The Birth of Modern Astronomy

The birth of Modern Astronomy marks a radical, momentous shift in our understanding of the world, the universe, and reality. It was the work of the fathers of modern Astronomy — Copernicus, Galileo, Kepler, Brahe — that completely transformed our understanding of the world. Not only observationally and mathematically proving the Heliocentric (Sun-centered) Model of the solar system, but laying the foundations of modern science too.

They were able to change popular opinion, conclusions based on religious doctrine and ancient thinking, literally millennia of tradition, using logical and mathematical argument. which they began to support with experiementation. They began testing and analyzing the world as opposed to thinking about it and determining truth based on which ideas seemed to the best.

However, we cannot forget the giants of the past. Their great advances would not be possible without the work of the ancient astronomers that we covered in Ancient Astronomy. The advancements of Aristarchus, Eratosthenes, Aristotle, and Hipparchus were preserved in the works of Ptolemy, which survived in his Almagest — treasured in the Islamic world by truly great scientists of those cultures. Their work added to the progress of the ancients, which eventually made their way into Europe, resulting in the Renaissance (“rebirth”) of Ancient Greek science, setting the stage for modern science.

Contents

• The Dark Ages of Europe and the Golden Age of Islam
• The Rebirth of Ancient Knowledge in the Renaissance

The Dark Ages of Europe and the Golden Age of Islam

In the Medieval Period (specifically the Middle Ages of Europe) war and conflict was the norm. There were constant power struggles. Centuries of Norse Viking raids throughout France and England, bloody familial power struggles among bloodlines of Frankish and Germanic kings. The rule of petty tyrants over small territories in the vacuum of power after the fall of the Roman empire, and the conflict of religions, dominated this period of European History.

At this same time the Islamic Empire, stretching from the Middle East across the Northern coasts of Africa, made great strides in the development of astronomy. Scientists of the Islamic world actually translated, preserved, mastered, and advanced upon the great strides made by the scientists and astronomers of Ancient Greece. The works and advances of these famous Greeks were all compiled by the Roman astronomer and scientist Ptolemy in his encyclopaedic magnum opus remembered as the Almagest.

The Almagest was essentially the astronomy textbook of the Islamic Empire (as it was for the European scientists if the coming centuries). It contained everything that one needed to know about astronomy and the necessary mathematics to train generations of astronomers. It was this text that helped Islamic people calculate the positions of Sun and Moon for their daily prayers, in addition to the direction of Mecca from wherever they are in the world. This text was readily available in the Islamic world after they took over Egypt (Ptolemy being based in Alexandria).

After the birth of Islam in the 700’s CE the Islamic Golden Age spanning from about 750–1300 saw the development of great centers of learning appear across the Islamic world, the first being the House of Wisdom in Baghdad. Many of the names of the brightest stars and astronomical technical terminology that we use today in the English language (such as the word “zenith”) came from the semitic Arabic language.

The Rebirth of Ancient Knowledge in the Renaissance

Eventually Europe emerged from the Middle Ages, a time when the European mind was dominated by the carnage of war and famine — conditions that have historically been antithetical to scientific, artistic, and intellectual progress. They opened both their borders and their minds. They sought knowledge once more, reclaiming elements of the cultures of Ancient Greece and Rome that had been temporarily forgotten.

As trade with the Islamic world began once again, this book, the Almagest, along with the work of Islamic scholars, made its way back into the region. The science of astronomy made its way back into the European mind once more, as well as history, art, wisdom and traditions from multiple cultures both contemporary and past flooded Europe resulting in a period that the French called The Rebirth.

The Renaissance ( “rebirth”, and is often considered to have begun with Leonardo da Vinci, followed shortly by the great Michelangelo.

Leonardo was a scientist and inventor, and is credited with many amazing discoveries and works. However, in regards to the birth of modern astronomy and the foundations of technical science, while we can trace some developments back to him, the scholars who we are chiefly concerned with are those such as Nicolaus Copernicus, Galileo Galilei, Johannes Kepler, and Tycho Brahe.

Copernicus

One of the greatest intellectual revolution was the displacement of the Earth from the center of the universe. This discovery was initiated by Nicolaus Copernicus — a Polish cleric of the 1500’s, born in the town of Turn, which was a mercantile town on the Vistula River. [1] His training was in law and medicine, however his main interests were in astronomy and mathematics. [1]

He performed the most accurate investigation into the motions of the planets, reviewing the existing theories of planetary motion going back to the Greeks, and ultimately solving them for the first time, leading to the true Sun-centered (Heliocentric Model) of the Universe.

