“Even the progress of civilization cannot overcome the limits of physics!”
An Astrophysicist's "Real Universe" Story for Pseudo-Space Merchants
★ Winner of the 2023 Galileo Prize (Premio Galileo 2023) Scientific Writing Award

“You will be able to take a fresh look at the limits and possibilities of escaping Earth.
That limitation isn't particularly inconvenient.
It's not because our scientific capabilities are lacking, but because even this is part of the natural order.
If you're curious about Elon Musk's next move, this book has the answer." - Recommended by Professor Hwang Ho-seong (Department of Physics and Astronomy, Seoul National University)

It's like seeing the return of the 'Age of Apollo'.
Manned lunar exploration, which seemed to have disappeared after Apollo 8 in 1971, is making a spectacular comeback thanks to plans by emerging powers such as Europe and China.
But now, unlike in the past, exploration is planned with the purpose of living on the moon, rather than as a one-time event where we 'stop by and come back'.
Ambitious private space companies like SpaceX are promising to build cities beyond the moon and on Mars within this century, and every media outlet—from dramas and movies to documentaries and news—is presenting this blueprint as if it will soon become reality.
So, will we really see all these sights in our lifetime? Or will they be realized in the next generation?

"You Can't Go to Mars" is a book that explores humanity's dream of "migrating to space" and the realistic limitations that dream faces from a scientific perspective.
Renowned Italian astrophysicist Amedeo Balbi points out that the current space exploration craze is as much about romantic dreams about the human future as it is about scientific progress, and he explores the difficulties we face when these dreams collide with real-world technological, biological, and ethical issues.
It explores the fundamental realities surrounding the movement of 'space exploration': whether establishing human colonies on other planets is possible, what technological challenges will be encountered, whether humans can adapt to new environments beyond Earth, and, above all, whether it is worth it.

Moreover, the journey into space goes beyond mere technological achievements; it also explores the conditions that humanity must meet to establish itself as a cosmic being.
The author emphasizes a more responsible approach to the future of space exploration, pointing out that “space exploration is a process of pursuing a bold dream for humanity’s future, but to realize this dream, we must apply the lessons learned from Earth and find ways to adapt to the strict order of space.”
This book will help you understand the various forms of space exploration taking place today, and furthermore, gain a new perspective on the 'blue Earth' on which we stand.

Yes, that's right.
The Earth is truly amazing.
So it feels like it was made just for us.
For thousands of years we have believed that.
But later science showed us that the truth was on the other side.
To be precise, we, the species, were created for the Earth.
Our species, like all other species that have appeared on Earth, was slowly formed through natural selection and was created to adapt to its given environment.

--- From "Prologue: "What a Wonderful World""

In about a billion years, the amount of energy the Earth receives from the Sun will have increased by 10 percent compared to today, and the average temperature of the Earth's surface will have reached about 50 degrees Celsius.
This will have disastrous consequences.
The oceans will evaporate, and the water vapor in the atmosphere will form an increasingly thick layer, which will in turn increase temperatures, causing more evaporation, and so on.
After a few million years, all the water on Earth's surface will evaporate into the atmosphere and eventually disperse into space.
At that point, Earth will become a barren wasteland, and the possibility of complex life forms surviving will be virtually eliminated.
The biosphere that has surrounded the Earth for billions of years will no longer exist.
--- From "The End of the World Script"

That's why the idea of ​​leaving Earth altogether as a plan B for the future of humanity is capturing people's hearts.
Although the number is not particularly large, there are quite a few people who are passionate about this idea, both past and present.
The most famous of these is the widely known and beloved physicist Stephen Hawking (1942-2018).
Like Reese, he was convinced that humanity had little chance of surviving beyond the centuries, and at every opportunity he argued that our species' only hope for long-term survival lay in space travel and the colonization of other planets.
--- From “You Must Leave Earth to Survive”

right.
Most people don't realize that our entire existence is protected by a thin protective shield from the hostile environment of the universe.
We live in the atmosphere, the sea we call air.
All that we call 'the world' is nothing more than a layer of gas a few tens of kilometers thick where we live from the time we are born until we die.
On the surface of the Earth, moving 100 kilometers away doesn't really change anything.
It's just a matter of seeing a nice view or going on a picnic by the sea.
But once you climb 100 kilometers up, everything is over without proper protective gear.
That is, you will face death.

--- From "A Beautiful Place, Its Opposite Space"

Mercury's proximity to the Sun makes it extremely hostile to life, and it's also extremely difficult to explore with robotic probes.
From an energy standpoint, surprisingly, it takes more energy to reach Mercury than to leave the solar system.
Mercury moves so fast that any spacecraft approaching it would have to travel at a similar speed and overcome the Sun's enormous gravity to enter orbit.
For this reason, Mercury is the planet least visited by humans among the inner planets of the solar system, and no probe has ever landed on its surface.

