orbit the sun. The firmament moves because the earth turns. The seasons change because the earth wobbles as it orbits the sun. Planets sometimes appear to move backwards only because the earth moves. Earth’s distance to the sun is insignificant compared to the sun’s distance to the stars.

*More
poems* . . .

Copernicus was not the first person to propose a heliocentric universe; however, Copernicus provided a predictive mathematical model.

Copernicus placed the center of the universe near but not at the sun. Understanding how gravity controls the orbits of planets and moons escaped him, as well as Kepler and Galileo.

Andreas Osiander wrote an preface for the first edition of *De
revolutionibus orbium coelestium* that stated that the Copernican
theory was not intended as a description of the literal truth but
only as a simpler mathematical description of astronomical
observations to improve the calendar.

See also in *The book of science:*

- 140—
*Geocentrism*—Claudius Ptolemy - 1609—
*Planetary orbits*—Johannes Kepler - 1610—
*Observational astronomy*—Galileo Galilei - 1687—
*Principia Mathematica*—Isaac Newton - 1705—
*Halley’s comet*—Edmond Halley - 1781—
*Discovery of Uranus*—William Herschel - 1801—
*Discovery of an asteroid*—Giuseppe Piazzi, Carl Friedrich Gauss - 1838—
*Distance to a star*—Friedrich Bessel - 1842—
*Doppler effect*—Christian Doppler - 1845—
*Spiral galaxies*—William Parsons - 1929—
*Expanding universe*—Georges Lemaître, Edwin Hubble

Readings on wikipedia:

]]>In 1542, Pedro Nunes invented the nonius, a scale that improved accuracy of scientific instruments, which Tycho Brahe used and Pierre Vernier based his scale on.

Tycho Brahe put a nonius on his astronomic quadrant to improve the accuracy of his stellar observations. The astrolabe with alidade is an ancient instrument. Soon after Nunes invented the nonius, astrolabes became obsolete.

*More
poems* . . .

The vernier scale was a refinement of the nonius and is still called a nonius in some languages. Both designs improve accuracy by taking advantage of our ability to recognize how closely two lines are aligned. Reliable machines for drawing and marking arcs, called dividing engines, were not available until we get to Henry Hindley around 1739.

See also in *The book of science:*

- 1572—
*Supernova*—Tycho Brahe - 1631—
*Vernier scale*—Pierre Vernier - 1638—
*Micrometer*—William Gascoigne - 1739—
*Dividing engine*—Henry Hindley

Readings in wikipedia:

]]>In 1538, Paracelsus, observing that the dose makes the poison, made the first contribution to the science of toxicology.

Alle Dinge sind Gift und nichts ist ohne Gift, macht nur die Dosis etwaseinGift oderkeinGift, so dass ein Gift ist zu viel von etwas, und zu wenig von allem, ohne Ausnahme, ist kein Gift.

*More
poems* . . .

Paracelsus showed that syphilis was contracted by contact and treated with carefully measured doses of mercury. He is credited with introducing the first pain-killer to the west, the opiate laudanum. He was the first to point out that psychology affects physiology, that unconscious fantasizing about certain diseases can make a person more vulnerable to them.

See also in *The book of science:*

Readings on wikipedia:

]]>In 1499, Johannes Trithemius showed several ways that a secret message could be hidden in an unrelated document.

Johannes Trithemius claimed that Jerome said that many mysteries, intended for only the most learned philosophers and poets, lay hidden in the original Greek of the Apocalypse of John. In hisSteganographiaJohannes Trithemius wove a hundred forms of secret writing into a three-volume treatise about how to use angels to communicate over long distances.

*More
poems* . . .

Steganography is a form of cryptography that can be combined with ciphers, codes, and encryption. These terms are often used loosely; however, it can be useful to give them distinct meanings. Steganography is a means of hiding a message; a cipher is a one-to-one alphabetic substution; a code is a one-to-many substitution such as binary or Morse code; encryption uses a mathematical scheme to disguise any digital message.

