Chapter 2 1. Force field

"Raise the shield!" In countless episodes of Star Trek, this was the first order Captain Kirk yelled to his crew, raising the force field to protect the Enterprise from enemy fire. In "Star Trek", the force field is so important that the direction of the battle can be measured by the support of the force field.Each time energy was drawn from the force field, the Enterprise's hull took more and more destructive blows, until eventually it inevitably capitulated. What is a force field?In science fiction, it's so simple, it's misleading: a thin, invisible but impenetrable barrier that redirects things like lasers and rockets.At first glance, force fields are so simple that their creation as a kind of barrier on the battlefield seems imminent.It was expected that some offensive inventor would one day announce the discovery of defensive force fields.But the truth is much more complicated than that.

Just as Edison's light bulb revolutionized modern civilization, force fields may have a profound impact on every aspect of our lives.Armies could use force fields to become impenetrable, creating an impenetrable shield against enemy missiles and bullets; bridges, highways, and roads could theoretically be built with the push of a button; Break ground with skyscrapers built entirely out of force fields.The force field covering the entire city allows the residents living in it to cancel the influence of the weather at will. These weather conditions include strong winds, blizzards and tornadoes.With the safety cover formed by the force field, cities can be built under the ocean, and glass, steel and mortar can be completely replaced.

Oddly enough, though, force fields are perhaps one of the most difficult devices to create in the lab.In fact, some physicists believe that creative fields may not be possible unless their properties are redefined. The concept of force fields arose out of the work of the great 19th century British scientist Michael Faraday. Faraday was born into a working family (his father was a blacksmith) and eked out a living as a bookbinder's apprentice for a long period in the early 19th century.The young Faraday was fascinated by the breakthrough brought about by the unraveling of the mysterious nature of the two new forces.These two new forces are: electricity and magnetism.Faraday greedily did everything he could to learn about these problems and attended lectures given by Professor Humphrey Davy at the Royal Academy in London.

One day, Professor David's eye was seriously injured in a chemical accident, so he hired Faraday as his secretary.Faraday gradually gained the confidence of the Royal Academy scientists and was allowed to conduct important experiments independently, although he was often ignored.Year after year, Professor Davy became more and more jealous of the outstanding abilities displayed by his young assistant.Faraday had become a rising star in experimental circles, eventually eclipsing Professor Davy's reputation. After David died in 1829, Faraday was free to make a series of astonishing breakthroughs that led to the creation of the dynamo.The generator was able to power entire cities and changed the course of world civilization.

The key to Faraday's greatest discovery was his "force field."If someone sprinkled iron filings on a magnet, he would find that the filings would take on the shape of a spider's web filling the entire space.These are Faraday's lines of force, which graphically depict how electric and magnetic force fields are spread out in space.For example, if one plots the magnetic field of the whole earth, he will find that the lines of force come out from the N pole region, and then fall back to the earth at the S pole region.Likewise, if one draws the electric field lines of a lightning rod in a thunderstorm, one will find that the lines of force are concentrated at the tip of the rod.In Faraday's view, "empty space" is not empty at all, but filled with lines of force that can move distant objects (because Faraday was poor in his early years, he did not receive enough mathematics education, so the densely packed in his notebook Not equations, but hand-drawn diagrams of these lines of force. Ironically, his lack of mathematical training led him to create the beautiful diagrams of force lines that can be found in any physics textbook today. Scientifically speaking, physics The image is often more important than the mathematical language used to describe it).

Historians have speculated how Faraday discovered the force field, one of the most important concepts in all of science.In fact, all of modern physics is written in Faraday's force field language.In 1831, he made a pivotal breakthrough in force fields that changed civilization forever.One day, while moving a child's magnet across a metal coil, he noticed that he was able to create a current in the wire without even touching the wire.This means that the field invisible to the magnet can push the electrons in the wire across "empty space," creating an electric current. Faraday's force field was once dismissed as useless, scribbled with nothing to do, but it's a real, physical force that can move objects and generate energy.The light by which you read this page today may have been lit by Faraday's discoveries about electromagnetism.A rotating magnet creates a force field that pushes electrons in a wire, causing them to move in the form of an electric current that can then light a light bulb.This same principle is used to generate the electricity that powers cities around the world.For example, water flowing through a dam creates a huge magnetic force in a turbine, which then pushes electrons in the wire, creating a current that is sent to the user through a high-voltage wire.

