#カク ミチオ

The neutrino is sometimes called the ghost particle, because it can penetrate entire planets and stars without being absorbed. At this very instant, your body is being radiated by a flood of neutrinos from deep space, some of which traveled through the entire planet Earth. In fact, some of these neutrinos could penetrate a block of solid lead that stretches from the Earth to the nearest star.

The God Equation: The Quest for a Theory of Everything - Michio Kaku

 Throughout history, scientists and philosophers believed that there was some sort of life force that animated living things. When a mysterious soul entered a body, it suddenly became animate and acted human. Many believed in something called dualism, where the material body coexisted with a spiritual soul.

 Schrödinger, however, believed that the code of life was hidden inside some master molecule that obeyed the laws of quantum mechanics. Einstein, for example, banished the ether from physics. Likewise, Schrödinger would try to banish the life force from biology.

The God Equation: The Quest for a Theory of Everything, Michio Kaku

 The origin of the universe has also fascinated physicists, especially when Newton gave us a compelling theory of gravity. But when Newton tried to apply his theory to the universe we see around us, he encountered problems.

 In 1692, he received a disturbing letter from clergyman Richard Bentley. In the letter, Bentley asked Newton to explain a hidden, possibly damaging flaw in his theory. If the universe is finite, and if gravity is always attractive, rather than repulsive, then eventually all the stars in the universe will be attracted to one another. In fact, with enough time, they will all coalesce into a single, gigantic star. So a finite universe should be unstable, and must eventually collapse. Since this does not happen, there must be a flaw in Newton’s theory.

 Next, he argued that Newton’s laws predicted an unstable universe even if the universe were infinite. In an infinite universe, with an infinite number of stars, the sum of all forces tugging on a star from the left and right would also be infinite. Hence, these infinite forces would eventually tear the stars apart, and hence all stars would disintegrate.

 Newton was disturbed by this letter, because he had not considered applying his theory to the entire universe. Eventually, Newton came up with a clever but incomplete answer to this question.

 Yes, he admitted, if gravity is always attractive, and never repulsive, then the stars in the universe might be unstable. But there was a loophole in this argument. Assume that the universe is, on average, totally uniform and infinite in all directions. In such a static universe, all the forces of gravity cancel one another out, and the universe becomes stable once again. Given any star, the forces of gravity acting on it from all the distant stars in different directions eventually sum to zero, and hence the universe does not collapse.

 Although this was a clever solution to this problem, Newton realized there was still a potential flaw to his solution. The universe might be uniform on average, but it cannot be exactly uniform at all points, so there must be tiny deviations. Like a house of cards, it appears to be stable, but the tiniest flaw will cause the entire structure to collapse. So Newton was clever enough to realize that a uniform infinite universe was indeed stable but was always teetering on the edge of collapse. In other words, the cancellation of infinite forces must be infinitely precise or else the universe will either collapse or be ripped apart.

 Thus, Newton’s final conclusion was that the universe was infinite and uniform on average, but occasionally God has to tweak the stars in the universe, so they do not collapse under gravity.

The God Equation: The Quest for a Theory of Everything - Michio Kaku

Trillions upon trillions of years from now, the stars of the universe will have exhausted all their nuclear fuel and become dark. Only black holes will survive in this bleak era. But even black holes must eventually evaporate, leaving nothing but a drifting sea of subatomic particles. Hawking asked himself another question: What happens if you throw a book into a black hole? Is the information in that book lost forever?

 According to quantum mechanics, information is never lost. Even if you burn a book, by tediously analyzing the molecules of the burned paper, it’s possible to reconstruct the entire book.

 But Hawking stirred up a hornet’s nest of controversy by saying that information thrown inside a black hole is indeed lost forever, and that quantum mechanics therefore breaks down in a black hole.

 As previously mentioned, Einstein once said that “God does not play dice with the world”—that is, you cannot reduce everything to chance and uncertainty. Hawking added, “Sometimes God throws the die where you cannot find them,” meaning that the dice may land inside a black hole, where the laws of the quantum may not hold. So the laws of uncertainty fail when you go past the event horizon.

 Since then, other physicists have come to the defense of quantum mechanics, showing that advanced theories like string theory, which we will discuss in the next chapter, can preserve information even in the presence of black holes. Eventually, Hawking conceded that perhaps he was wrong. But he proposed his own novel solution. Perhaps when you throw a book into a black hole, the information is not lost forever, as he previously thought, but it comes back out, in the form of Hawking radiation. Encoded within the faint Hawking radiation is all the information necessary to re-create the original book.

whether information is lost in a black hole is still an ongoing question, fiercely debated among physicists. But ultimately we may have to wait until we have the final quantum theory of gravity that includes graviton quantum corrections.

The God Equation: The Quest for a Theory of Everything - Michio Kaku

The black hole that was photographed by the Event Horizon Telescope lies inside the galaxy M87, 53 million light-years from Earth. The black hole is truly a monster, weighing in at a staggering five billion times the mass of the sun. Our entire solar system, even past Pluto, could easily fit inside the black silhouette in the photograph.

The God Equation: The Quest for a Theory of Everything - Michio Kaku

 It would take another two hundred years for the next big breakthrough, which came from the study of electricityandmagnetism.

 The ancients had known that magnetism could be tamed; the invention of the compass by the Chinese harnessed the power of magnetism and helped launch an age of discovery. But the ancients feared the power of electricity. Lightning bolts were thought to express the anger of the gods.

 The man who finally laid the foundation for this field was Michael Faraday, a poor but industrious youth who lacked any formal education. As a child, he managed to get a job working as an assistant at the Royal Institution in London. Normally, someone of his low social standing would forever sweep the floor, wash bottles, and hide in the shadows. But this young man was so tireless and inquisitive that his supervisors allowed him to perform experiments.

 Faraday would go on to make some of the greatest discoveries in electricity and magnetism. 

• He showed that if you take a magnet and move it inside a hoop of wire, then electricity is generated in the wire. 
• One could also show the reverse, that a moving electric field can create a magnetic one.
• This was an amazing and important observation, since the relationship between electricity and magnetism was then totally unknown.

 It gradually dawned on Faraday that these two phenomena were actually two sides of the same coin. This simple observation would help to open up the electric age.

He also invented the concept of a field, one of the most important concepts in all of physics.

• A field consists of these lines of force spread throughout space. Magnetic lines surround every magnet, and the magnetic field of the Earth emanates from the north pole, spreads through space, and then returns to the south pole.
• Even Newton’s theory of gravity can be expressed in terms of fields, so that the Earth moves around the sun because it moves in the sun’s gravitational field.

 Faraday’s discovery helped to explain the origin of the magnetic field surrounding the Earth.

• Since the Earth spins, the electric charges inside the Earth also spin.
• This constant motion moving inside the Earth is responsible for the magnetic field. (But this still left open a mystery: Where does the magnetic field of a bar magnet come from, since there is nothing moving or spinning in it? We will return to this mystery later.) 

Today, all the known forces of the universe are expressed in the language of fields first introduced by Faraday.

The God Equation: The Quest for a Theory of Everything by Michio Kaku