--- From "Where should I (not) go?"

Because the moon has almost no atmosphere, its surface temperature varies greatly.
When exposed to sunlight, it reaches temperatures of up to 130 degrees Celsius, and when not exposed, it drops to -170 degrees Celsius.
A lunar day, or the moon's rotation cycle, takes about 29 Earth days, and humans have to endure not only extreme temperature changes but also long, lightless nights, which is a great hardship.


Although this characteristic can be inefficient when using sunlight as an energy source, it can be very useful in some areas of the lunar polar regions that are never in shade.
Also, because the Moon always has the same side facing Earth (the far side, also called the "Dark Side of the Moon," is not visible from Earth but receives the same amount of sunlight), only permanent settlements built on the visible near side can communicate directly with us (communication with the far side requires a separate lunar orbit relay satellite).

--- From "The Great Wilderness, Near and Far"

The Mars Project was realistic, at least on paper, and its grandeur was enough to capture the public's imagination.
His ideas received significant attention at the time through popular magazines, television programs, and even a documentary series produced by Walt Disney.
After the success of the Apollo missions, von Braun used his fame to promote the Mars program, which was aimed at implementation in the 1980s.
Later, the initial plan was revised and a proposal was made to the U.S. government to have two spacecraft each carrying six crew members.
The proposal was seriously considered by President Nixon, but was ultimately abandoned, despite von Braun's influence, in favor of the Space Shuttle program (a reusable space shuttle program that ended in 2011 after 30 years, including two major disasters that killed 14 astronauts).

--- From "The Mars Project on Paper"

One of the most efficient orbital maneuvers was developed in 1925 by German scientist Walter Hohmann (1880–1945).
He came up with the concept after reading Kurd Lasswitz's (1848-1910) science fiction novel Auf zwei Planeten (On Two Planets), published in 1897, which coincidentally dealt with Mars and the then-popular idea of ​​intelligent life.


In any case, the so-called 'Hohmann transfer orbit' deals with how a spacecraft can maneuver from one orbit to another with minimal fuel consumption.
In principle, this maneuver requires two rocket ignitions.
The first ignition occurs when leaving the starting orbit, and the second ignition occurs when entering the destination orbit.
While on a path to change orbit, the spacecraft moves by inertia and does not consume fuel in the process.

--- From "Common Travel Methods to Mars"

One thing to remember is that the flight dynamics of a Mars rover require much more sophisticated technology than a lunar rover.
For example, as distance from Earth increases, real-time communication gradually becomes less efficient and two-way electromagnetic signal delay increases.
When Earth and Mars are closest, light takes about 4 minutes to travel between them, but when they are farthest away, it takes about 24 minutes.
Therefore, in the event of an emergency, astronauts are virtually unable to receive assistance from Earth's technical staff.


Additionally, since the spacecraft accelerates at high speed after ignition to leave low Earth orbit, it is difficult to perform corrective maneuvers if a problem occurs.
In this situation, it is very difficult to turn back.
If something similar to the Apollo 13 accident were to happen on a spacecraft bound for Mars, it would be a far more tragic situation.
--- From "A Common Journey to Mars"

The spectacular Martian landscapes captured by robotic rovers over the past few decades may at first glance appear not so different from exotic places on Earth.
So, for those who dream of adventure, it might be tempting to board the first spaceship with a backpack and sunglasses on.
But the real situation is very different.
After a dangerous and arduous journey, humans who arrive on Mars will face a harsh environment incomparable to any desolate and barren place on Earth.
In effect, you will have to minimize outdoor activities and spend most of your time in artificial spaces isolated from the outside environment, such as underground.
--- From "Mars is Beautiful, But"

Biosphere 2 is designed like a giant terrarium.
It was the most artificial Martian (or extraterrestrial) ecosystem ever created among the experiments conducted up to that point.
But unfortunately, problems arose almost immediately after the start.
They planned to eat mainly vegetables, supplementing the lack of animal protein with small amounts of milk, meat, and eggs from livestock.
However, not only was growing vegetables and raising livestock much more difficult than expected, but the vegetables that were available for consumption were limited to sugar beets and potatoes, making it difficult to obtain sufficient calories and nutrients.


After a few months, oxygen levels inside the structure also began to drop to worrying levels.
As the carbon dioxide gradually accumulated, all eight participants developed symptoms of altitude sickness, including drowsiness, sluggish movements and slurred speech.
As many of the animals that had entered together died, species with strong survival instincts such as cockroaches and ants began to fill the entire Biosphere 2.
In addition, frequent conflicts arose over operations and management, and interpersonal problems arose among participants.

--- From "Survival in a Sealed Glass"

You might wonder why Musk's plans are so grand.
Why would they devise such a complex plan to relocate such a large group of people, rather than a simple mission involving just a few people? The reason is simple.
Because his plan is an economic strategy, not a scientific or engineering plan.
In fact, he has no concrete plans for how to solve the problems of space travel and the enormous difficulties of survival on Mars.