In point of fact, Copernicus didn’t just change science, he changed the universe — at least our conception of it — a radical reformation that corrected thousands of years of dogma. Copernicus concluded that the Sun is a star, and that the Earth is a planet like all the others that orbit the Sun, and that the Moon is a moon, and the only body to orbit the Earth.

Nicolaus Copernicus expounded on his theories in De Revolutionibus Orbium Coelestium (On the Revolution of Celestial Orbs) that he published in 1543 — the year of his death (which was by design, because the Church had a great deal to say about this heretical work). [1]

At the time of Copernicus, the Ptolemaic Model of the Universe was becoming increasingly inaccurate, requiring significant adjustments to predict planetary positions correctly. [1] Copernicus, like many before him, knew that the model had flaws and wanted to improve upon it. Yet even he was not free of the traditional prejudices. [1]

He began with many of the same traditional assumptions (like the idea of the “perfect circle” that must, in the end, describe the motions of the planets as combinations of uniform circular motions). On the other hand, he didn’t assume that the Earth was the center of the universe. He persuasively argued that the Sun was the center in his heliocentric system. [1] While his ideas were debated widely among scholars, they were not accepted widely until in excess of a century after his death — due in part to advancements in the theory made by future scientists. In the end, his ideas could not be denied, and they literally (and conceptually) changed the world.

One of the most common arguments made against the Heliocentric Model — and the Spherical Earth by Flat-Earthers, even today — is that we would feel its motion. Both the motion of the Earth spinning on its axis and the motion of Earth hurtling through space. Many people believe that this motion would be detectable — trees would be ripped from the ground, buildings would fall, dropped objects would not fall straight down, that people would be bent against the motion just to walk down the street. However, this “common sense” observation fails to take into account that on a smooth, straight highway or rail-line, you cannot feel that you are travelling +100 km/h hurtling through space until there is a bump or bend in the trajectory of motion. (The secret lies in inertia.)

Copernicus argued (just as Aristarchus of Samos did two millennia before) that the apparent motion of the Sun around Earth could be explained equally as well if the Earth was orbiting the Sun. He also understood that the apparent motion of the celestial sphere could be explained by the rotation of the Earth on its axis, while the distant stars remained stationary.

Addressing such arguments that the Earth spinning on its axis would tear it apart — while he could not refute this on scientific grounds, which required the Universal Law of Gravitation realized by Isaac Newton in the coming century — he argued that if the Earth was torn apart by such motions, the forces on the stars and celestial sphere would be even greater, and would cause the celestial sphere itself to shatter and by flung out into infinite space. [1] In essence, these exact same centripetal forces and faster motion in the Geocentric Model are even more devastating than those in the Heliocentric Model. [1]

The Heliocentric Model

One of the most revolutionary ideas found in De Revolutionibus is the displacement of the Earth from the center, relegated to an equal place with the other six planets (known at the time) to orbit the Sun. Understanding this, he was the first human ever to realize the correct design of the solar system. Placing the Sun at the center, and ordering the planets in the correct concentric orbits around the Sun. From nearest to furthest, in the correct order, he place: Mercury, Venus, Earth, Mars, Jupiter and Saturn.

Even more astounding, is that he deduced that the closer a planet was to the Sun, the greater its orbital speed had to be. It turns out that the Heliocentric Model was far more elegant than the Ptolemaic Model. With his theory he was able to explain with greater accuracy the complex retrograde motions of planets (without relying on the epicycles of Ptolemy) and work out a roughly correct scale for the solar system. [1]

Copernicus could not definitively prove that the Earth orbits the Sun. After all, with some adjustments, the millennia-old Ptolemaic model could have account equally well for the motions of the planets. [1] Yet what could not be ignored, once preconceptions were held at bay, is that the beauty, simplicity, and elegance of the Copernican Heliocentric Model was superior in every way to the old Ptolemaic system (as Copernicus himself pointed out). It brings to mind the remark made by Alfonso X, King of Castille, about the Ptolemaic Model:

“If the Lord Almighty had consulted me before embarking upon Creation, I should have recommended something simpler.”

As it turns out, the Lord Almighty did not need to consult Alfonso to devise a more beautiful, elegant system.