See also in *The book of science:*

- 118 BCE - 1953—
*Cipher*—Polybius, Julius Caesar, Giovan Battista Bellaso, Antoine and Bonaventure Rossignol, Charles Wheatstone, Frank Miller, Felix Delastelle, Fritz Nebel, Lester S. Hill, John F. Byrne - 1605—
*Bacon’s cipher*—Francis Bacon - 1976-1991—
*Public-key cryptography*—Whitfield Diffie, Martin Hellman, Ralph Merkle, Phil Zimmermann

Readings in wikipedia:

]]>In 1485, Leonardo da Vinci designed the first workable parachute.

An unnamed contemporary of Leonardo da Vinci depicted a conical parachute in the 1470s, but let’s say the parachute started with da Vinci because his twelve-yard pyramidal design was more well proportioned to carry the weight of a man, because the first person to test the idea, Fausto Veranzi, studied da Vinci, and because da Vinci’s design was recently proven to work.

*More
poems* . . .

Skydivers put themselves in a life-or-death situation and only by careful preparation do they avoid killing themselves. They do it not only because diving is exhilarating, but also because it is the closest humans get to a feeling of human-powered flight.

Thinking about free fall led Einstein to his general theory of relativity. A man in free fall would feel no force of gravity, and, given no force, would fall at a constant speed; however, on the contrary gravity causes him to accelerate.

See also in *The book of science:*

- 5th century BCE—
*Kite*—Mozi, Lu Ban - 1672,1742,1852—
*Magnus effect*—Isaac Newton, Benjamin Robins, Heinrich Gustav Magnus - 1699—
*Tribology*—Leonardo da Vinci, Guillaume Amontons - 1738—
*Bernoulli’s principle*—Daniel Bernoulli - 1903—
*Airplane*—Wilbur Wright, Orville Wright

Readings on wikipedia:

]]>In 1450, Nicolaus de Cusa described a simple hygrometer to measure humidity.

Nicolas de Cusa observedIf someone should hang a good deal of wool, tied together on one end of a large pair of scales, and should balance it with stones at the other end in a place where the air is temperate, it would be found that the weight of the wool would increase when the air became more humid, and decrease when the air tended to dryness.Leonardo da Vinci might have been the first to build one, in which the bundle of wool, absorbing more water when the air was more humid, gradually tipped the scale.

*More
poems* . . .

Scientists have created many ways to measure humidity. Here is an incomplete chronology assembled from the readings below (not original work):

- 1450: Nicolaus de Cusa described the first hygrometer.
- 1481: Leonardo da Vinci implemented de Cusa's idea.
- 1625: Santorrio Santorre made a hygrometer by hanging a weight on the string of a lyre.
- 1650: Ferdinand II, the Grand Duke of Tuscany, invented the condensation hygrometer.
- 1664: Francesco Folli designed the first practical hygrometer, a paper-ribbon hygrometer.
- 1687: Guillaume Amontons invented a hygrometer similar to a three-liquid barometer.
- 1755: Johann Heinrich Lambert made a hygrometer, and in 1774 first coined the term “hygrometer.”
- 1783: Horace Bénédict de Saussure invented the hair hygrometer.
- 1799: John Leslie measured the humidity using a differential thermometer with a dry-bulb and a wet-bulb (a psychrometer).
- Late 1700s: James Hutton invented the sling psychrometer.
- 1815: Joseph Louis Gay-Lussac derived the formula for calculating humidity from readings of the dry- and wet-bulb thermometers.
- 1818: Ernst August coined the name “psychrometer.”
- 1820: John Frederic Daniell invented the dew-point hygrometer.
- 1854: Henri Victor Regnault created a dew-point hygrometer using ether in a silver thimble.
- 1887: Richard Assmann invented the aspirated (ventillated) psychrometer.
- 1938: Dumore began research into developing the electric hygrometer.

See also in *The book of science:*

Readings in wikipedia:

]]>Linear perspective for artists was invented in Florence, beginning with demonstrations by Filippo Brunelleschi.

