Will there ever be a day when we'll be able to walk through walls, build ships that travel faster than the speed of light, read other people's minds, become invisible, move objects with the power of our thoughts, and instantly teleport our bodies into space? I have been fascinated by these questions since I was a child.Like many physicists, growing up I was fascinated by the possibilities of time travel, death ray guns, force fields, parallel universes, and more.Magic, fantasy, and science fiction were all expansive playgrounds for my imagination to run wild, and they began my lifelong love affair with the unthinkable.

I remember watching reruns of Flash Gordon on TV.Every Saturday I'm glued to the TV, marveling at the adventures of Flash, Dr. Zarkov and Dale Ardende and their dazzling futuristic tech gear : rocket ship, invisible shield, death ray gun, sky city.I never missed a week of airing.This show opened up a whole new world for me.I am thrilled at the thought of one day being able to take a rocket to a strange planet and explore its unique landscape.I was pulled into the magnetic field of these amazing inventions, knowing that my fate was somehow tied to the scientific wonders that were presented in this series.

As it turns out, my experience is not unique.Many brilliant scientists first became interested in science through exposure to science fiction.The great astronomer Edwin Hubble was obsessed with the work of Jules Verne.After reading Verne, Hubble left a promising legal job against his father's wishes to pursue a career in science, eventually becoming the greatest astronomer of the 20th century.Famed astronomer and best-selling author Carl Sagan found his imagination ignited by Edgar Rice Burroughs' John Carter on Mars novels, So I began to dream of one day exploring the sand grains of Mars like John Carter did.

I was a child when Albert Einstein died, but I remember whispers about his life and death.The next day I saw in a newspaper a photograph of his desk with the manuscript of his greatest unfinished research.I asked myself, what could be so important that even the greatest scientists of our time could not accomplish it?The newspaper article declared that Einstein had an impossible dream, a problem so difficult that humanity could not end it.It took me years to figure out what that manuscript was about: a magnificent, all-in-one theory of everything.His dreams—dreams that consumed the last 30 years of his life—helped me to focus on my own imagination.I hope that I can do my part to complete Einstein's work, to unify all the laws of physics into a theory.

When I was a little older, I realized that while Flash Gordon was a hero and always got the girls, it was actually the scientists who made the show work.Without Dr. Zakov, there would be no rocket ship, no trip to the planet Mongo, and no saving Earth.Heroism has to stand aside, there can be no science fiction without science. I began to understand that these stories were utterly impossible in terms of the science behind them, and that they were mere creations of the wild imagination.Growing up means putting such fantasies aside.I was told that in real life one has to let go of the unthinkable and embrace reality instead.

However, I concluded that if I was going to continue my fascination with the unthinkable, the answer was to go into physics.Without a solid foundation in cutting-edge physics, I would forever be left wondering about future technologies, not whether they would work at all.I realized I had to focus on higher mathematics and study theoretical physics.So I did that. In high school, I rigged a nuclear particle accelerator in my mom's garage as a science fair exhibit.I went to Westinghouse and collected 400 lbs of scrap transformer steel.I wound 22 miles of copper wire around my high school football field over Christmas.In the end, I made a betatron with a power of 2.3 million electron volts. It needs to consume 6 kilowatts of electricity (equivalent to the total power output by my house), and can generate a magnetic field equivalent to 20,000 times the earth's magnetic field. The goal is to be able to Create gamma rays powerful enough to produce antimatter.

My science fair project got me into national science fairs and finally made my dream come true with a scholarship to Harvard.There, I was finally able to pursue my goal of becoming a theoretical physicist and follow in the footsteps of my idol, Albert Einstein. These days, I get occasional emails from science fiction writers and screenwriters asking me to help them explore the limits of the laws of physics and make their stories more convincing. As a physicist, I realize that "impossible" is often a relative term.Growing up, I remember my teacher one day approaching the world map hanging on the wall, pointing to the coastlines of South America and Africa, "Isn't that a weird coincidence?" she said, "The difference between the two The coastlines fit together like a jigsaw puzzle! Some scientists speculate that they might have once been two parts of the same vast continent. But that would be stupid. There can't be a force that could push two huge continents apart." "Such Thoughts are hopeless," she concluded.

A year after that, we learned about dinosaurs.The teacher told us that dinosaurs ruled the earth for millions of years, and then one day they all disappeared.No one knows why they died out.Isn't that weird?Some paleontologists think a meteor from space might have killed them, but that's unlikely, it's more like something out of science fiction. Today, we know that continents do move during plate tectonics, and that a massive six-mile-wide meteor 65 million years ago was the most likely culprit that wiped out the dinosaurs and much of life on Earth.Over the course of my own short life, I've seen time and time again what seemed impossible become established scientific fact.So, isn't it possible that we could one day teleport ourselves from one place to another, or build a spaceship that could one day take us light-years to other planets?

