Retrograde motion is when a planet appears to move backward in its orbit relative to the rest of the night sky. Planets such as Mars and Jupiter can be seen in retrograde motion. Retrograde motion occurs due to the movements and relative positions of other planets around the sun. Earths’s orbit occasionally catches up with other planets’ orbit, causing an effect in which the planet seems to move backwards . Throughout history retrograde motion has been used to prove a heliocentric model of the solar system
For a deeper exploration of retrograde motion, you can check out this detailed article on NASA’s website.
Exploring how gravity on different planets in our solar system is different.
Gravity definition: Gravity is the force that attracts items to a planet or other body’s core. Gravity keeps the planets in orbit around the sun.
Since all the planets weigh differently, and have different radius this causes the gravitational pull of each planet to be different.
For example, if you weigh 100 pounds on Earth, you may see how differing gravity can affect you while you are on different planets, from below.
Image credit:NASA ( 2nd imagine from ” what is gravity?”
Why?: Weight is defined as mass being drawn by gravity towards the center of the nearest object applying gravitational pull. Weight varies depending on location. On Earth, the difference is insignificant. However, in space, things are constantly pulled into another object’s gravity well (such as the Earth, Sun, Moon or any other planets in our solar system) and experience free fall. In this scenario, the things are weightless. Other planets’ gravity forces vary, so objects have different weights.
Gravity on moon Orbit: Gravity keeps the planets in orbit around the sun and the moon in orbit around the Earth. The moon’s gravitational pull attracts the waters, resulting in ocean tides. Gravity forms stars and planets by attracting the material from which they are made.
The stronger the planet’s gravity, the faster the moon travels in order to remain in orbit. For example, as compared to Jupiter, the Earth’s moon travels much slower. Furthermore, a planet’s gravity can influence how far the moon can go. Moons can sustain a stable orbit at varied distances based on the planet’s mass and gravitational field.
You throw something up in the air and it falls down. Why? Gravity, obviously, everyone knows that. But what really is gravity?
By most common knowledge, gravity is one of the four fundamental forces, and has a lot more to it than just making things fall. Gravity actually works as an attraction between two masses, and is stronger the larger the mass of one thing is. That’s why everything falls down on Earth, its so large that it attracts everything to it’s center, so things “fall”. They don’t go down necessarily, they go towards the center. Even people like you and me have gravity, ours is just so small you can’t notice it.
Different sized masses will have different gravitational pulls. Earth’s for instance has a gravitational acceleration of 9.8 m/s^2, which basically means everything on/near Earth is constantly accelerating towards it’s center at that rate. Jupiter, the largest planet, has an acceleration of 24.8 m/s^2 while Mercury, the smallest, has an acceleration of just 3.7 m/s^2.
That sounds a lot better right? Gravity is a force that attracts masses towards other masses, based on how large they are. This is what Isaac Newton, one of the most important figures in physics, was able to come up with and for the most part, was correct.
Enter Albert Einstein. Einstein developed the theory of general relativity, which stated that gravity is a property of four-dimensional space-time. Space-time curves around mass, and the larger the mass, the larger the curve. This curve causes objects to be affected by gravity, or to our perspective, fall. We cannot see the curve because it is in the fourth dimension so we see it as a straight line.
Newton’s gravity is still going to be accurate for virtually everything in day to day life, but if you are dealing with things traveling or near light speed, Einstein’s theories are going to be key.
Ancient Mesopotamia is the earliest known source of modern astronomical research. Babylonian MUL.APIN texts provide data on stars’ locations and celestial descriptions dated to 1200 BCE. The group used their fingers and 360 units (comparable to modern 360 degrees) to chart the sky, distances, and celestial movement and occurrences. They used their star passages to be the first to create an astronomical ephemeris. The charting is the only depiction of their calculations as Babylonian astronomers did not create models.
Instructions on astronomical calculations can be found in the MUL.APIN texts. Babylonians measured speed over time to predict the motions of the planets. Their work succeeded for outer planets such as Saturn and Jupiter but did not work as well for Mars. Teije de Jong created visual depictions of their calculations on system A Mercury which can be found here. Recognizing the work of the Babylonian astronomers is important because their knowledge paved the way for Greek work which we often refer to as the origins of modern astronomy. We must recognize the dedication to astronomy that many ancient civilizations had which present students never learn.
A visual of the first Babylonian MUL.APIN text with celestial information. Two of these clay tablets paved the way for astronomy.