People in Florence had it figured out— how to trick the eye with an illusion of depth. Filippo Brunelleschi demonstrated its realism by comparing the view of the Florentine Baptistery from a doorway of the unfinished Il Duomo with his painting reflected in a mirror. Leon Battista Alberti wrote the first manual for artists. Piero della Francesca completed the picture by adding illustrations and showing how to represent solids in any area of the picture plane.

*More
poems* . . .

An artist expressing his or her feelings in art, even making abstract art, is an act of illusion, a sleight of hand. It is not a contradiction that a mathematics based on optics can help an artist create an illusion of a realistic scene. Our eyeballs project the world onto our retinas upside down and horizontally inverted. Given that our minds are not tied to the orientation of the image on our retinas, one might ask whether there is any limit to the mind’s ability to make things seem right when they are not.

Although Brunelleschi made his demonstration between 1413 and
1420, Alberti published *De pictura* in 1435, and Francesca
wrote *De Prospectiva Pingendi* around 1480. It took many
years for the practice to spread to other parts of Italy and
Europe.

See also in *The book of science:*

Readings on wikipedia:

- “Filippo Brunelleschi”
- “Leon Battista Alberti”
- “Piero della Francesca”
- “De pictura” by Leon Battista Alberti
- “De Prospectiva Pingendi” by Piero della Francesca
- “Perspective (graphical)”

In 1202, Fibonacci introduced to Europe the modern number system and arithmetical methods using them.

InLiber Abaci,Leonardo Pisano Bigollo, known today as Fibonacci, the son of Bonacci, popularized the use of the nine numerals, the zero sign, and the concept of place value. In this book (the “Book of Calculation”), Fibonacci showed how to solve business problems— conversions of currency and measurements, and calculations of profit and interest. Fibonacci also showed how to use the number system for purely mathematical concepts— perfect numbers, primes, and series including the eponymous Fibonacci series. Finally Fibonacci described numeric and geometric approximations and irrational numbers such as the square root of two.

*More
poems* . . .

Fibonacci contributed to Europe’s adoption of arithmetical methods using the modern numeral system, as opposed to using counting boards (like the abacus) with Roman numerals.

See also in *The book of science:*

- 300 BCE—
*Geometry*—Euclid - 495 BCE—
*Proof of the Pythagorean theorem*—Pythagoras - 628—
*Zero*—Brahmagupta - 1614—
*Logarithms*—John Napier - 1637—
*Cartesian coordinates*—René Descartes - 1656—
*Infinite and infinitesimal*—John Wallis - 1668,1799—
*Metric system*—John Wilkins (and the French Revolution) - 1768—
*Pi*—Johann Heinrich Lambert, Ferdinand von Lindemann - 1829—
*Non-Euclidean geometry*—Nicolai Lobachevsky, János Bolyai, Bernhard Riemann

Readings on wikipedia:

- “Fibonacci”
- “Liber Abaci,” by Leonardo Pisano Bigollo (Fibonacci)
- “Numeral system”
- “Hindu–Arabic numeral system”
- “Positional notation”
- “Fibonacci number”
- “Arithmetic”

By 1050 the Mayans had invented an intricate and accurate calendar that was adopted by the major Mesoamerican cultures.

The day of the Mayan creation—the beginning of the Mayan era—was 13.0.0.0.0: 13 b'ak'tuns, 0 k'atun, 0 tun, 0 winal, 0 k'in, 4 Ajaw 8 Kumk'u, or 11 August 3114 BCE, we would say. A k'in is a day. A winal is 20 k'ins. A tun is 20 winals. A k'atun is 20 tun. A b'ak'tun is 20 k'atun. That was on a Monday.

*More
poems* . . .

The Maya calendar was adopted by other Mesoamerican cultures, including the Aztec, Toltec, Huastec, Mixtec, Olmec, and Zapotec. My descriptions of the lords of night are modelled on Aztec mythology.

See also in *The book of science:*

- 2782 BCE—
*Egyptian calendar*—Old Kingdom of Egypt - 2637 BCE—
*Chinese calendar*—Huangdi - 46 BCE—
*Julian calendar*—Julius Caesar - 359—
*Hebrew calendar*— Hillel II, Maimonides

Readings in wikipedia:

]]>In 1040, Bi Sheng of the Song dynasty in China invented movable-type printing.