For Musk, ensuring the financial sustainability of his business is his only concern.
Musk predicts that as the price of tickets to Mars becomes cheaper, more people will want to board the spacecraft.
Therefore, it is advantageous to focus technological capabilities on lowering ticket prices.
That's why SpaceX is more interested in spaceships than survival on a Martian colony.

--- From "One-Way Ticket to Mars"

In theory, the process of making Mars habitable again might seem simple.
That is, by supplying greenhouse gases into the atmosphere, we can change the situation by increasing the pressure and temperature at the surface and melting the soil and polar ice.
This scenario suggests that a denser atmosphere and abundant water (even if it is difficult to breathe) will be created, and that by introducing photosynthetic organisms, including plants, which will emit oxygen, an environment conducive to human habitation will be created.
It seems so simple when explained like this, it makes you wonder why we don't already have a second blue planet in our solar system.
--- From "Terraforming, Can Mars Become Blue?"

It is difficult to predict an uncertain future.
What was impossible in a few years may become possible in hundreds of years.
But no matter what point you imagine, you must remember one simple fact:
Mars cannot be a replacement for Earth today.
It may not seem like it, but the Martian environment is just as hostile as the Moon.
Moreover, compared to the Moon, there are few advantages to settling on Mars.
The moon is a bit easier to get to.
To be blunt, people (including scientists and experts) cannot offer a single valid reason why we should leave Earth and go live on Mars.

--- From "Why We Can't Go to Mars"

Any hypothetical plan to migrate some of humanity off Earth would face enormous complexity.
To establish a settlement on the Moon or Mars, the only two theoretically viable options, we must be able to not only maintain an independent, isolated settlement on the surface of these worlds, but also safely transport large quantities of supplies and personnel.


If so, wouldn't it be better to completely abandon plans to settle on other celestial bodies and instead create an artificial environment suitable for humans in space? If there's no alternative to living in a sealed glass tube, it makes sense to build it somewhere more convenient for us to access.
This means that it might be better to build a massive space habitat (space colony) close to Earth rather than building a domed, sealed biosphere on Mars.

--- From "Space Island, Space Residence"

Building another human settlement beyond Earth is not only a challenging task in itself, with its hostile environment, risks, and technical challenges, but also the enormous cost of construction that must be addressed.
Whether it's a massive space colony like Jeff Bezos envisions, or Elon Musk's Martian city, transporting the necessary materials beyond Earth and assembling them in orbit, on the moon, or on the surface of Mars remains a difficult concept to imagine.
This is especially true considering that with today's technology, it costs tens of thousands of dollars to move a single kilogram of material out of Earth's atmosphere.

--- From "If There Was an Elevator to Heaven"

Even if we could relocate to other parts of the solar system, the natural disasters that threaten our survival in the short to medium term (within centuries or millennia) would not disappear.
For example, collisions with asteroids or comets would remain an unresolved problem on Mars or the Moon, and could have the same impact on habitable spaces in orbit.


The best way to deal with these threats, as we have seen, is through surveillance and prevention, so that when the worst happens, we can develop solutions to minimize the damage.
All of this requires new technologies and knowledge related to space observation and exploration.
The dangers arising from human actions will not disappear or diminish with the creation of extraterrestrial colonies.
Rather, it may be the opposite.

--- From "Beyond the Earth"

In recent years, there have been several media reports about the discovery of potentially habitable planets around other stars.
The news came with the startling estimate that there could be hundreds of millions of habitable planets in our galaxy alone.
When you hear news like this, you might think that planets like Earth are incredibly common in the universe.
But to properly evaluate this and put it into context, we need to understand what astronomers often mean by the term "potentially habitable."

--- From "What the 'habitable planet' says"

The reason we seek out new exoplanets is not to live there, but to study them and learn things we don't yet know: how life began, how life is distributed across the universe, how to make Earth more habitable, and what makes a planet inhospitable.
Therefore, it is fundamentally absurd to view every newly discovered habitable planet as a twin of Earth.
Nature on a grand scale may have found a variety of solutions to foster life, and we will learn more by exploring how our Earth differs from other planets.

--- From "Another Earth, Earth 2.0"

However, we must remember that we live in a universe where order exists beyond our control.
Walt Disney's famous quote, "If you can dream it, you can do it" doesn't apply to everything.
For example, the inability to exceed the speed of light is not a temporary technological limitation, but a fact of the order of reality.
As with the law of conservation of energy, we cannot travel from one point in space to another faster than the signal of light.
These limitations have nothing to do with the stage of development of our civilization.
It is part of the very fabric of nature, and all we can do is find ingenious solutions to get the most out of it within its given limits.

--- From "Epilogue: Technology Cannot Bypass the 'Limits of Physics'"