In the 15th century when Copernicus was active, it was not obvious if there were any methods to prove whether the Heliocentric or Geocentric model was correct. A long philosophy (going back to the Greek philosophers and maintained by the Roman Catholic Church) that pure human thought imbued and elevated by divine revelation was how universal truth was attained. In essence, persuasive words by great (or influential) minds was the way, while the scientific process — observation, hypothesis, and experimental validation — had not been recognized for its superiority.

“Nature, as revealed by our senses, was suspect.” [1] Aristotle reasoned that heavier objects fall faster than lighter objects (since the quality that made them heavier must make them fall faster too). Nobody bothered to test it, which any simple experiment dropping to different weights would prove unequivocally to be incorrect.

In Aristotle’s defence, if you drop a tunic or feather or leaf, it will certainly fall more slowly than a sword or shield. However, this is only because of air resistance, which they didn’t understand either at the time of Aristotle through to Copernicus. Even in the time of Copernicus, experiments had far less authority than pure reasoning.

(Interestingly, generations of physics teachers in the last century were adamant that if we were going to perform this experiment definitively, the Moon would be the place — since there is not atmosphere, no air, and thus no air resistance. In 1971, astronaut David Scott on the Apollo 15 mission to the Moon, brought with him a feather and hammer, performing the experiment once and for all “to the delight of physics nerds everywhere”. [1]

Today, testing new hypothesis with experimentation — the scientific method — is the norm. In general, the scientific community does not accept new ideas until they have been thoroughly vetted through testing, and confirmed. (The scientific community also has a track record of ignoring controversial ideas — and ostracising the scientist who came up with the theory — only for it to turn out to be ground-breaking and true later on. I suspect that the average IQ in the scientific community being unable to comprehend true genius is responsible. I call this The Rule of the Mediocre Majority.) With that being said, the reluctance to accept new ideas at face value is still the best approach.

Two researchers working for the University of Utah announced a new method to achieve cold fusion at room temperature. Scientists from more than 25 labs around the US rushed to confirm the validity of the method within weeks, but to no avail — and cold fusion remains to this day a novel (but unreachable) theory. [1]

All new theories must first be weighed against known scientific laws and observations. If they violate any (assuming the law itself is correct) then the theory is relegated back to the beta stage. Copernicus’ theory of heliocentrism absolutely explains what is observed in nature, at least as well as earlier models, and certainly with greater elegance.

The next step is to determine which prediction the new model makes that differ from its predecessors and competing ideas. In the model of Copernicus it explains the motions of the heavenly spheres, including retrograde motion, within a system that makes far more physical sense. One prediction where it is distinct is that if Venus orbits the Sun, it should go through the same phases of the Moon. If Venus orbits the Earth on the other hand, it would not go through this range of phases.

In the days of Copernicus, this experimental test of Heliocentrism vs Geocentrism was not imagined. [1] It wasn’t until Galileo’s use of the telescope c.1609 that the possibility emerged.

[Full Article: The Heliocentric Model]

Galileo and the Foundations of Modern Science

Many of the underpinning ideas of Modern Physics — those pertaining to the scientific method: observation, hypothesis, experimentation to test the hypothesis thoroughly through varies models, methods, and permutations of experiment, all the while gathering quantitative data — were pioneered by Galileo Galilei.

Galileo lived about a century after Copernicus. He was born in the Italian city of Pisa (and a contemporary of Shakespeare). [1] Like Copernicus, he began training in the field of medicine, but later switched to mathematics, his true passion. [1] He held faculty positions at the University of Padua, the University of Pisa, and later became the mathematician to the Grand Duke of Tuscany, Florence. [1]

Galileo’s greatest contributions (to modern science) were in the realm of mechanics. He studied motion, the actions of forces on objects, and was the first (I believe) to arrive at a calculation of speed(=distance/time), as well as deriving the foundations of the mathematics for gravitation and gravitational acceleration (which were incredible useful to Isaac Newton in the subsequent decades).

It was familiar to all people then, as now, that objects at rest tend to remain at rest. After all, if you drop a stone, sword, plow, or other object in a field near your home and — provided nobody moves it — it will be there tomorrow. Rest was regarded as the natural state of matter, but Galileo demonstrated that rest is no more natural than motion.

If you slide an object along a horizontal floor made of some rough material (concrete, gravel, or un-sanded wood) then it will quickly come to rest due to the friction between the object and the floor. The more polished the surface, the smoother that it is, the further the object will slide before returning to rest — even with the same initial speed — because there is less friction. On ice, which has a very low coefficient of friction, the object will slide very far.