During the Northern Song dynasty the commoner Bi Sheng cut characters into porcelain clay and fired them. He arranged these in an iron frame and pressed them into a thick paste of pine resin, wax, and paper ashes, creating the first movable-type printing method.

*More
poems* . . .

Gutenberg introduced the hand mould, the mechanical printing press, and oil-based inks that allowed duplex printing. He made his type with an alloy of lead, tin, and antimony. The Gutenberg Bible was rubricated (it included words printed in red) and illuminated (intial letters were elaborated and painted by hand). The technologies that led to his work were goldsmithing, cutting dies for stamping coins, and Roman screw presses for producing wine and olive oil.

See also in *The book of science:*

Readings on wikipedia:

]]>In 1025, Avicenna published an encyclopedia of medicine, establishing principles that are still followed.

Avicenna’s encyclopedia of medicine synthesized Galen, Aristotle, and traditional medical practice in India and became a standard medical textbook in Europe for over six hundred years.

*More
poems* . . .

Ibn-Sīnā’s full Arabic name is Abū ‘Alī al-Ḥusayn ibn ‘Abd Allāh ibn al-Hasan ibn Ali ibn Sīnā.

Although for us in the Western civilizations, his work is unusable today because of its focus on the humors and temperaments, it is still used in Yunani medicine.

See also in *The book of science:*

Readings on wikipedia:

]]>In 1025, Alhazen corrected the errors of Euclid and established the science of optics.

Alhazen was familiar with the work of Aristotle, Ptolemy, and Euclid and worked to correct the errors in their understanding of optics. Alhazen stressed the need for experimentation. Euclid was wrong; Aristotle was right; we see not from light emitted by our eyes but from light entering them. Alhazen held that light is emitted or reflected from objects at all angles but he struggled to understand how we see images clearly when a profusion of rays from every point hits the eyes at different angles. It must be, he said, that our eyes see only rays that hit them perpendicularly.

*More
poems* . . .

Alhazen’s book *Maqala fi al-Hala wa Qaws Quzah*
(“On the Rainbow and Halo”) proposed an incorrect
theory how a rainbow forms. The correct theory for the primary
rainbow was proposed by Theodoric of Freiberg in 1304, and
René Descartes explained the secondary rainbow in 1637.
Even so, Descartes did not understand the nature of color,
thinking that each color was a modification of white light. In
1672, Isaac Newton explained that white light is composed of a
spectrum of colored light.

See also in *The book of science:*

- 984,1602,1621,1637—
*Snell’s law*—Ibn Sahl, Thomas Harriot, Willebrord Snellius, René Descartes - 1620—
*Scientific method*—Francis Bacon - 1662—
*Fermat’s principle*—Pierre de Fermat - 1666—
*Theory of color*—Isaac Newton - 1800—
*Wave nature of light*—Thomas Young - 1888-1927—
*Cinematography*—Louis Le Prince, Thomas Edison, Auguste and Louis Lumière - 1925—
*Wave-particle duality*—Werner Heisenberg, Louis de Broglie, Erwin Schrödinger - 1947—
*Holography*—Dennis Gabor

Readings on wikipedia:

- “Alhazen”
- “Book of Optics” by Ibn al-Haytham (Alhazen)
- “Optics”
- “Reflection”
- “Refraction”
- “Diffraction”
- “Polarization”
- “Camera obscura”
- “Rainbow”

In 984, Ibn Sahl taught that the ratio of lengths of the refracted path and the straight path is constant for all angles of incidence.

In a glass of water, light bends at the surface, or at a greater angle, light reflects. In 984, Ibn Sahl taught that the ratio of lengths of the refracted path and the straight path is constant for all angles of incidence; therefore, lenses should have hyperboloidal surfaces. In 1602, Thomas Harriot rediscovered Sahl’s law, but he didn’t publish his work. In 1621, Willebrord Snellius also rediscovered it, and Huygens published his work postumously. By 1637, René Descartes rediscovered it again, and used the law to design microscopes and telescopes.

