Notes on physics books
Zheng Xupei, Class 6, Grade 2, Junior High School
This is a full summer vacation. The physics books I read are A Brief History of Everything, A Brief History of Time (popular version), A Brief History of Time (graphic version), A Brief History of Science (juvenile version), Scientific Explorer-Motion, Force and Energy, Scientific Explorer-Sound and Light, and so on.
The following are my reading notes, which combine all my knowledge:
I. Atomic theory
The basic working form of an atom is a molecule. A molecule is two or more atoms working together in a relatively stable form. The lifetime of atoms is very long. Because atoms have a long life, they can really roam around. Besides, atoms are very small-in fact, very small. A row of 500 thousand atoms can't cover a hair. At this ratio, an atom is too small to imagine. Of course, atoms are so useful because they are numerous, have a very long life, and are too small to be detected and identified. Atoms have three characteristics-small, numerous and almost indestructible-and everything is made of atoms.
Democritus (ancient Greece): He put forward the theory of atoms, and thought that everything was made up of atoms.
Dalton found that atoms are small, numerous and almost indestructible-everything is made of atoms.
Rutherford revealed that the composition of uranium radiation is complex. He called "soft" components alpha rays and "hard" components beta rays. And predict the existence of neutrons.
Bohr published the theory of hydrogen atom structure and explained the spectrum of hydrogen atom.
Heisenberg and Ivanenko independently published the hypothesis that the nucleus is composed of protons and neutrons.
Richard. Feynman said: "If you have to compress the history of science into one important sentence, it will be: everything is made of atoms."
Two. Force and motion
Force is the action of one object on another, and the actions between objects are mutual. When it comes to force, there are always two objects involved, one is exerting force and the other is stressed. Conversely, the force-applying object is also acted by the force-receiving object. The force that objects are subjected to because of the gravity of the earth is called gravity, and the friction force is the force that hinders the relative motion or relative motion trend between objects because of the relative motion or relative motion trend. The property that an object maintains a uniform linear motion state or a static state is called the inertia of an object. At any time, an object has inertia, and the inertia of the object is only related to the mass of the object. The greater the mass, the greater the inertia of the object, the smaller the mass and the smaller the inertia of continuing revolution, which has nothing to do with other factors.
Archimedes invented many machines, including Archimedes screw; Discover the principle of lever and the law of buoyancy; Research center of gravity.
Stephen (1542— 1620) demonstrated the decomposition of force.
Galileo discovered the resistance of medium to motion, the principle of inertia, the motion of free falling body, the motion of objects on inclined plane and the motion of projectiles, and gave the definitions of uniform motion and uniform acceleration motion.
Newton discovered Newton's three laws of motion and the law of universal gravitation. (Einstein's mechanics is a single event)
Three. Sound and light
All sounds are produced by the vibration of the sound source. The substance on which sound propagates is called "medium", and the speed of sound propagation in air is about 340 m/s; Generally speaking, the greater the density, the better the elasticity and the faster the sound travels.
The same entity-light-is both a wave and a particle. In order to explain interference and diffraction, light must be a wave; And the photoelectric effect makes it into particles.
Euclid expounded the law of straight-line propagation and reflection of light.
Snell (1580— 1626) summed up the laws of light reflection and refraction from experiments.
Huygens published On Light, put forward the wave theory of light, derived the laws of straight-line propagation, reflection and refraction of light, and explained the birefringence phenomenon.
Fizeau (1819-1896) measured the speed of light on the ground for the first time.
Doppler (1803— 1853) found the Doppler effect.