Galileo reasoned that if we could remove all opposite forces (i.e. friction or air resistance) the object would continue moving indefinitely. An object dropped from a great height, after all, continues to fall. It is only the opposing force of the ground that stops it. Theoretically, if we had a cliff with an infinite drop, that object would continue falling forever. (The closest we can get to that is the infinite expanse of space for vertical motion, or else something like an air-hockey table [which uses air] or magnetic levitation [used on the tracks of “bullet trains”] which bring friction to near-zero for sustained horizontal motion.)

Galileo argued that a force is required not just to start an object in motion, but also to return it to rest — start, stop, speed up, slow down, or change direction of motion of an object all require an external force.

Galileo made advancements too in his study of the way objects accelerate. An acceleration is any change in speed or direction. He watched objects as they fell in free-fall or else rolled down a ramp, and found that the accelerate uniformly, gaining equal increments of speed in equal intervals of time. [1]

He then formulated these laws — which he discovered — in precise mathematical terms. Laying the foundation of Modern Science, and specifically modern Classical Mechanics as he did so. This work allowed all future physicists, experimenters, and scientists to predict with mathematical calculations how far and fast an object will travel due to gravity in various lengths of time. [1] The first gravity equation, as it were.

In the 1590s Galileo adopted the Heliocentric Model of Copernicus — risking the ire of the Church. To put it mildly, this heretical worldview was not looked upon with favour by the Roman Catholic Church, who dominated Italy (and Europe) during this time. That the Earth was not the center of creation contradicted Biblical Doctrine, and was therefore a threat to their economic and political power. (In this sense, their reaction was almost prophetic in its foresight four centuries into the future.) Galileo had the integrity to follow the science, and the audacity not only to lecture on these topics in public, but to write in Italian rather than scholarly (and secular) Latin. [1]

Galileo was an important figure, whose ideas had influence. He saw not contradiction between the authority of the Church on religious matters, and the authority of nature on matters of science. [1] However, the Church did not see it this way. Galileo’s “dangerous” opinions forced a reaction from the Church, who issued a prohibitive degree in 1616 dismissing Copernican heliocentrism as “false and absurd” bringing the threat of punishment on anyone audacious (and reckless) enough to believe, teach, or defend these ideas. [1]

The Astronomical Observations of Galileo

We do not know for sure who came up with the idea to combine pieces of polished glass in such a way as to magnify distant objects. For all we know, ancient sailors or glassmakers could have stumbled on this phenomenon informally untold centuries before.

What we do know is that Hans Lippershey (1570-1619) a Dutch spectacle maker, created the first “spyglasses” in1608. [1] News of the spectacular novelty made its way to Galileo who — without ever actually seeing one of these spyglasses in person — constructed one of his own the year later, because he was able to grasp the physics principles involved. (As well as their significance in his work studying the stars.) The telescope that he designed had a three-power magnification (3×), making distant objects appear both three times larger, as well as thrice nearer.

[Full Article: Telescopes]

On 25 Aug 1609 Galileo gave a demonstration to city-officials of (the city-state of) Venice, displaying his newly-developed telescope capable of 9x magnification (making objects appear 9 times large/nearer). While the impact of this device on science and astronomy may not have been immediately grasped, its military possibilities certainly were. [1] Galileo’s salary was almost doubled, and he was granted lifetime tenure as a professor. (To the outrage of his colleagues, since this technology — while innovative — was not original.) [1]

While many had used the telescope before to observe things on Earth, Galileo realized in a moment of insight that the telescope could be turned towards the heavens, to study the stars. Before he did so he had to devise a stable mount, and improve optics (he increased magnification to 30x) before spending time gaining confidence in the telescope. [1]

In Galileo’s time the eyes were the final arbiter of truth of size, shape, and color of objects. [1] Lenses, mirrors, and prisms (often made of glass) were, in short, not trustworthy. They were known to distort images, either by making them larger, or smaller, flipping them upside down, or spreading white light into a spectrum of colors. [1] Galileo did not trust them. Not implicitly. Not yet.

Galileo had to perform repeated experiments to verify that they showed distant objects with accuracy, because only then could he believe what the telescope showed him when he looked at the night sky.

In late1909 he began his astronomical work with the telescope, quickly discovering a great many stars too faint for the naked eye to see alone. Many “nebulous blurs” resolved themselves into many individual stars — in particular, the band of the Milky Way, which appears almost as a glowing cloud as it stretches across the night sky, was made up of countless individual stars.