Galileo Galilei (15 February 1564 – 8 January 1642) contributed many findings related to astronomy, a few include: He took a spyglass and improved upon it so that it could be used to study astronomy. Using this new tool, he discovered that the moon is not smooth and had many imperfections such as craters and mountains. Furthermore, he found that Jupiter has moons orbiting the planet, which was one of the first proof that not everything orbits the Earth. Galileo also found sunspots (dark spots on the Sun), causing people to realize that celestial bodies were imperfect.
Major Events / Historical Figures (unrelated to astronomy)
During Galileo’s lifetime, the Thirty Years’ War occurred (1618 – 1648), which was a war where countries in Europe were at war due to religious (Protestant and Catholicism) conflicts. Also during this time (1620), the Mayflower (a ship of Puritans) departed Europe and founded Plymouth Colony in North America.
Another famous historical figure during this time period was William Shakespeare due to their extremely culturally influential and famous plays that are still being studied today.
Reflection
Seeing these major events / historical figures coincide with Galileo’s astronomy findings, it really puts into idea the sudden change in culture during this time period, especially religious changes as Galileo’s findings and the Thirty Years’ War affected Catholic beliefs (Celestial bodies are not perfect, evidence that Earth is not in the center of the Earth, war between Lutheranism and the religious freedom from the Catholic Church).
Isaac Newton (25 December 1642 – 20 March 1726/27)
Isaac Newton was important to astronomy due to Isaac Newton was crucial to astronomy because he developed the concept of universal gravitation, which explained why planets orbit the sun. This concept provided a unified theory for the motion of celestial bodies, essentially laying the foundation for our current, modern understanding of planetary movement. Another huge contribution to astronomy (and all other sciences) were his three laws of motion. He also invented the reflecting telescope.
Correlating Historical Events/People
The Fall of The Ming Dynasty (1644) – Ruling starting around 1368, towards the year 1618 The Ming Dynasty began experiencing earthquakes, famine, disease, plague and an overall weakening of their structure across the dynasty. A rival warlord saw this as their chance to overthrow them and so over the next few decades they started to gain small victories against them until eventually Beijing was taken over by another rebel group in 1644. They renamed themselves Great Qing in 1636 and went on to overthrow them with the added momentum the fall of Beijing gave. Great Qing established modern day China and only fell as recently as 1912.
The Great Turkish War (1683-1699) – During this time the Ottoman Empire was at its peak. They tried to move into Northern Europe in 1683 with the Battle of Vienna, but all of the countries joined ‘the league’ and fought against this empire to prevent their continuous growth (even though they were all fighting a separate war with France). Eventually in 1699, the Ottoman Empire was forced to sign the Treaty of Karlowitz which meant ceding large portions of Southern Europe ending their previous streak of uninhibited conquering.
Johannes Sebastian Bach (March 31 1685 – July 28 1750) – Bach was a Baroque composer who is known as one of the greatest of all time. He basically revolutionized music and is one of the first composers recognized as founding the Western Canon of music. The styles, forms, traditions, and harmonies that he organized and constructed influenced the evolution of western music through the present day.
Reflection
What is most interesting to me was learning about all of the different things happening all at once. The 17th century (And the 2nd half of the 2nd millennium in general) was really when we started accelerating in advancements as a human species. For example, it is just funny to think that while Bach was composing, the Ottomans were actively trying to take over parts of Europe very close to his backyard. It just puts lots of perspective in the complexity and variance in the human experience.
Brahe has been described as the greatest astronomer before the invention of the telescope. He was devoted towards building new measurement instruments with unprecedented levels of accuracy, which were necessary for his discoveries. A few of his most notable observations include the annual variation in the orbital speed of the moon, as well as his measurement of a comet’s orbital path.
Many historical events occurred in Brahe’s lifetime. In 1587 the colony of Roanoke was founded in what is now part of North Carolina. This later became the famous Lost Colony after the 115 or so colonists mysteriously disappeared. Later, in 1597, Romeo and Juliet was published, one of Shakespeare’s most famous pieces.
Elizabeth I lived from 1533 to 1603 and was the Queen of England from 1558 to 1603, a very similar period as Brahe’s life. She is an important piece in England’s history as she was the last monarch of the famous Tudor family; her period of rule is known as the Elizabethan era and has been described as “golden age” in English history for the flourishing of the arts, exploration, and science.