*More
poems* . . .

By Descartes’ time, rediscovering Snell’s law had became somewhat routine, with each discoverer finding his own means of deriving the same result, but the fundamental physics was still uncertain. Descartes assumed that the speed of light is infinite and his derivation of the law used the conservation of momentum. In 1662, Pierre de Fermat assumed that the speed of light is finite, rejected Descartes’ work, and derived the law using the principle of least time.

See also in *The book of science:*

- 1025—
*Optics*—Alhazen (Abū-‘Alī al-Ḥasan ibn al-Ḥasan ibn al-Ḥaytham) - 1662—
*Fermat’s principle*—Pierre de Fermat - 1678,1816—
*Huygensâ€“Fresnel principle*—Christiaan Huygens

Readings in wikipedia:

- “Ibn Sahl”
- “Thomas Harriot”
- “Willebrord Snellius”
- “René Descartes”
- “Snell’s law”
- “Snell’s window”
- “Refraction”
- “Refractive index”
- “Aspheric lens”
- “Dioptrique,” by René Descartes

In the 10th century, the Chinese were the first to use gunpowder to power rockets as weapons.

In 904, the legend says, the Southern Wu were prepared for the first time to use their skill with fireworks to advance themselves militarily. During the campaign of Runzhou, Zheng Fan ordered his troops to propel the “flying fire” on Yuzhang, guarded by rebel An Renyi.

*More
poems* . . .

Sign here to abolish celebratory fireworks. Fireworks were developed for festivities in China during the Tang dynasty as a means of expelling evil spirits. They produced more frightening lights and noises than banging pots and costumes with mirrors. Tell me, please. They frighten our pets, but do they expel evil spirits? Start here and maybe later we can abolish war.

See also in *The book of science:*

Readings on wikipedia:

]]>In the 9th century, the Tang dynasty developed gunpowder for fireworks and military weapons.

Taoist monks or alchemists in China combined sulfur and charcoal as a medicine. Searching for the elixer of immortality, they added saltpeter, creating gunpowder, the first chemical explosive and propellant. They used gunpowder at first for its incendiary effects, and were gradually able to increase the saltpeter to make it more explosive and more useful in weaponry.

*More
poems* . . .

The recipe for gunpowder was a state secret, and trade in nitrous raw materials was restricted. The Mongols conquered to obtain it. Around 1376, the Korean Choe Mu-seon bribed a Chinese merchant to get the formula, and figured how to extract potassium nitrate from soils.

See also in *The book of science:*

- 10th century—
*Rocket*—Chinese, Tang dynasty - 1780—
*Mysorean rockets*—Hyder Ali, Tipu Sultan - 1846—
*Guncotton*—Christian Friedrich Schönbein, Rudolf Christian Böttger, F. J. Otto - 1847—
*Nitroglycerin*—Ascanio Sobrero - 1867—
*Dynamite*—Alfred Nobel

Readings on wikipedia:

]]>820 CE: Algebra

Considering only positive numbers, al-Khwārizmī divided linear and quadratic equations into six basic types and showed how to solve them. Although his book was likely a compendium of existing knowledge, it stands as the first work to feature a strictly algebraic mathematical approach so that Latin translations of it in the 12th century introduced to the West not only the math but the terms algebra and, based on al-Khwārizmī’s name,algorithm.

*More
poems* . . .

Unfamiliarity with the notation can make a person feel as though a mathematical topic is beyond their intellectual powers when it is not.

See also in *The book of science:*

Readings on wikipedia:

]]>In 628, Brahmagupta wrote the first known text to describe how to use zero as a number.

Brāhmasphuṭa-siddhānta(“Correctly Established Doctrine of Brahma”) by Brahmagupta is the first known text to describe how to use zero as a number. It covers addition, subtraction, multiplication, and division with zeros and whether the result is positive or negative. Brahmagupta also gave rules for solutions to general linear equations, for calculating roots, powers, and sums of powers, for handling fractions, for calculating Pythagorean triples, for calculating the area of cyclic quadrilaterals, and for the value of π.

