When studying physics, sometimes your thoughts may drift in strange directions.
It's like when you think about mass in physics, you think about the heaviness of the heart.
(……) This book is a mix of science and non-science.
I would also like to point out that when writing two stories with different endings together, I focused on their similarities rather than their differences.
I don't think we need to divide everything into two, just like our lives.
We talk about science, but we don't want to talk only about science.
Science is ultimately a human endeavor.
I think about our insignificant and perhaps even more precious existence in the vast universe, and I gaze fondly at the tiny specks of dust sparkling in the sunlight streaming through the cracks in the curtains.
Looking at the vastness of the universe and the precious sunlight, I was reminded of the weak gravity and weak nuclear force in physics.
Even though we cannot see them, they exist, and the small and delicate things that come together make up the world we live in.
---From "Entering_Even if it's as small as dust, it's as precious as gold"

The Earth is insignificant not only in size but also in location.
The Sun is just an ordinary star on the outskirts of our galaxy, and the Earth is just an unremarkable planet orbiting it.
Many people feel disappointed by the insignificance of humanity when they think of the immense size of the universe and the infinitely small Earth within it.
On the one hand, one could be overcome by the sense of futility that humans are ultimately nothing more than a collection of sizeless elementary particles.
Whenever I face the vastness of the universe and the insignificance of human existence within it, I always think of the phrase “nevertheless.”
We are the only beings we know who have realized the beauty of the universe filled with emptiness through the power of reason.
So, I want to convey my heartfelt feelings to everyone.
Humans are all the more precious because they are insignificant.
---From "Void_From Atoms to the Universe, Almost Everything"

In modern quantum physics, the vacuum, meaning 'nothing' or 'truly empty', also plays an active role, much like the blank space in Mendeleev's periodic table.
Physics has discovered that a vacuum is paradoxically not a vacuum.
The vacuum of modern physics is like a vast and deep ocean.
Let's say you can't see the sea water that fills the ocean directly, but only the water droplets that splash up on the surface when you splash, and the air bubbles in the sea water that those splashes leave behind.
You can think of the water droplets that rise to the surface as particles, and the air bubbles in the seawater as antiparticles.
If a vacuum is like this, then it makes sense that a particle and its antiparticle can suddenly pair up and reveal their existence simultaneously, seemingly out of nowhere.
It is a vacuum vibration.
---From "Blank_The Sea of ​​Vacuum, Repeatedly Creating and Destructing"

Perhaps the law of action and reaction applies to the interaction between you and me as well.
The power of connection that your presence has on me may be as great as the power of connection that my presence has on you.
Even when the same gravity is applied, the Earth does not move, but only the apple reacts sensitively and moves.
A single word you say to me in passing can be a thrill of joy, a dagger to the heart, or a deafening wonder.
The reason why the same words move my heart to different degrees is probably because it ultimately depends not on the weight of your words, but on the quality of my heart.

---From "An Interaction Called Gravity"

Weight is determined not only by mass but also by the size of the gravitational field where the object is placed.
Even though I am the same person as yesterday, my heart may feel lighter or heavier than yesterday because the social situation in which I exist has changed.
Some people suddenly find themselves burdened with an enormous weight of existence due to changes in the social arena.
Just as a heavy star changes the gravitational field around it, a social being burdened by the heavy responsibilities it has been given can change its direction and change the course of society.

---From "Weight_The Gravitational Field That Determines the Weight of Existence"

What is a "old fart" can also be thought of as a correlation function in physics.
Let us define the location in time and space where the judgment criterion is formed as the origin (0,0).
It is foolish to try to judge the situation here, where the spatiotemporal location is (t,x) away from the origin, based on the standard formed at (0,0).
The greater the distance between the origin and (t,x), the lower the correlation.
You become a serious old fart who makes erroneous judgments but believes he is right.
---From "Old Man_The Coordinates of This Place Now"

“Even the wind blowing through the leaves made me suffer.” This is a line from Yun Dong-ju’s “Preface” that everyone knows.
The poet is sensitive to even the smallest external changes and suffers from life with his heart.
In statistical physics, we also talk about sensitivity.
Sensitivity measures how strongly we react to small external stimuli.
In the case of a bar magnet, when a small magnetic field is applied from the outside, the change in magnetism is divided by the strength of the magnetic field, and that value is the sensitivity.
The sensitivity is high because the magnetism changes significantly even with a small magnetic field.
If we define it like this and measure the poet's sensitivity with sentences from the "Prologue," the value is enormous.
The great suffering in the poet's heart was divided into the strength of a gentle breeze blowing through leaves, so the value could not help but be very large.
---From "Trembling_A Fierce Signal that Announces the Moment of Change"

Two people in love find each other attractive.
There is an attractive force between the two that pulls them closer to each other.
The source of attraction, which acts as a force of attraction, could be electromagnetic force, but it cannot be gravity, which is so weak.
It's not a love story between two atomic nuclei, so it can't be the strong nuclear force or the weak nuclear force, let alone the electromagnetic force.
(……) Your wonderful appearance reaches my retina in the form of a light particle (photon), which is a medium for electromagnetic interaction, crossing the space between us.
Light striking the photoreceptor cells of the retina generates electrical nerve signals that reach the visual center at the back of the head and are then transmitted to various parts of the brain, creating our emotions and perceptions in the form of electrical firing patterns of various nerve cells.
Science hasn't figured out all of this, but if it's love at first sight, you can thank electromagnetism.
---From "Friction: A Heating World, a Runaway Future"

Galileo's principle of relativity states that "the laws of motion seen by two observers moving at a constant speed are the same," and Einstein's theory of relativity adds to this principle that "for observers moving at a constant speed, the speed of light is the same for all observers."
The theory of relativity in physics is not about 'difference'.
Rather, it is a story about ‘sameness’ that does not change even if the standard changes.
The same laws apply, but if the standards are different, the phenomenon seen by each person will appear different.
---From "Standard_Sameness that does not change even if the standard changes"

I remember an ideal scene from the television documentary Cosmos, which has the same title as Carl Sagan's book.
This is a scene where sunlight coming through a small gap is refracted by a prism and broken down into pieces, and then spread out on the dark floor of a large room.
In the spectrum of light spread across the floor, rainbow colors are visible only in the middle of the room.
Even though electromagnetic waves clearly reach beyond this narrow visible light range, we cannot see them at all.
There is much more light that exists but is invisible than the light we see.
Just because you can't see it doesn't mean it doesn't exist.

---From "When the small things we forgot about appear in a gap"