prolog

Part 1: Zero Gravity and Satellites

Is it possible to achieve the dream of flying in the sky naked?
How to create zero gravity
The identity of zero gravity
Experience the future of weightlessness with Starship and Hyperloop
Experience weightlessness on an imaginary Earth
The Earth's rotation period is not 24 hours.
Why do satellites and missiles bend as they fly?

Part 2: Space Exploration of the Solar System

What is initial velocity?
Initial velocity to get to the moon and other planets
Gravity-assisted navigation is an invisible, free propulsion system.
Gravity-assisted navigation, also used for Mercury and solar exploration
What does the shape of a spacecraft's orbit mean?
Rockets, ion propulsion, and the photonic rocket of the future

Part 3: Asteroids, Comets, and the Earth's Orientation

Why are asteroids and comets bumpy?
Where did the energy from the asteroid impact that wiped out the dinosaurs come from?
What if a comet hits Earth?
Earth's defense against asteroid and comet impacts

Part 4: Artificial Gravity Required for Long-Term Manned Space Exploration

How did the Seattle train derailment happen?
Artificial gravity in sports
How to create artificial gravity in space
What if you juggle in artificial gravity?
The difference between flat and horizontal
The inertial force that explains weightlessness
The nature of artificial gravity and gravity as seen through inertial force

Part 5: Finding Extraterrestrial Objects

The first exoplanet observations and the Doppler effect
The Science of Shadows: Exoplanet Observations and X-ray Imaging
The Science of Mirages: What Would a Black Hole Look Like Up Close?
How do you measure distance?
Catching up on the first gravitational wave observation paper

Part 6: Manned Exploration of Exoplanets: Explained with Special Relativity

What happens when a spaceship approaches the speed of light?
The Twin Paradox: The Difference Between Knowing and Seeing
How fast can a manned spacecraft accelerate?
The energy required to accelerate to near the speed of light

Epilogue
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Everything about exoplanet exploration, where reality and science fiction meet.
Satisfy all your intellectual curiosity about space exploration.

In Le Voyage dans la Lune (1902), known as the world's first science fiction film, a manned spaceship is launched to the moon using a cannon.
It's a somewhat odd-looking launch method, closer to a cannonball than a spaceship, but the speed of the spaceship as it leaves the cannon barrel does a good job of representing its initial velocity.
This is because it expresses a spacecraft that flies only with the inertia of its initial velocity without using additional propulsion after launch.

The film 2001: A Space Odyssey (1968) details how to create artificial gravity on a spaceship.
It is a method of creating artificial gravity by rotating.
In The Martian (2015), there is a spaceship called Hermes that travels between Earth and Mars. This spaceship accelerates very slowly, so without special equipment, the spaceship is practically weightless.
In this film, astronauts also live in a living facility that creates artificial gravity through rotation.
“Don't Look Up” (2021) depicts a hypothetical crisis in which a comet collides with Earth, while “Armageddon” (1998) tells the story of an asteroid heading towards Earth.

As expressed in numerous science fiction films, we have continuously dreamed of 'space exploration' from the 20th century to the present 21st century, and have been working to develop science and technology to make it come true.
On June 21, 2022, South Korea successfully launched an artificial satellite using Nuri, a propulsion system developed with its own technology, and on August 5, 2022, the country also developed a lunar orbiter, Danuri, and placed it into orbit around the moon using a ballistic lunar transfer method.
Space exploration or the search for extraterrestrial bodies is no longer confined to the realm of science fiction.
As science advances, we dream of leaving Earth and exploring the vast, unknown universe.

But when watching a movie that travels through the distant universe, there are times when you wonder if such a setting makes scientific sense.
If the story writer is not familiar with the basic scientific laws or theories related to space travel, the story may lack scientific validity.
Conversely, if the audience or readers are not familiar with scientific laws and theories, even a well-crafted story may be misunderstood as lacking scientific validity.
It cannot be ignored that with little direct experience and limited information about space travel, we have to rely to some extent on our imagination to create and enjoy stories.
If there is any part that lacks scientific validity or is questionable, it is a good idea to look into it at least once.
You can understand science better and sometimes even learn scientific facts you didn't know before.

Published with this purpose, the new book, "The Physics of Space Exploration," introduces the general story and basic knowledge of space, and examines the launch of spacecraft toward habitable exoplanets and the many scientific knowledge related to it.
That is, it provides the scientific knowledge that is essential for our hopes and adventures in space, especially the foundation for studying physics, which is considered difficult.
Although physics accounts for a relatively large portion of the book, astronomy, earth science, and aerospace engineering also occupy a significant portion.
Therefore, it can be said that it covers a wide range of scientific fields related to space exploration.
Each page is filled with a variety of rich photographic materials, and most of the illustrations explaining scientific content were drawn by the author himself, making the content easy to understand and helping readers fully understand.

Find a 'habitable planet' with an environment similar to Earth!
Physics, aerospace engineering, astronomy, and earth science all in one volume.