*More
poems* . . .

We make a distinction between 0, the number of nothing, and 0, a digit that is used in numbers written with digits in our positional number system.

History shows that the digit 0 came first (using various symbols). The history of the number 0 came from Brahmagupta. The Islamic world already had the positional number system. Brahmagupta gave them the number 0. The Persian, Muḥammad ibn Mūsā al-Khwārizmī (the inventor of algebra), oversaw translation of Brahmagupta into Arabic. Al-Khwārizmī’s work in Latin translation in the twelfth century introduced the Hindu-Arabic numeral system to the Western world. Fibonacci, having learned from Arabic mathematicians, contributed to its adoption in the thirteenth century.

See also in *The book of science:*

- 1202—
*Number system*—Leonardo Pisano Bigollo (Fibonacci) - 1656—
*Infinite and infinitesimal*—John Wallis - 1768—
*Pi*—Johann Heinrich Lambert, Ferdinand von Lindemann

Readings on wikipedia:

- “Brahmagupta”
- “Brāhmasphuṭa-siddhānta” by Brahmagupta
- “Zero”
- “Muḥammad ibn Mūsā al-Khwārizmī”
- “Names for the number 0 in English”

Like the Babylonian calendar before it, the Hebrew calendar is lunisolar, both adding intercalary months to sync with the 19-year Metonic cycle.

The beginning of the Hebrew calendar predates Hillel the Nasi. In the sixth century BCE, during their captivity in Babylonia, the Jews adopted the Babylonian names of months. Before this, their months were numbered, not named. The Babylonian calendar, like the Hebrew calendar, was lunisolar. Gradually, over hundreds of years, teachers switched from direct observation of agricultural events to determine when to add an extra month to the year, and, to determine the start of each month, from direct observation of the first crescent moon to adding synodic months from the first year of the world, Anno Mundi 1, thought to have occurred on the sixth of September 3761 BCE just before midnight, Jerusalem time. In 1178, Maimonides codified rules for calculating the points and periods.

*More
poems* . . .

That there are twelve signs of the zodiac, twelve months of the year, twelve sons of Jacob, and twelve tribes of Israel should not be lost to the numerologists among us.

Zodiac Babylonian Hebrew Aries Nisanu Nisan Taurus Ayaru Iyar Gemini Simanu Sivan Cancer Dumuzu Tammuz Leo Abu Av Virgo Ululu Elul Libra Tashritu Tishrei Scorpio Arakhsamna Marcheshvan or Cheshvan Sagittarius Kislimu Kislev Capricorn Tebetu Tevet Aquarius Shabatu Shevat Pisces Adaru Adar

OK, well . . . we need a few years with thirteen months to keep our months in synch with our years.

See also in *The book of science:*

- 2782 BCE—
*Egyptian calendar*—Old Kingdom of Egypt - 2637 BCE—
*Chinese calendar*—Huangdi - 46 BCE—
*Julian calendar*—Julius Caesar - 1050—
*Maya calendar*—Mayan

Readings in wikipedia:

]]>In 285, Diophantus showed how to find integer solutions for different polynomial equations.

A diophantine equation has more than one unknown. We look for only integer solutions. We are interested in integers, whole numbers, not fractions or continuous lines. * Diophantine solutions of the Pythagorean theorem are Pythagorean triples, (3,4,5), (5,12,13), and so forth. Taxicab numbers, starting with 1729, can be expressed as the sum of the same number of cubes in two different ways. Whatever you multiply one square so the difference from another square is 1 are Pell numbers. These are the denominators of the closest rational approximations to the square root of 2.

*More
poems* . . .

Pythagorean triples are integer solutions to a^{2} + b^{2} = c^{2} where a < b.

The first taxicab number, 1^{3} + 12^{3} = 9^{3} + 10^{3} = 1729.

Pell numbers are integer solutions to x^{2} - 2y^{2} = ±1.

See also in *The book of science:*

Readings in wikipedia:

]]>In 200, The Han dynasty perfected woodblock printing for text and illustrations.