I think this really puts the timescale of astronomy into perspective, because I remember learning about the Lost Colony of Roanoke or Elizabeth I in school, and have a good conception of this relative time period, but did not realize significant astronomical study was occurring so long ago.
The dates of birth and death for major astronomical figures.
Nicolaus Copernicus/Born: February 19, 1473. Died: May 24, 1543
Galileo Galilei/Born: February 15, 1564 Died: January 8, 1642
Johannes Kepler/Born: December 27, 1571. Died: November 15, 1630
Isaac Newton/Born: January 4, 1643. Died: March 31, 1727
Tycho Brahe/Born: December 14, 1546 Died: October 24, 1601
Tycho Brahe and Johannes Kepler were alive at the same time (1600 to 1630). Kepler working with Brahe’s astronomical data led to his research in planetary motion. Their collaboration was signifgant to astronomy.
Johannes Kepler (1571-1630) was an astronomer from Germany. He was alive during the The Thirty Years’ War (1618–1648) which was a war fought in the Holy Roman Empire which includes parts of modern day Germany. This war drastically affected European political and social discourse. It was one of the longest wars in European history. more about the Thirty Years’ War.
Also alive during Kepler’s time was William Shakespeare,who’s work during this period included plays like “Hamlet” and “Othello”. Shakespeare’s work had an impact on the English language and literature. His works central to Western literary canon. Shakespeare’s works.
William Shakespeare (1564–1616): An English writer and playwright. He is the most influential author in the English language. more about Shakespeare.
My reflection
My research has shown me historical context affects the field of astronomy. In an interesting way Kepler’s contributions to astronomy happened while significant historical events like the Thirty Years’ War and the literature of Shakespeare. History shows us science is affected by social impact. It’s interesting to see how Kepler’s work on planetary motion intersected with such an eventful time in history.
Johannes Kepler’s most recognized contribution to astronomy are his three laws of planetary motion, published in 1609. First, planets’ orbital paths are elliptical, with the sun positioned at one focus. Second, during a planet’s orbit, equally sized sectors are swept out from the planet to the sun in equal amounts of time. Third, there is a mathematical relationship between a planet’s orbital period and the semi-major axis of their elliptical orbit. Although Isaac Newton later derived these laws through physical principles, Kepler originally considered these discoveries to be “celestial harmonies” determined by God.
Historical Events and Figures
In the 1590s, Dutch spectacle makers Zacharias and Hans Janssen created the first compound microscope, which was able to magnify an object between three to nine times its actual size. While Janssen’s instrument was simple compared to modern ones, its development was an important step in observing the microscopic world.
In 1619, the first Africans arrived in Hampton, Virginia. These people were originally from the Kingdom of Ndongo in West Central Africa but were enslaved by the Spanish and put aboard the San Juan Bautista heading for Mexico. They were captured by two English Privateers and traded as commodities in Virginia, laying the foundation for the race-based chattel slavery that defines much of America’s history.
William Shakespeare (1564–1616) is one of the most recognizable names in English literature. His works explored themes like love, life, power, jealousy, betrayal, and the human condition, which remain just as relevant today as they were 400 years ago.
Reflection
When considering historical figures and events, it is easy to imagine that they exist in a vacuum. “Shakespeare time” and “early microscopy time” look very different in my head, even though they actually overlapped temporally. This exploration reminded me that human activity can be incredibly diverse even within a short historical period. At the same time as astronomers were looking outward to the celestial world, optical scientists were looking inward to the microscopic world. And as artists were reaching new heights of humanistic expression, one of the greatest evils of our world was taking root in America. The world has always been eclectic and ruled by simultaneity.
The End of the English Civil War: It ended on September 3rd, 1651 with Oliver Cornwall’s victory at Worcester. It was a war that occurred in the British Isles between the supporters of Charles I and opposing groups in each of Charle’s Kingdoms.
The Age of Enlightenment: A European intellectual movement that focused on ideas about God, reason, nature, and humanity. It was a movement that resulted in developments in art, philosophy, and politics.
John Locke was a key figure in the European Enlightenment and the Constitution of the United States. He was also a member the Royal Society alongside Isaac Newton.
Brief Reflection
It was interesting looking back on Sir Isaac Newton’s life and some events he lived to see. It was also fun to research and look into. One takeaway I’ve gotten is that given that Newton lived during the beginning of this movement, I believe it is not far off to say that Newton most likely played a large role in its development. It was also interesting to make the connection between him and John Locke, both being key figures in the European Enlightenment. This was a fun exercise and I look forward to future investigations like this.