In other words, Michael Faraday's force field is the power that drives modern civilization, from electric bulldozers to today's computers, the Internet, and iPods all stem from the discovery of force fields. Faraday's force field has been an inspiration to physicists for a century and a half.These force fields gave Einstein great inspiration, he used the language of force field to describe and express his gravitational theory.Likewise, I was inspired by Faraday's work.Many years ago, I successfully expressed the theory of strings using Faraday's force field, thus establishing the string field theory.In physics, it is a high compliment to say that "he thinks like a line of force."

One of the crowning achievements of physics over the past two thousand years has been the isolation and identification of the four forces that govern the universe.All of them can be described in terms of Faraday's force field.Unfortunately, none of them have much of the force field properties that most science fiction describes.These forces are: Second, it might be possible to use a plasma to simulate some of the laws of force fields.Plasma is the "fourth state of matter".Solids, liquids and gases make up the three common states of matter, but the most common form of matter in the universe is plasma — a gas, or ionized atom.Because the atoms of the plasma are ripped apart, and electrons are ripped from the atoms, the atoms are charged and can be easily controlled with electric and force fields.

Plasma is the most abundant form of visible matter in the universe, making up the sun, stars and interstellar gas.Plasmas are unfamiliar to us because they are rare on Earth, but we can see them in the form of lightning, the sun, and the internal structures of plasma televisions. As mentioned above, if a stream of air is heated to a high enough temperature, a plasma can be created thereby, which can be shaped and changed shape by electromagnetic fields.For example, it can be transformed into a sheet or a window.Alternatively, this plasma window can be used to isolate a vacuum region from normal air.In principle, we might be able to create a simple, transparent interface between space and a spacecraft in order to prevent the air in a spacecraft from leaking out into space.

In Star Trek, such force fields are used to isolate the shuttle port where the small shuttles are parked from the vacuum of space.This is not only a good way to save money on props, but also an achievable device. The plasmonic window was invented by physicist Ady Herschcovitch in 1995 at Brookhaven National Laboratory on Long Island, New York.He developed the plasma window as a solution to the challenges of welding metals with electron beams.The welder's jet of high-heat blast melts the metal parts and welds them together.However, this has to be done in a vacuum.This requirement is quite embarrassing, because it means creating a vacuum box that may be as large as an entire room.

