“God is left-handed!”
-Wolfgang Pauli, Nobel Prize winner in Physics

If you distinguish between left and right, you will see modern physics!
The physicist who writes the most unique and daring articles
Highly recommended by Professor Park Kwon of Korea Advanced Institute of Science and Technology
Recommended author by Professor Jin-ui Kim of Seoul National University

“Can you explain the right side?”
-Movie "Happy Dictionary"

Could you explain your left hand to an alien? Imagine if humanity were to perish, leaving only "Heosaengjeon" (The Story of a Man Who Lives).
And let's say that some intelligent beings who visited Earth deciphered the following sentence from "Heosaengjeon".
“When you have children, hold the spoon in your right hand and let the one born a day earlier eat first.” Even if they have their own concept of left and right, we will never know which hand is designated as the ‘right hand’ in “Heosaengjeon.”
For these creatures, the preceding sentence means nothing more than “If you give birth to children, hold a spoon in your hand.”
What records should we add to the "Heosaengjeon" to let them know which hand is left or right?

Amazingly, until 1956, all physicists said that no records could tell us who was left-handed.
To distinguish between left and right hands, we need to distinguish between left and right, and to know the difference between left and right requires a higher level of modern physics.
But precisely because of that, the book argues that by distinguishing between the seemingly familiar differences between left and right, we can come to understand electricity and magnetism, the four fundamental forces of nature, and even symmetry breaking, dimensionality, and the deepest secrets of the universe.

So why is the distinction between left and right so deeply intertwined with the universe? Because, as physicists and mathematicians realized in the 20th century, symmetry and its breaking are among the most fundamental principles of nature.
For example, the law of conservation of energy is derived from the time-translational symmetry of the laws of nature, and the law of conservation of momentum and the law of conservation of angular momentum are derived from the space-translational symmetry and rotational symmetry of the laws of nature, respectively.
Furthermore, in general, the (continuous) symmetries of all physical laws correspond to conservation laws.
On the other hand, spontaneous symmetry breaking in quantum mechanics is already the most important means of understanding the origin of the universe and mass.

But knowing that the left and right hands are similar is understanding symmetry, and knowing that they are different is understanding the breaking of symmetry.
The left and right hands, which seem so familiar to us, contain the operating principles of our universe.
“To put it mildly, a very slight exaggeration, physics without symmetry is nothing.” (Nobel laureate in physics Philip Anderson)

“You might wonder who wouldn’t know the difference between the left and right hands, but as you read this book, you’ll be amazed at the depth of this question.
And you start to see the universe in a completely different way.
“Distinguishing between left and right hands is a violation of symmetry, which in turn is deeply connected to the mysterious nature of quantum mechanics, the fundamental operating principle of the universe.”
Park Kwon, Professor at Korea Advanced Institute of Science and Technology and author of "What's meant to happen will happen."

It may sound strange, but the goal of this book is to distinguish between left and right.
How can we tell them apart? A moment's reflection reveals that while they may seem familiar, distinguishing them isn't easy.
The amazing thing is that physics tells us how to distinguish between right and left.

--- p.4

Why do most people eat with their right hand? It's one of two things.
1. I don't know for sure, but there is a reason.
Earthlings are born with a natural ability to use their right hand better.
2. There is no reason, it is just a coincidence.
Although both hands can be used equally, more and more people have been taught and taught that they should eat with their right hand.

--- p.20

Andromedan: I don't know that letter.
Describe the shape of the letter L.
Earthling: First, draw a line segment and stand it up vertically.
Andromedan: Yeah.
(Draw a '|' and set it up.) Earthling: Then, attach a short stroke to the bottom of this line segment, and attach it so that it extends to the right.
Andromedan: Wait, right? We were talking about how right is defined.

--- p.36

However, if you apply too much ink and stamp, you can create the decalcomania that we discussed in the previous chapter.
In other words, when I fold the ballot, the ink on the box for the candidate I want to vote for may spread and stamp other boxes.
When that happens, if the voting stamp looks like the one in Figure 14, it is impossible to distinguish between the original and the flipped stamp.
This is because they all have bidirectional symmetry.

--- p.55-56

Imagine being the protagonist of a detective novel, being kidnapped by someone and being brought into a hotel blindfolded.
If you can only remove the blindfold after getting off the elevator, how can you know which floor you're on? Even if you get on the elevator with your eyes open, there are situations where you can't know.
If there are no floor markings inside the elevator, and the interior decoration of all floors outside the elevator is the same, you won't be able to tell which floor you are on even when the elevator stops and the doors open.
(…) The symmetry regarding straight line movement to the left, right, up, and down is called ‘translational symmetry.’

--- p.68-69

Even if you experiment with everything you've learned so far, you still won't know which direction the current flows.
Unfortunately, even when the concept of electric current was first defined, it was not clear what 'causes electricity to flow'.
I just made that promise without knowing anything.
Promise: Let's promise that the current flows from the (+) terminal of the battery to the (?) terminal.
(Inside the battery, it should come in through the (?) of the battery and go out to the (+) side.) Can I promise this? (…) In other words, even if you change all the (+) and (-) that have been discussed in this book so far, the contents of this book will not change!
--- p.110-111

The N pole, or the part that was at the top, turns to the left, and the S pole, or the part that was at the bottom, turns to the right.
The compass needle turned in one direction.
It could have gone the exact opposite way, so why did it only go one way? It's strange.
This is because, not only before the current flows, but also the current itself has bidirectional symmetry in terms of the left-right reversal operation.
If there is a reason to turn right, there should be a reason to turn left as well.

--- p.137

You can also memorize the direction of the North Pole using your right hand.
Wrap your right hand so that the direction of rotation matches the direction of current flow.
Then, the direction of the thumb becomes the direction that the N pole points.
You could call this the 'new right-hand rule'.
The important thing here is that the direction of the thumb is not the direction in which the current flows as before, but the direction in which the N pole rotates.
This new right-hand rule is not directly related to the right-hand rule we saw earlier.

--- p.147

If there is spin, even an uncharged particle becomes magnetized, just as a charged object would spin.
Therefore, electrically neutral neutrons and atoms are small magnets, and their orientation is determined solely by their spin.
At this time, the direction of the magnet is determined by the right-hand rule through the direction of the spin.
If you think of spin as rotation and wrap the four fingers of your right hand in the direction in which the particle rotates, the direction your thumb points is the direction of spin, which is the direction of the north pole of the magnet.

--- p.171

Now it's time to talk about an experiment to distinguish between the N and S poles.
This has to do with the violation of parity.
In 1954, many physicists were pondering the so-called 'tau-theta problem'.
Tau and theta particles decayed differently even though they had the same mass and half-life. 53 Normally, particles with the same mass and half-life are the same, but the tau particle decayed into three pi particles, and the theta particle decayed into two pi particles.

--- p.184