Unlike a stamp or seal for making an impression in clay or wax, a woodblock for printing is inked so that its raised areas and lines mirror its design to cloth or paper. Woodblock-printed books suited the Chinese language, with its vocabulary of more than forty thousand characters, better than movable-type printing.

*More
poems* . . .

Woodblock printing spread from China to Japan in the 8th century. The “pictures of the floating world” by Hokusai and Hiroshige had a big influence on French painters, particularly van Gogh.

See also in *The book of science:*

Readings on wikipedia:

]]>In 180, Galen tried to establish observation and reason as the basis for medical diagnosis and prognosis.

Galen of Pergamon was a Greek physician and philosopher who served in the Roman empire. Diagnosis of medical conditions before him relied on divination and mysticism. Galen said, “In order to diagnose, one must observe and reason.” Galen combined the theories of his Greek predecessors, including Hippocrates, with what he could learn of the human body from his own medical practice and from vivisecting and dissecting monkeys and pigs. Galen’s medical theories dominated Western medicine for more than thirteen hundred years.

*More
poems* . . .

Galen’s theories were only gradually overthrown, in anatomy by Andreas Vesalius, in the circulation of the blood by William Harvey, and in pathology by Rudolf Virchow. The practice of bloodletting persisted into the nineteeth century.

See also in *The book of science:*

- 400 BCE—
*Medicine*—Hippocrates - 70—
*Traditional medicine*—Pedanius Dioscorides - 1025—
*The Canon of Medicine*—Avicenna - 1538—
*Toxicology*—Paracelsus - 1543—
*Human anatomy*—Andreas Vesalius - 1614—
*Metabolism*—Santorio Santorio - 1628—
*Circulation of the blood*—William Harvey - 1854—
*Cholera and the pump*—John Snow - 1858—
*Communities of cells*—Rudolf Virchow - 1878—
*Germ theory*—Louis Pasteur

Readings on wikipedia:

]]>In 140, Ptolemy established that the structure of the universe was a series of nested crystalline spheres circling about the earth.

Claudius Ptolemaeus of Alexandria wrote the definitive texts on astronomy and astrology in the second century. In theAlmagest,Ptolemy described the obliquity of the ecliptic, shadows of gnomon at equinoxes and solstices, precession of the equinoxes, lunar parallax and apogee, solar and lunar eclipses, and retrograde motions of the planets. Ptolemy explained how the apparent motions of the stars, sun, moon, and the five planets, were described mathematically by a set of perfect spheres. Each planet circles in an epicycle. Each epicycle circles in a deferent. The center of all nested deferents is a point halfway between the stationary earth and the equant point. Ptolemy claimed that his celestial spheres were actually installed in the heavens— concentric transparent crystalline spheres spinning around above us.

*More
poems* . . .

Ptolemy, like Aristotle, deduced natural science from first principles. All orbits were circular because the circle is the most perfect geometric figure. Unlike Aristotle, Ptolemy tried to adjust the model to fit the observations.

See also in *The book of science:*

- 2782 BCE—
*Egyptian calendar*—Old Kingdom of Egypt - 134 BCE—
*Astronomy*—Hipparchus - 1543—
*Heliocentrism*—Nicolaus Copernicus - 1609—
*Planetary orbits*—Johannes Kepler - 1610—
*Observational astronomy*—Galileo Galilei - 1687—
*Principia Mathematica*—Isaac Newton

Readings on wikipedia:

- “Ptolemy”
- “Almagest” by Ptolemy
- “Tetrabiblos” by Ptolemy
- “Deferent and epicycle”
- “Geocentric model”

In 105, during the Eastern Han dynasty, Cai Lun introduced paper and papermaking.

The English word for paper is from the Egyptianpaparuswhich served the same purpose as paper, but not as light, durable, or flexible. The Chinese word for paper,zhĭ,means “silk from plant fibers.” Cai Lun introduced paper and papermaking to replace tablets of bone or bamboo, which were heavy, and silk, which was expensive. He taught how to separate, in water, fibers from hemp, rags, and the inner bark of mulberry trees and to pour this through a woven cloth to leave a thin mat of fibers to be pressed and dried.