In general, such feats would seem impossible to physicists today.Will they be possible within a few centuries?Or thousands of years later, when our technology is more advanced?Or in a million years?Put another way, if we somehow encountered a civilization a million years ahead of us, would their common technology appear "like magic" to us?This is one of the central questions throughout this book, will something be impossible hundreds or millions of years from now just because it is "impossible" today? Thanks to the great advances in science over the past century, notably the birth of quantum theory and general relativity, we can now roughly estimate when (if ever) some of these fantastical technologies will be possible .Even concepts that belonged to the realm of science fiction, such as time travel and parallel universes, are now being re-evaluated by physicists as more advanced theories, such as string theory, emerge.Think back to 150 years ago, those technologies that were declared "impossible" by the scientists of the time have now developed into a part of our daily life.Jules Verne wrote a novel in 1863: Paris in the 20th Century.The novel was dusted and forgotten for more than a century until Verne's great-grandson discovered it and it was first published in 1994.In it, Verne predicted what Paris might look like in 1960.His novels are filled with technologies that seemed apparently inconceivable in the 19th century, including the fax machine, a worldwide communications network, glass skyscrapers, gas-powered cars and high-speed elevated trains.

Unsurprisingly, Verne was able to make such remarkably precise predictions because he was immersed in the scientific world, drawing wisdom from the scientists around him.His deep understanding of the basic principles of science allowed him to make such amazing predictions. Regrettably, some of the greatest scientists of the nineteenth century took the opposite position and declared the realization of many, many technologies hopeless.Lord Kelvin, perhaps the most eminent physicist of the Victorian era (he is buried next to Isaac Newton in Westminster Abbey), declared that, like airplanes, they were "heavier than air" The" device is impossible to realize.He thought X-rays were a boring trick and that radio had no future.Lord Rutherford, the scientist who discovered the atomic nucleus, dismissed the possibility of building an atomic bomb, comparing it to "moonlight." Nineteenth-century chemists declared the search for the philosopherstone, the mythical substance that turns lead into gold, a scientific dead end. Nineteenth-century chemistry was based on the theory that elements like lead are immutable.Today, however, we can in principle turn lead into gold with today's nuclear particle accelerators.Consider how impractical today's televisions, computers and the Internet would have seemed at the turn of the 20th century.

