Recommendation
Author's Preface: A Novel-Like History of Gravity
Prologue: What Makes Things Fall and What Gives Them Weight?
1.
Adaptation Period: Gravity! From an Object to Overcome to an Object to Understand
2.
Lost in thought: the universe is so vast
3.
Falling into place: an orderly universe
4.
That's not it: A Refutation of Aristotle
5.
Falling is being pulled: Explaining falling in earthly language
6.
No guesses can be made about the pull: Analyzing the fall in celestial language
7.
That's right, it pulls! : Newton finishes
8.
The bitterness after victory: It makes sense, but it doesn't make sense.
9.
It's all a mistake: it's actually more accurate to say that it's being pushed away.
Epilogue: The Simplest Question That Moved Humanity
Acknowledgments: On the Revised Edition of Gravity Express
Gravity History Chronology
Introduction of main characters
References
Search

“What is gravity?” “It’s nothing… it’s everything.”
A long journey to discover the value of this simple question: "Why do we fall?"

Gravity Express is a story about the history of humans who were curious about gravity and tried to solve its principles.
Many people have asked the author, a biology major, why he chose the physics topic of gravity.
The author's answer was, "Because I thought it would be fun." The history of gravity was the story that the author personally found most thrilling while studying science, and it was also a perfect fit for a story.
The simple question, 'Why do we fall?' is actually not simple.
This is because the universe as we know it today is based on our knowledge of gravity as explained by humans.
This question, which leads us to guess our place and destiny in the universe, inevitably contains the image of 'human'.
The stories of gravity written by countless people contain various failures and frustrations, but also triumphs and joys.
It even has twists and turns.
There is a heart-wrenching urgency that seems to be within reach but cannot be.
The protagonists in it are eccentric, dreamy, overly timid, and even unexpectedly foolish.
Unlike high school science textbooks that only briefly present the final conclusion, this book deals with the history of these many people's failures in a meaningful way, allowing readers to share their feelings.

From Anaximander to Einstein, including 28 protagonists
A thrilling and captivating journey of 2,500 years with countless characters.

From ancient times to the present, how have people perceived gravity? Gravity has been a phenomenon of falling downwards, a pulling toward a center, and the attraction or repulsion of matter.
Let's follow the 2,500-year journey of humanity, which has viewed gravity so differently over the ages, to see what efforts it has made to understand gravity.


1.
Adaptation Period - Why Do We Fall? Humanity, looking up at the sky, begins to study falling.
For billions of years, life on Earth has had to contend with something that pulls and weighs it down.
Humans went a step further than just fighting something and began to think about the principles of weight and falling.
What's even more surprising is that humans have realized that things like weight and falling are the most fundamental starting points for thinking about the shape of the universe or guessing our own position in it.
Thus began humanity's long journey surrounding gravity.


2.
Lost in the Fall - Aristarchus, who thought the Earth moved
Anaximander believed that a "lazy" god had created a world that ran like an automaton.
The language of that machine blueprint is 'numbers'.
After learning numbers, humans began to measure the size of the world and the structure of celestial bodies.
The Earth, the Moon, and the Sun were larger than we could imagine, floating in the vastness of space.
But there was one phenomenon that confused this idea: all objects on Earth have weight and fall downwards.
Why don't we roll down on a spherical Earth? How does the Earth itself float? Why don't the moon and sun fall down? The story unfolds between Aristarchus, who believed the Earth was moving, and Aristotle, who refuted this theory with the phenomenon of falling objects.


3.
Falling into one's own place - Aristotle's search for an orderly universe
The spherical Earth and celestial bodies float in the vastness of space, and the sun and moon trace elegant circles.
On the other hand, on the ground, all objects fall below the Earth, or rather, towards the center of the Earth.
What logic allows this phenomenon to occur? The main culprit that complicates the problem is the self-evident phenomenon of objects falling.
At this time, the outstanding Greek scholar Aristotle solved the problem, finding the reason for the fall in the fundamental elements of matter and viewing the Earth as the center of the universe.


4.
That's not it - Buridan's Impetus and Copernicus's Heliocentrism
As time passed, people began to question Aristotle's logical view of the universe.
The actual phenomenon of falling objects and the long-observed movements of celestial bodies had parts that could not be explained by Aristotle's view of the universe.
The center of the universe is not the Earth, but the Sun.
But this time again, the phenomenon of falling caught the new idea in its tracks.
If the Earth is moving busily at the edge of space, how can objects fall directly to the ground? And how can the moving Earth remain so motionless? The story continues from Buridan, who looked at the motion of objects with new eyes, to Copernicus, who imagined a much simpler, sun-centered universe.

5.
Falling is being pulled - Kepler explains falling in earthly terms
The heliocentric model could not predict the movements of celestial bodies as accurately as the geocentric model.
However, Kepler, a man with a firm belief that the sun is the center of the universe and that the universe is necessarily harmonious, solved this weakness of the heliocentric theory.
Kepler, who thoroughly analyzed Tycho Brahe's observations and patiently traced the movements of celestial bodies, went on to believe that there must be a principle that humans can understand behind the movement of celestial bodies and the fall of objects to the ground, and he had the innovative idea that this principle might be 'mass', which we already know.
Kepler, as an astronomer, thought like a physicist.

6.
No guesses can be made about the attraction - Galileo, analyzing the fall in celestial language
Galileo, who believed only in 'experiments' and 'numbers', explains the great shortcoming of the geocentric theory, why we cannot feel the movement of the supposedly moving Earth at all.
We also come to the great realization that the true nature of the universe is completely different from our common sense, and that the only absolute existence is time.
Galileo was deeply interested in the motion of objects, and in his investigation of the nature of motion, he discovered an important clue that it was closely related to the falling of objects.

7.
Yes, it pulls! - Newton solves the age-old problem connecting heaven and earth.
Newton throws an apple.
The apple that was flying falls.
But if thrown with just the right amount of force, an apple could circle the Earth forever.
Why do terrestrial objects fall while celestial bodies float in space? The answer to this perplexing riddle was already discovered by scholars of the past, but it was a puzzle piece.
Newton put these pieces together correctly and finished it off with beautiful mathematics.
His answer was clear and simple.
All motions in the universe, including the phenomenon of falling, are explained by his formulas, considering only the forces of attraction between inertia and mass.
The universe is not two worlds, heaven and earth, but one world, and it revolves according to only one law.
If we know this law, we can explain and predict all movements in the universe.

8.
The bitterness after victory—it makes sense, but it doesn't make sense? The key lies in "light."
Newton's laws of gravity and mechanics are like a magic box: just input some numbers and it will tell you exactly what you need to do.
But the strange thing was that I had no idea why such an answer came out.
Curious minds continued to ponder the philosophical difficulties of Newton's theory, and eventually it was hit hard by other emerging disciplines.
Not everything in the universe revolves around Newton's theory.
The key to solving the dizzying problem of gravity, which had become dizzying again, was unexpectedly found in 'light', a physical entity that seemed to have nothing to do with gravity.


9.
It's all a mistake - Einstein overturns gravity, it's more repulsive than attractive.
Once again, all gravity is turned upside down.
That time and space are not absolute but rather changing quantities.
Could there be a story more incredible than this? With this astonishing idea, Einstein completely overturned our existing concepts of time and space and overturned Newton's laws of mechanics, which were considered complete.
With just these two things - the speed of light and the theory of relativity in Galileo's inertial frame - Einstein was able to discover the principle of gravity that even Newton could not explain.
The idea that gravity is a 'force' was an illusion!