*More
poems* . . .

“I shall write peace upon your wings, and you shall fly around the world so that children will no longer have to die this way.” —credited to Sadako Sasaki, who died from the effects of the nuclear bomb on Hiroshima

“Say, it’s only a paper moon / Sailing over a cardboard sea / But it wouldn’t be make-believe / If you believed in me.” —E. Y. Harburg and Billy Rose

See also in *The book of science:*

- 206 BCE—
*Compass*—Chinese, Han dynasty - 200—
*Woodblock printing*—Chinese, Han dynasty - 1040—
*Movable-type printing*—Bi Sheng - 1914—
*Glossmeter*—Leonard R. Ingersoll

Readings on wikipedia:

]]>In 70 CE, Pedanius Dioscorides completed his five-volume pharmacopeia, describing the identification, preparation, and uses of

Pedanius Dioscorides was a Greek surgeon who travelled with the Roman army. Wherever he went, he asked local people about their traditional remedies, and tried them out on the troops, recording the names and uses of about six hundred remedies, eventually included in his five-volume pharmacopeia that was copied, translated, and kept in continuous circulation for fifteen centuries.

*More
poems* . . .

Dioscorides, the original pharmacologist, incorporated observations from Galen and Krateuas, and, of course, received information from many people in places where he travelled; however, he is said to have clinically tested and verified everything before he published it.

See also in *The book of science:*

- 400 BCE—
*Medicine*—Hippocrates - 320 BCE—
*Botany*—Theophrastus - 180—
*Medical research*—Galen - 1799—
*Placebo effect*—John Haygarth - 1865—
*Regulating the body*—Claude Bernard - 1897—
*Aspirin*—Arthur Eichengrün, Felix Hoffmann

Readings on wikipedia:

]]>Hero of Alexandria invented the wind mill and the first coin-operated vending machine.

Hero of Alexandria, known also as Heron, invented machines that work on the pressure of air, steam, and water, or using a weight like a clock, a wind-powered organ, a fire engine with the first force-pump, automatic doors, a statue that poured wine, a ten-minute automated mechanical theatrical performance, the first coin-operated vending machine (dispensing holy water), a programmable cart, and the first steam turbine, a temple novelty, the aeolipile, powered by jets of steam.

*More
poems* . . .

It took a leap of the imagination to extend the idea of sails to power a stationary machine. Once you see it, however, it is easy to copy.

See also in *The book of science:*

- 260 BCE—
*Mechanical advantage*—Archimedes - 70—
*Windmill*—Hero of Alexandria (Heron) - 1765—
*Steam engine*—James Watt - 1860—
*Roots blower*—Philander Roots, Francis Marion Roots

Readings on wikipedia:

]]>In 46 BCE, Julius Caesar established the Julian calendar by edict, counting 12 months and 365 days, and adding every four years a leap day to February.

Julius Caesar established by edict the Julian calendar, reforming the Roman calendar in the year 46 BCE. The Romans originally began a month with each new crescent moon, and, like the Etruscans, counted eight days per week, which made each year ten or eleven days short. The Julian calendar year counts 12 months and 365 days, and every four years adds a leap day to February. This calendar gains about three days every four centuries, still having room for improvement.

*More
poems* . . .

Letters A through H used to mark all days of the year when the year was divided into nundinæ, cycles of eight days. Today all days of the year are marked with a letter A though G for each day of the week. The dominical letter of the year is determined by which day of the week the first day of January falls on. This helps with calculations for the liturgical year, to ensure, for example, that Ash Wednesday falls on a Wednesday, and Easter Sunday falls on a Sunday.

See also in *The book of science:*

- 2782 BCE—
*Egyptian calendar*—Old Kingdom of Egypt - 2637 BCE—
*Chinese calendar*—Huangdi - 359—
*Hebrew calendar*— Hillel II, Maimonides - 1050—
*Maya calendar*—Mayan

Readings in wikipedia:

]]>