Dr. Huskikovich's invention of the plasma window solved this problem.The plasma window, just 3 inches high and less than 1 inch in diameter, heats air to 12,000 degrees Fahrenheit, creating a plasma trapped by an electromagnetic field.As in any gas, these particles use pressure to keep the air from rushing into the vacuum space, thereby separating the air from the vacuum (when using argon in the plasma window, its flame is blue, as in "Star like the force fields in Ship Trek). Plasma windows are widely used in space travel and industrial production.In many cases, manufacturing processes require industrial microfabrication and processing, but working in a vacuum can be expensive.However, with plasma windows, we can cheaply control the vacuum at the touch of a button. So, can the plasma window also be used as an impenetrable shield?Can it withstand the onslaught from a light cannon?In the future, we can imagine more powerful and hotter plasma windows, powerful enough to damage or vaporize attacking projectiles.But to create a more realistic force field like in science fiction, we need a combination of several techniques layered on top of each other.It's possible that each layer won't be strong enough to stop a projectile, but their combination might. The outermost layer could be a pressurized plasma window, heated to a temperature high enough to vaporize the metal.The second layer can be a curtain of high-energy laser beams.The curtain consists of thousands of laser beams crossed in a cross shape, forming a grid that heats objects passing through, effectively vaporizing them.I will discuss lasers further in the next chapter. Behind this laser curtain, we can imagine a grid of assembled "carbon nanotubes," tiny tubes of individual carbon atoms that are one atom thick and many times stronger than steel.Although the current world record for the length of a single carbon nanotube is only about 15 millimeters, we can count on the possibility that carbon nanotubes of any length may one day be produced.Assuming the carbon nanotubes can be woven into a grid, they could become an extremely strong barrier that can repel most attackers.The barrier would be invisible because each carbon nanotube is atomically sized, but the carbon nanotube grid would be stronger than any conventional material. In this way, through the combination of plasma windows, laser curtains and carbon nanotube barriers, we can imagine creating an invisible wall that is basically impenetrable by most means. However, even this multi-layered barrier wouldn't quite match the properties of a force field in science fiction—it would be transparent, so it wouldn't be able to block laser beams.In a battle with laser cannons, this multi-level cover will be useless. To resist the laser, this bunker needs to have advanced technology of "photochromic material" at the same time.This is a process applied to sunglasses that automatically darken when exposed to UV radiation.Photochromic materials are based on molecules that can exist in at least two states: in one state, the molecule is transparent; but such molecules immediately change to a second state upon exposure to UV radiation, i.e. opaque. One day, we may be able to use nanotechnology to create a substance as strong as carbon nanotubes, whose optical properties change when exposed to laser light.In this way, a shield can withstand laser blasts and particle beams, or artillery fire.However, photochromic materials that are resistant to laser beams do not currently exist. In science fiction, the force field has another function besides resisting the attack of the laser gun, that is, as a platform against the gravitational force.In the movie "Back to the Future," Michael J. Fox rides a flying skateboard, which is exactly like a normal skateboard, except that it floats above the streets.According to the laws of physics we know today (which we will discuss in Chapter 10), such a gravity-defying device is impossible.But maglev skateboards and maglev cars may become a reality in the future, and will give us the ability to lift large objects at will.In the future, if "room-temperature superconductors" become a reality, we may be able to use the power of magnetic fields to lift objects. If we place two magnets N to N side by side, the two magnets will repel each other (if we rotate the magnets so that the N pole of one aligns with the S pole of the other, the two magnets will attract each other).This theorem, that like poles repel, can be used to lift enormous weights off the ground.Several countries have built advanced maglev trains, which use ordinary magnets to levitate their bodies slightly above the tracks.Suspended on a cushion of air without friction, they can travel at record-breaking speeds. In 1984, the world's first commercial automatic maglev system was put into operation in the UK, driving from Birmingham International Airport to the nearby Birmingham International Railway Station.Maglev trains have also been built in Germany, Japan and South Korea, although they were not designed as high-speed trains.The first commercial maglev train to operate at high speed was the High-Speed ​​Maglev Demonstration Operation Line (IOS) in Shanghai, China, traveling at a speed of 268 miles per hour.A maglev train in Japan's Yamanashi prefecture has reached speeds of 361 miles per hour, faster than regular trains with wheels. But these magnetic levitation devices are extremely expensive.One way to increase efficiency is to use superconductors, which completely lose electrical resistance when cooled to around absolute zero.Superconductivity was discovered in 1911 by Heike Onnes.If you cool some substances to less than 20K above absolute zero, the resistance will be completely lost.Usually, when we lower the temperature of a metal, its resistance gradually decreases (this is because the random vibrations of atoms in the wire hinder the flow of electrons, and these random motions are also reduced when the temperature is lowered, so the resistance to electron flow becomes smaller) .However, to Onnis' surprise, he found that the electrical resistance of certain materials suddenly dropped to zero at extreme temperatures. Physicists immediately recognized the significance of the result.Power lines lose a lot of energy in the process of carrying power over long distances.But if resistance could be eliminated altogether, power could be transmitted with almost no loss.In fact, if