Kepler and the exploration of the cosmos
Notes on giants - Number 8
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🏷️ Categories: History, Astronomy, Mathematics.
Johannes Kepler changed our view of the universe and the course of history itself.
He was born in 1571, at a time when Europe was under the oppression of the Church. But Kepler was not content with the status quo; he came into the world to question dogma and find the truth. While everyone believed that the cosmos was a simple and divinely perfect mechanism, he looked up to the sky and saw something else....
Something much more profound and difficult to understand for those of his time.
His search for truth was far from easy. During his life, he suffered personal tragedies, economic problems, he was threatened and persecuted. All for wanting to reveal a truth for which the world was not prepared.
Here is the story of a giant...
A life of obstacles
When she was young, her mother, Katharina Kepler, was accused of witchcraft and imprisoned. Despite using her scientific knowledge to defend her, persecution continued, all because of her strongly held religious beliefs. During her lifetime, Kepler suffered the death of her mother, wife, and several children (Mazer, 2011).
Despite all this, his passion for science and his courage never waned.
At that time, the Church had a monopoly on knowledge and decided what should be believed. It was a time of brutal censorship of critical thinking. The Church held that the Earth was the center of the universe and there was no debate.
To question that idea could mean your death.
Copernicus had the audacity to question the establishment in 1543. He said that the Sun was the center of the cosmos, and not the planet Earth, which put his life at risk. Kepler went further and stated that, in addition to the Earth not being the center of the cosmos, the planets did not follow circular orbits, at the risk of being persecuted (Holton, 1956).
Kepler's 3 laws
Today, 3 laws bear his name. Imagine how great his breakthrough was. These 3 laws that combined mathematics, physics and astronomy are as follows:
First law: planets have elliptical orbits.
This means that the orbit is shaped like an ellipse and the Sun is not always at the same distance. The distance varies constantly as the planet follows its orbit. This idea was a real revolution, because it broke with centuries of beliefs about the “perfection” of planetary orbits.
Second law: Same area in same time
This means that the planet moves faster when it is closer to the Sun and slower when it is farther away, but the area of the orbit is the same. Look at this image and you will understand.
In 1 month of orbit, the velocity changes, but the area will always be the same.
Impressive, isn't it? Imagine discovering this 400 years ago.
He published these 2 laws in his book Astronomia Nova, in 1609, where he also confirmed Copernicus' theory that the sun was the center, not the Earth.
Third law: The constant ratio
It is a relationship between the time a planet takes to complete its orbit and the size of its orbit. Kepler discovered that this time always bore a peculiar relationship. The larger the orbit of the planet, the longer it takes to travel, but this is not linear, it follows a ratio that he himself discovered.
T is the time it takes to make one complete revolution around the Sun.
a is the semi-major axis of the orbit (the average distance between the planet and the Sun).
The result of this formula is the same for all planets. For all of them.
It is very elegant to describe with such a small formula the motion of the planets.
Kepler synthesized the observations of Tycho Brahe, the Danish astronomer with whom he worked in Prague, and thus laid the foundations that Newton later used for his theories.
Imagine how great his contribution to science was.
Despite his legacy, his ideas were not well received and he had many disputes with the Church and even with other scientists of his time. Galileo Galilei harshly criticized his theory on the influence of the Moon on the tides. To which Kepler responded:
“The power of the Moon extends to the Earth, and draws the waters, insensibly that of the seas, but sensibly over the ocean, whose beds are large, and the waters have full liberty to rise and fall” - Kepler. Seen in Gregory (1715).
But if the Earth did not exert more gravity than the Moon....
If the earth were to stop drawing its waters to itself, all the waters of the sea would rise and flow towards the Moon.
For Galileo this did not make sense, but in the end, Kepler was right.
This is only one of his many disputes. To avoid problems, in many of his letters and writings he spoke of his scientific work only as an effort to understand the creative greatness of God. Mathematics was the language of the Creator and his discoveries the way to understand him.
With this respect for religion, he was able to avoid disputes and continue his research.
“Geometry is the radiance of the mind of God. The human being's participation in it is one of the reasons why humanity is the image of God.” — Kepler
Science fiction pioneer
As a lover of science, I can't help but look up at the sky and dream....
In 1608 he wrote Somnium (The Dream), which is considered one of the first works of science fiction in history. It is about a son's journey with his mother to the Moon during an eclipse, where he describes the satellite and space. Kepler dreamed of traveling to the Moon at a time when his contemporaries did not even understand the place of the planet Earth in space... (Asimov et al., 1981).
Kepler was ahead of his time and his legacy will live on forever.
Does this person look familiar?
It's Nobel laureate in physics Richard Feynman giving a lecture on Kepler's 3 laws. Feynman is another giant of whom we know his technique for learning. Here it is in case you don't know it yet.
Feynman Technique: Master the art of learning.
✍️ Your turn: What other people do you admire for challenging the beliefs of their time and transforming the world?
💭 Quote of the day: «There is a force on Earth that makes the Moon move.» — Johannes Kepler.
See you soon! 👋
References 📚
Asimov, I., Waugh, C. G., & Greenberg, M. H. (1981). Isaac Asimov presenta la mejor ciencia ficción del siglo XIX.
Gregory, D. (1715). The Elements of Astronomy, Physical and Geometrical.
Holton, G. (1956). Johannes Kepler's Universe: Its Physics and Metaphysics. American Journal Of Physics, 24(5), 340-351. URL
Kepler, J. (1608). Kepler's Somnium: El sueño, u obra póstuma sobre astronomía lunar.
Mazer, A. (2011). Shifting the Earth: The Mathematical Quest to Understand the Motion of the Universe.
Wonderful article!