Four. Theory of relativity
"Imagine a 90-meter-long train traveling at 60% of the speed of light. For those who stand on the platform and watch it pass by, the train looks only 70 meters long, and everything on the train is also reduced. If we can hear people talking in the car, their voices will sound vague and slow, just like playing a record too slowly, and their movements will look clumsy. Even the clock in the car seems to move at only four-fifths of the normal speed. However-that's the problem-people on the bus don't feel deformed. In their view, everything in the car seems to be normal. However, on the platform, we are strangely smaller and slower. You see, all this is related to your relative position with the moving object. If the concept of relativity seems a bit strange, it is only because we have never experienced this kind of interaction in our daily life. In fact, Einstein believed that time can be changed, and it is constantly changing. Time and even shape. One time is combined with three spaces-with Stephen? Hawking's words are inseparable-an incredible "time and space". Usually, time and space are explained in this way: imagine a flat and elastic thing-such as a carpet or a straight rubber mat-with a heavy and round object, such as an iron ball. The weight of the iron ball makes the cushion below slightly stretch and sink. This is roughly similar to the effect of a giant like the sun (iron ball) on time and space (bottom pad): the iron ball makes the bottom pad stretch, bend and tilt. Now, if you let a smaller ball roll on the mat, it will try to move in a straight line, just as Newton's law of motion requires. But when it is close to the big ball and the concave part of the bottom pad, it rolls to the lower part and is inevitably sucked away by the big ball. This is gravity-the product of space-time bending. Any object with mass can make a small pit on the bottom cushion of the universe. So as Dennis, Overby said that the universe is a "final settlement pad". From this perspective, gravity is not so much a thing as a result. Kaku's words: "It is not a' force', but a by-product of space-time bending. Kaku went on to say: "In a sense, gravity does not exist; What makes planets and stars move is the deformation of space and time. " -Excerpted from A Brief History of Everything.
It can be seen from here that the metaphor of the bottom cushion can only help us understand this degree, because it does not include the role of time. Having said that, in fact, our brains can only imagine this. It is almost impossible to imagine that space and time are woven into a space-time at the ratio of 3: 1 like a grid mat. Anyway, I think we will all agree that this is really a great insight for a young man staring out of the window of the patent office in the Swiss capital.
Verb (abbreviation of verb) BIGBANG
"Sooner or later, people will think of a question, that is, what will happen if you come to the edge of the universe and stick your head out of the curtain? Where will your head be (if it is no longer in the universe)? What will you see across the street? The answer is disappointing: you will never reach the edge of the universe. Not because it takes a long time to get there-although yes, it does take a long time-but because even if you go straight out and keep going, you will never reach the edge of the universe. On the contrary, you will go back to where you started (at this point, you are likely to be discouraged and give up this effort). The reason is that according to Einstein's theory of relativity (which we will talk about then), the universe is curved. As for how to bend, we can't imagine. At this moment, it is enough for you to know that we are not floating in an expanding bubble. To be exact, space is curved, which makes it infinite and limited. Properly speaking, we can't even say that space is expanding, because, as the Nobel Prize winner and physicist Steven? Weinberg pointed out: "The solar system and galaxies have not expanded, and space itself has not expanded. "On the contrary, galaxies are rapidly moving away from each other. This is a challenge to intuition. " -From the brief history of everything.
Arnold. Penzias and Robert? 1965 Wilson and Bell Laboratories in Holmdel, New Jersey, USA, when trying to use a large communication antenna, were constantly disturbed by a kind of background noise-a continuous hiss like steam, which made the experiment impossible. This noise is uninterrupted and unfocused. This is in line with George, an astrophysicist born in the Soviet Union in the 1940s. Gamov's hypothesis: If you look deep into space, you will find some cosmic background radiation left by BIGBANG. Gamov estimated that that kind of radiation would reach the earth in the form of microwaves after it passed through the vast universe. In a recent paper, he even suggested that this can be achieved by an instrument, which is Holmdel's bell antenna. Unfortunately, neither penzias nor Wilson, nor any experts on the Princeton team, have read Gamov's paper. The noise that penzias and Wilson heard was exactly what Gamow imagined. They have found the edge of the universe, at least the visible part of the universe/kloc-0.5 billion light years away.
The expansion theory holds that the universe suddenly experienced a violent expansion at the moment after the explosion. It keeps expanding-it actually runs away with itself, and its size doubles every 10-34 seconds. The whole process may only last less than 10-30 seconds-that is, one trillionth of a second-but the universe has changed from something that can be held in the hand to something at least 65,438 billion times larger. Expansion theory explains the pulsation and rotation that make our universe possible. Without this pulsation and rotation, there would be no mass of matter, so there would be no stars, only floating gas and eternal darkness.