Space technology, which began to be implemented in earnest in the late 1950s, sent humans into outer space in 1961 and to the surface of the moon, a celestial body beyond Earth, in 1969.
Unmanned space exploration also continued, with probes sent to every planet in the solar system by the 1980s.
In the 21st century, we have been exploring various celestial bodies, including Pluto, which was demoted to a dwarf planet, Ceres, a dwarf planet in the asteroid belt, and Comet Churyumov-Gerasimenko.
Korea, which has consistently invested in aerospace science and technology, successfully launched an artificial satellite with Nuri and also developed a lunar orbiter, Danuri.

There were also advancements in astronomical observation.
Exoplanet observations, which began in the 1990s, have yielded results that have led to the discovery of over 5,000 exoplanets by 2022.
Research results on so-called "habitable planets" that are located at an appropriate distance from their stars and may have an environment suitable for life are steadily being published.
The nearest star is a red dwarf called Proxima Centauri, 4.25 light-years from Earth.
A 2016 paper published in the scientific journal Nature revealed that there is a planet orbiting this star that may have an environment similar to Earth.
The story goes that even the nearest star has a planet that could be used as a destination.
Although we have yet to send humans to any celestial body other than the Moon, news of exoplanet discoveries leads us to imagine setting foot on a habitable exoplanet and developing a colony there.
It is an imagination filled with hope that this will be possible in the distant future when science and technology have developed tremendously.

"The Physics of Space Exploration" contains scientific knowledge that should be considered during the long journey of space exploration that connects the past, present, near future, and the very distant future.
It focuses particularly on scientific knowledge related to manned space exploration.
This book thoroughly explains, based on scientific knowledge, the fact that what we feel as gravity is not gravity, weightlessness created through free fall, the future weightlessness experience using Hyperloop, the initial speed and escape velocity of a spaceship, the effects of orbit and rotation on spaceship launch and flight, gravity-assist navigation that can increase spaceship speed without rocket propulsion, Earth's defense against asteroid or comet collisions, how to create artificial gravity necessary for long-term manned spaceflight, and special phenomena that occur in artificial gravity.

The latter part of the book explains the science behind finding exoplanets, mirages on Earth and in space, and observing gravitational waves that occur when black holes merge.
Finally, the events and results of manned space exploration toward an exoplanet in the very distant future are explained using the special theory of relativity.
We explore why places that take light hundreds of years to travel can be reached in just a few decades, the twin paradox, the process of accelerating a spaceship to near the speed of light, and the energy required to do so.

The book explains things with care not only for the general public but also for science enthusiasts.
Parts that may not be easy to understand through text alone have been supplemented with various illustrations.
Unless absolutely necessary, formulas are avoided whenever possible.
It also explains how to apply the basic principles of related science and technology.
We scientifically examined not only current and future science and technology, but also content that exists only in the imagination.
The author, Dr. Bok-Won Yoon, stated that he wrote this book in the hope that many people, from elementary, middle, and high school students to college students and adults, would gain scientific information related to space travel and satisfy their intellectual curiosity.
These days, non-fiction texts, including science texts, are appearing in the Korean language section of the College Scholastic Ability Test. This will be very helpful in building basic science knowledge to prepare for the CSAT.
Moreover, this book will likely serve as a companion that provides detailed scientific knowledge that should be verified when writing about space travel, and thus, it will be of particular value to science fiction writers in many ways.

For scientists to communicate with the general public…
Bringing knowledge based on fundamental physics to the public

Communicating science between scientists and the general public is not easy.
The biggest problem is that the content itself is difficult.
To overcome this problem, it is important for scientists to make an effort to explain science in an easy-to-understand way.
Despite such efforts, if communication with the public remains difficult, the role of those who serve as intermediaries between scientists and the public is also important.
This includes science communicators, including science journalists and YouTubers.
Scientists need to provide them with accurate scientific information and provide feedback on their activities with the public.


There is also the problem of the 'terminology barrier'.
The terms that scientists use naturally and habitually can be difficult for the general public to understand, or even to grasp, what they mean.
Scientists may not even be aware that the public finds these terms difficult.
If possible, we should try to rewrite it in simple terms, and if that is difficult, we should try to provide easy explanations of the terms.
There is also the scientist's 'problem of consideration'.
When it comes to scientific topics that the public wants to know about, we should avoid responding with things like, "If you want to know, study it" or "If you're not a specialist, you won't know even if you study it."
Such comments can be hurtful to some members of the public, and may subsequently lead them to block all communication with scientists.

The author recognized these problems and became the first to write and contribute scientific articles to a general audience.
My first article of 2014 was about the 'twin paradox' of special relativity.
The theory of relativity was a basic physics knowledge that all physicists had to learn, and since then, most of the books have been based on basic physics knowledge, and the contents of the books have mainly dealt with topics that the author was personally interested in.
I paid attention to what was reported in the news and didn't forget to check it by doing my own calculations.
The author believed that writing a story without any verification was not the right attitude for a scientist.

In this way, Dr. Yoon Bok-won compiled scientific knowledge related to space and space travel into a book and presented it to the public.
The book is divided into six parts.
Parts 1 through 5 cover scientific knowledge related to existing space exploration, while the final part, Part 6, focuses on space exploration of exoplanets, which is likely to occur in the very distant future.
The author says that what happens after Part 6 is left to the reader's imagination and the advanced science and technology of the distant future.