electricity were circulated in metal coils, the electricity could circulate for millions of years without loss of energy.In addition, these enormous currents can be used with little expense to create magnets of extraordinary strength.With such magnets, we can easily lift huge weights. Despite these miraculous powers, the problem with superconductors is that submerging large magnets in supercooled liquids in giant containers is prohibitively expensive.Keeping liquids supercooled would require gigantic refrigeration facilities, making superconducting magnets prohibitively expensive. But physicists may one day be able to create "room-temperature superconductors"—the holy grail of solid-state physicists.The discovery of room-temperature superconductors in the laboratory will spark a second industrial revolution.Strong magnetic fields that can lift cars and trains would become so cheap that levitating cars might become economically viable.With room-temperature superconductors, the flying cars dreamed up in Back to the Future, Minority Report and Star Wars could become a reality. In principle, one could wear a belt made of superconducting magnets that would allow one to leave the ground and float in the air with little effort.With such a belt, we can fly through the air like Superman.Room-temperature superconductors are so remarkable that they've been featured in countless science fiction novels, such as Larry Niven's 1970 Ringworld series. For decades, physicists have searched in vain for room-temperature superconductors.This has become a lengthy, messy procedure, testing materials one by one.But in 1986, a new class of matter known as a "high-temperature superconductor" caused a stir in the physics world when it was discovered that it would become a superconductor at a temperature of 90 degrees above absolute zero, or 90K.The floodgates seem to be open, and month after month, physicists race to break the next superconductor world record.For a brief moment, the achievability of room-temperature superconductors seemed to leap from the pages of science fiction and into our living rooms.But after years of rapid progress, research on high-temperature superconductors has slowed down. The current world record for a high-temperature superconductor is held by a substance called mercury-thallium-barium-calcium-copper oxide, which became a superconductor at 138K (-135°C).This relatively high temperature is still a long way from room temperature superconductors.But the record of 138K is still of great significance.Nitrogen liquefies at 77K, and the price of liquid nitrogen is about the same as ordinary milk.Therefore, ordinary liquid nitrogen can cool these high-temperature superconductors at a relatively low cost (of course, room-temperature superconductors do not need to be cooled at all). It is very embarrassing that there is currently no theory that can explain the properties of these high-temperature superconductors.In fact, a Nobel medal is waiting for some dedicated physicist who can explain how high-temperature superconductors (which are made of atoms arranged in special layers) work. Many physicists have theorized, explain how layering ceramic materials allows electrons to flow freely between the layers, forming superconductors. Exactly how this process works is still a mystery). Lacking this knowledge, physicists have unfortunately resorted to an aimless program of searching for new high-temperature superconductors.That means that fabled room-temperature superconductor could be discovered tomorrow, next year, or not at all.No one knows when or if the substance will be found. But once room-temperature superconductors are discovered, a frenzy of commercial applications will set off.A magnetic field millions of times stronger than Earth's magnetic field (about 0.5) may become ubiquitous. One of the common properties of superconductors is known as the Meissner effect.If you put a magnet on a superconductor, the magnet will levitate, as if lifted by some invisible force (the principle of the Meissner effect is that the magnet has the ability to create a "mirror image" inside the superconductor, so The magnet itself and the mirror image magnet repel. Another explanation for this effect is that the magnetic field cannot penetrate a superconductor. Instead, the magnetic field is repelled. Therefore, if a magnet is placed above a superconductor, its lines of force are The superconductor is repelled, so the lines of force push the magnet up, causing it to levitate). Applying the Meissner effect, we can imagine that future highways will be built from such special ceramics.So magnets placed in our belts and tires allow us to magically float toward our destination without friction or loss of energy. The Meissner effect only works on magnetic materials, such as metals.But it is also possible to levitate nonmagnetic materials using superconducting magnets, known as paramagnets and diamagnets.These substances are not inherently magnetic, they only become magnetic when exposed to an external magnetic field.Paramagnets are attracted by an external magnet, whereas diamagnetics are repelled by an external magnet. For example, water is a diamagnet.Since all living things are composed of water, they can be suspended in a strong magnetic field.In a magnetic field of about 15 (equivalent to 30,000 times the surface magnetic force), scientists have been able to levitate small animals, such as frogs.But if room-temperature superconductors become a reality, it should be possible to similarly levitate large non-magnetic objects by using the properties of diamagnets. All in all, the force fields so widely portrayed in science fiction do not fit the description of the four forces of the universe.But it is still possible to simulate the many properties of force fields by using multilayer shields made of plasmonic windows, laser curtain walls, carbon nanotubes and photochromic materials.But developing such a shield could be decades, if not a century away.If room-temperature superconductors are discovered, it might be possible to use powerful magnetic fields to lift cars and trains and send them zipping through space, just like in science fiction movies. With these factors in mind, I classify force fields as "incredible first class" -- things that are impossible with today's technology, but will be possible in improved form in a century or so.

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