More recently, black holes were considered science fiction.Einstein himself wrote a paper in 1939 "proving" that black holes could never form.However, as of today, the Hubble Space Telescope and the Chandra x-ray telescope have observed thousands of black holes in space. These technologies were considered "impossible" because the fundamental laws of physics and science were not known in the 19th and early 20th centuries.Given the vast gaps in scientific understanding at the time, especially at the atomic level, it is not surprising that these developments were considered impossible. Ironically, the serious study of the "impossible" often opens up the fertile and wholly unexpected frontiers of science.For example, more than a century of frustrating, pointless quest for "perpetual motion machines" has led physicists to conclude that such machines are impossible, forcing them to postulate the conservation of energy and the three major laws of thermodynamics. law.In this way, the futile quest to create perpetual motion machines opened up a whole new field of thermodynamics, in a way that laid the groundwork for the steam engine, the mechanical age, and modern industrial society. At the end of the 19th century, scientists decided that it was "impossible" that the Earth was billions of years old.Sir Kelvin flatly declared that the molten Earth could have cooled between 20 and 40 million years, refuting claims by geologists and Darwinist biologists that the Earth could be billions of years old.The "impossible" proved quite possible as Marie Curie and other scientists discovered the nuclear force, showing that the Earth's core was heated by decay, potentially keeping it molten for billions of years. We ignore the "impossible" at our own peril.In the 1920s and 1930s, the founder of modern rocketry, Robert Goddard, was severely criticized by those who believed that rockets could never operate in outer space, who wryly called his pursuit "the Goddard's follies".In 1921, the New York Times criticized Dr. Goddard's work thus: "Professor Goddard does not know the connection between action and reaction, nor that there must be something more suitable than a vacuum. He seems to lack the basic knowledge taught in high school." "Rockets are impossible," commented the editor, "because there is no propulsion air in outer space." Sadly, one The head of state actually understood what Goddard's "impossible" rocket meant—that was Adolf Hitler.During World War II, Germany's impossibly advanced V-2 rockets rained down on London, causing so much death and so much destruction that it nearly brought London to its knees. The study of the unthinkable may have also changed the course of world history.In the 1930s, it was widely believed, even by Einstein, that the atomic bomb was "impossible."From Einstein's equation E=mc2 (squared), physicists know that there is a huge amount of energy deep inside the nucleus, but that the energy released by a single nucleus is negligible.Atomic physicist Leo Szilard, however, remembers reading HG Wells' 1914 novel The World Set Free, in which Wells predicted The development of the atomic bomb.In his book, he claimed that the mystery of the atomic bomb would be solved by a physicist in 1933.Zilat came across the book by chance in 1932.Spurred on by this novel, he happened to conceive in 1933, the year Wells predicted 20 years earlier, to amplify the energy of a single atom by a chain reaction, thus splitting a uranium The energy generated by the nucleus can be multiplied trillions of times.Zilat then began a series of pivotal experiments and secret negotiations with Einstein and President Franklin Roosevelt that led to the Manhattan Project to build the atomic bomb. Time and time again, we've seen the study of the impossible open up new horizons, push the boundaries of physics and chemistry, and force scientists to redefine what they mean by "impossible."As Sir William Osler said: "The belief of one age is false in the next, and the folly of the past is the wisdom of tomorrow." Many physicists agree with TH White, the author of Once and Future King, who famously said: "What is not forbidden is necessary!" In physics, we can find the corresponding evidence all the time .Unless there are laws of physics that expressly forbid the creation of a new phenomenon, we will eventually discover its existence. (This has happened many times in the search for new subatomic particles. In exploring the limits of forbidden things, physicists often discover new laws of physics by accident.) There may be a corollary to White's famous quote: " Everything that is not impossible is inevitable!" For example, cosmologist Stephen Hawking tried to find a new law of physics that forbids time travel, proving that it is impossible, which he called the "chronology protection conjecture" .Unfortunately, after years of hard work, he was unable to prove this principle.In fact, to the contrary, physicists have now shown that the laws prohibiting time travel are beyond the scope of today's mathematics.Today, physicists have to treat the possibility of time machines with caution, since there are no laws of physics that deny their existence. The purpose of this book is to consider technologies that are considered "impossible" today and may become commonplace in the decades and centuries to come. There is an already "impossible" technology that is now proven possible: teleportation (at least at the atomic level).Even a few years ago physicists would say that teleporting or sending an object from one point to another violates the laws of quantum physics.The screenwriters who originally penned the script for the TV show Star Trek were so fed up with criticism from physicists that they included a "Heisenberg compensator" to explain their teleporter, well make up for this loophole.Today, thanks to recent major scientific breakthroughs, physicists can teleport atoms from one side of a room to the other in an instant, or photons across a river under the Danube. Predictions are always risky to make, especially hundreds or even thousands of years into the future.Physicist Niels Bohr was fond of saying, "Prediction is difficult, especially with regard to the future." But there was one fundamental difference between Jules Verne's time and today's.Today, the fundamental laws of physics are mostly known.Physicists today understand a staggering 43 orders of magnitude, from the proton inward to the expanding universe.Physicists can state with reasonable confidence what future technologies might look like, and better distinguish between those that are merely improbable and those that are truly impossible. In this book, therefore, I divide the "uncanny" into three categories. The first category I call "first-class inconceivable".They are technologies that are not currently possible, but do not violate the known laws of physics.So they might become possible in an improved form this century or the next.They include: teleportation, antimatter engines, some forms of telepathy, willpower, and invisibility. The second category I define as "second-class unbelievable".They are technologies that operate on the fringes of our understanding of the physical world.If at all possible, they will probably be realized within the next 1,000 to 1,000,000 years.They include: time machines, hyperspace travel and traversing wormholes. The last category I call "third-class inconceivable".They are technologies that violate the known laws of physics.Surprisingly, there are very few such incredible technologies.Once they are proven possible, it would mark a fundamental shift in our understanding of physics. I feel this classification is crucial because so many technologies in science fiction are dismissed by scientists as utterly impossible, when in fact what they are trying to say is that they are impossible for a civilization as primitive as humans is impossible.For example, visiting alien planets was generally considered impossible because of the great distances between them.While interstellar travel is clearly impossible for our civilization, perhaps it is feasible for civilizations that are hundreds, thousands or millions of years ahead of us.Therefore, it is very important to summarize such "unbelievable".Technologies that are impossible for our current civilization may not be equally impossible for other types of civilization.Claims about what is possible and what is not must take into account technology that is thousands or even millions of years ahead of us. Carl Sagan once wrote: "What does it mean for a civilization to be millions of years old? We have had radio telescopes and spaceships for decades, and our technological civilization is hundreds of years old." years ... millions of years of advanced technological civilization ahead of us, just as we are ahead of scrub baby monkeys and macaques." In my own research work, I have focused exclusively on fulfilling Einstein's dream of a truth in everything.Personally, I find it exhilarating to work on discovering a "final theory" that may ultimately answer some of the most difficult "incredible" questions in science today.These questions include: whether time travel is possible, what's in the center of a black hole, what happened before the Big Bang, etc.I still revel in my lifelong love affair with the unimaginable, and wonder if some of these unimaginable find their way into the realm of everyday life.