When he turned his telescope to the wanderers in our solar system, the planets, he would have been astounded to discover moons orbiting some of them. He found 4 Moons orbiting Jupiter, it periods between just under 2 to about 17 days. [1] This was an especially important discovery, because it clearly illustrated that not everything revolves around Earth. Other bodies had a quality about them that they too, could be the center of motion for another cosmic object, and that the Earth was not ordained as the ultimate center of all things.

Since gravity was not yet understood at this time (and its implications for planetary motion) defenders of the geocentric doctrine argued that the Moon would not be able to remain in orbit around the Earth. If the Earth was in motion, the Moon would certainly become unbound to Earth and fly off into space! (Even though an observation of Jupiter’s many moons clearly contradicted this assumption.)

(In honour of this discovery, NASA named the spacecraft that explored Jupiter the Galileo.)

Finally, with Galileo’s innovative 30× magnification telescope, he was able to thoroughly test the Heliocentric Model. In addition to discovering moons orbiting Jupiter (proving that a moving body can have objects in orbit, since the motion of Jupiter had been well-documented from ancient times) he also was able to see that Venus also has phases like the Moon, which can only happen if it is in orbit around the Sun. None of these observations were consistent with the Ptolemaic Model. (While Ptolemy’s model absolutely could explain the phases of Venus based on relative Venus-Earth-Sun geometry, the same as the Moon, his system predicted the wrong phases in the wrong order from Galileo’s observation.)

Galileo also observed the Moon and saw craters, mountain ranges, valleys, and flat, dark areas he thought could be water [1] — today we still call these lunar maria (“lunar seas”, from the Latin singular mare, “sea”) in honor, even though we know they are not water.

All of these discoveries changed our perception on the cosmos, and on astronomy, forever. Not only did they paint a vastly different picture of the cosmos, overturning millennia of doctrine, but suggested the Moon, and planets like Jupiter, might be far more similar to Earth than had previously been believed.

After Galileo, the denial of the Copernican model became an increasingly untenable position. The Earth was slowly dethroned from its position in the center of the Universe in place of the Sun, and finally recognized as one of the celestial bodies — another planet — in orbit around the Sun.

However, the Church would not go down without a fight, and Galileo was met with serious opposition.

The Protestant Reformation had just shaken the authority of the Roman Catholic Church and, with the Inquisition underway, Galileo was brought before the courts on charges of heresy. Ultimately he was charged, and placed under house arrest because of his influence (spared death, unlike many others). His books were on the list of forbidden books until 1836, even though they were read and discussed widely in countries where the Church was less powerful. Finally, in 1992 they issued a formal public apology to Galileo, admitting that their censorship was in error. [1]

Observing The Planets

At some point during the night, in any season, there will be a planet visible in the sky with the naked eye — one of the five planets known to the ancients: Mercury, Venus, Mars, Jupiter, or Saturn — if you know where to look.

They are brighter and more prominant than almost all other stars of the night sky (save a handful, like Sirius A&B) fist of all.

Venus is closer to the Sun than the Earth, and Mercury even closer, which will always be found near to the Sun. Since they are close to the Sun, and cannot be seen during the day, generally speaking, the best time to look for them is either just before the Sun rises at dawn, or just after the Sun sets at dusk.

In ancient times, Venus was the “morning star” when it rose just before the Sun and the “evening star” when it followed the Sun below the horizon at night. Venus is the brightest object in the sky, behind the Sun and Moon. At its brightest, it can cast a visible shadow. [1] Young military recruits have been known to attempt to shoot it out of the sky, thinking it a UFO or enemy craft. [1]

Mars can always be distinguished by its distinct red color. When close to Earth it can be nearly as bright as Venus, but is usually not as conspicuous. [1]

Jupiter is often the second-brightest plant, close in relative luminescence to the brightest stars.

Saturn is probably the dimmest of the planets visible to the naked-eye, and varies considerably. It is fainter when its orientation to Earth shows its rings edge on (less reflective surface area) and brighter when its rings are presented to us (more reflective surface area).

Mercury is quite bright, but is harder to notice since it is closer to the Sun — never more than 28° away. It must be viewed very close to sunrise/sunset when it is always against bright twilight skies. Furthermore, only when it is on either side of the Sun from our perspective, since it is behind the Sun through a section of its orbit, and in front through another (and impossible to see without equipment).

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